JPH08149856A - Power conversion controller - Google Patents

Abstract

PURPOSE: To provide a power conversion controller which can continue safe operation by suppressing the ripple of the DC voltage of a power converter even at the time of drop of regenerated power in regenerative operation. CONSTITUTION: A power converter equipped with a forward converter 3, a resisting chopper device 5, and an inverter 8 capable of regenerative operation, is equipped further with an operation command means which issues an operation command to the forward converter 3 if the DC voltage falls under the preset value, when the forward converter 3 is stopping during regenerative operation of the inverter 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power conversion control device for controlling a power conversion device equipped with a resistance chopper device in a DC intermediate circuit and an inverter capable of power running operation and regenerative operation as an inverse converter.

[0002]

2. Description of the Related Art For example, a power converter including a forward converter, a resistance chopper device and a voltage type inverter is already known as an AC power supply device capable of outputting a variable frequency and a variable voltage for a variable speed AC motor. An example of the main circuit configuration is shown in FIG.

In the power converter shown in FIG. 5, AC power is input from the AC power system 1 to the AC input terminal of the forward converter 3 via the forward converter transformer 2, and its DC output is a ripple reducing DC reactor. The voltage is input to the resistance chopper device 5, the power capacitor 7, and the DC terminal of the voltage type inverter 8 via 4. The resistance chopper device 5 comprises, in principle, a chopper 50 and a power consuming resistor 60 in series with it. The resistance chopper device 5 is actually composed of a plurality of sets of resistance chopper circuits connected in parallel, each consisting of a chopper switch and a power consumption resistor in series with the chopper switch. FIG. 6 illustrates a resistance chopper device having a four-group parallel configuration as an example thereof, and four chopper switches 51, 52, 53, 54 (generally referred to by the symbol “50” in FIG. 5) and 4 Individual resistors 61,
62, 63, 64 (generally referred to by the reference numeral "60" in FIG. 5) are provided. Each one chopper switch and each resistor constitute a resistance chopper circuit. The inverter 8 can be operated not only as an inverter in the power running mode but also as a rectifier in the regenerative mode. The AC terminal of the inverter 8 is connected to the load 10 via the inverter transformer 9. The load 10 may be, for example, a vehicle driving linear motor. In the following description, the load 10
Will be described as a linear motor for driving a vehicle.

In order to control the operation of the forward converter 3 and the inverter 8, a current detector 11 for detecting an output DC current I _d1 of the forward converter 3 and a current I _d2 shunted to the resistance chopper device 5.
Current detector 12 for detecting the current, the current detector 13 for detecting the DC main circuit current I _d3 on the load side of the resistance chopper device 5, and the DC mains at both ends of the resistance chopper device 5 (that is, the positive and negative polar terminals of the DC intermediate circuit). A voltage detector 14 for detecting the circuit voltage V _dc is provided.

FIG. 7 and FIG. 8 show a control circuit for controlling the resistance chopper device 5. Resistance chopper device 5
Is a PWM control (pulse width modulation control) type, and each chopper switch 51, 52, 53, 54 is ignition-controlled by a gate pulse created on the basis of a PWM carrier signal and a control signal.

FIG. 7 shows a control signal generating circuit 19 for obtaining a control signal for producing a gate pulse. DC voltage reference circuit 20, current reference circuit 21, constant voltage control circuit 2
2, a constant current control circuit 23, a limiter circuit 24, a control signal selection circuit 25, a subtractor 26 and a subtractor 27. The subtractor 26 calculates the difference between the DC voltage reference commanded from the DC voltage reference circuit 20 and the DC main circuit voltage V _dc detected by the voltage detector 14, that is, the DC voltage deviation, which is fed to the constant voltage control circuit 22. input. The constant voltage control circuit 22 calculates a manipulated variable for making the DC voltage deviation zero and inputs it to the control signal selection circuit 25. Current reference circuit 2
The difference between the current reference commanded from 1 and the direct current I _d1 detected by the current detector 11, that is, the current deviation is calculated by the subtractor 27 and input to the constant current control circuit 23.
The constant current control circuit 23 calculates an operation amount for making the current deviation zero and inputs it to the control signal selection circuit 25. The limiter circuit 24 is for determining the maximum conduction angle and the minimum conduction angle of the chopper switch 50, and inputs a limit signal for keeping the conduction angle within both limit values to the control signal selection circuit 25. The control signal selection circuit 25 creates a control signal for PWM control based on each input signal,
It is sent to (the comparison circuits 35 to 38 of) the gate pulse generation circuit 18 shown in FIG.

