WO2007108427A1

WO2007108427A1 - Voltage regulator

Info

Publication number: WO2007108427A1
Application number: PCT/JP2007/055453
Authority: WO
Inventors: Katsuji Shinohara; Kichiro Yamamoto; Kenichi Iimori
Original assignee: Kagoshima University
Priority date: 2006-03-23
Filing date: 2007-03-16
Publication date: 2007-09-27
Also published as: JPWO2007108427A1; JP4872090B2

Abstract

An output voltage (Vc) of a matrix converter (20) is generated by controlling switch operation of switch elements (21a-21d) arranged in the matrix converter (20). The phase and the amplitude of a voltage (Vo) on a load side are permitted to be target values by superimposing the generated output voltage (Vc) on an output voltage (Vt) of a single-phase transformer (10). An output voltage (Vt) of the single-phase transformer (10) is compensated by the output voltage (Vc) of the matrix converter (20).

Description

Specification

Voltage regulator

Technical field

The present invention relates to a voltage regulator, and is particularly suitable for use in regulating the output voltage of a transformer.

Background art

[0002] In recent years, power generation systems using wind power, sunlight, fuel cells, cogeneration, and the like have been put into practical use in consideration of energy problems and environmental problems. These power generation systems are generally connected to the terminal part of the power system (transformer output terminal). Therefore, in order to properly operate these power generation systems, it is necessary to make the output voltage of the transformer provided at the end of the power system constant. However, the output voltage of the transformer provided at the end of the power system changes according to the fluctuation of the load connected to the output terminal of the transformer. In particular, in the power generation system described above, since various generators are connected to the end portion of the power system, a reverse power flow occurs, and the output voltage of the transformer provided at the end portion of the power system increases. Problem arises.

[0003] To deal with such problems, a capacitor is connected in series on the input side of the transformer, and the output voltage of the transformer is adjusted by changing the terminal voltage of this capacitor using a power supply device equipped with an inverter. There is a technique (see Patent Document 1).

[0004] Further, a tap-switching voltage regulator and a static voltage regulator are connected in series to the distribution line, and the tap-switching voltage regulator and the static voltage regulator are used to connect the distribution line. There is also a technique for adjusting the voltage input from the power supply side and supplying it to the load side of the distribution line (see Patent Document 2). Here, the tap switching type voltage regulator includes a tapping adjustment transformer that inputs and transforms the voltage of the distribution line, and a tap control unit that switches and controls the tapping of the tapping adjustment transformer. Yes. In addition, the static voltage regulator is a power converter that converts the voltage obtained from the distribution line into a regulated voltage using an inverter, and a voltage that is converted by the power converter is transformed into a tap-switchable voltage regulator. A series transformer that is superimposed on the output voltage of the transformer and applied to the load side. Here, the tapping regulator Is switched when the output voltage of power fluctuation exceeds a threshold value.

[0005] However, in the wind power generation system and the solar power generation system described above, the output fluctuates greatly depending on the air volume and the amount of solar radiation, so the load of the transformer provided at the end of the power system (that is, the output) Voltage) fluctuates irregularly in a short time. Therefore, in the technique of using a capacitor as in the technique described in Patent Document 1 or switching the tap of the transformer as in the technique described in Patent Document 2, the voltage is adjusted following such fluctuations. There was a problem that it was difficult.

[0006] In addition, the technique described in Patent Document 1 has a problem that the configuration of the apparatus becomes complicated because the transformer itself needs to be modified.

In the technique described in Patent Document 2, the tap of the adjustment transformer with a tap is switched based on a command from the power converter, so that a tap-switching voltage regulator and a static voltage regulator are connected. There was a problem that the configuration of the device was complicated because it was necessary to coordinate

[0007] Therefore, the output terminal of the voltage adjusting AC power source including the converter and the inverter is connected in series to the input side of the transformer, and the voltage adjusting AC power source has the same frequency as the AC power source for the transformer. There is a technology that adjusts the output voltage of a transformer by supplying the above voltage to the input side of the transformer (see Patent Document 3).

However, since the conventional technique described above uses an inverter, it is necessary to convert AC power to DC power, smooth the DC power with an electrolytic capacitor, and then convert it again to AC power. is there. Therefore, there is a problem that the loss in the circuit for adjusting the voltage becomes large. Moreover, the electrolytic capacitor has a large volume and a short life. Therefore, there is a problem that the circuit for adjusting the voltage becomes larger and the service life is shortened.

