JP2002233180A - Power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a DC voltage with high precision without having to use a complex circuit configuration by a method, wherein the DC voltage is obtained by utilizing the input/output and voltage/current of a power converter and a control value which controls the power converter. SOLUTION: A primary voltage Vac of a transformer 2 is detected, power P flowing into an AC motor 4 is calculated, and a DC voltage Vdc of the power converter is calculated from the primary voltage Vac of the transformer 2 and the power P flowing into the AC motor 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power conversion device for performing power conversion of an AC power supply and outputting desired polyphase AC power.

[0002]

2. Description of the Related Art Conventionally, as a power conversion device for converting an AC power supply into a desired three-phase power and outputting the converted power, the purpose is to increase the capacity and the voltage of the power conversion device and to improve the output waveform. The configuration shown in FIG. 11 is known.

In this conventional power converter, three-phase AC power is supplied to a single-phase inverter 3 from a three-phase power supply 1 via a transformer 2 having a plurality of windings on the secondary side. The output of the single-phase inverter 3 is connected in series, one of which is connected as a neutral point, and the other is connected to a three-phase induction motor (M) 4, so that three-phase AC power is supplied to the induction motor 4. Supply. The rotation speed of the induction motor 4 is detected by a speed detector 5 and input to a control circuit 6. The current output from the power converter is detected by the current detector 7 and the control circuit 6
Is input to

The control circuit 6 determines output voltage references Vu, Vv, Vw so that the speed of the electric motor 4 becomes a predetermined speed, and outputs it to the PWM control circuit 8. The PWM control circuit 8 controls a gate signal of each single-phase inverter 3 so as to generate an output voltage corresponding to the output voltage references Vu, Vv, Vw. When one of the single-phase inverters 3 fails, the failure signal of the single-phase inverter 3 is output to the PWM control circuit 8.
To stop the operation of the power converter.

FIG. 12 is a detailed diagram of the control circuit 6 of FIG. The control circuit 6 is a widely known circuit (for example, published by Denki Shoin, "New Life Electronics", section 6.2.4), and separates the current of the induction motor 4 into a torque current and an exciting current, and Control.

In the control circuit 6, the speed controller 9 adjusts the torque command T * so that the deviation between the speed command ωr * and the speed ωr becomes zero. On the other hand, the excitation command Φ * is usually kept constant. In the figure, the set value of the excitation command Φ * is denoted by Φset. These values are converted into orthogonal two-phase d-axis and q-axis current commands Id * and Iq * by the operation shown in the block diagram of FIG. 12, and the deviation from each of the current feedback signals Id and Iq is zero. The voltage commands Vd and Vq for the d-axis and the q-axis are
Adjust

The slip frequency ωs is determined from the torque command T * and the excitation command Φ *, and the speed signal ωr fed back from the speed detector 5 is added to the slip frequency ωs to determine the frequency ω1 output from the power converter. . Using the output phase θ1 obtained by integrating this output frequency ω1, the three-phase to two-phase converter 1 detects the three-phase current detection values Iu, Iv, Iw.
1, the d-axis and q-axis currents Id and Iq are determined, and the two-phase to three-phase converter 12 determines output voltage references Vu, Vv and Vw from the d-axis and q-axis voltage commands.

FIG. 13 is a detailed view of the single-phase inverter 3 of FIG. The power from the secondary winding of the transformer 2 is converted into DC power by the diode rectifier circuit 13 and the DC smoothing capacitor 14, and further converted to power having an arbitrary frequency and voltage by the single-phase inverter circuit 15. The failure detector 16 detects an abnormality of the single-phase inverter 3 and outputs a failure signal to P in FIG.
Output to the WM control circuit 8.

An example of the abnormality of the single-phase inverter 3 is considered to be an increase in the DC voltage Vdc. Normally, when the DC voltage Vdc rises above a predetermined value, it is common practice to stop the power converter by detecting a failure so that components in the single-phase inverter 3 are not damaged by the overvoltage.

[0010]

However, in the power converter constructed as described above, when the output frequency of the power converter is lower than the rotational speed of the AC motor 4, the mechanical energy of the AC motor is reduced. Is regenerated by the power converter, the DC voltage is charged by the regenerative energy, the DC voltage rises, an overvoltage failure is detected, and the device stops even though it is not a failure.