The gate pulse generating circuit 18 (FIG. 8) is composed of a circuit for generating four gate pulses corresponding to the resistance chopper device 5 of the four-group parallel configuration. Common oscillator 3
4 sets of PWM carrier generation circuits 31, 32, 3 for generating 4 sets of PWM carrier signals based on the output signal of 0
3, 34, and the PWM carrier signals, which are their output signals, are input to the respective first input terminals of the comparison circuits 35, 36, 37, 38. The PWM carrier generation circuits 31 to 34 generate carrier signals having respective phase differences according to predetermined phase reference signals. Each second of the comparison circuits 35 to 38
The control signal output from the control signal generation circuit 19 of FIG. The comparator circuits 35 to 38 each generate a gate pulse based on both input signals,
The AND circuits 39, 40, 41, 42 are input to the respective first input terminals. The AND circuits 39 to 42 substantially function as switches, and the gate pulse ON / OFF signal is input to each second input terminal as a signal of "1" or "0". More specifically, AND circuits 39 to 42
Resistance chopper device 5 as an ON / OFF signal for
A "1" signal is input when the operation is performed, and a "0" signal is input when the operation is stopped including an emergency such as a failure. Thus, the gate pulse is turned on as an output signal of the gate pulse generation circuit 18 from the AND circuits 39 to 42.
Comparing circuits 35 to 38 on condition that a command is issued.
The gate pulse formed by the above is output and supplied as a firing control pulse to the corresponding chopper switches 51, 52, 53, 54 (FIG. 6).

FIG. 4 shows a forward converter 3 for converter cooperative control.
And a device for issuing an operation / stop command to the resistance chopper device 5. The converter operation command issued from the converter common monitoring device (not shown) is input to the AND circuit 77. In the AND circuit 77, the operation command is given to the resistance chopper device 5 under the AND condition that there is no failure signal.
And to AND circuits 90 and 91 for the forward converter 3 as respective first input signals. The AND circuits 90 and 91 function as switches, and the second input signals thereof are given from the OR circuits 86 to 87 as operation command blocking signals, that is, operation stop commands. AND
The output signals of the circuits 90 and 91 are used as operation commands to the resistance chopper device 5 and the forward converter 3.

A stop command and a failure signal for the converter are input to the OR circuit 85, and the output signal is the first input of each of the OR circuits 86 and 87. Forward converter 3 in FIG.
The output signal of the current detector 11 for detecting the current I _d1 is input to the level detection circuit 71, and when the detected current value I _d1 reaches the current setting value, for example, 15% or more, a “1” signal is output. To do. A predetermined hysteresis width is set for this current setting value, after the "1" signal is output, it is maintained within that hysteresis width, and a "0" signal is output when the current value falls below the hysteresis width. To do.

When the output signal of the current detector 12 for detecting the current I _d2 of the resistance chopper device 5 is input to the level detection circuit 72, when the detected current value I _d2 becomes a current set value, for example, 5% or less. The "1" signal is output to. A predetermined hysteresis width is set for the current setting value, after it outputs a "1" signal, it is maintained within that hysteresis width, and a "0" signal is output when the current value exceeds the hysteresis width. To do. The AND circuit 76 includes the level detection circuit 7
The output signals of Nos. 1 and 72 and the operation state signal of the inverter 8 (“1” during power running operation, “0” during regenerative operation) are input. Therefore, when the power running operation is performed and the output conditions of the level detection circuits 71 and 72 are both satisfied, the AN
The signal “1” is output from the D circuit 76. AND circuit 7
The output signal of 6 becomes the second input signal of the OR circuit 86 through the delay circuit 81. The output signal of the OR circuit 86 is AND
It acts as a switch-off signal of the circuit 90 and is used to output a stop command to the resistance chopper device 5.

