JP6963476B2 - Power converter and method for detecting abnormalities in the reactor of the power converter - Google Patents

Description

The present invention relates to a power conversion device and a method for detecting an abnormality in a reactor included in the power conversion device.

From the viewpoint of environmental problems and economic effects, the demand for power storage systems equipped with solar cells and storage batteries is increasing. The DC power generated by the solar cell and the DC power charged in the storage battery are boosted or stepped down by the converter circuit, and the DC power is converted into AC power by the bidirectional inverter circuit, and the AC power is converted into DC power. In a power storage system equipped with a power conversion device, a reactor is used as an indispensable electric component together with a switching element and a capacitor.

When a toroidal core type is adopted as this reactor (also called an inductor or a coil), for example, a donut type core is used, so that the winding density is high inside the donut type core due to the structure, and adjacent windings are used. In the worst case, the windings may come into contact with each other and short-circuit each other. When this short circuit occurs, the inductance value of the reactor decreases and the ripple current increases, and as a result, the temperature of the reactor rises sharply, which may lead to burning.

In order to detect such a temperature rise, Patent Document 1 discloses a technique of using a temperature sensor to measure the ambient temperature of a filter capacitor of a power conversion device.
By applying this technique, it is possible to detect a short circuit between windings of a reactor used in a power storage system, that is, a rare short circuit.

FIG. 24 is a schematic view of a toroidal core type reactor to which a thermal fuse is attached. A thermal fuse is attached to the reactor, the thermal fuse and the lead wire are connected by soldering, etc., and the lead wire and the cable harness are connected by caulking.
With this thermal fuse, abnormal overheating due to a rare short circuit (short circuit between windings) of the reactor is detected, and if it is determined to be abnormal by the detection signal, the operation of the power conversion device can be stopped and protected.

Japanese Unexamined Patent Publication No. 8-196802

However, it is possible to detect a rare short circuit by attaching a thermal fuse to the reactor, but by using a thermal fuse, cracks in the connection between the thermal fuse and the lead wire and the connection between the lead wire and the cable harness are made. There is a problem that poor contact of the crimped portion occurs, leading to erroneous detection.

The present invention has been made in consideration of the above circumstances, and provides a power conversion device capable of detecting a reactor abnormality while preventing erroneous detection, and a reactor abnormality detection method included in the power conversion device. The purpose.

The present invention uses an existing current detector that measures the current flowing through the reactor and measures the ripple current at the drive frequency superimposed on the current flowing through the reactor. When a rare short circuit occurs in the reactor, the inductance value of the reactor decreases and the ripple current increases. Therefore, the rare short circuit of the reactor can be detected by measuring the ripple current.

That is, the present invention includes a converter circuit composed of a switching element that inputs DC power via a reactor and outputs it by boosting or stepping down the voltage of DC power, and a current detector that detects the current flowing through the reactor. In a power converter equipped with a control unit that turns on / off the switching element of the converter circuit and monitors the output of the current detector, the control unit is a reactor based on the ripple current value of the current output signal of the current detector. A state detection circuit that calculates a comparison target value for detecting the state of, an effective current detection circuit that detects the effective current value of the current output signal of the current detector, and a predetermined threshold value corresponding to the effective current value are calculated. The threshold calculation unit, the determination unit that determines that the reactor is abnormal when the comparison target value exceeds a predetermined threshold, and the determination unit that determines that the reactor is abnormal, stops the output of the control signal to the switching element of the converter circuit. It is a power conversion device characterized by including a switching element control unit.

According to this configuration, an abnormality in the DC reactor used in the converter circuit can be reliably detected, and damage to the power converter can be prevented.

Further, the threshold calculating unit is characterized Rukoto issuing calculate the threshold by substituting the effective current value to a linear function.

According to this configuration, since the threshold value for determining the abnormality of the ripple current value is calculated corresponding to the effective current value, it can be appropriately determined according to the usage environment of the power conversion device.

The power conversion apparatus of the present invention includes an inverter circuit for the type of AC power via a reactor switching elements is converted into DC power, or DC power through a reactor is converted into AC power by the switching element output In a power conversion device including a current detector that detects the current flowing through the reactor and a control unit that turns on / off the switching element of the inverter circuit and monitors the output of the current detector, the control unit detects the current. A state detection circuit that calculates the comparison target value for detecting the reactor state based on the ripple current value of the current output signal of the device, and an effective current detection circuit that detects the effective current value of the current output signal of the current detector. When converting AC power to DC power, a predetermined fixed value is set regardless of the effective current value, and when converting DC power to AC power, a threshold calculation unit that calculates a predetermined threshold corresponding to the effective current value, A determination unit that determines that the reactor is abnormal when the value to be compared exceeds a predetermined threshold, and a switching element control unit that stops the output of the control signal to the switching element of the inverter circuit when the reactor is determined to be abnormal. It is characterized by having.

According to this configuration, the abnormality of the AC reactor used in the inverter circuit can be reliably detected, and damage to the power conversion device can be prevented.

Further, the threshold value calculation unit of the power conversion apparatus of the present invention is to calculate the inductance value of the reactor from the effective value of the current flowing through the reactor, and an inductance value obtained by multiplying a predetermined rate to the inductance value, the converter circuits of the input voltage The ripple current value flowing through the inductance is calculated from the output voltage value and the drive frequency, and the ripple current value is converted into a numerical value comparable to the comparison target value to obtain a predetermined threshold value.
Further, the threshold calculation unit calculates the inductance value of the reactor from the effective current value flowing through the reactor, and the inductance value obtained by multiplying the inductance value by a predetermined ratio, the input voltage value and the output voltage value of the inverter circuit, and the drive frequency. Therefore, the ripple current value flowing through the reactor is calculated, and the ripple current value is converted into a numerical value comparable to the comparison target value to obtain a predetermined threshold value.

According to this configuration, even if the input voltage value of the power converter changes, it is possible to calculate a predetermined threshold value of the ripple current value corresponding to the input voltage, and it is possible to reliably detect an abnormality in the reactor. ..

In addition, the inductance value of the reactor calculated from the effective current value flowing through the reactor is approximated by a predetermined polynomial with the effective current value as a variable, and the measured effective current value is input to the polynomial to enter the effective current value. It is characterized by calculating the inductance value for.

According to this configuration, since the inductance value of the reactor with respect to the effective current value is calculated, it is possible to calculate a predetermined threshold value for determining the abnormality of the ripple current even if the effective current value changes.

Further, the state detection circuit of the power conversion device of the present invention is characterized in that the ripple current value is continuously sampled in a predetermined phase of a commercial frequency.

According to this configuration, since the ripple current value flowing through the reactor can be detected even with an AC signal having a commercial frequency, it is possible to reliably detect an abnormality in the reactor and prevent damage to the power conversion device.

