JP2002238268A - Controller of power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the occurrence of a leak current caused by the existence of the floating capacity of each part of DC, by reducing the fluctuation of potential to ground of each part of DC, without using an insulating transformer. SOLUTION: In the controller of a power converter, which is linked to a three-phase system where one of the transformer winding connected in V or connected in delta is grounded at the midpoint of the winding and converts DC power into AC power and supplies it to the three-phase system, the power converter is composed of three sets of half bridge circuits 4, 5, and 6, and the output currents of the two sets of half bridge circuits 4 and 6 out of three sets of half bridge circuits 4, 5, and 6 are controlled into desired values, and the output voltage of the left one set of half bridge circuit 5 out of the three sets of half bridge circuits 4, 5, and 6 is controlled into a phase and an amplitude equivalent to the voltage difference between the output line of the half bridge circuit 5 concerned and the ground potential.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a power converter that converts DC power into AC power and supplies the AC power to a three-phase system. The present invention relates to a power converter control device capable of reducing fluctuations and reducing the occurrence of leakage current due to the presence of stray capacitance in each DC part.

[0002]

2. Description of the Related Art FIG. 11 is a block diagram showing a typical configuration example of a system using such a conventional power converter control device.

In FIG. 11, DC power of a DC power supply 1 is converted into desired AC power by an inverter bridge 2 which is a power converter, and the AC power is supplied to a three-phase three-wire system 3 in an interconnected manner. You.

The inverter bridge 2 is composed of three sets of half bridge circuits 4, 5, and 6 connected between the positive and negative electrodes of the DC power supply 1.

The half-bridge circuit 4 connects the switches 7 and 8 in series, the half-bridge circuit 5 connects the switches 9 and 10 in series, and the half-bridge circuit 6 connects the switches 11 and 12. It is configured by connecting in series.

Here, the switches 7, 8, 9, 10, 1
1G, 1G with anti-parallel diode added
Generally, a semiconductor switch such as a BT is used.

On the system side of the bridge output points of the half bridge circuits 4, 5, and 6, reactors 13, 14, and 15 are provided.
Current detector 1 for detecting the current of reactors 13 and 15
6, 17 are connected.

On the DC side of the inverter bridge 2, by connecting capacitors 18 and 19 having a sufficiently large capacity in series, two DC power supplies necessary for the half bridge circuits 4, 5 and 6 are secured. I have.

The two DC power supplies serve as input power supplies common to the half-bridge circuits 4, 5, and 6.

Each of the half-bridge circuits 4, 5, and 6 generates an AC voltage between an intermediate point between the capacitors 18 and 19 and a bridge output point.

By switching this AC voltage into a PWM waveform and switching at a high frequency, a relatively smooth current can flow in the reactors 13, 14, and 15, but the ripple of the current due to the switching is superimposed.

In order to reduce the outflow of the ripple current to the system 3, an intermediate point between the capacitors 18 and 19 is provided.
Capacitors 20, 21, 22 are connected between the reactors 13, 14, 15 and the system 3 side.

In FIG. 11, each line of the system 3 is denoted by R, S, and T. If the electric system is a three-wire system, the current of the remaining one wire is automatically determined by determining the current of the two wires.

Here, it is assumed that the half-bridge circuit 4 and the half-bridge circuit 6 control the R and T currents of the system 3.

The half bridge circuit 5 plays an auxiliary role, and enables voltage control between an intermediate point between the capacitors 18 and 19 and the S line of the system 3.

The output is controlled by the output reference generators 23 and 2
This is performed based on the reference signals from 4, 25.

Output reference generator 23 and output reference generator 25
Outputs the current reference, and the current control
Based on the current detection signal from the current detector 17, the current controller 26 and the current controller 27 execute the operation.

The current controllers 26 and 27 have, for example, a proportional-integral control function and output an output command signal.

The PWM modulators 28, 29 and 30 generate a PWM signal based on the output command signal. The PWM modulator 28 controls the switch 7 and the switch 8, the PWM modulator 29 controls the switch 9 and the switch 10, and the PWM modulator 29 controls the switch 9 and the switch 10. Modulator 30 is switch 1
1 and the switch 12 are respectively driven.

Here, the command signal input to the PWM modulator 29 relates to voltage control.

Voltage control is performed by a voltage controller 32 based on a voltage reference from an output reference generator 24 and an output signal from a voltage detector 31 for detecting the voltage of the capacitor 21. The voltage controller 32 has, for example, a proportional-integral control function. In the case of a three-phase output, the outputs of the output reference generator 23 and the output reference generator 25 are sine waves having a phase difference of 120 degrees.

A sine wave generator 33 is provided and input to a phase shifter 34 for delaying the phase of its output by 120 degrees.

The output of the phase shifter 34 is
Another phase is input to a phase shifter 35 which delays the phase by 120 degrees.

The outputs of the sine wave generator 33, the phase shifter 34, and the phase shifter 35 are sine waves having a phase difference of 120 degrees from each other.

The direction in which the phase is shifted depends on the phase sequence of the system voltage.

The outputs of the sine wave generator 33 and the phase shifter 35 are input to the output reference generators 23 and 25, respectively.

FIG. 12 is a block diagram showing a configuration example of the output reference generator 23 and the output reference generator 25.

In FIG. 12, the amplitude signal from the current amplitude setting unit 36 is multiplied by a multiplier 37 to be output from the output reference generator 23 and the output reference generator 25.

FIG. 13 shows the PWM modulators 28, 29 and 30.
FIG. 3 is a block diagram illustrating a configuration example of FIG.

In FIG. 13, the PWM modulators 28 and 2
In 9 and 30, the modulator 38 performs PWM modulation based on the input signal, and the drive circuit 39 generates a drive signal.

First, consider the case where the system 3 grounds one terminal of the V connection or the delta connection on the low voltage side of the transformer as shown in FIG.

Here, it is assumed that a line serving as a ground potential is connected to an inverter as an S line.

In this case, the output from the output reference generator 24 is always set to zero.