On the other hand, the operation / stop command to the forward converter 3 is issued as follows. The output signal of the current detector 11 that detects the DC output current I _d1 of the forward converter 3 is input to the level detection circuit 74, and when the detected current value I _d1 becomes the current setting value, for example, 5% or less. Output a "1" signal. The output signal of the current detector 12 that detects the current I _d2 of the resistance chopper device 5 is input to the level detection circuits 73 and 75. The level detection circuit 73 outputs a "1" signal when the detected current value I _d2 becomes a current set value, for example, 5% or less. A predetermined hysteresis width is set for the current setting value, and after the "1" signal is output, it is maintained within that hysteresis width and a "0" signal is output when the current value exceeds the hysteresis width. To do. Level detection circuit 75
Outputs a "1" signal when the detected current value I _d2 exceeds the current setting value of 15%. A predetermined hysteresis width is set for the current setting value, after the "1" signal is output, it is maintained within that hysteresis width and a "0" signal is output when the current value falls below the hysteresis width. .

The output signal of the level detection circuit 73 and the operation state signal of the inverter 8 are input to the AND circuit 78, and when the current of the resistance chopper device 5 is less than the predetermined value 5% and the regenerative operation is performed, The output becomes "1". The “1” output signal of the AND circuit 78 becomes a switch-off signal of the AND circuit 92 via the delay circuit 82. The output signals of the level detection circuits 74 and 75 and the operation state signal of the inverter 8 are input to the AND circuit 79. Both level detection circuits 74, 7
The AND circuit 79 outputs "1" when the respective 5 output the respective level detection signals and are in the regenerative operation. This “1” output signal is passed through the delay circuit 83 and the AND circuit 9
Entered in 2. "1" output from the AND circuit 92
The signal turns off the AND circuit 91 via the OR circuit 87, and the AND circuit 91 issues a stop command to the forward converter 3.

Next, referring to FIGS. 9 to 11, the forward converter 3,
The control characteristics of the resistance chopper device 5 and the inverter 8 will be described.

FIG. 9 shows the control characteristics of the forward converter 3 having the same control characteristics as a general forward converter, in which the vertical axis represents the DC voltage detected by the voltage detector 14 and the horizontal axis represents the direct current voltage. The direct current detected by the current detector 11 is shown. The forward converter 3 has a constant control angle (α) control characteristic that is determined by the impedance of the AC voltage system 1 and the transformer 2 for the forward converter, a constant voltage characteristic that constantly controls a DC voltage by a constant voltage control system, and the converter itself. The operation is performed according to one of the constant current characteristics (chain line) for performing DC voltage droop by the constant current control system for preventing overload.

FIG. 10 shows the control characteristics of the resistance chopper device 5, in which the vertical axis represents the DC voltage and the horizontal axis represents the resistance chopper current detected by the current detector 12. In addition to the characteristic of the resistor 60 (chain line), the constant voltage characteristic of controlling the DC voltage by the constant voltage control system (solid line), and the constant current characteristic of the constant current control system (solid line), the resistance chopper device 5 The maximum conduction angle characteristic (broken line) and the minimum conduction angle characteristic (two-dot chain line) are provided. In this case, the voltage reference value of the constant voltage control system is set to be several percent higher than the voltage reference value of the forward converter 3.

FIG. 11 shows the control characteristics of the inverter 8. The vertical axis represents the DC voltage and the horizontal axis represents the current detector 13.
The DC current detected by is shown as the inverter current. If the load 10 is constant, the electric power passing through the inverter 8 is constant, and the power running operation operation characteristic and the regenerative operation operation characteristic are hyperbolas.

Next, control coordination of the entire power converter shown in FIG. 5 will be described with reference to FIGS. 12 and 13. The current value is the current of the forward converter 3 (current detector 1
The current detected by 1) will be used as a reference.

