JP2006158155A - Power converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power converter which promptly detects an electric power failure without superposing a DC component on an AC current, and increasing distortion of the ac current. <P>SOLUTION: The power converter includes a power converting circuit 1 connected to AC power supply 7 through a reactor 4, and its control means 100 includes an electric power failure detecting means 20 which detects the electric power failure from the abnormal frequency of a voltage at the AC current side of the power converting circuit 1. The control means 100 includes a DC voltage adjusting means 11 to distinguish power running and regeneration running, a reference sine waveform generating means 14 which generates a sine waveform using a phase of the voltage at the AC current side of the power converting circuit 1, and a references AC waveform generating means 13 which generates an AC waveform with a change ratio near 0°of the sine waveform made sharp. Moreover, the control means includes a switching means 15 to switch outputs of the generating means 13, 14 according to an operating mode, a multiplication means 16 to generate the voltage command value of the power converting circuit 1 using the outputs of the generating means 13, 14, an AC current adjusting means 17, a subtraction means 18, and a pulse-width modulation means 19. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power conversion device that is connected to an AC power source, converts AC power to DC power and supplies the load to a load, and more specifically, has a feature in a method for controlling an AC side voltage for detecting a power failure of the AC power source. The present invention relates to a power conversion device.

FIG. 6 is a configuration diagram showing a conventional technique of this type of power conversion device.
The power conversion device shown in FIG. 6 is connected to the power conversion circuit 1 that performs AC / DC conversion by turning on and off the semiconductor switching element, the smoothing capacitor 2 connected to the DC side, and the AC side of the power conversion circuit 1. Reactor 3, AC voltage detector 4 that detects the voltage of AC power supply 7, AC current detector 5 that detects AC current, DC voltage detector 6 that detects the voltage across smoothing capacitor 2, and power And a control unit 400 for controlling the conversion circuit 1. Reference numeral 8 denotes a load to which DC power is supplied.

  The control unit 400 includes a DC voltage adjusting unit 11, a reference phase generating unit 12, a reference sine waveform generating unit 14, a multiplying unit 30, an AC current adjusting unit 17, a subtracting unit 18, and a pulse width modulation. Means 19 and power failure detection means 20 are provided.

The operation of the control means 400 is as follows.
First, a DC voltage command value v _d ^* and a DC voltage detection value v _d detected by the DC voltage detector 6 are input to the DC voltage adjusting means 11, and the detected value v _d is used as the command value v _d ^* . The AC current amplitude command value I _s ^* is calculated by proportional integral control calculation processing for matching.
Reference phase generator 12 receives the AC voltage detected value v _s detected by the AC voltage detector 4, generates and outputs the reference phase theta.
Reference sine wave generating means 14, the reference phase θ outputted from the reference phase generating means 12 as input, and outputs a reference sine wave sinθ of the AC voltage detected value v _s with the same period and the same phase.
Multiplying means 30, an AC current amplitude command value I _s ^* outputted from the DC voltage control means 11, by multiplying the reference sine wave sinθ output from the reference sinusoidal wave generating unit 14, the AC current command value i _s ^* Is calculated.

AC current adjusting unit 17 performs a proportional control calculation process for matching an alternating current detection value i _s detected by the AC current detector 5 to the AC current command value i _s ^*, calculates the voltage manipulated variable v _a ^* .
Subtraction means 18, by subtracting the voltage manipulated variable v _a ^* from the AC voltage detected value v _s, and calculates a power converter voltage command value v _c ^*.
The pulse width modulation unit 19 generates an on / off signal of the semiconductor switching element in the power conversion circuit 1 in accordance with the power converter voltage command value v _c ^* , and transmits this on / off signal to the power conversion circuit 1. ing.
Meanwhile, the power failure detection means 20 inputs the AC voltage detected value v _s, the abnormal voltage amplitude of the AC power supply 7, and detects an abnormal power outage periodicity, and outputs the operation stop command to the pulse width modulation means 19 .

By operating the control means 400 as described above, the control for making the DC voltage detected value v _d coincide with the DC voltage command value v _d ^* while the AC side power factor 1 is maintained is executed.