Since the output of the half bridge circuit 5 is controlled to zero voltage, the voltage difference between the intermediate point between the capacitors 18 and 19 and the S line becomes zero, and the intermediate point between the capacitors 18 and 19 is set to the ground potential. Become equal.

As a result, the potential of each DC component with respect to the ground is always constant.

Next, consider the case where the system 3 is star-connected on the low voltage side of the transformer and the neutral point is grounded, as shown in FIG.

The phases and amplitudes of the three line voltages are determined by the system 3, but within the power converter, the three phase voltages are undefined.

Here, by determining the phase and amplitude of one of the three phase voltages, the remaining two phase voltages are automatically determined.

FIG. 15 is a vector diagram showing such a situation.

In FIG. 15, VRS represents the voltage vector of the R line with respect to the S line, VST represents the voltage of the S line with respect to the T line,
VTR indicates a voltage vector of the T line with respect to the R line.

Each voltage vector has a phase difference of 120 degrees from each other and the same amplitude.

The three undefined phase voltages VR, VS, VT
By determining the point O shown in FIG. 15, the phase and the amplitude are determined.

The point O is determined by determining one phase and amplitude of the three phase voltages.

In this embodiment, the phase voltage VS is changed to the line voltages VRS and VRS.
It is determined by calculating from ST, and the control of VS is performed by the voltage control of the power converter.

From FIG. 15, the phase of VS is 150 degrees (5 / 6π) behind that of VRS, and the amplitude is 1 / √ of the line voltage.
3 times.

The phase voltage VS is determined by the line voltage VRS and the line voltage V
It is obtained from ST by the following equation (1).

VS = (VST−VRS) / 3 (1) When this vector operation is performed using a scalar quantity, the following is performed.

The line voltages VRS and VST are expressed by the following equations (2) and (3) when the amplitude is V, the angular frequency is ω, and the time is t.

VRS = V × sin (ωt) (2) VST = V × sin (ωt−2 / 3π) (3) VS is delayed by 150 degrees from VRS, and the amplitude is 1 / √3 times the line voltage. Therefore, VS is given by the following equation (4): VS = V / √3 × sin (ωt−5 / 6π) (4) Here, when VST−VRS is calculated, the following equation (5) is obtained. Becomes

VST−VRS = V × sin (ωt−2 / 3π) −V × sin (ωt) = V × ((− 3/2) sin (ωt) − (√3 / 2) cos (ωt)) = V × √3 × sin (ωt−5 / 6π) (5) From the above equations (4) and (5), VS is obtained by the following equation (6), as in the above equation (1). You can see that.

VS = (VST−VRS) / 3 (6) FIG. 14 is a block diagram showing a configuration example of the output reference generator 24.

In FIG. 14, a voltage detector 40 and a voltage detector 41 for detecting the line voltage of the system 3 are provided.

The voltage detector 40 detects the voltage of the S line with respect to the R line, and the voltage detector 41 detects the voltage of the S line with respect to the T line.

The outputs of the voltage detector 40 and the voltage detector 41 are added by an adder 42.

The output of the adder 42 is input to a third multiplier 43 and converted into a signal of 1/3.

By using the output of the third multiplier 43 as the output of the output reference generator 24, the above equation (6) can be realized.

Here, since the voltage detector 40 detects the voltage of the S line with respect to the R line, it detects -VRS on the right side of the above equation (6).

Further, since the voltage detector 41 detects the voltage of the S line with respect to the T line, VST on the right side of the above equation (6) is obtained.
Is detected.

As a result, the output from the adder 42 calculates (VST-VRS) on the right side of the above equation (6).

Since the third multiplier 43 multiplies this signal by 1/3, the output from the third multiplier 43 is obtained by the above (6).
VS, which is the left side of the equation.

In FIG. 14, the output from the third multiplier 43 becomes the output of the output reference generator 24. As a result of the voltage control by the voltage detector 31 and the voltage controller 32, the voltage of the capacitor 21 becomes Control is performed so as to follow the calculated VS reference.

The point O shown in FIG. 15 is determined by the calculation and control of the voltage VS. The potential at the point O is the same as the potential at the neutral point when the transformer of the system 3 has a star connection. become.

When the upper transformer has a star connection and the neutral point is grounded, the point O is at the ground potential.

This point O is a reference point of the phase voltage and coincides with the potential of the intermediate point between the capacitors 18 and 19 in FIG.
The midpoint of 19 is fixed at the ground potential, the fluctuation of the DC potential of each part with respect to the ground is reduced, and the leakage current can be reduced.

[0065]

By the way, in the conventional power converter control device as shown in FIG. 11, the transformer on the system 3 side and its grounding form are based on the assumptions in FIGS. 16 (a) to 16 (d). I have.

However, among the grounding systems on the system 3 side, for example, as shown in FIG. 17, there is a system in which one of V-connected or delta-connected transformer windings is grounded at the midpoint of the winding.

In this method, when the line voltage is 200 V,
Single-phase three-wire 200V with grounded midpoint and three-phase three-wire 200
V can be supplied by one transformer.

In the grounding method shown in FIG. 17, in a conventional power converter not using an insulating transformer, either a control method for a system in which one end of the transformer is grounded or a control method for a system in which the neutral point of the transformer is grounded is used. Even if applied, the ground voltage of the DC section of the power converter will oscillate at the commercial frequency.

For example, in the case where the system corresponding to the system in which the line voltage is 200 V in FIG. 17 and the system corresponding to the system in which one line of FIG. Is controlled to zero.

However, the ground voltage of the S line is 100 V AC.
100V AC for each part of DC of power converter
Vibrates at

When the stray capacitance of the DC circuit including the solar cell is large, it is considered that a leakage current is generated by the oscillating voltage. If the system has a leakage protection function, the leakage current prevents the leakage current. Unnecessary operation may occur.

On the other hand, by inserting an insulating transformer between the output of the power converter and the system 3 including the ground, potential fluctuations on the DC side can be reduced, but this insulating transformer is a relatively large component. Therefore, there is a problem that the power converter becomes large.