[0009] Further, in the technique described in Patent Document 3, the voltage obtained through the converter and the inverter is supplied to the input side of the transformer, so that the loss of the circuit for adjusting the voltage is particularly large. At the same time, since the inverter always operates, the life of the circuit for adjusting the voltage is particularly shortened.

Patent Document 1: Japanese Patent Laid-Open No. 11 136945 Patent Document 2: Japanese Patent Laid-Open No. 11-289666

Patent Document 3: Japanese Unexamined Patent Publication No. 2000-148267

Disclosure of the invention

The present invention has been made in view of such problems, and an object thereof is to provide a high voltage regulator with low loss and high reliability.

[0012] The voltage regulator of the present invention has a voltage conversion circuit connected in series to the feeder side wire of the transformer, and a control circuit for controlling the voltage conversion circuit, the voltage conversion circuit, A plurality of switch elements, and the output voltage of the transformer is converted into an AC voltage corresponding to the switch operation of the plurality of switch elements, and the control circuit outputs the AC voltage of the plurality of switch elements. The switch operation is controlled, and a voltage obtained by superimposing the output voltage of the voltage conversion circuit on the output voltage of the transformer is supplied to the load side. Brief Description of Drawings

FIG. 1 is a diagram showing an example of the configuration of a voltage regulator according to an embodiment of the present invention.

FIG. 2 is a view showing an embodiment of the present invention and showing an example of the configuration of a switch element.

FIG. 3 is a diagram showing an embodiment of the present invention and showing an example of a detailed configuration of a control circuit.

[FIG. 4A] FIG. 4A shows an embodiment of the present invention, and shows an example of the relationship between the output voltage of the single-phase transformer and the compensation voltage when the amplitude of the output voltage of the single-phase transformer is smaller than the target voltage. FIG.

FIG. 4B shows an embodiment of the present invention, and shows an example of the relationship between the output voltage of the single-phase transformer and the compensation voltage when the amplitude of the output voltage of the single-phase transformer is larger than the target voltage. FIG.

[FIG. 5A] FIG. 5A is a diagram showing an embodiment of the present invention and showing an example of “waveform of output voltage of single-phase transformer” used for simulating the voltage regulator shown in FIG. It is.

[FIG. 5B] FIG. 5B shows an embodiment of the present invention, and shows a waveform (simulation voltage) of a compensation voltage (an output voltage of a matrix converter) for compensating the “output voltage of the single-phase transformer” shown in FIG. 5A. It is the figure which showed an example of a (result of Chillon).

[FIG. 5C] FIG. 5C shows an embodiment of the present invention, in which the “output voltage of the single-phase transformer” shown in FIG. 5A is compensated with the compensation voltage (output voltage of the matrix converter) shown in FIG. 5B. FIG. 6 is a diagram showing an example of a waveform (simulation result) of a “load-side voltage” obtained as described above.

FIG. 6 shows an embodiment of the present invention and is a diagram showing another example of the configuration of the switch element.

FIG. 7 shows an embodiment of the present invention and is a diagram showing an example of the configuration of a voltage regulator for adjusting the output voltage of a three-phase transformer.

BEST MODE FOR CARRYING OUT THE INVENTION

[0014] Hereinafter, an embodiment of the present invention will be described.

FIG. 1 is a diagram illustrating an example of the configuration of the voltage regulator according to the present embodiment. In FIG. 1, the voltage regulator includes a matrix converter 20, a single-phase insulating transformer 30, and a control circuit 40.

The matrix converter 20 includes switch elements 21a to 21d, a capacitor 22, and a reactor 23. The matrix converter 20 is connected in series with the output side of the single-phase transformer 10 through the single-phase isolation transformer 30. ing.

First, the connection of the matrix converter 20 will be described in detail.

As shown in FIG. 1, one end of the switch element 21a is mutually connected to one end of the winding on the output side of the single-phase transformer 10, and the other end of the switch element 21a is connected to the single-phase isolation transformer 30. Connected to one end 31a on the input side.

One end of the switch element 21b is connected to one end of the switch element 21d, and the other end of the switch element 21b is connected to the other end of the switch element 21a (one end of the input side of the single-phase isolation transformer 30 3 la ) And connected to each other.

[0016] One end of the switch element 21c is connected to one end of the switch element 21a, and the other end of the switch element 21c is connected to the other end 31b on the input side of the single-phase insulating transformer 30. ing.

