JP3367341B2 - Control method of PWM control self-excited rectifier - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for a PWM control self-exciting rectifier that converts AC power from a commercial power source into DC power by a self-exciting rectifier and supplies the load.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing a conventional example of a PWM control self-exciting rectifier of this type. In FIG. 4, 1 is a commercial power supply, 10 is a PWM control self-exciting rectifier,
Reference numeral 2 is a load such as an inverter connected to the output of the PWM control self-exciting rectifier 10.

The PWM control self-exciting rectifier 10 is an IGB
Anti-shunt type semiconductor element such as T and diode are anti-parallel
Main circuit of a self-excited rectifier that is connected and bridged
11, AC reactor of self-excited rectifier 12, self-excited rectifier
Capacitor 13 for smoothing the output of the power supply, phase power of commercial power supply 1
Phase voltage detector 14 for detecting pressure, R phase of commercial power supply 1
Insulation converter 15 for insulation conversion of voltage, insulation converter 15
Angle synchronized with the phase of the R-phase voltage of the commercial power supply 1
Angle signal generation that generates signals (θ, θ = 0 ° to 360 °)
Generating means 16 generates a sine wave based on the angle signal (θ)
The reference sine wave generator 17, which adds 120 ° to the angle signal
Calculated value (θ₁) A reference sine that produces a sine wave based on
Wave generator 18, voltage setting value of voltage setting device 19 and capacitor
DC voltage across sensor 13 is detected via isolation converter 20
Voltage that performs voltage adjustment operation based on the deviation from the detected voltage value
Output of regulator 21 and voltage regulator 21 and reference sine wave generator
R-phase current obtained by multiplying the output of 17 by the multiplier 22
Command value (i_R ^*) And the output of the voltage regulator 21 and the reference sine wave
T obtained by multiplying the output of the generator 18 by the multiplier 23
Phase current command value (i_T ^*) And S phase current command value
(I_S ^*), This i_R ^*, I_S ^*, I_T ^*And current
R-phase current detection value (i_R), S-phase
Flow detection value (i_S), T-phase current detection value (i_T)
The deviation is calculated by the current regulators 25, 26 and 27.
The output of each of the current regulators 25, 26, 27 and the reference
Output of sine wave generator 17 and output of reference sine wave generator 18
The voltage command value calculation circuit 28 to which
Calculates the pressure command value and calculates the voltage command value and carrier signal.
Pulse width in the comparator 30 according to the output of the generator 29
Modulation (PWM) control is performed and the output of this comparator 30 is controlled.
Of the main circuit 11 of the self-excited rectifier by the gate drive circuit 31.
A structure for applying a gate signal to each self-arc-extinguishing type semiconductor device.
It is a success.

FIG. 5 is a detailed circuit diagram of the voltage command value calculation circuit 28 shown in FIG. In FIG. 5, the S-phase reference sine wave signal is added by the adder 28a from the R-phase reference sine wave signal which is the output of the reference sine wave generator 17 and the T-phase reference sine wave signal which is the output of the reference sine wave generator 18. Is converted into a sine wave signal of each phase whose amplitude is adjusted by the gain adjusting function of each of the amplifiers 28b, 28c, 28d, and the sine wave signal of each phase and the current regulators 25, 26, 2 are converted.
7 and the respective outputs are added by adders 28e, 28f, and 28g, and each phase voltage command value (v _R ^* , v _S ^* ,
v _T ^* ) is generated and these voltage command values are input to the comparator 30.

In FIG. 5, amplifiers 28b, 28c, 2 are shown.
The gain of each 8d is adjusted to be a sine wave signal having an amplitude based on the rated voltage of the commercial power supply 1.

[0006]

According to the conventional control method of the PWM control self-exciting rectifier 10, the gains of the amplifiers 28b, 28c, 28d included in the voltage command value calculation circuit 28 are based on the rated voltage of the commercial power supply 1. Therefore, there is a risk that the current of the commercial power source 1 becomes unbalanced due to the imbalance of the gain adjustment.

An object of the present invention is to provide a control method for a PWM control self-exciting rectifier that solves the above problems.