FIG. 12 shows the characteristics when the inverter 8 is in the power running operation (inverter operation) state. Each conversion is performed when the vehicle starts running and the inverter 8 is running at a current of less than 10%. The converter (forward converter 3, resistance chopper device 5, inverter 8) is operated at operating point (1), and the resistance chopper device 5 is operated by current control so that the current value of the forward converter 3 becomes 10%. Controlled by. The forward converter 3 controls the DC voltage to a constant value (100%) by voltage control.
Is controlled to. When the motor speed increases, passes the operating point (2), and the inverter current exceeds 10% and reaches the operating point (3), the resistance chopper device 5 is shifted to the stopped state, and the output current of the forward converter 3 is All are supplied to the load 10 via the inverter 8. When the vehicle approaches the destination and slows down, and the inverter current decreases to 10% or less, the resistance chopper device 5 shifts to the driving state again, and in reverse to the above, shifts from the driving point (2) to (1). The forward converter 3 is controlled so as to maintain a current of 10%. The difference between the output current of the forward converter 3 and the input current of the inverter 8 is absorbed by the resistance chopper device 5. That is, the forward converter 3
The current change amount of the inverter 8 under the condition that the current is maintained at 10% is absorbed by the resistance chopper device 5.

On the other hand, when the inverter 8 is in the regenerative operation (forward converter operation) state during the regenerative braking of the load 10 (vehicle motor) (see FIG. 13), the regenerative power of the load 10 (vehicle motor) drives the inverter 8. It flows in the opposite direction, is consumed by the resistor 60 of the resistance chopper device 5, and brakes the load 10.
Since the forward converter 3 is in the operating state immediately after starting the regenerative operation, each converter is operating at the operating point (1), and the resistance chopper device 5 controls so that the forward converter current becomes 10%. To be done. Next, the forward converter 3 shifts to the stopped state and the operating point (2) is reached. At this time, the resistance chopper device 5 has a value (for example, 10% higher than the DC voltage control reference value of the forward converter 3).
3%) as a DC voltage control reference value, and as a result, the resistance chopper device 5 controls the DC voltage and the regenerative current flows into the resistor 60. The increase / decrease in the regenerative current is absorbed by the resistance chopper device 5. When the regenerated electric power further decreases, the forward converter 3 is moved to the operating state, which is the operating point (3).

[0020]

As described above, in the electric power converter which is in the coordinated control operation as described above, when the inverter 8 is in the regenerative operation state, the forward converter 3 immediately after the vehicle brake is applied and the regenerative operation is started. Are operated and controlled so that the forward converter current I _d1 flows by 10%. Next, the forward converter 3 shifts to a stopped state, and the resistance chopper device 5 changes the DC voltage control reference value of the forward converter 3 by several% (for example, 103%) as a DC voltage control reference value. The direct current voltage V _dc is controlled by the resistance chopper device 5, and the regenerative current flows into the resistor 60.

In this case, the increase / decrease of the regenerative current is absorbed by the resistance chopper device 5, and if the regenerative power from the inverter 8 is equal to or less than the power at the minimum conduction angle operation of the resistance chopper device 5, the DC voltage V _dc decreases. . In order to prevent this voltage drop, the current I _d2 of the resistance chopper device 5 is monitored and the forward converter 3 is operated. However, if the operation of the forward converter 3 is delayed in this operating region, the DC voltage V _dc drops and the system stops. It will lead to the situation of.

Therefore, an object of the present invention is to provide a power conversion control device capable of suppressing the voltage fluctuation of the DC intermediate circuit and continuing the stable operation even when the regenerative power in the regenerative operation is reduced.

[0023]

In order to achieve the above object, the invention according to claim 1 is a forward converter for converting AC power from an AC power system into DC power, and this forward converter and an AC load. And a resistance chopper device that is connected in parallel between the direct current terminals of the forward converter and the inverter, which is composed of a chopper switch and a resistor in series with it, and that is connected between In the power conversion control device for controlling the power conversion device, the voltage detection means for detecting the voltage between the DC terminals and the voltage detected by the voltage detection means when the inverter is in regenerative operation and the forward converter is stopped. When the voltage becomes less than or equal to a preset voltage set value, a voltage detection means for detecting it and an operation command for issuing an operation command to the forward converter in response to the detection output of this voltage detection means It is characterized in that a stage.