The state detection circuit of the control unit of the power conversion device is a ripple current extraction circuit that extracts the ripple current from the current flowing in the reactor and converts it into a zero-volt reference waveform, and an absolute value circuit that converts the ripple current into an effective value. It is characterized in that the comparison target value is calculated based on the effective value.

According to this circuit configuration, the effective value of the ripple current flowing through the reactor can be detected accurately, and the abnormality of the reactor can be reliably detected.

Further, the present invention inputs a reactor or DC power in a converter circuit composed of a switching element that inputs DC power via a reactor and boosts or lowers the voltage of the DC power and outputs the current, and converts the DC power into AC power to convert the reactor. This is a method for detecting an abnormality in a reactor in an inverter circuit that outputs via, and detects the state of the reactor based on the step of detecting the current flowing through the reactor with a current detector and the ripple current value of the current output signal of the current detector. A step of calculating a comparison target value, a step of detecting the effective current value of the current output signal of the current detector, a step of calculating a predetermined threshold value from the effective current value, and a comparison target value and a predetermined threshold value. This is a method for detecting an abnormality in the reactor provided in the power conversion device, which includes a step of comparing the currents and a step of determining that the reactor is abnormal when the value to be compared exceeds a predetermined threshold value.

According to this method, the abnormality of the reactor can be reliably detected without using a thermal fuse.

As described above, according to the present invention, since the reactor abnormality can be detected without using the thermal fuse, it is possible to reliably stop the power conversion device when the reactor abnormality occurs while preventing erroneous detection.

It is a schematic circuit diagram of the power storage system which comprises the power conversion apparatus which concerns on embodiment of this invention. It is a main block diagram of the control part of a power storage system. It is a current waveform flowing through a PV reactor. It is a schematic diagram which shows the position which simulated the rare short part. It is a figure which shows an example of a rare short part and an inductance value. It is the current waveform flowing through the PV reactor and the output waveform of the detection circuit. It is a figure which shows the relationship between the effective current and the ripple current of a PV reactor. It is a state detection circuit of a PV reactor. It is an effective current detection circuit of the PV reactor. It is an output waveform of a signal detection circuit simulating the current flowing through a PV reactor. It is a figure which shows the relationship between the ripple current of a PV reactor and a threshold value. It is a figure which shows the relationship between the ripple current of a DC reactor and a threshold value. This is the current waveform flowing through the AC reactor. It is a ripple current with respect to the system voltage phase of the AC reactor. It is a figure which shows the relationship between the effective current and the ripple current of an AC reactor. It is a state detection circuit of the AC reactor. It is an output waveform of a signal detection circuit simulating the current flowing through an AC reactor. It is a figure which shows the relationship between the ripple current of an AC reactor and a threshold value. It is a figure which shows the relationship between the input voltage and the ripple current of a power generation conversion apparatus. This is an example showing the superimposition characteristics of the PV reactor. It is a figure which shows the difference of the ripple current by the variation of the effective current and the inductance value. It is a figure which shows the correlation of the threshold value of a ripple current and the A / D threshold value. It is a flow chart of a rare short determination of a reactor. It is a schematic diagram of a reactor attached with a thermal fuse.

The power conversion device of the present invention and a method for detecting an abnormality in a reactor included in the power conversion device will be described with reference to the drawings.

(First Embodiment)
FIG. 1 is a schematic circuit diagram of a power storage system configured by the power conversion device according to the first embodiment of the present invention.

The power storage system 100 shown in FIG. 1 includes a generated power conversion device 101 including a one-way converter circuit 6 for boosting or stepping down the DC power generated by the solar cell 1 (the figure shows a boosting circuit) and a system input. The AC power from 28 is converted into DC power, the DC power is charged to the storage battery 11, and the storage power conversion device 102 including the bidirectional converter circuit 16 for boosting or lowering the DC power from the storage battery 11 and the sun. An AC / DC power converter 103 equipped with a bidirectional inverter circuit 20 that converts DC power from a battery or storage battery into AC power, and also converts AC power from the system input 28 into DC power, a control unit 24, and a household load 29. , Important load 30, switch 25, switch 26 and switch 27.
The system input 28 is a commercial power source supplied from an electric power company or the like, and is connected to the switches 25 and 26.
The household load 29 is an electric product or the like used at home, and the important load 30 is a lighting device or an electric product or the like that needs to supply electric power in the event of a power failure among the household loads.

The generated power conversion device 101 includes a capacitor 2, a voltage detector 3, a current detector 4, a PV (Photovoltaic) reactor 5, and a one-way converter circuit 6.
The generated power conversion device 101 boosts or lowers the DC power generated by the solar cell 1. The boosted or stepped-down DC power is converted into AC power by the bidirectional inverter circuit 20 and discharged to the system input 28, and is supplied to the critical load 30 in the event of a power failure. Further, the storage battery 11 is charged as needed.

The stored power converter 102 includes a capacitor 12, a voltage detector 13, a current detector 14, a DC reactor 15, a bidirectional converter circuit 16, a capacitor 17, and a voltage detector 18.
The stored power conversion device 102 charges the storage battery 11 with the DC power converted from the AC power from the system input 28 via the bidirectional converter circuit 16, and the DC power of the storage battery 11 passes through the bidirectional converter circuit 16. The DC power is boosted or stepped down, converted to AC power, discharged to the system input 28, and supplied to the critical load 30 in the event of a power failure.

The AC / DC power converter 103 includes a capacitor 19, a bidirectional inverter circuit 20, an AC reactor 21, a current detector 22, and a voltage detector 23.
The AC / DC power conversion device 103 converts the DC power of the solar cell 1 and the storage battery 11 into AC power and supplies it to the system input 28 or, if necessary, the household load 29 and the critical load 30, and the AC from the system input 28. The electric power is converted into DC electric power, and the storage battery 11 is charged.

Further, the power storage system 100 includes a switch 25, a switch 26, and a switch 27. The switch 25 is a switch for synchronously turning on and disconnecting the system input 28 and the input / output terminals of the bidirectional inverter circuit 20. The switch 26 is a switch that supplies electric power from the system input 28 to the household load 29 and the critical load 30.
The switch 27 is a switch that switches between supplying power from the system input 28 and supplying power from the bidirectional inverter 20 to the critical load 30.

FIG. 2 is a main block diagram of the control unit of the power storage system. The control unit 24 includes a state detection circuit 24 (1), an effective current detection circuit 24 (2), a threshold value calculation unit 24 (3), a determination unit 24 (4), and a switching element control unit 24 (5). Further, voltage values from the voltage detectors 3, 13, 18 and 23 are input to the control unit 24, and the detected voltage values are output to the threshold value calculation unit 24 (3).
The state detection circuit 24 (1) receives a current output signal from the current detector 4, 14 or 22, detects the ripple current value flowing through the reactor, and compares the state of the reactor based on the ripple current value. The target value is calculated and output to the determination unit 24 (4).