[0008]

A self-exciting rectifier for converting AC power of a commercial power source into DC power by a self-exciting rectifier and supplying the load, wherein a DC voltage of an output of the self-exciting rectifier is detected, A voltage adjustment calculation is performed so that this DC voltage becomes a predetermined value, and a reference sine wave signal of each phase synchronized with the current command value (DC amount) obtained by this voltage adjustment calculation and the phase of the commercial power supply. By calculating the phase current command value (AC amount) by and, each phase current of the commercial power source is detected so as to follow the phase current command value, and the current adjustment calculation is performed.
A voltage command value (AC amount) of each phase is calculated from the output of the adjustment current of each phase and the sine wave signal of each phase obtained by adjusting the reference sine wave signal to a predetermined amplitude, and the voltage command of each phase is calculated. In a control method of a PWM control self-excited rectifier, which generates a PWM-controlled gate signal of each phase by a value and a carrier signal, and controls the self-extinguishing type semiconductor element of the self-excited rectifier by the gate signal of each phase. According to a first aspect of the present invention, an adjustment value of the amplitude of the reference sine wave signal of each phase for generating the sine wave signal of each phase is detected by detecting each phase current when the phase current command value is zero. The effective value or the rectified value of the value is obtained, and the actual value or the rectified value is set and held as a calculated value obtained by performing a proportional / integral calculation, and the second invention is the above-mentioned method for generating the sine wave signal of each phase. Adjust the amplitude of the reference sine wave signal for each phase to The effective value or rectified value of the deviation between the phase current command value and the detected value of each of the phase currents is obtained, and the calculated effective value or rectified value is set to a calculated value obtained by proportional / integral calculation. The amplitude adjustment value of the reference sine wave signal of each phase for generating the sine wave signal of each phase is calculated by proportional / integral calculation of the current command value (DC amount) when the power supplied to the load is zero. Set and hold the calculated value.

A self-exciting rectifier for converting the AC power of a commercial power source into a DC power by a self-exciting rectifier and feeding the load, wherein the DC voltage of the output of the self-exciting rectifier is detected. The voltage adjustment calculation is performed so that the voltage becomes a predetermined value, and the current command value (DC amount) obtained by adding the detection value of the load current to the calculation value obtained by the voltage adjustment calculation and the phase of the commercial power supply are synchronized. Each phase current command value (AC amount) is calculated with the reference sine wave signal of each phase, and each phase current of the commercial power supply is detected so as to follow this phase current command value, and the current adjustment calculation is performed. , The phase voltage command value (AC amount) is calculated from the output of the adjustment current of each phase and the sine wave signal of each phase obtained by adjusting the reference sine wave signal to a predetermined amplitude, and the voltage of each phase is calculated. PW by command value and carrier signal
In the control method of the PWM control self-excited rectifier, which generates M-controlled gate signals of each phase, and controls the self-extinguishing type semiconductor element of the self-excited rectifier by the gate signals of each phase, the fourth invention provides: An adjustment value of the amplitude of the reference sine wave signal of each phase for generating the sine wave signal of each phase,
The adjustment calculation value of the voltage is set to a calculation value which is a proportional / integral calculation.

According to a fifth aspect of the present invention, in the fourth aspect, the commercial power supply is determined to be out of power when the calculated value obtained by performing the proportional / integral calculation of the voltage adjustment calculation value is equal to or less than a predetermined determination value. According to the first to fourth aspects, the amplitude of the sine wave signal of each phase is automatically and individually adjusted to a value corresponding to the voltage of the commercial power source, and the amplitude of the sine wave signal between the phases is unbalanced. The unbalanced current of the commercial power source due to is also eliminated.

Further, in the second and fourth aspects of the invention, in addition to the operation of the invention, the sine wave signal can automatically follow the fluctuation of the voltage of the commercial power source. The fifth
In addition to the operation of the fourth aspect of the invention, it is possible to detect a power failure of the commercial power source.

[0012]

1 is a block diagram of a PWM control self-exciting rectifier showing an embodiment of the present invention. Components having the same functions as those of the conventional example shown in FIG. The description is omitted. That is, in FIG. 1, the PWM control self-excited rectifier 40 is provided with a voltage command value calculation circuit 41, and the PWM control self-excited rectifier 50 is provided with a voltage command value calculation circuit 51.