According to a second aspect of the present invention, in the power conversion control device according to the first aspect, the resistance chopper device is configured such that a plurality of sets of resistance chopper circuits each including a chopper switch and a resistor connected in series are connected in parallel. The operation stop command means for issuing an operation stop command to a part of the resistance chopper circuit of the resistance chopper device in place of the operation command means for issuing an operation command to the forward converter in response to the detection output of the voltage detection means. It is characterized by having.

According to a third aspect of the present invention, in the power conversion control device according to the first aspect, the chopper switch of the resistance chopper device is configured as a PWM control type, and responds to the detection output of the voltage detection means. Instead of the operation command means for issuing an operation command to the forward converter, means for changing the frequency of the PWM carrier signal for controlling the resistance chopper device to a lower value is provided.

According to a fourth aspect of the present invention, in the power conversion control device according to the first aspect, instead of the voltage detection means, an operation mode for detecting when the inverter switches from regenerative operation to power running operation Detection means is provided, and the operation command means issues an operation command to the forward converter in response to the detection output of the operation mode detection means.

[0027]

According to the invention described in claim 1, by controlling the operation timing of the forward converter in response to the output of the voltage detecting means, the fluctuation of the DC voltage is suppressed even when the regenerative power is lowered, Stable operation can be secured.

According to the second aspect of the present invention, by stopping the operation of a part of the resistance chopper circuit of the resistance chopper device in response to the detection output of the voltage detecting means, the direct current is maintained even when the regenerative power is reduced. It is possible to suppress fluctuations in voltage and ensure stable operation.

According to the third aspect of the present invention, by changing the frequency of the PWM carrier signal of the resistance chopper device to a lower value in response to the detection output of the voltage detecting means, even when the regenerative power decreases. It is possible to suppress fluctuations in DC voltage and ensure stable operation.

According to the fourth aspect of the present invention, the operation mode detecting means for detecting the switching of the inverter from the regenerative operation to the power running operation is provided, and the operation is performed in response to the detection output of the operation mode detecting means. By issuing the operation command to the forward converter by the command means, it is possible to suppress the fluctuation of the DC voltage even when the regenerative power is reduced, and to ensure stable operation.

[0031]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an essential part of an embodiment of the invention described in claim 1 of the present invention. FIG. 1 shows another level detection circuit 100 in addition to the three level detection circuits 73, 74 and 75. Level detection circuit 73,
Reference numerals 74 and 75 are the same as the level detection circuits denoted by the same reference numerals in FIG. The output signal of the current detector 11 that detects the DC output current I _d1 of the forward converter 3 is input to the level detection circuit 74, where it is identified that the detected current I _d1 becomes substantially equal to the current setting value of 10%. Sometimes it outputs a "1" signal. A predetermined hysteresis width is set for the current setting value, and after the "1" signal is output, it is maintained within the hysteresis width, and when the current value exceeds the hysteresis width, it becomes a "0" signal. The level detection circuit 73 includes the detection current I _d2 of the current detector 12, that is, the resistance chopper device 5.
"1" when the detected value of the current flowing in the input current is input and it is determined that the detected current I _d2 becomes almost equal to the current setting value of 5%.
The signal is output. A predetermined hysteresis width is set for the current setting value, after outputting the "1" signal, it is maintained while it is within the hysteresis width, and when the current value exceeds the hysteresis width, it becomes a "0" signal. . The level detection circuit 75 outputs a "1" signal when it determines that the detected current value I _d2 has become substantially equal to the current setting value of 15%. A predetermined hysteresis width is set for the current setting value,
After the "1" signal is output, it is maintained within the hysteresis width, and when the current value is below the hysteresis width, the "0" signal is output. The level detection circuit 100 includes a detection voltage of the voltage detector 14, that is, a DC voltage V of the converter.
_dc is introduced, where the detected DC voltage is 95% of the voltage setting value.
When it becomes less than%, a detection output is issued.