In order to solve this problem, it is sufficient to detect an increase in the DC voltage Vdc before detecting an overvoltage failure and control the output frequency to increase so as not to perform a regenerative operation. When performing this control, it is necessary to take in the DC voltage value Vdc of each single-phase inverter 3 into the control circuit 6.

However, as shown in FIG. 11, in a power converter having a multiple connection inverter configuration using a plurality of single-phase inverters 3, the DC voltage detection circuit is very complicated and expensive because there are a plurality of DC circuits. There is. In addition, even in the case of a single inverter regardless of the multiple connection inverter, it is common to perform voltage detection while insulating the control circuit and the DC circuit. And the control circuit are insulated,
There is a problem that the voltage detection circuit becomes complicated, reliability is reduced, and detection accuracy is reduced.

In view of the above-mentioned problems in the prior art, the present invention obtains a DC voltage by using the input or output voltage and current of the power converter and the control amount for controlling the power converter. It is an object of the present invention to provide a power converter capable of obtaining a DC voltage with high accuracy without using a circuit configuration.

Another object of the present invention is to provide a power converter that does not stop by erroneously detecting an overvoltage fault by utilizing the obtained DC voltage.

[0015]

According to a first aspect of the present invention, there is provided a transformer comprising a multi-phase primary winding and a poly-phase secondary winding, and a multi-phase transformer connected to the secondary winding of the transformer. A rectifier circuit that converts an AC voltage into a DC voltage, an inverse converter circuit that is connected to the rectifier circuit and converts the DC voltage into an AC voltage corresponding to a voltage reference signal, and an output of the inverse converter circuit in series or in parallel. An input voltage detecting means for detecting a voltage on a primary side of the transformer, wherein the input voltage detecting means detects the voltage on the primary side of the transformer, and supplies the polyphase AC power to the polyphase AC motor. Motor input power calculating means for calculating the power flowing into the motor; and DC voltage calculating means for calculating the DC voltage from the voltage on the primary side of the transformer and the power flowing into the AC motor. It is.

In the power converter according to the first aspect of the present invention, the voltage on the primary side of the transformer is detected, the power flowing into the AC motor is calculated, and the voltage on the primary side of these transformers and the AC motor are calculated. And the DC voltage of the power converter is calculated from the power flowing into the power converter.

According to a second aspect of the present invention, in the power converter according to the first aspect, the DC voltage calculating means determines that the power flowing into the AC motor is equal to or more than a predetermined value, the DC voltage calculating means is provided on the primary side of the transformer. Calculating the DC voltage from a voltage and the power flowing into the AC motor, and integrating the power flowing into the AC motor when the power flowing into the AC motor is equal to or less than a predetermined value. It is.

In the power converter according to the present invention, when the power flowing into the AC motor is equal to or more than a predetermined value, the DC voltage is calculated from the voltage on the primary side of the transformer and the power flowing into the AC motor. If the power flowing into the AC motor is equal to or less than a predetermined value, the DC voltage is obtained by integrating the power flowing into the AC motor.

A third aspect of the present invention provides a multi-phase primary winding and a multi-phase secondary winding.
A transformer comprising a secondary winding, a rectifier circuit connected to the secondary winding of the transformer, for converting a multi-phase AC voltage to a DC voltage, and a rectifier circuit connected to the rectifier circuit, for converting the DC voltage to a voltage. An inverting circuit for converting to an AC voltage corresponding to a reference signal, and connecting the outputs of the inverting circuit in series or in parallel to generate polyphase AC power, and supplying the polyphase AC power to the polyphase AC motor In the power converter, input voltage detecting means for detecting a voltage on a primary side of the transformer, input current detecting means for detecting a current on a primary side of the transformer, and a voltage on a primary side of the transformer And a DC voltage calculating means for calculating the DC voltage from the current on the primary side of the transformer.

In the power converter according to the third aspect of the present invention, the voltage on the primary side of the transformer is detected, the current on the primary side of the transformer is detected, and the voltage on the primary side of these transformers is detected. The DC voltage of the power converter is calculated and obtained from the current.