Now, the above-described control unit 400, the processing of subtracting the voltage manipulated variable v _a ^* from the AC voltage detected value v _s, and calculates the power converter voltage command value v _c ^*. Therefore, when a power failure occurs while power is being regenerated from the apparatus side to the AC power supply 7 side, the apparatus induces the same AC voltage as that during power supply. At this time, when the load that consumes power exactly the same as regenerative power of the apparatus is maintained balanced supply and demand electric power In the AC power supply side, a change in the voltage value and frequency of the AC voltage detected value v _s There was a problem that the power failure detection means 20 could not detect a power failure and the power conversion circuit 1 continued to operate and induce an alternating voltage.

As means for solving the above problem, for example, a conventional technique described in Patent Document 1 described below is known. FIG. 7 is a schematic diagram that is substantially the same as the apparatus configuration described in FIG.
In the prior art described in Patent Document 1, in the control unit 500 of FIG. 7, the frequency detection unit 41, the first and second phase function generation units 42 and 43, before the reference sine waveform generation unit 14, a switching means 44, an adding unit 45, and changing the alternating current command value i _s ^* frequency between regenerative and time of the power conversion circuit 1 powering. In FIG. 7, the same components as those in FIG. 6 are denoted by the same reference numerals.

The operation of this prior art is as follows.
Frequency detecting means 41 detects the frequency f of the AC voltage detected value v _s.
The first phase function generating means 42 outputs the power running correction phase Δθ _p shown in FIG. 8 according to the frequency f, and the second phase function generating means 43 corresponds to FIG. 9 according to the frequency f. The regenerative correction phase Δθ _b shown in FIG.
The switching means 44 has a positive AC current amplitude command value I _s ^* , that is, during powering, selects the first phase function generating means 42 side to output a correction phase Δθ _p and a negative AC current amplitude command value I _s ^*. That is, at the time of regeneration, the second phase function generating means 43 side is selected and the correction phase Δθ _b is output.
The adding means 45 adds the reference phase θ and the correction phase Δθ (Δθ _p or Δθ _b ) output from the switching means 44 and outputs the output to the reference sine waveform generating means 14.
Subsequent operations are the same as those in FIG.

In the prior art described in Patent Document 1, by operating the control unit 500 as described above, a difference is generated between the reactive power generated in the power running mode and the regenerative mode, and thereby the AC voltage detection value v _s at the time of a power failure. In order to solve this problem, the frequency fluctuations occur.

Japanese Patent Laid-Open No. 10-248102 (paragraphs [0011] to [0014], FIG. 1 etc.)

However, in the prior art described in Patent Document 1, the frequency of the alternating current command value i _s ^* is different from the frequency of the power supply voltage, and the waveforms shown in FIGS. 10 and 11 are obtained. For this reason, there is a problem in that a direct current component is superimposed on an alternating current, and thus the transformer is easily demagnetized, and current distortion is increased.
SUMMARY OF THE INVENTION An object of the present invention is to provide a power converter that can quickly detect a power failure without superimposing a direct current component on an alternating current or increasing current distortion.

In order to solve the above problem, the invention described in claim 1 is provided with a power conversion circuit that is connected to an AC power source via a reactor, converts AC power into DC power, and supplies the power to a load. In the power conversion device comprising a power failure detection means for detecting a frequency abnormality of the AC side voltage of the power conversion circuit and detecting a power failure of the AC power source, the control means,
The control means includes
An operation mode discrimination means for discriminating a power running operation and a regenerative operation of the power conversion circuit;
First waveform generating means for generating a sine waveform based on the phase of the AC side voltage of the power conversion circuit, and a second waveform generation for generating an AC waveform with a steep change rate of the sine waveform near 0 ° Means,
Switching means for switching the outputs of the first and second waveform generating means according to the determination result by the operation mode determining means;
Means for generating a voltage command value of the power conversion circuit using the output of the first or second waveform generating means via the switching means.

The invention described in claim 2 is the invention according to claim 1,
When the regenerative operation is determined by the operation mode determining means, the switching means switches to the second waveform generating means and outputs the AC waveform.

The invention described in claim 3 is the invention according to claim 1 or 2,
When the operation mode determining means determines that the power running operation is performed, the switching means switches to the first waveform generating means and outputs the sine waveform.