Further, the effective current detection circuit 24 (2) receives the current output signal from the current detectors 4, 14 or 22, detects the effective current value flowing through the reactor, and outputs it to the threshold value calculation unit 24 (3).
Further, the threshold value calculation unit 24 (3) calculates a predetermined threshold value for determining whether or not the ripple current value is abnormal based on the effective current value flowing through the reactor.
The determination unit 24 (4) compares and determines the comparison target value and the predetermined threshold value. When the comparison target value exceeds a predetermined threshold value, a stop signal of the switching element is output to the switching element control unit 24 (5).

The switching element control unit 24 (5) receives the stop signal from the determination unit 24 (4), and the one-way converter circuit 6, the bidirectional converter circuit 16 or the bidirectional inverter circuit 20 corresponding to the reactor determined to be abnormal. Stop control.
Although the threshold value calculation unit 24 (3), the determination unit 24 (4), and the switching element control unit 24 (5) of the control unit 24 are not shown, the program of the microcomputer (microcomputer) of the control unit 24 is executed. The function is realized by being performed.

(PV reactor)
The power storage system 100 shown in FIG. 1 includes three reactors, a PV reactor 5, a DC reactor 15, and an AC reactor 21. The anomaly detection means of the reactor of the present invention, that is, the function realized by each block of the control unit 24 shown in FIG. 2, can be applied to any reactor.
First, an example applied to the PV reactor 5 will be described.

Normally, the current flowing through the reactor is superposed with the ripple current due to the drive frequency of the switching element used in the power storage system 100. FIG. 3 is a current waveform flowing through the PV reactor 5.
The horizontal axis of FIG. 3 is time, and the vertical axis is current. Two waveforms are displayed in FIG. The waveform on the upper side of FIG. 3 is a current waveform on which the ripple current is superimposed, but since the frequency of the ripple current is high and the waveform of the ripple current cannot be confirmed, the enlarged waveform is shown on the lower side. In this embodiment, the frequency of the triangular wave is 24 kHz.

When a rare short circuit (short circuit between windings) occurs, the inductance value of the reactor decreases, so the ripple current flowing through the reactor increases.
Due to the structure of the toroidal core type reactor, it is not known where the windings will be short-circuited, but a rare short-circuit location was simulated to measure the ripple current. FIG. 4 is a schematic view showing a position simulating a rare short portion.

FIG. 5 is a diagram showing an example of the rare short portion and the inductance value (L value). The horizontal axis of FIG. 5 is a short circuit portion of the winding shown in FIG. 4, and the vertical axis is the L value at that time.
According to this, the L value of the reactor is reduced to less than half even when the winding at the end of winding is in contact with the adjacent winding.

The rare short between the "end of winding" shown in FIG. 4 and the winding a adjacent thereto is referred to as a "1T adjacent short". Further, in the case of the DC reactor or AC reactor described below, since the windings are multiple, the adjacent rare shorts in the case of the same line are "1T adjacent same line shorts", and the rare shorts with other lines (different lines). Is called "1T adjacent different line short".
Further, the measured L values when the DC reactor was normal, when the 1T adjacent line was shorted, and when the 1T adjacent different line was shorted were 870 μH, 410 μH, and 670 μH, respectively. In the AC reactor, 230 μH, 100 μH, and 160 μH, respectively (the value of one of the two windings of the U phase and the W phase, which is about four times as large when the two windings are connected and measured). Met.

Here, the converter circuit 6 shown in FIG. 1 is a step-up type, and the ripple current ΔIL (A) flowing through the PV reactor 5 is an input voltage Vin (V), an output voltage Vout (V), an inductance L (H), and so on. Assuming that the drive frequency is f (Hz)
ΔIL = Vin × (Vout-Vin) / (Vout × f × L) ・ ・ ・ (1)
It is represented by. That is, if the L value decreases due to a rare short, the ripple current increases in inverse proportion to the decreased L value.

FIG. 6 shows a current waveform flowing through the PV reactor 5 and an output waveform of the detection circuit. The waveform shown in FIG. 6 is a waveform displayed on an oscilloscope when the L value simulating a rare short is about 1/3 of the normal state. The lower three waveforms are enlarged views of the upper waveform. (1) PV reactor current waveform, (2) output waveform by the current detector 4, and (3) microcomputer input value (described later) are shown. The PP value (Peak to Peak value) of the triangular wave of the ripple current is about 18A, which is an increase from the PP value of 4.5A measured when the L value is normal.
The effective value of this reactor current was about 10A, and the microcomputer input value of the ripple current was 3.1V.

Here, the microcomputer input value is an output value in which the ripple current of the reactor detected by the current detector 4 is converted into a DC level output by the state detection circuit 24 (1) of the control unit 24. This output value is input to the microcomputer (microcomputer) of the control unit 24.

FIG. 7 is a diagram showing the relationship between the effective current and the ripple current of the PV reactor 5. The horizontal axis is the effective current value flowing through the PV reactor 5, and the vertical axis is the PP value of the ripple current. The changes in the two ripple currents are shown when the effective current of the PV reactor 5 is changed and the L value is "default (meaning at normal time, the same applies hereinafter)" and when "1T adjacent short" is simulated.

Here, in the graph of FIG. 7, in the default (normal state), when the effective current value exceeds 2A, the ripple current value is almost constant, but in the case of a 1T adjacent short circuit, the effective current value is 10A. The ripple current value is increasing until it reaches the level.
Since the ripple current value calculated by the above equation (1) is an equation that has nothing to do with the effective current value, the ripple current value does not originally increase even if the effective current value increases. The increase is due to the following reasons.

That is, the PP value of the ripple current shown in FIG. 6 is about 18A, and the effective value of the ripple current is the effective value of the reactor current (about 10A) as it is. In this case, when the effective current value flowing through the PV reactor 5 becomes small, the on-time of the switching element of the one-way converter circuit 6 becomes short, and therefore the PP value of the triangular wave becomes small. That is, the smaller the effective current value, the smaller the ripple current value.

Next, an example of the state detection circuit 24 (1) for detecting the state of the PV reactor 5 will be described. FIG. 8 is a state detection circuit 24 (1) of the PV reactor 5. The ripple current value flowing through the PV reactor 5 is finally determined by the processing of the program of the microcomputer of the control unit 24. Therefore, it is necessary to convert it into a signal that can be processed by the microcomputer.

However, since the input signal to the microcomputer has a high frequency and cannot be captured as a constant value with the ripple current of the drive frequency as it is, it is necessary to convert it into a DC or a low frequency waveform (about a commercial frequency).
A state detection circuit 24 (1) is provided to detect this ripple current value and convert it into a signal (comparison target value) to be taken into the microcomputer based on the ripple current value, and detect an abnormality in the reactor by comparing with the threshold value. This eliminates the need for a thermal fuse and eliminates erroneous detection due to poor connection with the thermal fuse.