[0013]

1 is a block diagram showing a first embodiment of the present invention.
3 is a detailed circuit configuration diagram of a voltage command value calculation circuit 41 of the PWM control self-exciting rectifier 40 of FIG. In FIG. 2, the voltage command value calculation circuit 41 uses the S-phase reference signal from the R-phase reference sine wave signal output from the reference sine wave generator 17 and the T-phase reference sine wave signal output from the reference sine wave generator 18. An adder 42 that calculates a sine wave signal and a multiplier 43r that receives the R-phase, S-phase, and T-phase reference sine wave signals as multiplicands,
43s, 43t and the current command value (i _R ^* ,
i _S ^* , i _T ^* ) and the current detection value of each phase (i _R , i _S , i
_T )) and the effective value calculation circuit 44 for calculating the effective value of each of these deviations, and the PI calculators 45r, 45s for inputting the respective effective values and performing the proportional / integral calculation. 45t and PI calculators 45r, 4
A holding circuit 46 that holds the output values of 5s and 45t by a holding command input from the outside and sets them as multipliers of the multipliers 43r, 43s, and 43t, and the multipliers 43r, 43s, and 4
3t each output of sine wave signal and current regulator 2
Adders 47 that add the respective outputs of 5, 26, and 27 to generate each phase voltage command value (v _R ^* , v _S ^* , v _T ^* )
r, 47s, and 47t.

The operation of the voltage command value calculation circuit 41 shown in FIGS. 1 and 2 will be described below. For example, a no-load operation state is provided when the PWM control self-exciting rectifier 40 is started, and the hold command release signal is input by an operation control circuit (not shown) of the self-exciting rectifier, and the output of the voltage regulator 21 is zero, for example. When held at, the current command value (i _R ^* ,
i _S ^* , i _T ^* ) are also held at zero.

At this time, only the current detection values (i _R , i _S , and i _T ) of each phase are input to the effective value calculation circuit 44, and the PI according to each effective value of the effective value calculation circuit 44. The output values of the arithmetic units 45r, 45s, and 45t are multipliers of the multipliers 43r, 43s, and 43t because the release signal is input to the holding circuit 46, and the output values of the multipliers 43r, 43s, and 43t are output. The amplitude of the sine wave signal corresponding to is corresponding to the voltage of the commercial power source 1, and the current detection values (i _R , i _S , i _T ) of each phase are set to values that are substantially zero. The adjustment operation is completed by holding the output of the holding circuit 46 according to the holding command, and the PWM control self-excited rectifier 40 enters a normal operating state.

FIG. 3 is a detailed circuit configuration diagram of the voltage command value calculation circuit 51 of the PWM control self-exciting rectifier 50 of FIG. 1 showing the second embodiment of the present invention. The voltage command value shown in FIG. Those having the same function as the arithmetic circuit 41 are designated by the same reference numerals. That is, in the voltage command value calculation circuit 51 of FIG. 3, the holding circuit 46 in the voltage command value calculation circuit 41 shown in FIG. 2 is deleted, and the multipliers of the multipliers 43r, 43s, 43t are PI calculators 45r, 45s. , 45 t, respectively.

The operation of the voltage command value calculation circuit 51 shown in FIGS. 1 and 3 will be described below. When the PWM control self-exciting rectifier 50 is in a normal operating state, the effective value calculation circuit 44 has a current command value (i _R ^* , i _S ^* , i _T ^* ) of each phase and a current detection value (i _R ) of each phase. , I _S , i _T ) and the deviations from the effective value calculation circuit 44.
The output value of each of the I calculators 45r, 45s, 45t becomes a multiplier of each of the multipliers 43r, 43s, 43t, and the amplitude of the sine wave signal output from each of the multipliers 43r, 43s, 43t corresponds to the voltage of the commercial power supply 1. Then, the effective values of the deviations are set to values that are substantially zero.

That is, the voltage command value calculation circuit 51 is
Since the above-described settling operation is always performed, the settling operation is performed corresponding to the fluctuation of the voltage of the commercial power source 1. The target settling operation can be performed by providing a rectifier circuit instead of the effective value calculation circuit 44 shown in FIGS. FIG. 6 is a block configuration diagram of a PWM control self-exciting rectifier showing a third embodiment of the present invention. Components having the same functions as those of the conventional example shown in FIG. Is omitted.