The invention described in claim 4 is, in claim 2,
The AC waveform from the second waveform generating means output via the switching means makes the rate of change around 0 ° of the current command value of the power conversion circuit steep, and based on this current command value, the power The rate of change around 0 ° of the voltage command value of the conversion circuit is made steep.

According to the invention described in claims 1, 2, and 4, when a power failure occurs when power is being regenerated from the power conversion circuit to the AC power source without superimposing a DC component on the AC current, The frequency of the voltage induced on the AC power supply side of the conversion circuit is made lower than the frequency when the power supply is healthy to create an abnormal frequency state, and a power failure can be detected promptly by the operation of the power failure detection means.
According to the third aspect of the present invention, it is possible to prevent the AC current distortion from increasing when power is supplied from the AC power source to the power conversion circuit.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, FIG. 1 is a block diagram showing a first embodiment of the present invention, and 100 is a control means of the power conversion circuit 1. In the main circuit and control means 100 of the power conversion apparatus shown in FIG. 1, the same components as those in FIGS. 6 and 7 are denoted by the same reference numerals and description thereof will be omitted. Hereinafter, different parts will be mainly described.

That is, the control unit 100 of FIG. 1, a reference phase generating means 12 of the AC voltage detected value v _s, a reference sine wave generating means (first waveform generating means) for the reference phase θ is input from the generation unit 12 14 and reference AC waveform generating means (second waveform generating means) 13, switching means 15 for switching and outputting the output signals of these generating means 13 and 14 in accordance with the AC current amplitude command value I _s ^* , and AC and a multiplication means 16 for multiplying the output of the current amplitude command I _s ^* a switching unit 15, the AC current command value i _s ^* is input to the AC current regulating means 17 which is output from the multiplying means 16 . The connection configurations and operations of the DC voltage adjusting means 11, the multiplying means 16, the AC current adjusting means 17, the subtracting means 18, the pulse width modulating means 19, the power failure detecting means 20, and the like are the same as those shown in FIGS.

In the above structure, the reference sine wave generator 14 as a first waveform generating means outputs a reference sine wave sinθ conventional as well as AC voltage detected value v _s with the same period and the same phase.
On the other hand, the reference AC waveform generating means 13 as a second waveform generating means, in response to the reference phase θ of the AC voltage detected value v _s, sinusoidal that steep slope near 0 ° as shown in FIG. 2 Outputs the reference AC waveform. It is assumed that the positive and negative periods of this reference AC waveform are equal.
Switching means 15, in response to positive and negative alternating current amplitude command value I _s ^*, an AC current amplitude command value I _s ^* is positive, i.e., selects the reference sine wave generator 14 side in the power running mode, the reference sine wave sinθ Is output. Further, the alternating current amplitude command value I _s ^* is negative, i.e. selects the reference AC waveform generating means 13 side in the regenerative mode, outputs a reference AC waveform in FIG. 2 described above.
The DC voltage adjusting means 11 and the switching means 15 constitute an operation mode determining means in the claims.

Here, the AC voltage detected value v _s of the power failure is induced by the output of the power conversion circuit 1. When the slope of the output voltage of the power conversion circuit 1 near 0 ° is made steep, the slope of the induced voltage near 0 ° becomes gentler than the output voltage due to the action of the reactor 3. As a result, as shown in FIG. 3, the frequency of the AC voltage detection value v _s (induced voltage) at the time of the power failure is lower than the frequency when the power supply voltage is healthy (power supply), and the AC voltage detection value v _s An abnormal frequency state can be created.

In the first embodiment, during power regeneration from the DC side of the power conversion circuit 1 to the AC power supply 7 side, the reference AC waveform generated by the reference AC waveform generating unit 13 is output to the multiplying unit 16 via the switching unit 15, and this reference By making the slope of the alternating current command value i _s ^* near 0 ° steep according to the alternating current waveform, the slope of the output voltage near 0 ° is made steep.
Therefore, even if a power failure occurs during regeneration without superimposing a direct current component on the alternating current as in the prior art and suppressing the distortion of the alternating current to a very small portion near 0 °, the power failure detection means 20 also causes a power failure. Can be detected quickly, and a stop command can be sent to the pulse width modulation means 19 to stop the operation of the power conversion circuit 1.

