JP2020150688A - Series multiplex power conversion device - Google Patents

Abstract

To output a voltage lower than a minimum on-pulse width in a series multiplex power conversion device.SOLUTION: A threshold control unit 30 replaces a positive side gate threshold of each unit operated at a positive side peak time point of a voltage command value Vref, based on an update timing of the gate threshold and the determination value of the number of units currently in operation, and replaces a negative side gate threshold of each unit operated at a negative side peak time point of the voltage command value Vref, to restore the replaced gate threshold at a zero cross point of the voltage command value Vref to an original value. A PWM control unit PWM compares, on a unit-by-unit basis, the voltage command value Vref with the positive and negative gate thresholds each taking a constant value at least during a 1/4 period of the voltage command value Vref to generate a switching element gate signal.SELECTED DRAWING: Figure 1

Description

The present invention relates to a one-pulse multiplexing series multiplex power converter in which two or more single-phase inverter units are connected in series, and particularly relates to a gate generation method that suppresses the influence of the minimum on-pulse width.

Patent Document 1 describes an example of a series multiplex power converter in which two single-phase inverter units are connected in series.

FIG. 6 shows the configuration of a series multiplex power converter in which six inverter units are connected in series to multiplex the voltage. As a method of generating a gate signal in a series multiplex power converter having such a configuration, there is a one-pulse control method for obtaining a gate signal by comparing a voltage command value Vref with a fixed gate threshold value as shown in FIG.

The relationship between the gate thresholds Vth1a and Vth1b of the unit 1 and the gate signals GU1, GV1, GX1, GY1 (that is, the on / off state of the switching element) is as follows.
・ If Vref> Vth1a, GU1 is turned on, GX1 is turned off, if Vref <Vth1a, GU1 is turned off, and GX1 is turned on.
・ If Vref> Vth1b, GY1 is turned on, GV1 is turned off, and if Vref <Vth1b, GY1 is turned off and GV1 is turned on.

The other units 2 to 6 also generate a gate signal. By this method, a stepped output voltage Vout is obtained as the total of the output voltages (hereinafter referred to as unit output voltages) Vo1 to Vo6 of each unit. If the absolute value of the voltage command value Vref is less than the gate threshold corresponding to the unit, the output voltage of the unit becomes 0.

In the example of FIG. 6, the configuration is 6 units, but as the number of units increases, an output voltage Vout closer to a sine wave can be obtained.

Japanese Unexamined Patent Publication No. 2000-324845

Consider a case where the voltage command value Vref increases, exceeds the gate threshold corresponding to the unit that has not output the voltage until then, and the number of units outputting the voltage increases (the number of operating units increases).

FIG. 8 shows the output voltage when the operation is changed from 2 units to 3 units. When the absolute value of the voltage command value Vref exceeds the gate thresholds Vth3a and Vth3b of the unit 3, the unit output voltage Vo3 is output and three units are operated.

The switching element cannot be driven in the on-time below the minimum on-pulse width to protect the element. Therefore, the minimum voltage width that one unit can output is limited by the minimum on-pulse width.

Therefore, the unit output voltage Vo3 can output only a voltage equal to or larger than the minimum on-pulse width even if the comparison result of the voltage command value Vref and the gate thresholds Vth3a and Vth3b is less than the minimum on-pulse width. There is a problem that a larger voltage is output.

FIG. 9 shows a comparison between the voltage command value Vref of FIG. 8 and the gate threshold value Vth3a in the unit 3 and an enlarged view of the unit output voltage Vo3. Ideally, the unit output voltage Vo3 is output only while the voltage command value Vref exceeds the gate threshold value Vth3a, but the minimum on-pulse width outputs a voltage wider than the ideal pulse width. It ends up.

A similar problem occurs when the number of vehicles in operation decreases. In addition, it occurs not only between 2 and 3 units but also for all operating units.

From the above, it is a problem to output a voltage less than the minimum on-pulse width in the series multiplex power converter.

The present invention has been devised in view of the above-mentioned conventional problems, and one aspect thereof is a one-pulse multiplexing system in which a plurality of bridge cell units are connected in series and a single-phase voltage having an output frequency of 1 kHz or higher is output. A multi-power converter that determines the peak time and zero crossing time of the voltage command value and outputs it as the update timing of the gate threshold, and compares the gate threshold of each unit with the voltage command value. On the positive side of the voltage command value based on the operating number determination unit that determines the number of units currently operating and outputs it as the operating number determination value, the update timing of the gate threshold, and the operating unit determination value. The positive gate threshold of the unit operating at the peak time is replaced, the negative gate threshold of the unit operating at the negative peak time of the voltage command value is replaced, and at the zero cross point of the voltage command value. The gate signal of the switching element is generated by comparing the voltage command value and the positive / negative gate threshold output from the threshold control unit with the threshold control unit that restores the replaced gate threshold value and each unit. It is characterized in that it is provided with a PWM control unit.