As described above, one end of the switch element 21d is connected to one end of the switch element 21b, and the other end of the switch element 21d is connected to the other end of the switch element 21c (single-phase insulation transformer 30). Is connected to the other end (3 lb) on the input side.

[0017] One end of the capacitor 22 is mutually connected to one end of the winding on the output side of the single-phase transformer 10 (one end of the switch element 21a), and the other end of the capacitor 22 is connected to the switch elements 21b and 21d. Connected to the connection point.

One end of the reactor 23 is connected to the other end of the capacitor 22 (the connection point of the switch elements 21b and 21d). The other end of the reactor 23 is connected to the other side of the output side of the single-phase transformer 10 Connected to the ends.

One end 32a on the output side of the single-phase isolation transformer 30 is connected to one end of the feeder line on the output side of the single-phase transformer 10, and the other end 32b on the output side of the single-phase isolation transformer 30 is Connected to the terminal 50a on the load side.

[0018] Next, the configuration of the switch element 21 will be described. FIG. 2 is a diagram showing an example of the configuration of the switch element 21.

As shown in FIG. 2, the switch element 21 of the present embodiment includes two RBIGBTs (reverse blocking IGB T; Reverse

Blocking Insulated-Gate Bipolar Transistor) 21 la, 2 ib are connected in reverse parallel. Thus, in the present embodiment, the switch element 21 is configured using a reverse blocking device that performs a switching operation while maintaining a reverse breakdown voltage.

[0019] Returning to FIG. 1, when the control circuit 40 has a difference between the output voltage Vt (phase and amplitude) of the single-phase transformer 10 and the target voltage Va (phase and amplitude), So that the matrix converter 20 (switch elements 21a to 21d) outputs a compensation voltage Vc so that the voltage Vo (phase and amplitude) on the side becomes the same as the target voltage Va (phase and amplitude). Controls the switch operation of elements 21a to 21d. Thereby, the matrix converter 20 applies the compensation voltage Vc between the load-side terminal 50a and one end of the output-side winding of the single-phase transformer 10 in accordance with the switch operation of the switch elements 21a to 21d. To do. Thus, the compensation voltage Vc is superimposed on the output voltage Vt of the single-phase transformer 10, and the control is realized such that the voltage Vo (phase and amplitude) on the load side becomes the target voltage Va (phase and amplitude). .

FIG. 3 is a diagram illustrating an example of a detailed configuration of the control circuit 40.

In FIG. 3, the voltage detection circuit 41 is the output voltage Vt (amplitude and phase) of the single-phase transformer 10. It is a circuit for detecting. The voltage detection circuit 42 is a circuit for detecting the compensation voltage Vc (the amplitude and phase thereof) that is the output voltage of the single-phase isolation transformer 30.

[0021] The subtraction circuit 43 calculates a difference between the “target voltage Va of the load-side voltage Vo” input from the outside and the “output voltage Vt of the single-phase transformer 10” detected by the voltage detection circuit 41. This is a circuit for calculation. In the following description, the difference between the target voltage Va and the output voltage Vt of the single-phase transformer 10 is referred to as a compensation command voltage VcT as necessary.

The subtraction circuit 44 is a circuit for calculating a difference between the “compensation command voltage V” obtained by the subtraction circuit 43 and the “compensation voltage Vc” obtained by the voltage detection circuit 42. In the following description, the difference between the compensation command voltage VcT and the compensation voltage Vc is referred to as a compensation differential voltage AVc as necessary.

The proportional control circuit 45 multiplies the “compensation differential voltage AVc” obtained by the subtraction circuit 44 by the proportional gain K to perform a proportional operation, and the compensation differential voltage obtained by performing this proportional operation. AVc is output to the square wave generation circuit 46.

The triangular wave generation circuit 47 generates a carrier triangular wave Vd having an amplitude corresponding to the magnitude of the “output voltage Vt of the single-phase transformer 10” detected by the voltage detection circuit 41 and outputs it to the square wave generation circuit 46. To do. That is, the triangular wave generation circuit 47 generates the carrier triangular wave Vd by modulating the triangular wave with the output voltage Vt of the single-phase transformer 10 and outputs it to the square wave generation circuit 46.