According to a fourth aspect of the present invention, there is provided a multi-phase primary winding and a multi-phase secondary winding.
A transformer comprising a secondary winding, a rectifier circuit connected to the secondary winding of the transformer, for converting a multi-phase AC voltage to a DC voltage, and a rectifier circuit connected to the rectifier circuit, respectively. A reverse conversion circuit for converting to an AC voltage corresponding to a signal, and an output of the reverse conversion circuit connected in series or parallel to generate polyphase AC power, and power for supplying the polyphase AC power to the polyphase AC motor A converter that determines a voltage reference signal to the power converter based on a torque reference and an excitation reference of the AC motor; and a frequency detector that detects a frequency output by the power converter or a speed of the AC motor. And an AC voltage for calculating an AC voltage output by the power converter from the frequency output by the power converter or the speed of the AC motor and the excitation reference. A force calculation means, in which from the computed value of the voltage reference signal and the AC voltage to which the power converter is output to the power converter comprising; and a DC voltage calculating means for calculating the DC voltage.

According to a fourth aspect of the present invention, a voltage reference signal to the power converter is determined based on the torque reference and the excitation reference of the AC motor, and the frequency output by the power converter or the speed of the AC motor is determined. And calculates the AC voltage output by the power converter from the frequency output by the power converter or the speed of the AC motor and the excitation reference. Then, a DC voltage of the power converter is calculated and obtained from the voltage reference signal for the power converter and a calculated value of the AC voltage output by the power converter.

According to a fifth aspect of the present invention, in the power conversion device according to any one of the first to fourth aspects, when the DC voltage is equal to or higher than a predetermined value, the DC voltage is output in a direction to increase the frequency output from the power conversion device. It is provided with a DC voltage correcting means for correcting or a frequency decrease suppressing means for suppressing the decrease in the frequency.

According to a fifth aspect of the present invention, when the DC voltage of the power converter obtained by the calculation in the first to fourth aspects becomes equal to or higher than a predetermined value, the frequency output by the power converter is obtained. To correct the DC voltage in the direction in which the power conversion device increases, or to suppress a decrease in the frequency output by the power converter.

According to a sixth aspect of the present invention, in the power converter of the first to fourth aspects, output stopping means for stopping output of the power converter when the DC voltage exceeds a predetermined value is provided. is there.

According to a sixth aspect of the present invention, the output of the power converter is stopped when the DC voltage of the power converter obtained by the calculation in the first to fourth aspects becomes a predetermined value or more. .

According to a seventh aspect of the present invention, in the power converter of the first to fourth aspects, output voltage calculating means for calculating an AC voltage output from the power converter from the calculated value of the DC voltage and a voltage reference signal. It is provided.

According to a seventh aspect of the present invention, an AC voltage output from the power converter is calculated from the DC voltage of the power converter and the voltage reference signal obtained by the calculation in the first to fourth aspects of the present invention. Ask.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings.

(First Embodiment) A first embodiment of the present invention will be described with reference to FIG. In the components of the power converter according to the first embodiment shown in FIG.
The same components as those in the conventional example shown in FIG. 11 are denoted by the same reference numerals. 11 is different from the conventional example of FIG. 11 in that an effective value Vac of the primary voltage of the transformer 2 (hereinafter referred to as “input voltage”) is detected by an input voltage detector 17, read by a control circuit 6 A, and The point is that the voltage Vdc is used for calculation processing.

FIG. 2 shows a control block diagram of the control circuit 6A. In the components of the control circuit 6A shown in FIG. 2, the same components as those of the control circuit 6 of the conventional example shown in FIG. 12 are denoted by the same reference numerals. The difference from the conventional example of FIG. 12 is that the output P of the AC motor 4 is obtained from the torque command T * and the speed ωr, and the DC voltage Vdc is calculated using the output P and the input voltage Vac.

The calculation of the DC voltage Vdc is based on the AC voltage Vdc.
Although ac and the DC voltage Vdc are in a substantially proportional relationship, when the load of the transformer 2 increases, the characteristic that the DC voltage Vdc decreases by the impedance drop of the transformer 2 is simulated.

According to the power converter of the first embodiment, since the DC voltage Vdc is obtained by calculation, a power converter that does not require a DC voltage detection circuit or a transmission circuit that takes in the DC voltage into the control circuit is configured. be able to.

In the first embodiment, the electric power flowing into the electric motor 4 is substantially equivalent to the electric motor output P and the torque command T
Although it is obtained from the product of * and the speed ωr, it may be configured to detect and obtain the voltage and current output by the power conversion device, or may be obtained from the voltage reference signal commanded to the power conversion device and the current detection value, etc. It may be configured.