Further, as one aspect thereof, the threshold control unit sets only the upper two positive gate thresholds having a large absolute value of the gate threshold among the operating units at the peak time on the positive side of the voltage command value. It is characterized in that, at the time of the peak on the negative side of the voltage command value, only the upper two negative gate thresholds having a large absolute value of the gate threshold are replaced among the operating units.

Further, as another embodiment, the threshold control unit rearranges the magnitudes of the absolute values of the positive gate thresholds of all the operating units in reverse order at the peak time on the positive side of the voltage command value. At the time of the peak on the negative side of the voltage command value, the magnitude of the absolute value of the negative gate threshold value of all the operating units is rearranged in the reverse order.

According to the present invention, it is possible to output a voltage less than the minimum on-pulse width in the series multiplex power converter.

The block diagram of the series multiplex power conversion apparatus in Embodiments 1 and 2. A time chart (in the case of three operating units) showing the voltage command value, the gate threshold value, the unit output voltage, and the output voltage in the first embodiment. A time chart (in the case of 6 operating units) showing the voltage command value, the gate threshold value, the unit output voltage, and the output voltage in the first embodiment. A time chart (in the case of three operating units) showing the voltage command value, the gate threshold value, the unit output voltage, and the output voltage in the second embodiment. A time chart (in the case of 6 operating units) showing the voltage command value, the gate threshold value, the unit output voltage, and the output voltage in the second embodiment. The schematic diagram which shows an example of the series multiplex power conversion apparatus. Time chart of each signal in the conventional 1-pulse multiplexing method. A time chart showing each signal when the number of operating vehicles increases (2 units → 3 units). Enlarged view of FIG.

Hereinafter, embodiments 1 and 2 of the series multiplex power conversion device according to the present invention will be described in detail with reference to FIGS. 1 to 5.

[Embodiment 1]
In the first embodiment, a method of outputting a voltage less than the minimum on-pulse width will be described by taking the series multiplex power conversion device shown in FIG. 1 as an example. First, the main circuit configuration of the series multiplex power converter shown in FIG. 1 will be described.

As shown in FIG. 1, the series multiplex power conversion device according to the first embodiment includes six first to sixth units (bridge cells) 1 to 6. In the first unit 1, switching elements U1, V1, X1, Y1 are bridge-connected. The DC voltage source C1 is connected between the common connection point of the switching elements U1 and V1 and the common connection point of the switching elements X1 and Y1.

The common connection point between the switching element U1 of the first unit 1 and the switching element X1 is connected to one end of the reactor L. The common connection point of the switching elements V1 and Y1 of the first unit 1 and the common connection point of the switching elements U2 and X2 of the second unit 2 are connected. Similarly, the second unit 2 and the third unit 3, the third unit 3 and the fourth unit 4, the fourth unit 4 and the fifth unit 5, and the fifth unit 5 and the sixth unit 6 are connected. A capacitor C is connected between the other end of the reactor L and the common connection point of the switching elements V6 and Y6 of the sixth unit 6.

The voltage between the common connection point of the switching elements U1 and X1 and the common connection point of the switching elements V1 and Y1 is defined as the unit output voltage Vo1. Similarly, the unit output voltage of the second to sixth units 2 to 6 is set to Vo2 to Vo6. Further, the total output voltage Vout is defined between the common connection point of the switching elements U1 and X1 of the first unit 1 and the common connection point of the switching elements V6 and Y6 of the sixth unit 6. In the first embodiment, for example, a single-phase voltage having an output frequency of 1 kHz or more is output.

Further, the series multiplex power conversion device includes a phase determination unit 10, an operating number determination unit 20, a threshold value control unit 30, and a PWM control unit PWM.

The phase determination unit 10 determines the gate threshold update timing (phase 0 °, 90 °, 180 °, 270 °) from the phase θ of the voltage command value Vref, and outputs the output to the threshold control unit 30.

The operating number determination unit 20 determines the number of units currently in operation by comparing the gate threshold value of each unit with the voltage command value Vref, and outputs the operating number determination value to the threshold value control unit 30.