The detection output signal of the level detection circuit 73 is AN
The detection output signals of the level detection circuits 74 and 75, which are input to the first input terminal of the D circuit 78, are output to the first input terminal of the AND circuit 79.
And to the second input terminal. Level detection circuit 10
The detection output signal of 0 is input to the first input terminal of the AND circuit 101. The operation state signals (“1” during operation, “0” during operation) of the inverter 8 are commonly input to the second input terminals of the AND circuits 78 and 101 and the third input terminal of the AND circuit 79, respectively. It The output signal “1” of the AND circuit 79 is input to the AND circuit 92 via the delay circuit 83 as a stop command for the forward converter 3. The output signal “1” of the AND circuit 78 is input to the AND circuit 92 as a stop cancel command via the delay circuit 82 and the OR circuit 102. The output signal "1" of the AND circuit 101 is also input to the AND circuit 92 via the OR circuit 102 as a stop release command.

The circuit of FIG. 4 which issues a command to start / stop the resistance chopper device 5 and the forward converter 3 is also used in the present invention.

The operation of the resistance chopper device 5 configured as described above will be described for the case where the inverter 8 is in the power running operation and the case where it is in the regenerative operation.

The inverter 8 carries out a power running operation (inverter operation) to start vehicle running, and the forward converter 3 outputs 15%, the inverter 8 outputs 10%, and the resistance chopper device 5 outputs up to 5% as rough values of the operating current. Is raised, the level detection circuit 71 (FIG. 4) causes the output current I _{d1 of the} forward converter 3 to rise.
When the current exceeds 15% of the set value, a level detection signal is output, and the level detection circuit 72 (FIG. 4) causes the current I _d2 of the resistance chopper device 5 to _fall below 5% of the set value. Output the detection signal. At this time,
Since the inverter 8 is in the power running mode, the AND circuit 7
After the AND condition of 6 is satisfied and the delay circuit 81 is set for the time limit,
A stop signal is input to the AND circuit 90 via the OR circuit 86, and the operation of the resistance chopper device 5 is stopped.

When the vehicle approaches the destination and the current I _d1 of the forward converter 3 becomes about 10% to reduce the speed and the output of the level detection circuit 71 becomes "0", the A of the AND circuit 76 becomes
The ND condition is no longer satisfied, the AND circuit 90 is released from the switch-off state, and the resistance chopper device 5 receives the AN signal.
An operation command is output from the D circuit 77. As a result, the resistance chopper device 5 shifts to the operating state, and the current I _d1 of the forward converter 3 is controlled.

Next, the case where the inverter 8 is in the regenerative operation (forward converter operation) will be described with reference to FIGS. 1 and 4. Immediately after the vehicle is braked and the regenerative driving operation is started, the forward converter 3 is operating, and when the current I _d1 of the forward converter 3 becomes 10% or less of the set value, the level detection circuit 74 outputs a detection output, Further, when the current I _d2 of the resistance chopper device 5 becomes 15% or more of the set value, the level detection circuit 75 outputs a detection output, and at this time, the inverter 8 is in the regenerative operation state. Is satisfied, the AND condition of the AND circuit 92 is satisfied, and after the delay circuit 83 is set, the AND circuit 92 outputs a stop command. This stop command is issued by the AND circuit 91.
To turn off. As a result, the AND circuit 91 issues a stop command to the forward converter 3 to stop the operation of the forward converter 3, and the resistance chopper device 5 causes the resistance chopper device 5 to output a value several percent higher than the DC voltage control reference value of the forward converter 3. For example, 103%) is controlled by a constant voltage characteristic having a DC voltage control reference value, and the DC voltage V _dc is controlled by the resistance chopper device 5 to bring a regenerative current into the resistor 60. In this case, the increase / decrease of the regenerative current is absorbed by the resistance chopper device 5.