Furthermore, the first embodiment has a simple configuration utilizing the characteristic that the DC voltage Vdc is reduced by the impedance drop of the transformer 2 when the load on the transformer 2 is increased. The current flowing through the transformer 2 is calculated from the power, the conversion efficiency of the power converter, the input voltage, and the like, and the impedance drop is strictly calculated from the current and the impedance of the transformer 2 to obtain the DC voltage Vdc. Good.

(Second Embodiment) A second embodiment of the present invention will be described with reference to FIGS. Second
The overall configuration of the power converter according to this embodiment is the same as that of the first embodiment shown in FIG. The detailed configuration of the control circuit 6A is as shown in FIG. 3, which is different from that of the first embodiment shown in FIG. In FIG. 3, the same components as those of the control circuit according to the first embodiment shown in FIG. 2 will be described using the same reference numerals.

The difference between the control circuit 6A of this embodiment and that of the first embodiment shown in FIG. 2 is that the polarity of the motor output P is determined by the polarity determiner 18 and the polarity is positive. The point is that the DC voltage Vdc is calculated and output in the same manner as in the first embodiment, and is switched to output the DC voltage Vdc calculated by the DC voltage calculator 19 during regeneration in the case of a negative value.

The regenerative DC voltage calculator 19 operates as follows. The single-phase inverter 3 in the power converter of FIG. 1 has the same configuration as the single-phase inverter 3 shown in FIG.
3 is provided. Therefore, when the power converter enters the regenerative state, all the diodes are turned off, and the input of the rectifier circuit 13 is disconnected from the DC circuit. That is, all the electric power from the electric motor 4 is charged in the DC smoothing capacitor 14. The regenerative DC voltage calculator 19 uses the regenerative electric power from the electric motor 4 at the time of regeneration to generate the smoothing capacitor 14.
Is charged and the DC voltage Vdc is calculated by simulating the rise of the DC voltage. The specific method of the calculation is as follows.

The charging energy Uo of the smoothing capacitor 14 before entering the regenerative state can be obtained by Expression 1 using the DC voltage Vdc at that time.

[0040]

(Equation 1) Here, C is the capacitance of the capacitor.

The relationship between the DC voltage Vdc, the electric power P, and the charging energy U of the capacitor when t seconds have elapsed after entering the regenerative state can be obtained by equation (2).

[0042]

(Equation 2) From this equation (2), the operation value Vdc of the DC voltage is obtained by equation (3).

[0043]

[Equation 3] That is, as shown by the internal block of the DC voltage calculator 19 during regeneration in FIG. 3, the initial value Uo of integration is set in the integrator from the DC voltage at the time when regeneration starts, and the power P during regeneration is integrated. By calculating the square root, the DC voltage Vdc during regeneration is calculated.

According to the second embodiment, the same effect as that of the first embodiment can be obtained, and the DC voltage Vdc can be correctly obtained even when the electric power is supplied from the electric motor 4.

(Third Embodiment) A third embodiment of the present invention will be described with reference to FIGS. FIG.
In the components of the power converter according to the present embodiment shown in FIG. 1, the same components as those in the first embodiment shown in FIG. 1 are denoted by the same reference numerals. This embodiment differs from the first embodiment in FIG. 1 in that the current detector 7A and the input current detector 20 use the primary current effective value Iac of the transformer 2 (hereinafter referred to as “input current”). ) Is detected, and the control circuit 6B reads the input current Iac and uses it for the arithmetic processing of the DC voltage Vdc.

The control operation of the control circuit 6B according to the third embodiment will be described with reference to FIG. In the components of the control circuit 6B shown in FIG. 5, the same components as those of the control circuit 6 of the conventional example shown in FIG. 12 are denoted by the same reference numerals. The difference from the conventional example of FIG. 12 is that the DC voltage Vdc is calculated using the input voltage Vac and the input current Iac.

In the calculation of the DC voltage Vdc, the DC voltage Vd
Although c is substantially proportional to the input AC voltage Vac, it simulates the characteristic that when the current of the transformer 2 increases, the DC voltage Vdc decreases by the impedance drop of the transformer 2.

Also in the third embodiment, since the DC voltage Vdc is obtained by calculation, it is possible to configure a power conversion device that does not require a DC voltage detection circuit or a transmission circuit for taking the DC voltage into the control circuit. .