The threshold value control unit 30 controls the gate threshold value of each unit at the gate threshold value update timing (phase 0 °, 90 °, 180 °, 270 °) based on the gate threshold value update timing and the operating number determination value. At the time of the phase 90 ° 270 ° (peak) of the voltage command value Vref, the gate threshold value is replaced according to the number of operating units. When the phase of the voltage command value Vref is 0 ° and 180 ° (zero cross), the exchanged gate threshold value is restored.

The PWM control unit PWM performs pulse width modulation control of a one-pulse control method. The PWM control unit PWM compares the voltage command value Vref with the gate threshold value output from the threshold value control unit 30, and generates a gate signal. The gate threshold is a positive or negative gate threshold that takes a constant value for at least 1/4 cycle of the voltage command value Def. At the time of comparison, dead time processing and minimum on-pulse processing are performed.

Next, a method of outputting a voltage smaller than the minimum on-pulse width will be described. In the first embodiment, the pulse width at the uppermost stage of the output voltage Vout is output by overlapping the output voltages of the two units, thereby avoiding the pulse width limitation due to the minimum on-pulse width of each unit.

In the first embodiment, a method of changing only the gate threshold value of the upper two units having a large absolute value of the gate threshold value among the operating units will be described.

In the PWM control unit PWM, the comparison between the voltage command value Vref and the gate threshold value of each unit is performed in the same manner as in the conventional case. The operating number determination unit 20 determines the operating number at that time at the peak unit (phase 90 °, 270 °) of the voltage command value Vref. The threshold control unit 30 has the unit having the largest absolute value of the positive gate threshold among the units operating at the time of the phase 90 ° (peak portion) of the voltage command value Vref, and the absolute value of the positive gate threshold. Swaps the gate threshold of the second largest unit. In addition, among the units operating at the time of the phase 270 ° (peak part) of the voltage command value Vref, the unit having the largest absolute value of the negative gate threshold value and the unit having the largest absolute value of the negative side gate threshold value are second. Swap the gate thresholds for larger units. Further, the gate threshold values exchanged at the phases 0 ° and 180 ° of the voltage command value Vref are restored. After that, the voltage command value Vref and the gate threshold value are compared in the same manner as when the output is started.

FIG. 2 shows an example in the case of operating three units. A case of outputting a positive voltage will be described. When the voltage command value Vref exceeds the gate thresholds Vth1a, Vth2a, and Vth3a on the positive side of the units 1 to 3, the units 1 to 3 output positive voltages, respectively. The number of operating units is determined when the phase of the voltage command value Vref is 90 ° (peak portion), and the upper two gate thresholds having the largest absolute values among the gate thresholds Vth1a, Vth2a, and Vth3a on the positive side of the operating units 1 to 3 are determined. Select. Here, since the upper two gate thresholds having large absolute values are the gate thresholds Vth3a and Vth2a, the gate thresholds Vth3a and the gate thresholds Vth2a are exchanged (underlined in FIG. 2).

After the phase of the voltage command value Vref is 90 °, the gate threshold value after replacement and the voltage command value Vref are compared, and the output becomes 0 in the order of unit 2, unit 3, and unit 1. As a result, the uppermost voltage of the output voltage Vout is composed of the superposition of the unit output voltages Vo2 and Vo3 of the units 2 and 3. Since the pulse width of each unit output voltage Vo1 to Vo6 is sufficiently larger than the minimum on-pulse width, the output voltage Vout can be configured without being limited to the minimum on-pulse width.

The gate threshold value is returned to the original order when the phase of the voltage command value Vref is 180 ° (zero cross). Similarly, when outputting a negative voltage, the upper two units (gate thresholds Vth3b, Vth2b) having a large absolute value of the negative gate threshold among the units operating at the phase 270 ° (peak part) of the voltage command value Vref. ) Is replaced. After that, the gate threshold value is returned to the original order at the time of the phase 360 ° (zero cross) of the voltage command value Vref.

FIG. 3 shows an example in the case of 6 units. A case of outputting a positive voltage will be described. When the voltage command value Vref exceeds the gate thresholds Vth1a, Vth2a, Vth3a, Vth4a, Vth5a, and Vth6a of units 1 to 6, units 1 to 6 each output a positive voltage. The operating number determination unit 20 determines the operating number at the time of the voltage command value Vref = 90 ° (peak unit). The threshold value control unit 30 selects two gate threshold values having a large absolute value from the gate threshold values Vth1a, Vth2a, Vth3a, Vth4a, Vth5a, and Vth6a on the positive side of the units 1 to 6 during operation. Here, since the two positive gate thresholds having large absolute values are the gate thresholds Vth6a and Vth5a, the gate thresholds Vth6a and the gate thresholds Vth5a are exchanged (underlined in FIG. 3).