The state detection circuit 24 (1) shown in FIG. 8 is composed of four circuits: a triangular wave detection circuit, an absolute value circuit, a non-inverting circuit, and an RC circuit.
The triangular wave detection circuit (corresponding to the "ripple current extraction circuit" of the present invention) extracts only the ripple current (triangle wave) due to the drive frequency from the current flowing through the reactor and converts it into a waveform based on 0V. The 0V reference waveform is used to prevent the occurrence of offset of the operational amplifier.
The absolute value circuit converts the 0V reference waveform into a positive value (effective value). The non-inverting circuit adjusts the gain of the obtained effective value so as to be the optimum value in the microcomputer input voltage range. The RC circuit converts the drive frequency waveform into a DC or commercial frequency waveform that can be input to the microcomputer.

In this embodiment, an absolute value circuit (effective value) is used for the conversion circuit, but if the input value to the microcomputer can be converted to a DC value or an AC value of about a commercial frequency, a similar circuit can be used instead of the absolute value circuit. It may be.

Here, the output value of the absolute value circuit is used as the effective value as it is, the gain can be adjusted by the non-inverting circuit, and the average value is calculated by multiplying the reading value of the microcomputer by a predetermined coefficient. However, it can be easily converted to an effective value.

FIG. 9 is an effective current detection circuit 24 (2) of the PV reactor 5. The effective current value flowing through the PV reactor 5 is detected from the current detection signal by the current detector 4. It is composed of a differential input circuit through which low-frequency components are passed by a capacitor.
The effective current value flowing through the PV reactor 5 is detected, and the threshold value is calculated from this effective current value.

Next, the waveform of the simulation result of each circuit of the state detection circuit 24 (1) is shown in FIG. FIG. 10 is an output waveform of each circuit of the signal state detection circuit 24 (1) simulating the current flowing through the PV reactor 5. The horizontal axis is time and the vertical axis is voltage value. The waveform on the right side of FIG. 10 is an enlarged view of the waveform on the left side near the horizontal axis of 15 ms.

FIG. 10A shows a simulated signal of the output of the current detector 4, the average value of the simulated signal is about 2.5 V, and the ripple current is superimposed. FIG. 10B shows the output value of the triangular wave detection circuit, which has a waveform of about ± 2V with respect to 0V. FIG. 10C is an output value of the absolute value circuit, which is an absolute value of about 2 V (a waveform obtained by folding a negative value into a positive value). FIG. 10D shows the output value of the final stage, which is about 3V as the input value of the microcomputer.
In this way, the ripple current flowing through the PV reactor 5 is converted into a DC value by the state detection circuit 24 (1), input to the microcomputer, and determined.

FIG. 11 is a diagram showing the relationship between the ripple current of the PV reactor 5 and the threshold value. The horizontal axis is the effective current value flowing through the PV reactor 5, and the vertical axis is the microcomputer input value. In FIG. 11, three graphs of the reactor (1) default time (normal time), (2) 1T adjacent short time simulating a rare short time, and (3) threshold value are displayed.
The vertical axis of FIG. 7 is the ripple current PP value, but the vertical axis of FIG. 11 is the microcomputer input value replaced with a signal that can be determined by the microcomputer.

FIG. 11 shows the difference between the ripple current value at the default time of the PV reactor 5 and the ripple current value at the time of 1T adjacent short circuit. The threshold value for determining the abnormality of the ripple current value is a fixed value of 0.65 V in consideration of noise when the effective current value is less than 1.5 A. Assuming that the threshold value in the range of 1.5A to 5.75A of the effective current value is the threshold value y (V) and the effective current x (A),
y = 0.2x + 0.35 ... (2)
It is calculated by a linear formula. Further, the threshold value of the effective current value of 5.75 A or more is a fixed value of 1.5 V.

Whether or not the comparison target value is abnormal is determined by comparing the comparison target value input to the microcomputer with the threshold value (including the fixed value) calculated from the effective current value of the reactor. The linear formula and fixed value for calculating this threshold value can be changed by the power storage system 100.
Therefore, by comparing the microcomputer input value (comparison target value) with the threshold value calculated from the effective current value and determining whether or not the comparison target value exceeds the threshold value, the existing value can be used without using a thermal fuse. A current detector can be used to detect rare short circuits in the reactor.

If the effective current value is less than 1.5 A, the threshold value is a fixed value of 0.65 V in order to prevent erroneous determination due to noise. In this case, when the effective current is small, if the change in the L value simulated above is used, the ripple current input value at the time of abnormality and the threshold value are almost the same, and it is difficult to determine that the abnormality can be determined. Even so, the threshold value is set to a fixed value so that the determination can be made when the change in the L value due to the actual rare short is large rather than the L value simulating the rare short.
Further, when the current value flowing through the reactor is small, even if a rare short circuit occurs and it is not determined to be abnormal, the current value is small, so that it is unlikely to burn out. After that, if the effective current value becomes 1.5 A or more, the determination becomes possible.

(DC reactor)
Next, an example of the DC reactor 15 will be described.
The PV reactor 5 described above is a one-way power conversion that boosts or lowers the DC power supply from the solar cell 1, but the bidirectional converter circuit 16 in which the DC reactor 15 is used is bidirectional. In this case as well, the conversion from the storage battery 11 to the DC power on the input side of the bidirectional inverter circuit 20 is the same operation as in the case of the PV reactor 5, so the description thereof will be omitted.
However, since the input voltages from the solar cell 1 and the storage battery 11 of each converter circuit are different, the ripple current value is different. Therefore, it is different from the threshold value in the case of PV reactor 5.

Here, the input voltage of the one-way converter circuit 6 is in the range of 50V to 450V, but the input voltage when the ripple current is measured is 200 to 210V, and the output voltage is 380V. Further, when the ripple current of the bidirectional converter circuit 16 was measured, the input voltage and the output voltage were almost the same as those of the one-way converter circuit 6.

FIG. 12 is a diagram showing the relationship between the ripple current of the DC reactor 15 and the threshold value. In FIG. 12, four graphs are displayed: (1) default (normal), (2) 1T adjacent same line short, (3) 1T adjacent different line short, and (4) threshold value. The horizontal axis of FIG. 12 is the effective current value, and the vertical axis is the microcomputer input value.

According to this, the threshold value for determining the abnormality of the ripple current value is set to a fixed value of 0.65 V in consideration of noise when the effective current value is less than 1.4 A. In the range of the effective current value of 1.4A to 5.15A, assuming that the threshold value y (V) and the effective current x (A),
y = 0.2x + 0.37 ... (3)
It is a threshold value calculated by a linear formula. Further, the threshold value of the effective current value of 5.15 A or more is set to a fixed value of 1.4 V.

On the other hand, since the bidirectional converter circuit 16 is bidirectional, the case of charging the storage battery 11 will also be considered. In this case, the effective current flowing through the DC reactor 15 is almost constant because it is the charging current for the storage battery 11. Therefore, the threshold value of the comparison target value calculated based on the ripple current value flowing through the DC reactor 15 may be a predetermined fixed value regardless of the effective current value.
In this way, even with the DC reactor 15, by determining the microcomputer input value (comparison target value) with the threshold value corresponding to the effective current value, the existing current detector can be used without using a thermal fuse, and the reactor can be used. Rare shorts can be detected.