An object of the present invention is to provide a power converter capable of reducing the fluctuation of the ground potential of each DC unit and reducing the occurrence of leakage current due to the presence of the stray capacitance of each DC unit without using an insulating transformer. To provide a control device.

[0074]

In order to achieve the above object, according to the first aspect of the present invention, one of V-connected or delta-connected transformer windings is grounded at a winding midpoint. In a control device of a power converter that is connected to a three-phase system and converts DC power to AC power and supplies the AC power to the three-phase system,
The power converter is composed of three sets of half-bridge circuits,
The output current of the two half-bridge circuits is controlled to a desired value among the half-bridge circuits, and the output voltage of the remaining half-bridge circuit among the three half-bridge circuits is set to the half-bridge circuit. And an amplitude corresponding to the voltage difference between the output line and the ground potential.

Therefore, in the power converter control apparatus according to the first aspect of the present invention, since the potential of each DC section is fixed by the above means, the stray capacitance between the DC section and ground is fixed. Phenomena of charging and discharging are reduced, and generation of leakage current due to vibration of the DC part can be reduced.

According to a second aspect of the present invention, in the power converter control device according to the first aspect, the voltage difference between the output line of the half-bridge circuit for controlling the output voltage and the ground potential is controlled. The corresponding phase is estimated from one or two line voltages, and the amplitude corresponding to the voltage difference between the output line of the half-bridge circuit that controls the output voltage and the ground potential is the detected value or the calculated value of the line voltage. The control is performed based on the voltage reference obtained by estimating from.

Therefore, in the power converter control device according to the second aspect of the present invention, since the potential of each DC portion is fixed by the above means, the stray capacitance between the DC portion and the ground is fixed. Phenomena of charging and discharging are reduced, and generation of leakage current due to vibration of the DC part can be reduced.

According to a third aspect of the present invention, in the control device for a power converter according to the second aspect of the present invention, the voltage control is applied to a system line not connected to both ends of the grounded transformer winding. By connecting the output of the half-bridge circuit and determining the phase corresponding to the voltage difference between the output line of the half-bridge circuit and the ground potential based on the signal obtained by adding and subtracting the two line voltage detection signals. The control is performed based on the set voltage reference.

Therefore, in the power converter control device according to the third aspect of the present invention, since the potential of each DC portion is fixed by the above means, the stray capacitance between the DC portion and the ground is fixed. Phenomena of charging and discharging are reduced, and generation of leakage current due to vibration of the DC part can be reduced.

According to a fourth aspect of the present invention, there is provided a power converter control device which is connected to a three-phase system, converts DC power into AC power, and supplies the AC power to the three-phase system. The output current of two half bridge circuits is controlled to a desired value among the three half bridge circuits, and the remaining one half of the three half bridge circuits is formed. The output voltage of the bridge circuit
The three-phase system controls the phase and the amplitude corresponding to the voltage difference between the output line of the half-bridge circuit and the ground potential. Output voltage can be controlled depending on whether the three transformer windings are star-connected and the midpoint is grounded at one end, or V- or delta-connected at one end of the transformer winding. The output reference of the half bridge circuit is switched.

Therefore, in the power converter control device according to the present invention, since the potential of each DC portion is fixed by the above means, the stray capacitance between the DC portion and the ground is fixed. Phenomena of charging and discharging are reduced, and generation of leakage current due to vibration of the DC part can be reduced.

According to a fifth aspect of the present invention, in the power converter control device of the fourth aspect of the present invention, the three-phase system includes one of V-connected or delta-connected transformer windings. If grounded at the midpoint of the winding, connect to a system line that is not connected to both ends of the grounded transformer winding.
If the output of a half-bridge circuit that can control the output voltage is connected, and one end of the V-connected or delta-connected transformer winding is grounded, the output voltage-controllable half-bridge is connected to the grounded system line. Connect the output of the bridge circuit and set the phase of the voltage reference of the half-bridge circuit that can control the voltage to the two line voltages including the output line of the half-bridge circuit that controls the output voltage regardless of the system grounding method. The detection signals are made to have the same phase as the signal obtained by adding and subtracting the detection signals.

Therefore, in the power converter control apparatus according to the present invention, since the potential of each DC section is fixed by the above means, the stray capacitance between the DC section and ground is fixed. Phenomena of charging and discharging are reduced, and generation of leakage current due to vibration of the DC part can be reduced.

According to a sixth aspect of the present invention, in the power converter control device according to the fifth aspect, the three-phase system is grounded at one end of the V-connected or delta-connected transformer winding. The output of the controllable half-bridge circuit is mechanically short-circuited,
The switching operation of the half-bridge circuit is prevented.

Therefore, in the power converter control device according to the present invention, since the potentials of the DC components are fixed by the above means, the stray capacitance between the DC components and the ground is fixed. Phenomena of charging and discharging are reduced, and generation of leakage current due to vibration of the DC part can be reduced.

[0086]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(First Embodiment: Corresponding to Claim 1) FIG. 1 is a block diagram showing a configuration example of a system using a control device of a power converter according to this embodiment, and FIG.
The same parts as those described above are denoted by the same reference numerals and description thereof will be omitted, and only different parts will be described here.

The system 3 is a three-phase three-wire system in which the midpoint of one winding of the transformer is fixed to the ground potential.

Further, three lines are used for the R line, S line, T
Here, it is assumed that when connected to a line, the midpoint between ST is the ground potential.

As shown in FIG. 1, in this embodiment, S
A voltage detector 44 for detecting a voltage difference between the line and the ground is provided.

The output from the voltage detector 44 is input to the voltage controller 32 and used as a reference signal for voltage control.

Further, the voltage controller 32 includes the voltage detector 3
An output command signal is generated so that the voltage portion detected by 1 becomes equal to the reference signal, and the output command signal is input to the PWM modulator 29.

Next, the operation of the power converter control device according to the present embodiment configured as described above will be described.

The description of the operation of the same parts as in FIG. 11 is omitted, and only the operation of the different parts will be described here.

In FIG. 1, since the voltage detector 44 detects the voltage difference between the S line and the ground, the reference signal input to the voltage controller 32 is the ground voltage of the S line.