(Fourth Embodiment) A fourth embodiment of the present invention will be described with reference to FIG. The power converter according to the fourth embodiment has the same basic circuit configuration as that of the conventional example shown in FIG. 11, but the control circuit 6 is replaced by a control circuit 6 'shown in FIG.
In the configuration of

The control circuit 6 'of this embodiment shown in FIG.
Of the components described above, the same components as those in the control circuit of FIG. 12 will be described using the same numbers. The difference from the conventional control circuit of FIG. 12 is that the voltage command V * is calculated from the product of the magnetic flux command Φ * and the speed ωr, and the output voltage references Vu, V
PWM control circuit 8 from modulation rate calculator 21 based on v and Vw
Of the DC voltage Vdc from the ratio V * / α.
Is calculated.

Next, a specific method of this calculation will be described.
It is known that the vector control circuit 6 'shown in FIG. 6 can control magnetic flux and torque with high accuracy. The input voltage V of the motor 4 is equal to the equation (4).

[0052]

(Equation 4) On the other hand, the modulation factor α and the output voltage of the power converter (= motor 4
The relationship between the input voltage) V and the DC voltage Vdc is given by equation (5).

[0053]

(Equation 5) Here, K: proportional constant.

From the equations (4) and (5), the DC voltage V
dc can be obtained by equation (6).

[0055]

(Equation 6) In the fourth embodiment, the detection of the voltage and current on the primary side of the transformer 2 which is required in the first to third embodiments is unnecessary, and the detection of the DC voltage Vdc is performed only by the control variable. There is an advantage that is possible. There is also an advantage that the DC voltage can be detected both during power running and during regeneration.

In the present embodiment, the speed ωr is used for the DC voltage calculation, but the output frequency ω1 can be used instead.

(Fifth Embodiment) A fifth embodiment of the present invention will be described with reference to FIGS. The circuit configuration of this embodiment is similar to that of the first embodiment.
However, the difference is that the control circuit 6A has the configuration shown in FIG. In the components of the control circuit 6A shown in FIG. 7, the same components as those in the control circuit of FIG. 2 will be described using the same numbers.

The control circuit 6A of this embodiment differs from the control circuit of the first embodiment shown in FIG.
DC voltage Vdc detected by calculation and DC voltage reference Vdc *
Is input to the negative limiter 22, and the voltage controller 23 corrects and inputs the speed command ωr * in the increasing direction only when the difference output is positive.

By setting DC voltage command Vdc * lower than the overvoltage protection level for single-phase inverter 3 of the power converter, the speed of AC motor 4 is accelerated before the overvoltage protection is activated when the DC voltage rises. DC voltage V
dc can be suppressed, and the device can be prevented from being erroneously stopped by overvoltage protection.

Although not shown, the speed reference from the outside of the power converter may be used as the speed reference of the power converter by limiting the rate of change. Is in a regenerative state, and when the DC voltage Vdc exceeds the DC voltage reference Vdc *, the change in the speed reference of the power converter is set to 0. This means that the correction is performed in the increasing direction, and is included in the present invention.

Also, in the fifth embodiment, the first
Although the DC voltage Vdc calculated in the embodiment is used, the DC voltage Vdc calculated in any of the second to fourth embodiments described above may be used as the DC voltage Vdc.

(Sixth Embodiment) A sixth embodiment of the present invention will be described with reference to FIGS. In the components of the power converter according to the sixth embodiment shown in FIG. 8, the same components as those of the first embodiment shown in FIG. 1 are denoted by the same reference numerals. This embodiment is different from the power converter of the first embodiment shown in FIG. 1 in that a failure signal of each single-phase inverter 3 is not input to the PWM control circuit 8A, and that the DC voltage Vdc Is higher than the overvoltage protection level, the control circuit 6C outputs a stop signal GB to the PWM control circuit 8A to stop the device.

The control operation of control circuit 6C will be described with reference to FIG. In the components of the control circuit 6C shown in FIG. 9, the same components as those of the control circuit 6A of FIG. 2 will be described using the same numbers.

The control circuit 6C of this embodiment differs from the control circuit of FIG. 2 in that the DC voltage Vd
c is compared with the DC voltage protection setting Vdc ** by the comparator 24, and when the DC voltage Vdc exceeds the protection setting Vdc **, a stop signal GB is output to the PWM control circuit 8A.

With this configuration, it is not necessary for each single-phase inverter 3 to individually detect the overvoltage protection of the DC voltage. However, the present invention includes a case where the DC overvoltage protection and the DC overvoltage protection of the present embodiment are used in combination in each single-phase inverter 3.