Next, FIG. 4 is a block diagram showing a second embodiment of the present invention.
This embodiment differs from the first embodiment, the control unit 200, the AC voltage amplitude calculating means 21 for calculating the amplitude of the AC voltage detected value v _s provided, the amplitude value V outputted from the computing means 21 _The multiplication means 22 multiplies the output of the switching means 15 by _s and inputs it to the subtraction means 18.

In this embodiment, in order to calculate the power converter voltage command value v _c ^* , the multiplication result of the reference sine waveform at the time of power running or the reference AC waveform at the time of regeneration and the amplitude value V _s that is the output of the switching means 15. The voltage manipulated variable v _a ^* is reduced, and other configurations and operations are the same as those in the first embodiment.
In the present embodiment, the power running mode, an AC voltage command value corresponding to the regenerative mode generated by multiplying means 22, calculates a power converter voltage command value v _c ^* by subtracting the voltage manipulated variable v _a ^* from the command value can do.

FIG. 5 is a block diagram showing a third embodiment of the present invention.
This embodiment is different from the second embodiment in that the control means 300 uses the reference AC voltage amplitude value V ₀ instead of the amplitude value V _{s in} FIG. This is the same as in the second embodiment.
According to the present embodiment, the AC voltage amplitude calculation means 21 in FIG. 4 is not required, and there is an advantage that the configuration of the control means 300 can be simplified.

It is a block diagram which shows 1st Embodiment of this invention. It is a figure which shows the output waveform of the reference | standard alternating current waveform generation means in 1st Embodiment. It is a figure which shows the alternating voltage waveform at the time of the power failure in 1st Embodiment. It is a block diagram which shows 2nd Embodiment of this invention. It is a block diagram which shows 3rd Embodiment of this invention. It is a block diagram of the power converter device which shows a prior art. It is a schematic diagram which shows the structure of the prior art described in patent document 1. It is operation | movement explanatory drawing of the 1st phase function generation | occurrence | production means in FIG. It is operation | movement explanatory drawing of the 2nd phase function generation | occurrence | production means in FIG. It is a wave form diagram of an alternating current command value in the prior art of patent documents 1. It is a wave form diagram of an alternating current command value in the prior art of patent documents 1.

Explanation of symbols

1: Power conversion circuit 2: Smoothing capacitor 3: Reactor 4: AC voltage detector 5: AC current detector 6: DC voltage detector 7: AC power supply 8: Load 11: DC voltage adjusting means 12: Reference phase generating means 13 : Reference AC waveform generation means 14: reference sine waveform generation means 15: switching means 16, 22: multiplication means 17: AC current adjustment means 18: subtraction means 19: pulse width modulation means 20: power failure detection means 21: AC voltage amplitude calculation Means 100, 200, 300: Control means

Claims (4)

The power conversion circuit is connected to an AC power source via a reactor, converts AC power to DC power and supplies the load to the load, and the control means of the power conversion circuit detects the frequency abnormality of the AC side voltage of the power conversion circuit. In the power conversion device comprising a power failure detection means for detecting and detecting a power failure of the AC power supply,
The control means includes
An operation mode discrimination means for discriminating a power running operation and a regenerative operation of the power conversion circuit;
First waveform generating means for generating a sine waveform based on the phase of the AC side voltage of the power conversion circuit, and a second waveform generation for generating an AC waveform with a steep change rate of the sine waveform near 0 ° Means,
Switching means for switching the outputs of the first and second waveform generating means according to the determination result by the operation mode determining means;
Means for generating a voltage command value of the power conversion circuit using an output of the first or second waveform generating means via the switching means;
A power conversion device comprising: In the power converter device according to claim 1,
When the operation mode determination unit determines that the operation is regenerative operation, the switching unit switches to a second waveform generation unit and outputs the AC waveform. In the power converter device according to claim 1 or 2,
The power conversion apparatus according to claim 1, wherein when the operation mode determination unit determines that the power running operation is performed, the switching unit switches to the first waveform generation unit and outputs the sine waveform. In the power converter device according to claim 2,
The AC waveform from the second waveform generating means output via the switching means makes the rate of change around 0 ° of the current command value of the power conversion circuit steep, and based on this current command value, the power A power conversion device characterized in that the rate of change around 0 ° of the voltage command value of the conversion circuit is steep.

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