The voltage controller 32 includes capacitors 18 and 19
A signal is generated to the PWM modulator 29 so that the output voltage between the intermediate point of the S and the S line becomes equal to the reference signal.

By the operation of the half bridge circuit 5, the output voltage between the intermediate point between the capacitors 18 and 19 and the S line becomes
It becomes equal to the ground voltage of the S line which is the reference signal. As a result, the intermediate point between the capacitors 18 and 19 is fixed at the ground potential.

If the capacitances of the capacitors 18 and 19 are sufficiently large, the oscillation of each voltage of the capacitors 18 and 19 becomes small irrespective of the output from the inverter bridge 2, and the potential of each DC portion is fixed from the ground potential. Can be considered

By fixing the potential of each DC part,
The phenomenon of charging and discharging the stray capacitance between the DC parts and the ground is reduced, and the occurrence of leakage current due to the vibration of the DC parts can be reduced.

In this embodiment, the case where the system 3 is grounded at the midpoint between the STs of the transformer windings is described. However, the present invention is not limited to this, and the midpoint between the RS and the TR is grounded. In this case, it goes without saying that the potential of each DC component is fixed with the same circuit and control configuration as in the present embodiment.

When the ground point is not grounded at the midpoint of the transformer winding, for example, when it is grounded at the neutral point of the star-connected transformer, or at one end of the V connection or the delta connection. Even in this case, with the same circuit and control configuration as the present embodiment, the potential of each DC component is fixed,
The phenomenon of charging and discharging the stray capacitance between the DC parts and the ground is reduced, and the occurrence of leakage current due to the vibration of the DC parts can be reduced.

As described above, in the power converter control device according to the present embodiment, the power converter is constituted by three sets of half-bridge circuits, and two sets of half-bridge circuits are included in the three sets of half-bridge circuits. The output current of the circuit is controlled to a desired value, and the output voltage of the remaining one of the three half-bridge circuits corresponds to the voltage difference between the output line of the half-bridge circuit and the ground potential. Since the phase and amplitude are controlled, it is possible to reduce the fluctuation of the ground potential of each part of the DC and reduce the occurrence of leakage current due to the presence of the stray capacitance of each part of the DC, without using an isolation transformer. Become.

(Second Embodiment: Corresponding to Claim 2) FIG. 2 is a block diagram showing a configuration example of a system using a control device of a power converter according to the present embodiment.
The same parts as those described above are denoted by the same reference numerals and description thereof will be omitted, and only different parts will be described here.

The system 3 is of a three-phase three-wire system in which the midpoint of one winding of the transformer is fixed to the ground potential.

The three wires are R, S, and T of the power converter.
Here, it is assumed that when connected to the line, the midpoint between ST is the ground potential.

As shown in FIG. 2, in this embodiment, S
A voltage detector 41 for detecting a voltage between T is provided to detect the potential of the S line with respect to the T line.

The output from the voltage detector 41 is input to a half multiplier 45.

Further, the output from the half multiplier 45 is input to the voltage controller 32 and used as a reference signal for voltage control.

Further, the voltage controller 32 generates a control signal so that the voltage portion detected by the voltage detector 31 becomes equal to the reference signal, and inputs the control signal to the PWM modulator 29.

Next, the operation of the power converter control device according to the present embodiment configured as described above will be described.

The description of the operation of the same parts as in FIG. 11 is omitted, and only the operation of the different parts will be described here.

In FIG. 2, a voltage detector 41 detects a voltage difference between the S line with respect to the T line and the ground.

The voltage signal between STs, which is the output from the voltage detector 41, is converted by the half multiplier 45 into a signal having the same phase as the voltage between STs and an amplitude of 1/2.

On the other hand, since the midpoint between the STs is grounded, the potential of the S line with respect to the ground has the same phase as the voltage between the STs, and the amplitude is １ ／.

Therefore, the output from the half multiplier 45, that is, the reference signal in the voltage control which is the input of the voltage controller 32 is a signal indicating the ground voltage of the S line.

The voltage controller 32 includes capacitors 18 and 19
A signal is generated to the PWM modulator 29 so that the output voltage between the intermediate point of the S and the S line becomes equal to the reference signal.

By the operation of the half bridge circuit 5, the output voltage between the intermediate point between the capacitors 18 and 19 and the S line becomes
It becomes equal to the ground voltage of the S line which is the reference signal. As a result, the intermediate point between the capacitors 18 and 19 is fixed to the ground potential.

If the capacitances of the capacitors 18 and 19 are sufficiently large, the oscillation of each voltage of the capacitors 18 and 19 becomes small irrespective of the output from the inverter bridge 2, and the potential of each DC part is fixed from the ground potential. Can be considered.

By fixing the potential of each DC component,
The phenomenon of charging and discharging the stray capacitance between the DC parts and the ground is reduced, and the occurrence of leakage current due to the vibration of the DC parts can be reduced.

In the present embodiment, the case where the system 3 is grounded at the midpoint between the STs of the transformer windings is described. However, the present invention is not limited to this. When the voltage detector 41 is provided between the RS and the middle point between the TRs is grounded, it is needless to say that the potential of each DC component is fixed by providing the voltage detector 41 between the TRs.

As described above, in the power converter control device according to the present embodiment, one or two phases corresponding to the voltage difference between the output line of the half-bridge circuit for controlling the output voltage and the ground potential are set. A voltage reference obtained by estimating from the line voltage and estimating the amplitude corresponding to the voltage difference between the output line of the half-bridge circuit that controls the output voltage and the ground potential from the detected or calculated value of the line voltage. It is possible to reduce the fluctuation of the ground potential of each part of the DC and reduce the occurrence of leakage current due to the presence of the stray capacitance of each part of the DC, without using an isolation transformer. .

(Third Embodiment: Corresponding to Claim 3) FIG. 3 is a block diagram showing a configuration example of a system using a control device of a power converter according to this embodiment, and FIG.
The same parts as those described above are denoted by the same reference numerals and description thereof will be omitted, and only different parts will be described here.