That is, in FIG. 6, the PWM control self-exciting rectifier 60 is provided with a voltage command value calculation circuit 61.
A detailed circuit configuration diagram of the arithmetic circuit 61 is shown in FIG. 7, the voltage command value calculation circuit 61 has an adder 42, multipliers 43r, 43s, 43t, and adders 47r, 47s, which have the same functions as the voltage command value calculation circuit 41 shown in FIG.
In addition to 47t, an adder 62, a PI calculator 63, and a holding circuit 64 are provided.

The operation of the voltage command value calculation circuit 61 shown in FIGS. 6 and 7 will be described below. For example, when the PWM control self-exciting rectifier 60 is started, a no-load operation state is provided, and a hold command release signal is input by an operation control circuit (not shown) of the self-exciting rectifier, and in this state, the adjusting operation of the voltage regulator 21 is performed. As a result, the DC voltage across the capacitor 13 rises, and at this time, the deviation between the output value of the voltage regulator 21 and a predetermined reference value (zero) is obtained by the adder 62, and this deviation is proportional / integrated by the PI calculator 63. The calculated value is calculated and the multiplier 43r, 43s, 4 is supplied via the holding circuit 64 to which the release signal is input.
Multipliers 43r, 43s, 4
The amplitude of the sine wave signal, which is the output of each of the 3t, operates so as to correspond to the voltage of the commercial power source 1, and as a result, the output of the voltage regulator 21 is settled to a value at which it becomes almost zero. The adjustment operation is completed by holding the output of the holding circuit 64 at the output value of the arithmetic unit 63 according to the holding command, and the PWM control self-excited rectifier 60 enters a normal operating state.

FIG. 8 shows P showing a fourth embodiment of the present invention.
It is a block configuration diagram of a WM control self-exciting rectifier, FIG.
Components having the same functions as those of the conventional example shown in FIG. That is, in FIG.
The WM control self-exciting rectifier 70 is provided with a DC current detector 32 and an adder 33 for detecting the current flowing in the load 2 in addition to the conventional PWM control self-exciting rectifier 10, and the output of the voltage regulator 21. The value detected by the DC current detector 32 is added to the value by the adder 33, and this added value is used as a new current command value (DC amount). It is well known that the control performance of the output voltage is improved by controlling the device with the new current command value (DC amount) as compared with the conventional control method.

Further, this PWM control self-excited rectifier 70
Is provided with a voltage command value calculation circuit 71, and a detailed circuit configuration diagram of the calculation circuit 71 is shown in FIG. In the voltage command value calculation circuit 71 of FIG. 9, the holding circuit 64 in the voltage command value calculation circuit 61 shown in FIG.
Each of the multipliers of r, 43s, and 43t is configured to be the output value of the PI computing unit 63, and further includes a comparator 72 that determines whether the output value of the PI computing unit 63 is below a predetermined determination value. ing.

The operation of the voltage command value calculation circuit 71 shown in FIGS. 8 and 9 will be described below. In a normal operating state of the PWM control self-exciting rectifier 70, a deviation between the output value of the voltage regulator 21 and a predetermined reference value (zero) is calculated by an adder 62, and this deviation is proportional / integrated by a PI calculator 63. And calculate this proportional
The integral calculation value becomes a multiplier of each of the multipliers 43r, 43s, 43t, and the amplitude of the sine wave signal which is the output of each of the multipliers 43r, 43s, 43t corresponds to the voltage of the commercial power supply 1, and as a result, the output of the voltage regulator. Is set to a value that is approximately zero.

That is, the voltage command value calculation circuit 71 is
Since the settling operation is always performed, the settling operation corresponding to the fluctuation of the voltage of the commercial power source 1 is performed, and the output of the PI calculator 63 at this time has a value corresponding to the voltage of the commercial power source 1. The commercial power supply 1 can be regarded as a power failure in a state of being equal to or less than the determination value of the comparator 72, and the output of the comparator 72 can be input to the operation control circuit (not shown) to stop the device.

In the embodiment of the present invention described above, the commercial power source is 3
Although the example of the phase has been described, the commercial power supply can be a single phase or a multi-phase, and the control constant of the proportional / integral calculation of the PI calculator is sufficiently slower than the control response of the current control system by the current controller. By setting in this way, the stability of the entire control system of this PWM control self-exciting rectifier is not impaired.