The square wave generating circuit 46 has a comparator (comparator) that compares the compensation differential voltage AVc output from the proportional control circuit 45 with the carrier triangular wave Vd output from the triangular wave generating circuit 47. By the comparison operation by the comparator (comparator), pulse width modulation (PWM) is performed and a PWM signal (square wave) is obtained. This PWM signal becomes the gate signal Vg of the switch elements 21a to 21d.

Here, the square wave generating circuit 46 is a switch that operates (turns on) based on the gate signal Vg according to the value of the output voltage Vt of the single-phase transformer 10 and the value of the compensation command voltage V. A selection circuit for selecting the elements 21a to 21d is provided.

Specifically, when the output voltage Vt of the single-phase transformer 10 and the compensation command voltage V are both positive values (Vt> 0, VcT> 0), the selection circuit selects the switch element 21b based on the gate signal Vg. Turn on 21c. In addition, the selection circuit switches the switching element based on the gate signal Vg even when the output voltage Vt of the single-phase transformer 10 and the compensation command voltage VcT are both negative values (Vt 0, VcT 0). Turn on 21b and 21c.

[0025] In addition, when the output voltage Vt of the single-phase transformer 10 is a positive value and the compensation command voltage V is a negative value (Vt> 0, VcT <0), the selection circuit has a gate signal Vg Based on the above, the switch elements 21a and 21d are turned on. The selection circuit also has a gate signal Vg when the output voltage Vt of the single-phase transformer 10 is negative and the compensation command voltage VcT is positive (Vt <0, VcT> 0). Based on the switch elements 21a and 21d.

When the value of compensation command voltage Vc 'is 0 (zero), matrix converter 20 is not operated.

As described above, in the present embodiment, the control circuit 40 performs feedback control using proportional control so that the compensation command voltage V and the actual compensation voltage Vc match! The As a result, the voltage Vo on the load side can be stabilized (same as the target voltage Va).

[0027] Returning to FIG. 1, the capacitor 22 and the reactor 23 are low-pass filters for preventing harmonic components based on the switch operation of the switch elements 21a to 21d from flowing to the power supply side. In addition, the single-phase isolation transformer 30 is inserted in order to prevent a short circuit between the input side and the output side of the matrix converter 20!

[0028] Fig. 4 is a diagram conceptually showing an example of the relationship among the voltage Vo on the load side, the output voltage Vt of the single-phase transformer 10, and the compensation voltage (output voltage of the matrix converter 20) Vc. is there. Specifically, FIG. 4A conceptually shows an example of the relationship between the output voltage Vt of the single-phase transformer 10 and the compensation voltage Vc when the amplitude of the output voltage Vt of the single-phase transformer 10 is smaller than the target voltage Va. 4B shows the relationship between the output voltage Vt of the single-phase transformer 10 and the compensation voltage Vc when the amplitude of the output voltage Vt of the single-phase transformer 10 is larger than the target voltage Va. FIG. 3 is a diagram conceptually showing an example.

For example, as shown in FIG. 4A, when the amplitude force of the output voltage Vt of the single-phase transformer 10 is smaller than the target voltage Va shown by the broken line, the amplitude of the compensation voltage (output voltage of the matrix converter 20) Vc is It is the value obtained by subtracting the amplitude of the output voltage Vt of the single-phase transformer 10 from the target voltage Va. The phase is in phase with the output voltage Vt of the single-phase transformer 10. By superimposing such compensation voltage (output voltage of matrix converter 20) Vc force output voltage Vt of single-phase transformer 10, the amplitude of load-side voltage Vo becomes (approaches) target voltage Va.

In addition, as shown in FIG. 4B, when the amplitude force of the output voltage Vt of the single-phase transformer 10 is larger than the target voltage Va shown by the broken line, the amplitude of the compensation voltage (output voltage of the matrix converter 20) Vc is The target voltage Va is subtracted from the amplitude of the output voltage Vt of the single-phase transformer 10, and the phase deviates from the output voltage Vt of the single-phase transformer 10 by 180 °. By superimposing such compensation voltage (output voltage of matrix converter 20) Vc force output voltage Vt of single-phase transformer 10, the amplitude of load-side voltage Vo becomes (approaches) target voltage Va.

[0031] In FIG. 4, by controlling the switch operation of the force switch elements 21a to 21d shown as an example of adjusting (compensating) the amplitude of the output voltage Vt of the single-phase transformer 10, It is also possible to adjust (compensate) the phase of the output voltage Vt of the phase transformer 10.