The system 3 is a three-phase three-wire system in which the midpoint of one winding of the transformer is fixed to the ground potential.

[0124] The three wires are R, S, and T of the power converter.
Here, when connected to a line, it is assumed that the midpoint between TRs is the ground potential.

FIG. 4 is a block diagram showing a configuration example of the output reference generator 24. As shown in FIG.

In FIG. 4, the detection signals of the voltage detectors 40 and 41 are the same as those in FIG. 14, the voltage detector 40 detects the potential of the S line with respect to the R line, and the voltage detector 41 detects the potential of the T line. The potential of the S line with respect to the line is detected.

The outputs from the voltage detectors 40 and 41 are input to an adder 42 in the output reference generator 24, and the output is input to a half multiplier 46.

Further, the output from the half multiplier 46 is
The output from the output reference generator 24 is output to the voltage controller 32.
To be used as a reference signal in voltage control.

Further, the voltage controller 32 generates a control signal so that the voltage portion detected by the voltage detector 31 becomes equal to the reference signal, and inputs the control signal to the PWM modulator 29.

Next, the operation of the power converter control device according to the present embodiment configured as described above will be described.

The description of the operation of the same parts as in FIG. 11 is omitted, and only the operation of the different parts will be described here.

FIG. 5 is a vector diagram showing the voltage of each part.

Here, the system 3 is grounded at the midpoint between the TRs, and this grounding point is O, and the voltages of the R, S, and T lines with respect to the grounding points are VR, VS, and VT, respectively.

The voltage of the R line with respect to the S line is VRS, T
The voltage of the S line for the line is VST, and the voltage of the T line for the R line is VTR.

In this example, the ground potential Vs of the S line is obtained by calculating from the line voltages VRS and VST, and the voltage control of the power converter is performed based on VS.

From FIG. 5, it can be seen from FIG. 5 that VS has a phase delayed by 150 degrees (5 / 6π) from VRS and the amplitude is (√) of the line voltage.
3) / 2 times.

The ground potential VS of the S line is equal to the line voltages VRS and V
It is obtained from ST by the following equation (7).

VS = (VST−VRS) / 2 (7) When this vector operation is performed using a scalar amount, the following is performed.

The line voltages VRS and VST are expressed by the following equations (8) and (9) when the amplitude is V, the angular frequency is ω, and the time is t.

VRS = V × sin (ωt) (8) VST = V × sin (ωt−2 / 3π) (9) VS is delayed by 150 degrees from VRS, and the amplitude is (√) of the line voltage.
3) / 2, VS is given by the following equation (10).

VS = (V√3) / 2 × sin (ωt−5 / 6π) (10) Here, when VST−VRS is calculated, the following equation (11) is obtained.

VST−VRS = V × sin (ωt−2 / 3π) −V × sin (ωt) = V × ((− 3) sin (ωt) − (√3 / 2) cos (ωt)) = V × √3 × sin (ωt−5 / 6π) (11) From the above equations (10) and (11), VS is calculated by the following equation (12) in the same manner as in the above equation (7). It turns out that it is required.

VS = (VST−VRS) / 2 (12) The potential of the S line with respect to the R line and the potential of the S line with respect to the T line, which are the outputs from the voltage detectors 40 and 41, are stored in the output reference generator 24. Is added by the adder 42, and the half multiplier 46
As a result, the output of the output reference generator 24 becomes 1/2.

By the method of determining the output from the output reference generator 24, the above-mentioned equation (12) can be realized.

Since the voltage detector 40 detects the potential of the S line with respect to the R line, -V on the right side of the above equation (12) is used.
This means that RS has been detected.

Further, the voltage detector 41 detects the S
Since the potential of the line is detected, VST on the right side of the above equation (12) is detected.

As a result, the output from the adder 42 calculates (VST-VRS) on the right side of the above equation (12).

Since the half multiplier 46 multiplies this signal by １ ／, the output from the half multiplier 46, that is, the output from the output reference generator 24, is the left side of the above equation (12). VS.

As described above, the output from the output reference generator 24 is such that the reference signal in the voltage control which is the input of the voltage controller 32 is a signal indicating the ground voltage of the S line.

The voltage controller 32 includes capacitors 18 and 19
A signal is generated to the PWM modulator 29 so that the output voltage between the intermediate point of the S and the S line becomes equal to the reference signal.

By the operation of the half bridge circuit 5, the output voltage between the intermediate point between the capacitors 18 and 19 and the S line becomes
It becomes equal to the ground voltage of the S line which is the reference signal. As a result, the intermediate point between the capacitors 18 and 19 is fixed to the ground potential.

If the capacitances of the capacitors 18 and 19 are sufficiently large, the oscillation of each voltage of the capacitors 18 and 19 becomes small irrespective of the output from the inverter bridge 2, and the potential of each DC portion is fixed from the ground potential. Can be considered.

By fixing the potential of each DC component,
The phenomenon of charging and discharging the stray capacitance between the DC parts and the ground is reduced, and the occurrence of leakage current due to the vibration of the DC parts can be reduced.

As described above, in the control device of the power converter according to the present embodiment, the output of the half-bridge circuit for voltage control is connected to the system line not connected to both ends of the grounded transformer winding. The phase corresponding to the voltage difference between the output line of the half bridge circuit and the ground potential is controlled based on a voltage reference obtained by determining a signal obtained by adding and subtracting two line voltage detection signals. Therefore, it is possible to reduce the fluctuation of the potential with respect to the ground of each DC part and to reduce the generation of the leakage current due to the existence of the stray capacitance of each DC part without using the insulating transformer.

(Fourth Embodiment: Claims 4 and 5)
The configuration of the system using the control device for the power converter according to the present embodiment is the same as that in FIG. 11 described above, and will be described here.

FIG. 6 is a block diagram showing a configuration example of the output reference generator 24. As shown in FIG.

In FIG. 6, a voltage detector 40 for detecting a voltage between RS and a voltage detector 4 for detecting a voltage between ST are provided.
1 is provided, and outputs from the voltage detectors 40 and 41 are input to an adder 42 in the output reference generator 24.