[0026]

According to the present invention, by adding a simple circuit function to the control method of the conventional PWM control self-exciting rectifier, the amplitude of the sine wave signal of each phase is the voltage of the commercial power source. Is automatically and individually adjusted to a value corresponding to, and the unbalanced current of the commercial power source due to the imbalance of the amplitude of the sine wave signal between the phases is also eliminated.

Further, according to the third to fourth inventions, the information of the current deviation is not required, and therefore the current control system can use the conventional control method as it is. Further, according to the fifth invention,
In addition to the above effects, it also has the function of detecting a power failure of the commercial power supply.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of a PWM control self-exciting rectifier showing an embodiment of the present invention.

FIG. 2 is a detailed circuit configuration diagram showing a first embodiment of the present invention.

FIG. 3 is a detailed circuit configuration diagram showing a second embodiment of the present invention.

FIG. 4 is a block configuration diagram of a PWM control self-exciting rectifier showing a conventional example.

FIG. 5 is a detailed circuit configuration diagram showing a conventional example.

FIG. 6 is a block configuration diagram of a PWM control self-exciting rectifier showing a third embodiment of the present invention.

FIG. 7 is a detailed circuit configuration diagram showing a third embodiment.

FIG. 8 is a block configuration diagram of a PWM control self-exciting rectifier showing a fourth embodiment of the present invention.

FIG. 9 is a detailed circuit configuration diagram showing a fourth embodiment.

[Explanation of symbols]

1 ... Commercial power supply, 2 ... Load, 10, 40, 50, 60, 7
0 ... PWM control self-exciting rectifier, 11 ... Main circuit of self-exciting rectifier, 12 ... AC reactor, 13 ... Capacitor, 1
4 ... Phase voltage detector, 15 ... Insulation converter, 16 ... Angle signal generating means, 17, 18 ... Reference sine wave generator, 19 ... Voltage setting device, 20 ... Insulation converter, 21 ... Voltage regulator, 22,
23 ... Multiplier, 24 ... Current detector, 25-27 ... Current regulator, 28 ... Voltage command value arithmetic circuit, 28a ... Adder, 2
8b to 28d ... Amplifier, 28e to 28g ... Adder, 29
... carrier signal generator, 30 ... comparator, 31 ... gate drive circuit, 32 ... direct current detector, 33 ... adder, 41,
51, 61, 71 ... Voltage command value arithmetic circuit, 42 ... Adder, 43r, 43s, 43t ... Multiplier, 44 ... Effective value arithmetic circuit, 45r, 45s, 45t ... PI arithmetic unit, 46 ...
Holding circuit, 47r, 47s, 47t ... Adder, 62 ... Adder, 63 ... PI calculator, 64 ... Holding circuit, 72 ... Comparator.

─────────────────────────────────────────────────── --- Continuation of front page (56) References JP-A-8-214550 (JP, A) JP-A-7-337019 (JP, A) JP-A-7-200084 (JP, A) JP-A-6- 133553 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H02M 7/217 H02M 1/08 H02M 7/219

Claims (5)