When the regenerative current further decreases, it may be detected by the current or the voltage. When the forward converter 3 is started by the current detection circuit, the current I _{d2 of the} resistance chopper device 5 is detected. Becomes less than 5% of the current setting value of the level detection circuit 73, the level detection circuit 73 detects it, and the inverter 8 is in the regenerative operation state. Therefore, the AND condition of the AND circuit 78 is satisfied, and the delay occurs. After the setting time of the circuit 82, the "1" signal is input to the OR circuit 102, the AND circuit 92 is switched off, the stop release signal of the forward converter 3 is output, and the forward converter 3 is output via the AND circuit 91. Is restarted.

On the other hand, when the rate of decrease in regenerative power is steep,
In the current detection circuit, the operation of the forward converter 3 is delayed by the set time limit of the delay circuit 82, so that it appears in the main circuit phenomenon as a decrease in the DC voltage V _dc . This is because the power consumed at the minimum conduction angle of the resistance chopper device 5 is larger than the regenerative power generated by the inverter 8.

When the DC voltage V _dc becomes 95% or less of the voltage setting value of the level detection circuit 100, the level detection circuit 100 outputs a detection output, the AND condition of the AND circuit 101 is established, and the OR circuit 102 is operated. The AND circuit 92 is switched off, the stop release signal of the forward converter 3 is output, and the forward converter 3 is restarted.

According to the embodiment described above, when the inverter 8 is in the regenerative operation and the regenerative power of the inverter 8 is rapidly reduced, the forward converter 3 is promptly started to change the DC voltage V _dc . Can be suppressed.

In the embodiment described above, the DC voltage V _dc of the converter is detected and the forward converter 3 is operated. However, by reducing the operation area of the resistance chopper device 5, the inverter 8 can be operated. The reduction area of the regenerative operation of the resistance chopper device 5 can be widened.

FIG. 2 shows an embodiment in which a part of the multi-group chopper device is stopped, and FIG. 3 shows an embodiment in which the PWM carrier frequency is lowered.

FIG. 2 shows that, instead of restarting the forward converter 3, the first resistance chopper of the resistance chopper circuit which constitutes the first group, that is, the resistance chopper device 5, of the chopper device of the four-group parallel structure. shows an embodiment that is configured to the shutdown circuit is different from the PWM carrier control circuit in FIG. 8 detects the level of the DC voltage V _dc, the DC voltage V _dc falls below 98% A level detection circuit 110 that outputs a “1” signal is provided, and its output is output to the NOT circuit 10
4 and inputs the AND condition of the output of the NOT circuit 104 and the gate pulse ON / OFF signal to the AND circuit 1
If the DC voltage V _dc is 98% or more, the gate pulse output condition is satisfied and the AND circuit 39
The gate pulse 1 is output from (see FIG. 8). The PWM carrier generation circuit 31, the comparison circuit 35, and the AND circuit 39 are the same as those shown in FIG.

When the direct current voltage V _dc falls below 98% when the regenerative current of the inverter 8 drops, the output signal of the level detection circuit 110 changes to "1", so that the output signal of the AND circuit 105 becomes "0". , The first group chopper switch 51
Output pulse is eliminated, the operation is performed only by the remaining three groups, and the capacity of the resistance chopper device 5 can be reduced.

In the apparatus of FIG. 3, the frequency of the PWM carrier generation circuit is set when the DC voltage V _dc drops below 98% by the output of the level detection circuit 110 and the operation command to the resistance chopper device 5. A frequency switching command for lowering is sent to the oscillator 30 to lower the PWM carrier frequency. Thereby, the capacity of the resistance chopper device 5 can be reduced, and the current average value thereof can be reduced.

Further, the signal control circuit can be configured so that the inverter 8 is in the power running mode and the forward converter 3 is activated to reduce the delay of the detection signal.

[0048]

According to the present invention, the resistance chopper device consumes at the minimum conduction angle when the inverter is in the regenerative operation (forward converter operation) with a small electric power or when the regenerative state is changed to the power running state. Even if the regenerative power value is lower than the power to be used, the DC voltage is monitored, the forward converter is restarted, and the capacity of the resistance chopper device is reduced. It is possible to prevent a voltage drop and maintain stable operation of the power converter.