The output from the adder 42 is input to a third multiplier 43 and a half multiplier 46.

Further, a zero output device 47 for always generating a command value of zero voltage is provided.

Further, the output signals of the third multiplier 43, the half multiplier 46, and the zero output unit 47 are input to the selector 48. The selector 48 outputs one of the plurality of inputs. It has a function to select one. Then, the selected signal is used as an output signal of the output reference generator 24, and is used as a reference signal in voltage control.

On the other hand, as shown in FIG. 7A, when one end of a V-connected or delta-connected transformer is grounded as shown in FIG. 7A, a star-shaped connection is formed as shown in FIG. When the neutral point of the transformer is grounded,
As shown in (c), any three-phase alternating current is used when the midpoint of one winding of the transformer is grounded.

When the three lines are connected to the R, S, and T lines of the power converter, the grounding position and the R, S, and T lines are connected as shown in FIG. ), The S line is at ground potential,
In the case of FIG. 7C, the middle point between TRs is set to the ground potential.

The selector 48 is connected to the system 3 side as shown in FIG.
When one end of a V-connected or delta-connected transformer is grounded as shown in FIG. 7A, the output signal from the zero output device 47 is output as a star connection as shown in FIG. 7B. When the neutral point of the applied transformer is grounded, the output signal from the third multiplier 43 is used to further connect the neutral point of one winding of the transformer to ground as shown in FIG. If so, the output signal from the half multiplier 46 is selected.

Next, the operation of the power converter control device according to the present embodiment configured as described above will be described.

The description of the operation of the same parts as in FIG. 11 is omitted, and only the operation of the different parts will be described here.

FIG. 8 is a vector diagram showing the voltage of each part.

Here, in the case of FIG. 7A to FIG. 7C, the system 3 is grounded at any point on the line connecting the middle point between the point S and TR in the figure. V to ground point
S is parallel to the line connecting the midpoint between point S and TR.

Note that the voltage of the R line with respect to the S line is VRS, T
The voltage of the S line for the line is VST, and the voltage of the T line for the R line is VTR.

In this example, the ground potential VS of the S line is obtained by calculating from the line voltages VRS and VST, and the voltage control of the power converter is performed based on VS.

Here, as shown in FIG. 7 (a), the ground potential is VSa on the S line when one end of the V-connected or delta-connected transformer is grounded, as shown in FIG. 7 (b). When the neutral point of the star-connected transformer is grounded, the ground potential is set to VSb on the S line, and as shown in FIG. 7 (c), the middle point of one winding of the transformer is grounded. S
The potential to ground of the line is set to Vsc.

From FIG. 8, VSa, VSb, and VSc are V
It is common that the phase lags RS by 150 degrees (5 / 6π).

The amplitude of VSa is zero, VSb is 1 / √3 times the line voltage, and Vsc is (√3) / 2 times the line voltage.

The ground potential VS of the S line is the line voltage VRS and V
It is obtained from ST by the following equations (13) to (15).

VSa = 0 (13) VSb = (VST−VRS) / 3 (14) Vsc = (VST−VRS) / 2 (15) When this vector operation is performed with a scalar amount, the following is performed. .

The line voltages VRS and VST are expressed by the following equations (16) and (17) when the amplitude is V, the angular frequency is ω, and the time is t.

VRS = V × sin (ωt) (16) VST = V × sin (ωt−2 / 3π) (17) VS is delayed by 150 degrees from VRS, and the amplitude is 0 of the line voltage.
VSa, VSb, and VSc are given by the following (18) to (20) since they are twice, or 1 / √3 times, or (√3) / 2 times.
It becomes an expression.

VSa = 0 (18) VSb = V / √3 × sin (ωt−5 / 6π) (19) Vsc = (V√3) / 2 × sin (ωt−5 / 6π) (20) where , VST-VRS, the following equation (21) is obtained.

VST−VRS = V × sin (ωt−2 / 3π) −V × sin (ωt) = V × ((− 3/2) sin (ωt) − (√3 / 2) cos (ωt)) = V × √3 × sin (ωt−5 / 6π) (21) From the above equations (18) to (20) and equation (21), VS
It can be seen that a, VSb, and VSc can be obtained by the following equations (22) to (24), similarly to the above equations (13) to (15).

VSa = 0 (22) VSb = (VST−VRS) / 3 (23) Vsc = (VST−VRS) / 2 (24) S line for the R line, which is the output from the voltage detectors 40 and 41 And the potential of the S line with respect to the T line are added by the adder 42 in the output reference generator 24, and the third
The output of the output reference generator 24 is obtained as an amount of 1/3 or 1/2 or as a zero output by the third / half multiplier 46.

By the method of determining the output from the output reference generator 24, the above equations (22) to (24) can be realized.

Since the voltage detector 40 detects the potential of the S line with respect to the R line, the voltage detector 40 detects -VRS on the right side of the above equations (23) and (24).

The voltage detector 41 detects S
Since the potential of the line is detected, the above equation (23), (2)
4) Detect VST on the right side of the equation. As a result, the adder 42
Calculates the (VST-VRS) on the right side of the above equations (23) and (24).

The third multiplier 43 and the half multiplier 46 are
Since this signal is multiplied by ３ and 倍, the zero output unit 4
7, the output from the third multiplier 43, the half multiplier 46,
That is, the output from the output reference generator 24 is the above (2)
VS, which is the left side of equations (2) to (24).

As described above, the output from the output reference generator 24 is such that the reference signal in the voltage control which is the input of the voltage controller 32 is a signal indicating the ground voltage of the S line.

The voltage controller 32 includes capacitors 18 and 19
A signal is generated to the PWM modulator 29 so that the output voltage between the intermediate point of the S and the S line becomes equal to the reference signal.

By the operation of the half bridge circuit 5, the output voltage between the intermediate point between the capacitors 18 and 19 and the S line becomes
It becomes equal to the ground voltage of the S line which is the reference signal. As a result, the intermediate point between the capacitors 18 and 19 is fixed to the ground potential.