FIG. 5 is a diagram showing an example of the waveform of the output voltage Vt of the single-phase transformer 10, the waveform of the compensation voltage (output voltage of the matrix converter 20) Vc, and the waveform of the voltage Vo on the load side. is there. Specifically, FIG. 5A is a diagram showing an example of “waveform of output voltage Vt of single-phase transformer 10” used when simulating the voltage regulator shown in FIG. In the example shown in FIG. 5A, the simulation was performed with the amplitude of the output voltage Vt of the single-phase transformer 10 being 112.8 (141 X 0.8) [V].

FIG. 5B shows an example of a waveform (simulation result) of compensation voltage (output voltage of matrix converter 20) Vc for compensating “output voltage Vt of single-phase transformer 10” shown in FIG. 5A. It is a figure. 5C is obtained by compensating the `` output voltage Vt of the single-phase transformer 10 '' shown in FIG. 5A with the compensation voltage (output voltage of the matrix converter 20) Vc shown in FIG. FIG. 6 is a diagram showing an example of a waveform (simulation result) of “load-side voltage Vo”.

[0034] As described above, in the present embodiment, the switching operation of the switch elements 21a to 21d provided in the matrix converter 20 is controlled to generate and generate the compensation voltage (the output voltage of the matrix converter 20) Vc. The compensation voltage Vc is superimposed on the output voltage Vt of the single-phase transformer 10 so that the phase and amplitude of the voltage Vo on the load side are the same as (closer to) the phase and amplitude of the target voltage Va I did it. That is, the output voltage Vt of the single phase transformer 10 is compensated by the compensation voltage (output voltage of the matrix converter 20) Vc. Therefore, the compensation voltage (the output voltage of the matrix converter 20) Vc is output following the sudden fluctuation of the voltage Vo on the load side by the switch operation of the switch elements 21a to 21d provided in the matrix converter 20. Can do. Further, unlike the inverter, the matrix converter 20 does not convert alternating current into direct current. This eliminates the need for short-life electrolytic capacitors. As a result, it is possible to provide a voltage regulator that has a lower loss, a smaller size, and a longer life than conventional ones.

[0035] The matrix converter is a device that can directly vary the frequency and amplitude of an AC power source with a fixed frequency and a fixed voltage without providing a power storage element inside. However, in the single-phase matrix converter, the output voltage of the single-phase matrix converter must be 0 (zero) in the vicinity of the phase where the input voltage of the single-phase matrix converter is 0 (zero). For this reason, in the embodiment using a single-phase matrix converter alone, it is difficult to control the output voltage.

However, in the voltage regulator of this embodiment, the single-phase matrix converter 20 is used to set the load-side voltage Vo to an ideal power supply voltage. The frequency of the output voltage Vc is the same as the frequency on the input side, and in the phase where the input voltage of the single-phase matrix converter 20 is 0 (zero), the output voltage Vc of the single-phase matrix converter 20 is also 0 (zero) is acceptable. For this reason, in the voltage regulator of this embodiment, the capability of the single phase matrix converter 20 can be used effectively.

[0037] In the present embodiment, two RBIGBTs are connected in antiparallel and the switch element 21 is arranged in a matrix shape. However, the single-phase transformer follows the fluctuation of the voltage Vo on the load side. If the output voltage Vt of 10 can be adjusted, the type and arrangement of the switch element 21 are not limited to this. For example, the switch element 21 may be configured as shown in FIG. FIG. 6 is a diagram showing another example of the configuration of the switch element 21.

In the example shown in FIG. 6, the switch element 21 is configured using two IGBTs 212a and 212b and two diodes 213a and 213b in order to have the same function as the example shown in FIG. . However, in the example shown in FIG. 6, diodes 213a and 213b are connected between the emitters and collectors of IGBTs 212a and 212b with the emitter side as the anode side. The power swords of the diodes 213a and 213b (the collectors of the IGBTs 212a and 212b) are connected to each other.

In the present embodiment, the compensation command voltage Vc indicating the difference between the output voltage Vt (phase and amplitude) of the single-phase transformer 10 and the target voltage Va (phase and amplitude) By adjusting the compensation voltage Vc, which is the output voltage of the isolation transformer 30, to achieve control so that the voltage Vo (phase and amplitude) on the load side becomes the target voltage Va (phase and amplitude) I did it. However, this is not always necessary. For example, either the phase or the amplitude of the output voltage Vt of the single-phase transformer 10 may be set to the target value. Further, the phase and amplitude of the output voltage Vt of the single-phase transformer 10 may be within an allowable range. Furthermore, the phase of the voltage Vo on the load side and the amplitude force target value (or within an allowable range) may be used.