(AC reactor)
Next, an example of the AC reactor 21 will be described.
FIG. 13 is a current waveform flowing through the AC reactor 21. The horizontal axis of FIG. 13 is time, and the vertical axis is current. The upper view shown in FIG. 13 is a waveform showing an alternating current including a ripple current, but since the frequency of the ripple current is high and the waveform of the ripple current cannot be confirmed, an enlarged view thereof is shown on the lower side. The frequency of the triangular wave is 24 kHz, which is the same as in the case of PV and DC reactors.

Here, the ripple current flowing through the AC reactor 21 changes because the output voltage Vout of the above equation (1) is a commercial power source (note that the step-down converter circuit is different from the equation (1)). Therefore, the ripple current flowing through the AC reactor 21 changes with respect to the alternating current phase of the commercial frequency as shown in FIG. 13, and cannot be converted into a constant DC value like the DC reactor 15, and the commercial frequency The AC waveform has twice the period.
FIG. 14 shows a ripple current with respect to the phase of one cycle of the system voltage of the AC reactor 21. The input value to the microcomputer can be processed as a constant DC value if it is continuously detected at the timing of the same phase with a phase of 90 ° or 270 °.

FIG. 15 is a diagram showing the relationship between the effective current and the ripple current of the AC reactor 21. The horizontal axis is the effective current value, and the vertical axis is the PP value of the ripple current. In FIG. 15, three graphs are displayed: (1) default (normal time), (2) 1T adjacent same line short, and (3) 1T adjacent different line short.
The ripple current PP value shown in FIG. 15 is such that the effective current value increases stepwise from around 15A. This is because the discharge from the storage battery 11 was the only discharge up to the effective current of about 15 A, but the discharge of the solar cell 1 was added after the effective current exceeded 15 A, and the input conditions were changed.
Further, in the case of the AC reactor 21, even if the effective current value becomes small, the ripple current value does not become 0 as in the PV reactor 5 and the DC reactor 15.

FIG. 16 is a state detection circuit 24 (1) of the AC reactor 21.
The circuit is the same as the state detection circuit 24 (1) of the PV reactor 5 shown in FIG. 8, but the absolute value circuit is different. The absolute value circuit applied to the ripple current of the PV reactor 5 is composed of one operational amplifier, and in the case of the AC reactor 21, it is composed of two operational amplifiers.
The effective current detection circuit 24 (2) is basically the same as the circuit shown in FIG. 9 in the case of the AC reactor 21, but the constants of the resistor and the capacitor are different.

FIG. 17 is an output waveform of a signal detection circuit simulating the current flowing through the AC reactor 21. The horizontal axis of this simulated waveform is time, and the vertical axis is voltage. The waveform on the right side of FIG. 17 is an enlarged view of the waveform on the left side near the horizontal axis of 15 ms.
FIG. 17A is a simulated signal of the output of the current detector 22. In this simulated signal, the ripple current is superimposed on the AC waveform having an average value of 2.5 V. FIG. 17B shows an output value of the triangular wave detection circuit, which is a waveform of ± about 2V with respect to 0V. FIG. 17C shows an output value of the absolute value circuit, which is an absolute value of the ripple current (a waveform obtained by folding back a negative value into a positive value) and is a waveform of about 2 V. FIG. 17D shows the output value of the final stage and the input value of the microcomputer.
In this way, the ripple current flowing through the AC reactor 21 is converted into a waveform of a commercial frequency, continuously sampled at a predetermined voltage phase of the commercial frequency, and input to the microcomputer as a constant DC value for determination.

FIG. 18 is a diagram showing the relationship between the ripple current of the AC reactor 21 and the threshold value. In FIG. 18, four graphs are displayed: (1) default (normal time), (2) 1T adjacent same line short, (3) 1T adjacent heterogeneous short, and (4) threshold value.
Note that FIG. 18 is a diagram in which the ripple current PP value of FIG. 15 is replaced with the microcomputer input value, and a graph displaying the threshold value is added.

According to this, if the threshold value for determining the ripple current value as abnormal is the threshold value y (V) and the effective current x (A),
y = 0.02x + 0.85 ... (4)
It is calculated by a linear formula.

Therefore, the rare short circuit of the AC reactor is detected by determining the comparison target value calculated based on the ripple current value flowing through the AC reactor, using the value calculated by the effective current value flowing through the AC reactor as a predetermined threshold value. be able to.

Here, since the bidirectional inverter circuit 20 is bidirectional, a case where AC power is converted into DC power from the system input 28 and the storage battery 11 is charged is also examined. In this case, the current flowing through the reactor 21 is substantially constant because it is the charging current for the storage battery 11.
Therefore, the threshold value of the comparison target value calculated based on the ripple current value flowing through the AC reactor 21 may be a predetermined fixed value regardless of the effective current value.

The three reactors have been described above, but in each reactor, the comparison target value (microcomputer input value) calculated based on the ripple current flowing in the reactor is determined by the threshold value corresponding to the effective current value flowing in the reactor. This makes it possible to detect a rare short circuit in the reactor using an existing current sensor without using a thermal fuse.

(Second Embodiment)
In the first embodiment, a method of detecting an abnormality in the reactor when the input voltage value and the output voltage value of the converter circuit are substantially constant has been described. Actually, in the solar cell 1 of the power storage system 100 shown in FIG. 1, the amount of power generation fluctuates depending on the conditions such as the weather, and the output voltage value of the solar cell 1 changes accordingly. Further, the output voltage value of the storage battery 11 also changes depending on the remaining amount of the battery. These output voltage values become the input voltage values of the converter circuit.
Therefore, in the second embodiment, a method of detecting an abnormality in the reactor when the input voltage value of the converter circuit changes will be described.

In the second embodiment, the method of calculating the threshold value by the threshold value calculation unit 24 (3) shown in FIG. 2 is different from that of the first embodiment, but since the other configurations are the same, overlapping description is omitted. do. Further, the inductance value of each reactor is different from that of the first embodiment due to the review of the reactor specifications.
In the second embodiment, the generated power conversion device 101 including the step-up converter circuit mainly including the PV reactor 5 will be described.

FIG. 19 is a diagram showing the relationship between the input voltage and the ripple current of the generated power conversion device 101. The horizontal axis is the input voltage value, and the vertical axis is the ripple current value. The curve shown in FIG. 19 is a calculated value of the ripple current of the step-up converter circuit. This calculated value is calculated by the equation (1), the input voltage Vin is variable and is the voltage value (V) shown on the horizontal axis, the output voltage Vout is 410 (V), and the inductance (L) value of the PV reactor 5 is 958. (ΜH), the drive frequency f of the one-way converter circuit 6 is 24 k (Hz).
Further, the measured value of the ripple current when the input voltage is 59V, 228V, 368V is indicated by an “x” mark.