If the capacitances of the capacitors 18 and 19 are sufficiently large, the oscillation of each voltage of the capacitors 18 and 19 becomes small irrespective of the output from the inverter bridge 2, and the potential of each DC portion is fixed from the ground potential. Can be considered.

By fixing the potential of each of the DC parts,
The phenomenon of charging and discharging the stray capacitance between the DC parts and the ground is reduced, and the occurrence of leakage current due to the vibration of the DC parts can be reduced.

As described above, in the power converter control device according to the present embodiment, the power converter is constituted by three sets of half-bridge circuits, and two sets of half-bridge circuits among the three sets of half-bridge circuits. The output current of the circuit is controlled to a desired value, and the output voltage of the remaining one of the three half-bridge circuits corresponds to the voltage difference between the output line of the half-bridge circuit and the ground potential. Controlling the phase and amplitude, the system 3 grounds one of the V-connected or delta-connected transformer windings at the midpoint of the winding, or connects the three transformer windings in a star connection to the midpoint. The output reference of the half-bridge circuit capable of controlling the output voltage is switched depending on whether it is grounded or grounded at one end of the V-connected or delta-connected transformer winding. Is If one of the transformer windings is grounded at the winding midpoint, connect the output of a half-bridge circuit that can control the output voltage to a system line that is not connected to both ends of the grounded transformer winding. If the V-connection or delta-connection transformer winding is grounded at one end, the output of a half-bridge circuit that can control the output voltage can be connected to the grounded system line to control the voltage. The voltage reference phase of the half-bridge circuit is set to be in phase with the signal obtained by adding and subtracting two line voltage detection signals including the output line of the half-bridge circuit that controls the output voltage regardless of the system grounding method. Therefore, it is possible to reduce the fluctuation of the potential with respect to the ground of each DC part and to reduce the generation of the leakage current due to the existence of the stray capacitance of each DC part without using the insulating transformer.

(Fifth Embodiment: Corresponding to Claim 6) FIG. 9 is a block diagram showing a configuration example of a system using a control device of a power converter according to this embodiment.
The same parts as those described above are denoted by the same reference numerals and description thereof will be omitted, and only different parts will be described here.

Further, a method of using the voltage detectors 40 and 41,
Since the configuration of the output reference generator 24 is the same as that of FIG. 6, the same parts as those of FIG. 6 are denoted by the same reference numerals, and description thereof will be omitted. Only different parts will be described here.

In FIG. 9, when one end of the V-connected or delta-connected transformer is grounded as shown in FIG. 7 (a), the system 3 generates a transformer one-end ground signal. If the neutral point of the star-connected transformer is grounded as shown in FIG.
As shown in (1), when the midpoint of one winding of the transformer is grounded, it is assumed that the transformer one end ground signal is not generated.

In this embodiment, a short-circuit switch 49 that is closed by the generation of a ground signal at one end of the transformer is provided between an intermediate point between the capacitors 18 and 19 and the S line.

The signal grounded at one end of the transformer is input to the PWM modulator 29.

FIG. 10 is a block diagram showing a configuration example of the PWM modulator 29.

In FIG. 10, the PWM modulator 29 receives a signal from the voltage controller 32, generates a drive signal for the half bridge circuit 5, and outputs the signal from the modulator 3
8 and the drive circuit 39 are the same as in FIG.

Here, a switch 50 is provided between the modulator 38 and the drive circuit 39. The switch 50 is closed when the transformer one end ground signal is not generated, and the switch 50 is opened when the transformer one end ground signal is generated. .

Next, the operation of the power converter control device according to the present embodiment configured as described above will be described.

The description of the operation of the same part as in FIG. 11 is omitted, and only the operation of the different part will be described here.

When the neutral point of the star-connected transformer is grounded, as shown in FIG. 7B, or as shown in FIG. When the middle point of the transformer is grounded, the transformer one end ground signal is not generated.

In this case, the short-circuit switch 49 in FIG.
Since the switch 50 in the PWM modulator 29 of FIG. 10 is closed, the same operation as in the above-described fourth embodiment is performed.

As shown in FIG. 7A, when one end of a V-connected or delta-connected transformer is grounded as shown in FIG. 7A, a transformer one-end ground signal is generated.

In this case, the short-circuit switch 49 in FIG.
The switch 50 in the PWM modulator 29 of FIG. 10 is opened.

When the short-circuit switch 49 is closed,
The voltage between the midpoint of the capacitors 18 and 19 in FIG. 9 and the S line becomes zero.

The switch 50 in the PWM modulator 29
Is opened, the input of the drive circuit 39 disappears, and the half bridge circuit 5 stops switching.

Therefore, by closing the short-circuit switch 49, the voltage between the intermediate point between the capacitors 18 and 19 and the S line can be reduced to zero without operating the half-bridge circuit 5.

Since the S line is at the ground potential, the capacitor 1
The midpoint between 8 and 19 is fixed to the ground potential.

If the capacitances of the capacitors 18 and 19 are sufficiently large, the oscillation of each voltage of the capacitors 18 and 19 becomes small irrespective of the output from the inverter bridge 2, and the potential of each DC portion is fixed from the ground potential. Can be considered.

By fixing the potential of each DC component,
The phenomenon of charging and discharging the stray capacitance between the DC parts and the ground is reduced, and the occurrence of leakage current due to the vibration of the DC parts can be reduced.

As described above, in the power converter control device according to the present embodiment, when system 3 is grounded at one end of the V-connected or delta-connected transformer winding, the output voltage is controlled. Since the output of the possible half-bridge circuit is mechanically short-circuited and the switching operation of the half-bridge circuit is prevented, the fluctuation of the potential of each DC part with respect to the ground is reduced without using an isolation transformer, It is possible to reduce the occurrence of leakage current due to the presence of stray capacitance.

[0211]

According to the present invention described above, it is possible to reduce the variation of the ground potential of each DC section and the generation of leakage current due to the existence of the stray capacitance of each DC section without using an insulating transformer. A control device for a possible power converter can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a system using a control device of a power converter according to the present invention.

FIG. 2 is a block diagram showing a second embodiment of a system using the power converter control device according to the present invention.