The gate threshold value after replacement is compared with the voltage command value Vref, and the output becomes 0 in the order of unit 5, unit 6, unit 4, unit 3, unit 2, and unit 1. As a result, the uppermost voltage of the output voltage Vout is composed of the superposition of the unit output voltages Vo5 and Vo6 of the units 5 and 6. Since the pulse width of each unit output voltage Vo1 to Vo6 is sufficiently larger than the minimum on-pulse width, the output voltage Vout can be configured without being limited to the minimum on-pulse width.

The gate threshold value is returned to the original order when the phase of the voltage command value Vref is 180 ° (zero cross). Similarly, when outputting a negative voltage, the upper two units (gate thresholds Vth6b, Vth5b) having a large absolute value of the negative gate threshold among the units operating at the phase 270 ° (peak part) of the voltage command value Vref. ) Is replaced. After that, the gate threshold value is returned to the original order at the time of the phase 360 ° (zero cross) of the voltage command value Vref.

As shown above, according to the first embodiment, since each unit is not limited by the minimum on-pulse width, the output voltage Vout smaller than the minimum on-pulse width can be output as a series multiplex power converter. Become. Further, the first embodiment has the same output voltage waveform as the conventional gate generation method except for the portion having the minimum on-pulse width.

[Embodiment 2]
In the first embodiment, a method of exchanging the gate thresholds of the upper two units having a large absolute value of the gate threshold among the operating units has been described, but in the second embodiment, the gates of all the operating units have been described. A method of changing the threshold value will be described.

The comparison between the voltage command value Vref in the PWM control unit PWM and the gate threshold value of each unit is performed in the same manner as in the conventional case. The operating number determination unit 20 determines the operating number at the time of the phase 90 ° (peak unit) of the voltage command value Vref. The threshold value control unit 30 rearranges the gate threshold values on the positive side of the unit operating at the time of the phase 90 ° (peak unit) of the voltage command value Vref in the reverse order. Further, the gate threshold value on the negative side of the unit operating at the time of the phase 270 ° (peak portion) of the voltage command value Vref is rearranged in the reverse order. In addition, the gate threshold values exchanged at the phases 0 ° and 180 ° of the voltage command value Vref are restored. After that, the voltage command value Vref is compared with each gate threshold value in the same manner as usual, and a gate signal is generated.

FIG. 4 shows an example in the case of operating three units. A case of outputting a positive voltage will be described. When the voltage command value Vref exceeds the gate thresholds Vth1a, Vth2a, and Vth3a of the units 1 to 3, the units 1 to 3 each output a positive voltage.

The number of operating units is determined when the phase of the voltage command value is 90 °. Since three units are operated, the magnitudes of the absolute values of the gate thresholds Vth1a, Vth2a, and Vth3a on the positive side of the units 1 to 3 are reversed. Specifically, the gate thresholds Vth1a, Vth2a, and Vth3a were changed in ascending order of the absolute value of the gate threshold on the positive side, and Vth3a, Vth2a, and Vth1a were arranged in the reverse order from the smallest absolute value of the gate threshold on the positive side. Sort to (underlined part in Fig. 4).

The rearranged positive gate thresholds Vth3a, Vth2a, Vth1a are compared with the voltage command value Vref, and the unit output voltages Vo1, Vo2, and Vo3 become 0 in the order of unit 1, unit 2, and unit 3.

As a result, the uppermost voltage of the output voltage Vout is composed of the superposition of the unit output voltages Vo1 and Vo3 of the units 1 and 3. Since the pulse width of each unit output voltage Vo1 to Vo6 is sufficiently larger than the minimum on-pulse width, the output voltage Vout can be configured without being limited to the minimum on-pulse width.

The gate threshold value is returned to the original order when the phase of the voltage command value Vref is 180 ° (zero cross). Similarly, when outputting a negative voltage, the magnitude of the absolute value of the negative gate threshold value of the unit operating at the time of the phase 270 ° of the voltage command value Vref is reversed. After that, the gate threshold value is returned to the original order at the time of the phase 360 ° (zero cross) of the voltage command value Vref.

FIG. 5 shows an example in the case of operating 6 units. A case of outputting a positive voltage will be described. When the voltage command value Vref exceeds the gate thresholds Vth1a, Vth2a, Vth3a, Vth4a, Vth5a, and Vth6a on the positive side of units 1 to 6, units 1 to 6 output positive voltages, respectively.