As shown in FIG. 19, the calculated value and the measured value of the ripple current are almost the same. Therefore, when the input voltage changes, if the input voltage Vin (V) is used as a variable and the output voltage Vout (V), the inductance value (H), and the drive frequency f (Hz) are known, the ripple current value is obtained from the equation (1). Can be calculated.
Here, the output voltage is controlled to be constant, and the drive frequency is also an eigenvalue of the power storage system 100. On the other hand, the inductance value does not change depending on the frequency because the drive frequency is constant, but the inductance value changes depending on the DC superimposition characteristic, that is, the current value.

FIG. 20 is an example showing the superimposition characteristics of the PV reactor 5 used in the present embodiment. The horizontal axis is the current value, and the vertical axis is the inductance value. It can be seen from the figure that the inductance value decreases as the current value increases. From this characteristic, it is shown that if the current value flowing through the PV reactor 5 is known, the reactor value corresponding to the current value can be calculated.

As an example according to this embodiment, the inductance value of the PV reactor 5 is calculated from the effective current value. The polynomial for calculating the inductance (L) value from the curve showing the characteristics of the inductance value shown in FIG. 20 is assumed that the effective current value is X (A).
L value ^{= 0.025X 3 -0.9752X 2 -9.9426X + 950.42} ··· (5)
Can be represented by.
The characteristic curve of PV reactor 5 shown in FIG. 20 and the polynomial are substantially the same, and are displayed as one overlapping curve.

In the second embodiment, the effective current value flowing through the reactor 5 (or 15, 21) is measured by the current detector 4 (or 14, 22), and the threshold calculation unit 24 (3) is used to measure the measured effective current value. The inductance value is calculated based on the equation (5) (or the equations (8) and (9) described later), and the measured values and drive frequencies of the input voltage and the output voltage of the converter circuit 6 (or 16) or the inverter circuit 20 are calculated. From, the ripple current value is calculated based on the equation (1) (or the equation (7) described later). From this ripple current value, assuming that the product specification of the inductance value of the reactor is in the range of ± 20%, for example, the threshold value is determined in consideration of the range of variation of the reactor. The threshold value calculated by the threshold value calculation unit 24 (3) is compared with the comparison target value obtained by the state detection unit 24 (1) based on the measured value of the ripple current, and the abnormality of the reactor is determined.

Next, the calculation of the determination value of the inductance for determining the abnormality (rare short) of the ripple current will be described.
If there is a variation of ± 20% in the product specifications as the inductance value of the PV reactor 5, when the PV reactor 5 with the upper limit inductance value of + 20% is rarely short-circuited, the value larger than the lower limit inductance value of -20% , Cannot be judged as a rare short. Therefore, for example, it is necessary to set a value in which the upper limit inductance value of + 20% is 2/3 or less as a judgment value of rare short so that the value is smaller than the lower limit inductance value of −20%.

That is, the value obtained by multiplying the upper limit inductance value of + 20% by 0.6 is used to determine the rare short of the PV reactor 5 so that the rare short can be determined even if there is a PV reactor 5 having an upper limit of the inductance value of + 20%. It was set as a value. When viewed from the center value (center value) of the inductance value specification, it is the case where the center value drops to 0.72. Therefore, the inductance value for determining the abnormality of the PV reactor 5 is a value obtained by multiplying the inductance value calculated from the effective current value by 0.72 (a predetermined ratio), and the ripple current is calculated based on that value, and this ripple current value is calculated. The threshold value for rare short determination is determined based on.
Although the predetermined ratio of the rare short determination of the inductance value is 0.72, it is not fixed, and the predetermined ratio may be changed by the battery system 100 or by changing the specifications of the PV reactor 5. ..

FIG. 21 is a diagram showing a difference in ripple current due to variation in effective current and inductance value. The horizontal axis is the effective current value, and the vertical axis is the ripple current value. In FIG. 21, four curves showing the ripple current, the measured value of the ripple current, and the ripple current value by the simulation are displayed. The input voltage value for which the ripple current shown in FIG. 21 was calculated was 235V, and the output voltage value was 410V.
All four curves are calculated values, (1) ripple current when the inductance value is the center value, (2) ripple current whose inductance value is the lower limit of -20% of the specification, and (3) inductance value is the specification. The ripple current of the upper limit of + 20% of the above, and (4) the threshold of the ripple current are shown.

For these four curves, the inductance value is calculated from the effective current value by the polynomial of the characteristics shown in FIG. 20, and the calculated value is multiplied by 0.8, 1.2, and 0.72, respectively, to obtain the inductance value. Is used to calculate the ripple current according to the equation (1). Even if there is a PV reactor 5 having a specification of -20% of the inductance value, that is, a PV reactor 5 having the ripple current characteristic shown in the curve (2), the ripple current value of the threshold curve (4) is the curve (2). It exceeds the ripple current value of. According to this ripple current threshold value, it can be determined that the increase in the ripple current value due to the rare short circuit of the PV reactor 5 is abnormal even if the variation in specifications is taken into consideration.

Further, the “■” mark shown in FIG. 21 is the ripple current value of the normal value of the PV reactor 5, and the “●” mark is the ripple current value of the reactor simulating a rare short, which are measured values. Further, the “Δ” mark is a simulation value of the ripple current of the normal value of the PV reactor 5, and the “x” mark is the simulation value of the ripple current of the PV reactor 5 simulating a rare short circuit.
The measured and simulated values of the normal ripple current of the PV reactor 5 are also in agreement with the curve (1).
Also, in the case of rare short, the measured value and simulation value of the ripple current are on the same curve, and they are in good agreement.

Here, the ripple current value flowing through the PV reactor 5 is the ripple current component of the current value measured by the current detector 4 by the state detection circuit 24 (1) shown in FIG. 2, specifically, the circuit shown in FIG. Is converted to a DC value. The DC value is A / D (Analog to Digital) converted by the microcomputer of the control unit 24, and the measured ripple current is A / D converted value (corresponding to the "comparison target value" of the present invention. Hereinafter, "A / D" "Measured value").

On the other hand, the inductance value is calculated from the measured effective current value, and the ripple current threshold value calculated by Eq. (1) needs to be converted to a value comparable to the A / D measured value A / D converted by the microcomputer. There is.
That is, the ripple current value input to the microcomputer is A / D converted to 12 bits (0 to 4095) in the range of 0 to 3.3 V. The ripple current threshold value calculated by the threshold value calculation unit 24 (3) is also converted into a 12-bit numerical value.
Here, in the first embodiment, the microcomputer input value (comparison target value) based on the measured value of the ripple current and the threshold value are compared at the voltage level, but as in the second embodiment, for example, 12 bits each. You may convert it to the numerical value of and compare it.