FIG. 3 is a block diagram showing a third embodiment of a system using the power converter control device according to the present invention.

FIG. 4 is a block diagram showing a configuration example of an output reference generator according to the third embodiment.

FIG. 5 is a vector diagram for explaining the operation in the third embodiment.

FIG. 6 is a block diagram showing a configuration example of an output reference generator in a system using a control device for a power converter according to a fourth embodiment of the present invention.

FIG. 7 is a view for explaining the operation in the fourth embodiment.

FIG. 8 is a vector diagram for explaining an operation in the fourth embodiment.

FIG. 9 is a block diagram showing a fifth embodiment of a system using the power converter control device according to the present invention.

FIG. 10 is a block diagram showing a configuration example of a PWM modulator according to the fifth embodiment.

FIG. 11 is a block diagram showing a typical configuration example of a system using a conventional power converter control device.

FIG. 12 is a block diagram showing a configuration example of an output reference generator and an output reference generator in FIG. 11;

FIG. 13 is a block diagram showing a configuration example of a PWM modulator in FIG. 11;

FIG. 14 is a view for explaining the operation in FIG. 11;

FIG. 15 is a vector diagram for explaining the operation in FIG. 11;

FIG. 16 is a view for explaining the operation in FIG. 11;

FIG. 17 is a view for explaining the operation in FIG. 11;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... DC power supply, 2 ... Inverter bridge, 3 ... System, 4,5,6 ... Half bridge circuit, 7,8,9,10,11,12 ... Switch, 13,14,15 ... Reactor, 16,17 ... Current detectors 18, 19 ... capacitors, 20, 21, 22 ... capacitors, 23, 24, 25 ... output reference generators, 26, 27 ... current controllers, 28, 29, 30 ... PWM modulators, 31 ... voltage Detector 32 voltage controller 33 sine wave generator 34 35 phase shifter 36 amplitude setting device for interconnection 37 37 multiplier 38 modulator 39 driving circuit 40 41: voltage detector, 42: adder, 43: one-third multiplier, 44: voltage detector, 45: one-half multiplier, 46: one-half multiplier, 47: zero output device, 48 ... Selector, 49 ... Short-circuit switch, 50 ... Switch .

Continued on the front page (72) Inventor Kenichi Kimoto 1 Toshiba-cho, Fuchu-shi, Tokyo Inside the Fuchu office, Toshiba Corporation (72) Inventor Toshiaki Mochizuki 1-1-1, Shibaura, Minato-ku, Tokyo Toshiba Corporation Office (72) Inventor Kazuhiro Nakajima 1-1-1, Shibaura, Minato-ku, Tokyo F-term in the head office of Toshiba Corporation 5H007 AA01 CA01 CB04 CB05 CC14 CC23 DA06 DB01 DC02 DC05 EA02 5H740 BA11 BB05 BB09 NN02 NN17

Claims (6)

[Claims] 1. A three-phase system in which one of V-connected or delta-connected transformer windings is grounded at a winding midpoint, and converts DC power into AC power to convert the DC power into AC power. In the control device for a power converter to be supplied, the power converter is configured by three sets of half-bridge circuits, and output currents of two sets of half-bridge circuits among the three sets of half-bridge circuits are set to desired values. And controlling the output voltage of the remaining one half-bridge circuit among the three sets of half-bridge circuits to a phase and an amplitude corresponding to the voltage difference between the output line of the half-bridge circuit and the ground potential. A control device for a power converter. 2. The control device for a power converter according to claim 1, wherein a phase corresponding to a voltage difference between an output line of a half-bridge circuit controlling the output voltage and a ground potential is one or two phases. Estimated from the line voltage, the amplitude corresponding to the voltage difference between the output line of the half-bridge circuit controlling the output voltage and the ground potential was obtained by estimating from the detected value or the calculated value of the line voltage. A control device for a power converter, wherein the control is performed based on a voltage reference. 3. The control device for a power converter according to claim 2, wherein an output of a voltage-controlled half-bridge circuit is connected to a system line not connected to both ends of the grounded transformer winding, A phase corresponding to a voltage difference between the output line of the half bridge circuit and the ground potential is controlled based on a voltage reference obtained by determining a signal obtained by adding and subtracting two line voltage detection signals. A control device for a power converter, characterized in that: 4. A control device for a power converter that is connected to a three-phase system, converts DC power into AC power, and supplies the AC power to the three-phase system, wherein the power converter is configured by three sets of half-bridge circuits. And controlling the output currents of two half-bridge circuits of the three sets of half-bridge circuits to a desired value; and outputting the output voltage of the remaining one-half-bridge circuit of the three sets of the half-bridge circuits. Is controlled to a phase and an amplitude corresponding to the voltage difference between the output line of the half bridge circuit and the ground potential, and the three-phase system connects one of the V-connected or delta-connected transformer windings to a winding midpoint. The output voltage depends on whether the transformer windings are grounded, the three transformer windings are star-connected and the middle point is grounded, or the V winding or one end of the delta-connected transformer winding is grounded. Controllable half bridge Converter control apparatus being characterized in that to switch the output reference circuit. 5. The control device for a power converter according to claim 4, wherein the three-phase system is configured such that one of V-connected or delta-connected transformer windings is grounded at a winding midpoint. The output of the half-bridge circuit whose output voltage can be controlled is connected to the system line that is not connected to both ends of the grounded transformer winding. In this case, the output of a half-bridge circuit capable of controlling the output voltage is connected to a grounded system line, and the voltage reference phase of the half-bridge circuit capable of controlling the voltage is changed according to the system grounding method. A control device for a power converter, wherein a detection signal of two line voltages including an output line of a half-bridge circuit for controlling an output voltage has the same phase as a signal obtained by adding and subtracting the two signals. 6. The control device for a power converter according to claim 5, wherein the output voltage is reduced when the three-phase system is grounded at one end of a V-connected or delta-connected transformer winding. A control device for a power converter, wherein an output of a controllable half-bridge circuit is mechanically short-circuited so as not to perform a switching operation of the half-bridge circuit.