The GB signal from the control circuit 6C is converted into a PWM signal.
Outputting to the control circuit 8A and stopping the inverter is performed by changing the DC voltage Vdc obtained in the first to fifth embodiments or the seventh embodiment to the DC overcurrent protection setting Vdc.
It can also be done in comparison with **.

(Seventh Embodiment) A seventh embodiment of the present invention will be described with reference to FIGS. The power conversion device of the present embodiment has a circuit configuration common to the first embodiment shown in FIG. However, the difference from the first embodiment is that the control circuit 6A has the configuration shown in FIG. In the control circuit 6A shown in FIG.
The same components as those of the control circuit of FIG. 2 are denoted by the same reference numerals.

The difference between the control circuit 6A of the present embodiment and the control circuit of FIG. 2 is that the modulation rate α is obtained by using the modulation rate calculator 21 and the DC voltage Vdc and the modulation rate α obtained by the calculation are obtained. The point is that the output voltage Vmot of the power converter is obtained from the product.

With this configuration, an output voltage detection circuit is not required. Note that the output voltage obtained by the control circuit 6A of the present embodiment is a voltage display, output voltage control,
It can be used for overvoltage protection of output voltage. However,
The application of the obtained output voltage is not particularly limited, and the present embodiment is characterized in that a DC voltage is calculated and the output voltage is calculated based on the DC voltage.

Although the DC voltage Vdc calculated in the first embodiment is used in the seventh embodiment, the DC voltage calculated in the second to fourth embodiments is used instead. be able to.

Although not shown, the output voltage references Vu, Vv, Vw of the U, V, W phases and the DC voltage V
a method of calculating the output voltage of each phase from the product of dc and dc,
The present invention also includes a method for obtaining the d-axis and q-axis voltages from the product of the d-axis and q-axis output voltage references Vd and Vq and the DC voltage Vdc obtained by calculation.

The first to seventh embodiments have been described above. In each embodiment, a method of detecting a DC overvoltage in each single-phase inverter 3 has been described as an example.
Even if a DC overvoltage is not detected in each single-phase inverter 3, it is included in the present invention. In the first to seventh embodiments, the example in which the transformer 2 and the single-phase inverter 3 are multiplex-connected has been described. In other configurations of the power converter, the inverter is connected to the secondary side of the transformer. What is done is included in the present invention.

Further, in these embodiments, the speed control using the speed detector 5 has been described. However, in the case where the speed control is performed by speed estimation without using the speed detector, or when the speed control is performed. Instead, the present invention includes a case where the output frequency is adjusted.

[0074]

As described above, according to the present invention, the DC voltage of the power converter is calculated by calculation, so that it is not necessary to directly detect the DC voltage, and the DC voltage detection circuit can be simplified.

Further, in a state where the DC voltage rises due to power regeneration or the like, if the DC voltage rise is suppressed before the device stops operating due to overvoltage protection, the operation of the power converter can be continued. become.

Further, if the DC voltage is obtained by calculation and the output voltage of the power converter is obtained by calculation without using a detector, the AC voltage detection circuit can be simplified.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a power conversion device according to a first embodiment of the present invention.

FIG. 2 is a control block diagram of a control circuit according to the first embodiment.

FIG. 3 is a control block diagram of a control circuit according to a second embodiment of the present invention.

FIG. 4 is a circuit diagram showing a configuration of a power conversion device according to a third embodiment of the present invention.

FIG. 5 is a control block diagram of a control circuit according to the third embodiment.

FIG. 6 is a control block diagram of a control circuit according to a fourth embodiment of the present invention.

FIG. 7 is a control block diagram of a control circuit according to a fifth embodiment of the present invention.

FIG. 8 is a circuit diagram showing a configuration of a power conversion device according to a sixth embodiment of the present invention.

FIG. 9 is a control block diagram of a control circuit according to the sixth embodiment.

FIG. 10 is a control block diagram of a control circuit according to a seventh embodiment of the present invention.

FIG. 11 is a circuit diagram showing a configuration of a conventional power converter.

FIG. 12 is a control block diagram of a control circuit in a conventional example.