(57) [Claims] 1. A self-exciting rectifier for converting AC power of a commercial power source to DC power by a self-exciting rectifier and feeding the load, wherein a DC voltage of an output of the self-exciting rectifier is detected. Voltage adjustment calculation is performed so that the voltage becomes a predetermined value, and each phase is calculated by the current command value (DC amount) obtained by this voltage adjustment calculation and the reference sine wave signal of each phase synchronized with the phase of the commercial power supply. A current command value (AC amount) is calculated, each phase current of the commercial power source is detected so as to follow the current command value for each phase, the current is adjusted, and the current for each phase is adjusted. Voltage command value (AC amount) for each phase based on the output and the sine wave signal of each phase adjusted to the specified amplitude of the reference sine wave signal
Is generated, and each phase gate command signal PWM-controlled by each phase voltage command value and the carrier signal is generated, and the PWM control signal for controlling the self-extinguishing type semiconductor element of the self-excited rectifier is generated by each phase gate signal. In the control method of the excitation rectifier, the adjustment value of the amplitude of the reference sine wave signal of each phase for generating the sine wave signal of each phase, the phase current when the phase current command value is zero A method for controlling a PWM control self-exciting rectifier, which is characterized in that an effective value or a rectified value of the detected value is obtained, and the effective value or the rectified value is set and held as a calculated value obtained by performing a proportional / integral operation. 2. A self-exciting rectifier for converting AC power of a commercial power source into DC power by a self-exciting rectifier and feeding the load, wherein a DC voltage output from the self-exciting rectifier is detected. Voltage adjustment calculation is performed so that the voltage becomes a predetermined value, and each phase is calculated by the current command value (DC amount) obtained by this voltage adjustment calculation and the reference sine wave signal of each phase synchronized with the phase of the commercial power supply. A current command value (AC amount) is calculated, each phase current of the commercial power source is detected so as to follow the current command value for each phase, the current is adjusted, and the current for each phase is adjusted. Voltage command value (AC amount) for each phase based on the output and the sine wave signal of each phase adjusted to the specified amplitude of the reference sine wave signal
Is generated, and each phase gate command signal PWM-controlled by each phase voltage command value and the carrier signal is generated, and the PWM control signal for controlling the self-extinguishing type semiconductor element of the self-excited rectifier is generated by each phase gate signal. In the control method of the excitation rectifier, the adjustment value of the amplitude of the reference sine wave signal of each phase for generating the sine wave signal of each phase, the detected value of each phase current command value and each phase current A method for controlling a PWM control self-exciting rectifier, which is characterized in that the effective value of the deviation is calculated, and the effective value is set to a value obtained by proportional / integral calculation. 3. A self-exciting rectifier for converting AC power of a commercial power source into DC power by a self-exciting rectifier and feeding the load, wherein a DC voltage output from the self-exciting rectifier is detected. Voltage adjustment calculation is performed so that the voltage becomes a predetermined value, and each phase is calculated by the current command value (DC amount) obtained by this voltage adjustment calculation and the reference sine wave signal of each phase synchronized with the phase of the commercial power supply. A current command value (AC amount) is calculated, each phase current of the commercial power source is detected so as to follow the current command value for each phase, the current is adjusted, and the current for each phase is adjusted. Voltage command value (AC amount) for each phase based on the output and the sine wave signal of each phase adjusted to the specified amplitude of the reference sine wave signal
Is generated, and each phase gate command signal PWM-controlled by each phase voltage command value and the carrier signal is generated, and the PWM control signal for controlling the self-extinguishing type semiconductor element of the self-excited rectifier is generated by each phase gate signal. In the control method of the excitation rectifier, the adjustment value of the amplitude of the reference sine wave signal of each phase for generating the sine wave signal of each phase, the current command value when the power supplied to the load is zero. A method for controlling a PWM control self-exciting rectifier, which is characterized in that (DC amount) is set and held at a calculated value obtained by proportional / integral calculation. 4. A self-exciting rectifier for converting AC power of a commercial power source to DC power by a self-exciting rectifier and feeding the load, wherein a DC voltage of an output of the self-exciting rectifier is detected. The voltage adjustment calculation is performed so that the voltage becomes a predetermined value, and the current command value (DC amount) obtained by adding the detection value of the load current to the calculation value obtained by the voltage adjustment calculation and the phase of the commercial power supply are synchronized. Each phase current command value (AC amount) is calculated with the reference sine wave signal of each phase, and each phase current of the commercial power supply is detected so as to follow this phase current command value, and the current adjustment calculation is performed. , The phase voltage command value (AC amount) is calculated from the output of the adjustment current of each phase and the sine wave signal of each phase obtained by adjusting the reference sine wave signal to a predetermined amplitude, and the voltage of each phase is calculated. Each phase gate PWM controlled by command value and carrier signal PW for generating a signal and controlling the self-extinguishing type semiconductor device of the self-excited rectifier by the gate signal of each phase
In the control method of the M-controlled self-exciting rectifier, the adjustment value of the amplitude of the reference sine wave signal of each phase for generating the sine wave signal of each phase is proportional-integrally calculated with the adjustment calculation value of the voltage. A method of controlling a PWM control self-excited rectifier, characterized by setting a calculated value. 5. The control method for a PWM control self-exciting rectifier according to claim 4, wherein the commercial power supply is used when the calculated value obtained by proportional / integral calculation of the adjustment calculation value of the voltage becomes a predetermined judgment value or less. A method for controlling a PWM control self-exciting rectifier, characterized in that it is determined to be a power failure.