Furthermore, in the present embodiment, the case where the output voltage Vt of the single-phase transformer 10 is adjusted is shown as an example, but the output voltage of each phase of the n-phase transformer is adjusted (n is a natural number). You may do it. For example, it may be as shown in FIG. FIG. 7 is a diagram showing an example of the configuration of a voltage regulator for regulating the output voltage of the three-phase transformer.

In FIG. 7, the voltage regulator includes a three-phase matrix converter 200, a three-phase isolation transformer 300, and a control circuit 400.

The three-phase matrix converter 200 includes three matrix converters 20a to 20c having the same configuration as the matrix converter 20 shown in FIG. The three-phase isolation transformer 300 includes three single-phase isolation transformers 30a to 30c having the same configuration as the single-phase isolation transformer 30 shown in FIG.

The control circuit 400 determines whether or not the phase and amplitude of the voltage on the load side in each phase of the three-phase transformer 100 are target values, and the load in each phase of the three-phase transformer 100 (between each phase). And a circuit for controlling the switch operation of the switch elements 21a to 211 according to the voltage on the side.

That is, the three-phase transformer 100 is connected to the output terminals 100a, 100b, and 100c in series through the matrix converters 20a, 20b, and 20c through the three-phase isolation transformer 300, respectively. Then, the control circuit 400 controls the switch operations of the switch elements 21a to 211 by performing the operation described in the first embodiment for each phase. As a result, three-phase Voltage between output terminals 100a and 100b of transformer 100, voltage between output terminals 100b and 100c, voltage and force between output terminals 100c and 100a, respectively Output voltage (compensation voltage) of matrix converters 20a, 20b and 2 Oc Compensated by Vc.

As described above, by increasing the number of matrix converters 20, the output voltage of the multiphase transformer can be adjusted accurately and with low loss.

[0043] When a three-phase matrix converter having nine switch elements is used in the voltage regulator, it is necessary to wire the portion for injecting voltage into the single-phase isolation transformer with a star connection. Then, interference of compensation voltage Vc of each phase occurs. For this reason, the adjustment capability of the output voltage of each phase of the three-phase transformer 100 may be reduced. On the other hand, as shown in FIG. 7, when twelve switch elements 21a to 211 are used, the compensation voltage Vc can be applied independently to the single-phase isolation transformers 30a to 30c of each phase. For this reason, the output voltage of each phase of the three-phase transformer 100 can be adjusted with high accuracy.

It should be noted that the above-described embodiments are merely examples of specific examples for carrying out the present invention, and the technical scope of the present invention should not be construed as being limited thereto. Is. In other words, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.

Industrial applicability

[0045] According to the present invention, the output voltage of the transformer is converted into an AC voltage corresponding to the switching operation of the plurality of switch elements, and the converted AC voltage is superimposed on the output voltage of the transformer to be on the load side. It was made to be supplied. Thereby, the output voltage of a transformer can be adjusted using the alternating voltage according to the switch operation | movement of several switch elements. Therefore, it is not necessary to convert the output voltage of the transformer to direct current, so that an electrolytic capacitor is not necessary, and the output voltage of the transformer can be adjusted at high speed and reliably by the switching operation of a plurality of switch elements. Therefore, it is possible to provide a voltage regulator with low loss and high reliability.

Claims

The scope of the claims

[1] a voltage conversion circuit connected in series with the feeder wire on the output side of the transformer;

A control circuit for controlling the voltage conversion circuit,

The voltage conversion circuit includes a plurality of switch elements, converts the output voltage of the transformer into an AC voltage corresponding to the switch operation of the plurality of switch elements, and outputs the AC voltage. Controls the switch operation of the switch element,

A voltage regulator in which a voltage obtained by superimposing an output voltage of the voltage conversion circuit on an output voltage of the transformer is supplied to a load side.

2. The voltage regulator according to claim 1, wherein the plurality of switch elements are arranged in a matrix.

[3] The voltage regulator according to [1] or [2], wherein the switch element includes a reverse blocking device.

[4] n (n is a natural number) of the voltage conversion circuits,

4. The voltage regulator according to claim 1, wherein the voltage conversion circuit is connected in series to one side of the output side of the n-phase transformer. 5.