FIG. 22 is a diagram showing the correlation between the ripple current threshold value and the threshold value comparable to the A / D measured value (hereinafter, referred to as “A / D threshold value”). This relationship shows the relationship between the ripple current value measured when the reactor of the battery system 100 is normal and the A / D value converted to A / D by the microcomputer.
Ideally, it is a linear function that passes through the point (origin) where the A / D value is 0 when the ripple current value is 0, but in reality, it is based on the current detector 4 and the state detection circuit 24 (1). It is not a linear straight line passing through the origin.

In this embodiment, as shown in FIG. 22, assuming that the ripple current value is X (A), the A / D threshold value is
A / D threshold = 223.76X-43.459 ... (6)
It is calculated by the formula expressed by. As a result, the calculated ripple current value is converted from the current value (A) to a value having the same number of bits as the A / D measured value.
The formula for converting the ripple current value into the A / D threshold value is not fixed, but is changed depending on the constants of the circuit used in the battery system 100 and the like.

The above threshold calculation procedure is executed by the program of the microcomputer of the control unit 24. FIG. 23 is a flow chart for determining a rare short of the reactor.

In the flow diagram of the rare short determination in FIG. 23, it is determined in step S10 whether the effective current value is 2 A or more. When the effective current value is less than 2A (S10, NO), the process ends without determining the rare short circuit (S15).
Here, the reason why the rare short is not determined when the effective current value is less than 2A will be described. When the effective current value becomes smaller, the current flowing through the PV reactor 5 becomes only the ripple current component, and when the effective current value becomes smaller, the on-time of the switching element by the switching element control unit 24 (5) shown in FIG. 2 becomes shorter. This also reduces the ripple current value. Therefore, the equation (1) does not hold in the range where the effective current value is small.

Further, the reason why the rare short is not determined when the effective current value is less than 2A is that the situation where the effective current value flowing through the reactor is always less than 2A rarely occurs in the present embodiment. For example, when charging the storage battery, a rated current of about 10 A flows, and even when the output of the solar cell 1 is output to a household load or the storage battery 11 is charged, a current of 2 A or more flows. Therefore, if the effective current value is less than 2A, it is considered that there is no actual harm even if it is not determined as a rare short circuit. The judgment reference value is not limited to 2A and can be changed as appropriate.

In step S10 of the flow chart of FIG. 23, when the effective current value is 2A or more (S10, YES), the A / D measured value (simply described as “measured value” in the figure) is the A / D threshold value (in the figure, it is simply described as “measured value”). It is determined whether or not it is larger than (simply described as "threshold value") (S11). When the A / D measured value is not larger than the A / D threshold value (S11, NO), it is determined to be normal (S16), and the process ends.

On the other hand, when the A / D measured value is larger than the A / D threshold value (S11, YES), it is determined that the A / D measured value is larger than the A / D threshold value for a predetermined time (this implementation). In the form, it is determined whether 30 seconds) has passed (S12). If a predetermined time has not elapsed since the first determination that the A / D measured value is larger than the A / D threshold value (S12, NO), the determination in step S11 is repeatedly executed in a predetermined cycle. ..

Then, if it is determined that the A / D measurement value is not larger than the A / D threshold value in the second and subsequent determinations (S11, NO), the previous determination is determined to be normal as there is a possibility of noise or malfunction. (S16). On the other hand, when a predetermined time has elapsed since it was first determined that the A / D measured value is larger than the A / D threshold value (S12, YES), the repeated A / D measured value is higher than the A / D threshold value. Since it is determined to be large (S11, YES), it is determined that it is not noise or malfunction, and it is determined to be a rare short (S13). If it is determined to be a rare short circuit, the function of the power conversion device is stopped (S14), and the process is terminated.

In the rare short determination flow, the predetermined time is set to 30 seconds, but this predetermined time may be changed as appropriate.

In this way, the ripple current threshold for determining the rare short is the value obtained by calculating the inductance value of the PV reactor 5 from the effective current value, multiplying this inductance value by a predetermined ratio, and the input voltage value and output voltage of the converter circuit. The ripple current is calculated from the value and the drive frequency, converted into a numerical value (A / D threshold value) of the number of bits corresponding to the A / D value, and calculated. By comparing this A / D threshold value with the A / D measured value, a rare short circuit of the reactor is determined, and if a rare short circuit occurs, the function of the power conversion device is stopped to prevent the spread of burn damage. can do.

When calculating the inductance value of the PV reactor 5 from the effective current value, if a rare short circuit has already occurred, the effective current value due to the increased ripple current is used to determine the rare short circuit. It may be difficult to calculate the threshold. However, the effective current value due to the increasing ripple current is slightly increased, and as the effective current value increases, the inductance value decreases and the ripple current threshold value tends to increase. From these facts, as a result of applying it to the actual battery system 100, it was determined that this threshold value calculation method can be applied as a rare short determination criterion.

(DC reactor and AC reactor)
The case of the PV reactor 5 has been described as the second embodiment, but when the DC reactor 15 is used in the step-up converter circuit, it is the same as the case of the PV reactor 5, and the description thereof will be omitted.

When the converter circuit using the DC inductance 15 functions as a step-down type, unlike the equation (1), the ripple current ΔIL (A) flowing through the DC inductance 15 has an input voltage Vin (V) and an output voltage Vout (V). ), Inductance L (H), Drive frequency f (Hz)
ΔIL = Vout × (Vin−Vout) / (Vin × f × L) ・ ・ ・ (7)
It is represented by.

In this case, the output voltage Vout (V) changes, but the input voltage Vin (V) and the drive frequency f (Hz) are almost constant, and the ripple current can be calculated by calculating the inductance value from the effective current value. ..
Therefore, even when the circuit functions as a step-down converter circuit, the ripple current threshold value can be determined and the reactor abnormality can be determined as in the case of the step-up type.

On the other hand, in the case of the AC reactor 21, regardless of whether the inverter circuit is a step-down type or a step-up type, one voltage is an AC waveform. In that case, the input voltage and the output voltage of the AC waveform, for example, when the phase of the waveform is 90 °, can be regarded as DC values, respectively.
In this case, the current value and the voltage value are not effective values, and it is necessary to calculate the ripple current and the inductance value based on the peak value.

Here, the polynomial of the inductance value due to the superimposition characteristics of the DC reactor 15 and the AC reactor 21 is the center value of the reactor of each product specification in the present embodiment.
The polynomial of the inductance value due to the superimposition characteristic of the DC reactor 15 is that the inductance (L) value and the effective current value are X (A).
L value ^{= 0.0196X 3 -1.049X 2 -1.4258X + 836.44} ··· (8)
Can be represented by.

Similarly, the polynomial of the inductance (L) value due to the superimposition characteristic of the AC reactor 21 is not the effective current value, but the peak value of the current is X (A).
L value ^{= 0.0007X 3 -0.1055X 2 -0.5469X + 512.09} ··· (9)
Can be represented by.
It should be noted that these polynomials for calculating the L value are merely examples and are not fixed, but are changed due to a review of the reactor specifications and the like.