FIG. 13 is a circuit diagram showing a configuration of a single-phase inverter in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... 3 phase power supply 2 ... Transformer 3 ... Single phase inverter 4 ... Motor 5 ... Speed detector 6, 6 ', 6A, 6B, 6C ... Control circuit 7, 7A ... Current detector 8, 8A ... PWM control circuit 9 ... speed controller 10 ... current controller 11 ... three-phase to two-phase converter 12 ... two-phase to three-phase converter 13 ... rectifier circuit 14 ... smoothing capacitor 15 ... single-phase inverter circuit 16 ... fault detector 17 ... input voltage Detector 18 Polarity determiner 19 DC voltage calculator during regeneration 20 Input current detector 21 Modulation rate calculator 22 Negative limiter 23 Voltage controller 24 Comparator

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) HA03 HA09 HB08 HB16 JJ04 JJ22 JJ23 JJ30 LL01 LL21 LL22 LL23 LL32 LL52 LL60 MM03 5H576 BB06 DD02 DD04 EE01 EE11 GG02 GG04 HB02 HB05 JJ22 JJ23 LL01 LL22 LL24 LL28 LL30

Claims (7)

[Claims] 1. A transformer comprising a polyphase primary winding and a polyphase secondary winding, and a rectifier circuit respectively connected to the secondary winding of the transformer and converting a polyphase AC voltage into a DC voltage. A reverse conversion circuit connected to the rectifier circuit for converting the DC voltage into an AC voltage corresponding to a voltage reference signal, and connecting the output of the reverse conversion circuit in series or parallel to generate multiphase AC power. A power converter for supplying the polyphase AC power to a polyphase AC motor, an input voltage detecting means for detecting a voltage on a primary side of the transformer, and a motor input power for calculating a power flowing into the AC motor. A power converter comprising: an arithmetic unit; and a DC voltage arithmetic unit that calculates the DC voltage from a voltage on the primary side of the transformer and electric power flowing into the AC motor. 2. The method according to claim 1, wherein when the power flowing into the AC motor is equal to or greater than a predetermined value, the DC voltage calculating means determines the DC voltage based on a voltage on the primary side of the transformer and the power flowing into the AC motor. The power converter according to claim 1, wherein when the power flowing into the AC motor is equal to or less than a predetermined value, the power flowing into the AC motor is integrated. 3. A transformer comprising a polyphase primary winding and a polyphase secondary winding, respectively connected to a secondary winding of the transformer,
A rectifier circuit for converting a polyphase AC voltage to a DC voltage, an inverse converter circuit connected to the rectifier circuit for converting the DC voltage into an AC voltage corresponding to a voltage reference signal, and an output of the inverse converter circuit in series Or in parallel to generate polyphase AC power and supply the polyphase AC power to a polyphase AC motor, in a power converter, an input voltage detection means for detecting a voltage on a primary side of the transformer; Input current detecting means for detecting a current on the primary side of the transformer; DC voltage calculating means for calculating the DC voltage from a voltage on the primary side of the transformer and a current on the primary side of the transformer; A power conversion device comprising: 4. A transformer comprising a polyphase primary winding and a polyphase secondary winding, and a rectifier circuit connected to each of the secondary windings of the transformer for converting a polyphase AC voltage to a DC voltage. A reverse conversion circuit connected to the rectifier circuit for converting the DC voltage into an AC voltage corresponding to a voltage reference signal, and connecting the output of the reverse conversion circuit in series or parallel to generate multiphase AC power. A power converter that supplies the polyphase AC power to a polyphase AC motor, wherein a means for determining a voltage reference signal to the power converter based on a torque reference and an excitation reference of the AC motor; The power converter is output from the frequency detector that detects the output frequency or the speed detector that detects the speed of the AC motor, and the frequency output from the power converter or the speed of the AC motor and the excitation reference. AC voltage output calculating means for calculating the AC voltage to be applied, and DC voltage calculating means for calculating the DC voltage from the voltage reference signal for the power converter and the calculated value of the AC voltage output from the power converter. Power converter. 5. A DC voltage correcting means for correcting the DC voltage in a direction in which the frequency output by the power conversion device increases when the DC voltage becomes a predetermined value or more, or a frequency reduction for suppressing a decrease in the frequency. The power converter according to any one of claims 1 to 4, further comprising a suppression unit. 6. The power converter according to claim 1, further comprising output stop means for stopping the output of the power converter when the DC voltage becomes equal to or higher than a predetermined value. apparatus. 7. An output voltage calculating means for calculating an AC voltage output from the power converter from a calculated value of the DC voltage and a voltage reference signal.
5. The power converter according to any one of 4.