The operating number determination unit 20 determines the operating number at the time of the phase 90 ° (peak unit) of the voltage command value Vref. Since the threshold control unit 30 operates 6 units, the magnitudes of the absolute values of the gate thresholds Vth1a, Vth2a, Vth3a, Vth4a, Vth5a, and Vth6a on the positive side of the units 1 to 6 are reversed. Specifically, the gate thresholds Vth1a, Vth2a, Vth3a, Vth4a, Vth5a, and Vth6a are reversed in ascending order of the absolute value of the gate threshold on the positive side, and in ascending order of the absolute value of the gate threshold on the positive side. Is rearranged from Vth6a, Vth5a, Vth4a, Vth3a, Vth2a, Vth1a (underlined part in FIG. 5).

The rearranged positive gate thresholds Vth6a, Vth5a, Vth4a, Vth3a, Vth2a, Vth1a are compared with the voltage command value Vref, and the order is unit 1, unit 2, unit 3, unit 4, unit 5, unit 6. Output becomes 0.

As a result, the uppermost voltage of the output voltage Vout is composed of the superposition of the outputs of the unit output voltages Vo1 and Vo6 of the units 1 and 6. Since the pulse width of each unit output voltage Vo1 to Vo6 is sufficiently larger than the minimum on-pulse width, the output voltage Vout can be configured without being limited to the minimum on-pulse width.

The gate threshold value is returned to the original order when the phase of the voltage command value Vref is 180 ° (zero cross). Similarly, when a negative voltage is output, the magnitude of the absolute value of the negative gate threshold value of the unit operating at the time of the phase 270 ° (peak) of the voltage command value Vref is reversed. After that, the gate threshold value is returned to the original order at the time of the phase 360 ° (zero cross) of the voltage command value Vref.

As shown above, according to the second embodiment, the same action and effect as those of the first embodiment are obtained. Further, in the second embodiment, all the unit output voltage widths are closer to uniform than those in the first embodiment.

Although the above description has been made in detail only for the specific examples described in the present invention, it is clear to those skilled in the art that various modifications and modifications can be made within the scope of the technical idea of the present invention. It goes without saying that such modifications and modifications fall within the scope of claims.

10: Phase determination unit 20: Number of units in operation determination unit 30: Threshold control unit PWM: PWM control unit Vth1a to Vth6a, Vth1b to Vth6b ... Gate thresholds Vo1 to Vo6: Unit output voltage Vout: Output voltage Vref: Voltage command value U1 to U6 , V1 to V6, X1 to X6, Y1 to Y6: Switching elements C1 to C6: DC voltage source C: Capacitor L: Reactor GU1, GV1, GX1, GY1: Gate signal

Claims (3)

It is a 1-pulse multiplexing series multiplex power converter that connects multiple bridge cell units in series and outputs a single-phase voltage with an output frequency of 1 kHz or higher.
A phase determination unit that determines the peak time and zero cross time of the voltage command value and outputs it as the update timing of the gate threshold value.
By comparing the gate threshold value of each unit with the voltage command value, the number of units currently in operation is determined and output as the number of operating units determination value.
Based on the update timing of the gate threshold value and the operating number determination value, the gate threshold value on the positive side of the unit operating at the peak on the positive side of the voltage command value is replaced, and the peak on the negative side of the voltage command value is replaced. A threshold control unit that replaces the negative gate threshold of the unit that is operating at the time and restores the gate threshold that was replaced at the zero cross point of the voltage command value.
For each of the units, the PWM control unit that generates the gate signal of the switching element by comparing the voltage command value with the positive and negative gate threshold values output from the threshold value control unit.
A series multiplex power converter characterized by being equipped with. The threshold control unit
At the peak time on the positive side of the voltage command value, only the upper two positive gate thresholds having the largest absolute value of the gate thresholds are replaced among the operating units.
The series multiplexing according to claim 1, wherein only the upper two negative gate thresholds having a large absolute value of the gate thresholds are exchanged among the operating units at the peak time on the negative side of the voltage command value. Power converter. The threshold control unit
At the peak point on the positive side of the voltage command value, the magnitudes of the absolute values of the positive gate thresholds of all the operating units are rearranged in reverse order.
The series multiplex power conversion according to claim 1, wherein the magnitude of the absolute value of the negative gate threshold value of all the operating units is rearranged in the reverse order at the time of the peak on the negative side of the voltage command value. apparatus.

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