Further, in the case of the DC reactor 15 and the AC reactor 21, the conversion from the ripple current value to the A / D threshold value is A / D threshold value (DC reactor) = 169.68X, respectively, assuming that the ripple current value is X (A). -33.564 ... (10)
A / D threshold (AC reactor) = 141.17X-38.825 ... (11)
It is calculated by the formula expressed by.
As in the case of PV reactor 5, the conversion from the ripple current to the A / D threshold value does not have the same linear function due to the difference in the constants of the parts of the current detector and the state detection circuit used in this embodiment. ..

As described in the example of the PV reactor 5, these linear functions also show the relationship between the ripple current value measured when the reactor of the battery system 100 is normal and the A / D value converted to A / D by the microcomputer. It is a thing.
Further, the formulas for converting to these A / D threshold values are not fixed, but are changed depending on the constants of the circuit used in the battery system 100 and the like.

In the second embodiment, for the DC reactor 15 and the AC reactor 21, as described in the example of the PV reactor 5, the inductance value of the reactor is calculated from the current value, and the inductance value is multiplied by a predetermined ratio to ripple. By calculating the current value and comparing the threshold value set from the calculated ripple current value with the comparison target value based on the measured value of the ripple current, it is possible to determine the abnormality of the inductance.

Further, in the second embodiment, it is determined in step S10 of FIG. 23 whether or not the effective current value is 2A or more, and if it is less than 2A, the rare short is not determined (S15), but in step S10. You may start from step S11 without making a determination.

1 ... Solar cell, 2, 12, 17, 19 ... Condenser, 3, 13, 18, 23 ... Voltage detector, 4, 14, 22 ... Current detector, 5 ... PV Reactor, 6 ... One-way converter circuit, 11 ... Storage battery, 15 ... DC reactor, 16 ... Bidirectional converter circuit, 20 ... Bidirectional inverter circuit, 21 ... AC reactor, 24 ... control unit, 24 (1) ... state detection circuit, 24 (2) ... effective current detection circuit, 24 (3) ... threshold calculation unit, 24 (4) ... judgment unit, 24 (5) ... Switching element control unit, 25, 26 ... Switch, 27 ... Switch, 28 ... System input, 29 ... Household load, 30 ... Important load, 100 ... Power storage system, 101 ... Power generation conversion device, 102 ... Storage power conversion device, 103 ... AC / DC power conversion device.

Claims (9)

A converter circuit consisting of a switching element that inputs DC power via a reactor and boosts or steps down the voltage of the DC power and outputs it.
A current detector that detects the current flowing through the reactor, and
A control unit that turns on / off the switching element of the converter circuit and monitors the output of the current detector.
In a power converter equipped with
The control unit
A state detection circuit that calculates a comparison target value for detecting the state of the reactor based on the ripple current value of the current output signal of the current detector, and a state detection circuit.
An effective current detection circuit that detects the effective current value of the current output signal of the current detector, and
A threshold value calculation unit that calculates a predetermined threshold value corresponding to the effective current value,
A determination unit that determines that the reactor is abnormal when the comparison target value exceeds the predetermined threshold value, and
When it is determined that the reactor is abnormal, the switching element control unit that stops the output of the control signal to the switching element of the converter circuit and the switching element control unit.
A power conversion device characterized by being equipped with. The threshold calculation unit, a power converter according to claim 1, wherein Rukoto issuing calculate the threshold by substituting the effective current value to a linear function. An inverter circuit that inputs AC power via a reactor and converts it to DC power by a switching element , or converts DC power to AC power by the switching element and outputs it via the reactor.
A current detector that detects the current flowing through the reactor, and
A control unit that turns on / off the switching element of the inverter circuit and monitors the output of the current detector.
In a power converter equipped with
The control unit
A state detection circuit that calculates a comparison target value for detecting the state of the reactor based on the ripple current value of the current output signal of the current detector, and a state detection circuit.
An effective current detection circuit that detects the effective current value of the current output signal of the current detector, and
When converting the AC power to DC power, a predetermined fixed value is set regardless of the effective current value, and when converting the DC power to AC power, a threshold calculation is performed to calculate a predetermined threshold corresponding to the effective current value. Department and
A determination unit that determines that the reactor is abnormal when the comparison target value exceeds the predetermined threshold value, and
When it is determined that the reactor is abnormal, the switching element control unit that stops the output of the control signal to the switching element of the inverter circuit, and the switching element control unit.
A power conversion device characterized by being equipped with. The threshold calculating unit may calculate the inductance value of the reactor from the rms current through the reactor, and an inductance value obtained by multiplying a predetermined rate to the inductance value, said converter circuitry of the input voltage and the output voltage value If, from the drive frequency, to calculate a ripple current flowing through the reactor, the power conversion by converting the ripple current in the comparable figures and the comparison object value according to claim 1, wherein the predetermined threshold value Device. The threshold calculation unit calculates the inductance value of the reactor from the effective current value flowing through the reactor, and the inductance value obtained by multiplying the inductance value by a predetermined ratio, and the input voltage value and the output voltage value of the inverter circuit. The power conversion device according to claim 3, wherein the ripple current value flowing through the inductance is calculated from the drive frequency, and the ripple current value is converted into a numerical value comparable to the comparison target value to obtain the predetermined threshold value. .. Inductance value of the reactor is calculated from the rms current through the reactor, the approximated by a predetermined polynomial the effective current value as a variable, the effective by entering the effective current value measured in the polynomial The power conversion device according to claim 4 or 5 , wherein the inductance value with respect to the current value is calculated. The power conversion device according to claim 3, wherein the state detection circuit continuously samples a ripple current in a predetermined phase of a commercial frequency. The state detection circuit includes a ripple current extraction circuit that extracts a ripple current from the current flowing through the reactor and converts it into a zero-volt reference waveform, and an absolute value circuit that converts the ripple current into an effective value. The power conversion device according to any one of claims 1 to 7 , wherein the comparison target value is calculated based on the value. The reactor or DC power in a converter circuit composed of a switching element that inputs DC power via a reactor and boosts or steps down the voltage of the DC power and outputs it is converted to AC power and output via the reactor. This is a method for detecting an abnormality of the reactor in the inverter circuit.
The step of detecting the current flowing through the reactor with a current detector,
A step of calculating a comparison target value for detecting the state of the reactor based on the ripple current value of the current output signal of the current detector, and
The step of detecting the effective current value of the current output signal of the current detector, and
A step of calculating a predetermined threshold value from the effective current value, and
A step of comparing the comparison target value with the predetermined threshold value,
A step of determining that the reactor is abnormal when the comparison target value exceeds the predetermined threshold value, and
A method for detecting anomalies in a reactor provided in a power conversion device, which comprises.

Images