[Brief description of drawings]

FIG. 1 is a control block diagram of a main part of a device that controls a resistance chopper device according to an embodiment of the present invention.

FIG. 2 is a control block diagram of an apparatus for performing one-group stop of the resistance chopper device according to the embodiment of the invention of claim 2;

FIG. 3 is a control block diagram of a PWM carrier frequency switching device according to an embodiment of the present invention.

4 is a control block diagram of a forward converter and resistance chopper device used in conjunction with the device of FIG.

FIG. 5 is a main circuit configuration diagram of a power conversion device to which the present invention is applied.

FIG. 6 is a main circuit configuration diagram of a resistance chopper device having a 4-group parallel configuration.

FIG. 7 is a block diagram of a control device that controls the resistance chopper device.

FIG. 8 is a block diagram of an apparatus for controlling a PWM signal for a resistance chopper device.

FIG. 9 is a control characteristic diagram of the forward converter.

FIG. 10 is a control characteristic diagram of the resistance chopper device.

FIG. 11 is a control characteristic diagram of the inverter.

FIG. 12 is an overall control characteristic diagram during power running of the inverter in the power conversion device.

FIG. 13 is an overall control characteristic diagram during regenerative operation of the inverter in the power conversion device.

[Explanation of symbols]

 1 AC power system 2 Transformer for forward converter 3 Forward converter 4 DC reactor 5 Resistance chopper device 7 Power capacitor 8 Inverter 9 Inverter transformer 10 Load 11, 12, 13 Current detector 14 DC voltage detector 19 Resistance chopper device Control device 20 DC voltage reference circuit 21 Current reference circuit 22 Constant voltage control circuit 23 Constant current control circuit 24 Limiter circuit 25 Control signal selection circuit 26, 27 Adder circuit 30 Oscillator 31, 32, 33, 34 PWM carrier generation circuit 35, 36, 37, 38 Comparing circuit 39, 40, 41, 42 AND circuit 71, 72, 73, 74, 75 Level detecting circuit 76, 77, 78, 79 AND circuit 81, 82, 83 Delay circuit 85, 86, 87 OR Circuit 90, 91, 92 AND circuit 100, 110 Level detection circuit 10 1, 105 AND circuit 102 OR circuit 104 NOT circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H02P 7/00 101 K 7/63 302 R

Claims (4)

[Claims] 1. A forward converter for converting alternating current power from an alternating current power system to direct current power, an inverter connected between the forward converter and an alternating current load and capable of power running operation and regenerative operation, and a chopper switch. In a power conversion control device for controlling a power conversion device comprising a resistor chopper device connected in parallel between the DC terminals of the forward converter and an inverter consisting of a resistor in series with it, a voltage between the DC terminals When the inverter is in a regenerative operation and the forward converter is not in operation, the voltage detected by the voltage detector is detected when the voltage detected by the voltage detector is equal to or lower than a preset voltage set value. A power conversion device comprising: a voltage detection unit for detecting; and a driving command unit for issuing a driving command to the forward converter in response to a detection output of the voltage detection unit. Control device. 2. The power conversion control device according to claim 1, wherein the resistance chopper device is configured by connecting a plurality of sets of resistance chopper circuits each including a chopper switch and a resistor in series with the resistance chopper in parallel. In response to the detection output of the means, in place of the operation command means for issuing an operation command to the forward converter, an operation stop command means for issuing an operation stop command to a part of the plurality of resistance chopper circuits is provided. A power conversion control device characterized by the above. 3. The power conversion control device according to claim 1, wherein the chopper switch is configured as a PWM control type, and outputs an operation command to the forward converter in response to a detection output of the voltage detection means. A power conversion control device comprising means for changing the frequency of the PWM carrier signal for controlling the chopper switch to a lower value, instead of the operation command means for issuing. 4. The power conversion control device according to claim 1, further comprising, in place of the voltage detecting means, operation mode detecting means for detecting when the inverter switches from regenerative operation to power running operation, The power conversion control device, wherein the operation command means issues an operation command to the forward converter in response to a detection output of the operation mode detection means.