JP2003189640A - Power converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To keep stable control even under such a load which repeats powerrunning/regeneration frequently. <P>SOLUTION: A thyristor converter comprises a forward converter which supplies a DC power to a voltage type inverter load and an inverter which regenerates the regeneration electric power from the voltage type inverter into an AC power source. The electric power converter selectively operates/ controls the forward converter or the inverter through a current mirror loop so that the deviation of a DC-side main circuit voltage of the thyristor converter relative to a voltage reference comes to be zero. If the DC-side main circuit voltage drops, switching between the forward converter and the inverter is limited until the voltage reaches a prescribed level where the voltage type inverter is controlled with no obstruction. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a thyristor converter having a smoothing capacitor in a DC main circuit and comprising a forward converter for powering operation and an inverse converter for regenerative operation to provide a direct current to a load such as a voltage source inverter. The present invention relates to a power converter that supplies power.

[0002]

2. Description of the Related Art When operating a plurality of inverter devices represented by a DC input voltage source inverter having a smoothing capacitor on the input side, a system configuration using a common power converter for these loads is shown in FIG. Shown in.

In FIG. 4, an AC power source 1 is a thyristor converter including a forward converter 20 for converting AC power to DC and an inverse converter 21 for regenerating regenerative power from a load to the AC power source 1. Device 2 is connected. The DC terminal of the thyristor converter 2 is connected to a plurality of DC input type voltage source inverters 5 as loads via a smoothing circuit composed of a smoothing reactor 3 and a smoothing capacitor 4.
An AC motor 6 is connected to each inverter 5 as a load.

Control of the power converter configured as described above may include control of the thyristor converter 2, that is, the forward converter 20 and the inverse converter 21, and control of the voltage source inverter 5, but here, the load is used. Since the latter, that is, the voltage source inverter 5 which functions as the above, is not directly related to the gist of the present invention, its control will not be described in detail, and only the former, that is, the control of the thyristor converter 2 will be described below.

In the voltage control circuit (AVR) 9, the voltage reference signal Vref is compared with the DC voltage detection value Vfbk relating to the output voltage Vd of the forward converter 20 detected by the voltage detector 7, and the deviation (voltage Deviation) A current reference Iref for making Vdev zero is generated. Current control circuit (ACR) 10
At, the current reference signal Iref is compared with the AC side current detection value Ifbk of the thyristor converter 2 detected by the current detector 8 to generate a phase control signal PH that makes the deviation (current deviation) zero. To do. Based on this phase control signal PH, the operation of the thyristor converter 2 is controlled via the phase control circuit (PHC) 11. This allows the thyristor converter 2
DC side output voltage, that is, DC voltage Vd is the voltage reference Vref
Is controlled so that the value corresponds to.

The phase control circuit 11 outputs a gate signal G1 (for the forward converter 20) or a gate signal G2 (for the inverse converter 21) having an ignition phase according to the phase control signal PH, and the switching judgment is made. When the polarity of the current reference Iref determined by the circuit (CHG) 13 is positive, the determination signal A is output and the output of the gate signal G1 for controlling the operation of the forward converter 20 is permitted. Discrimination signal B if negative
Is output to permit the output of the gate signal G2 for controlling the operation of the inverse converter 21. In this way, the forward converter 20
One of the two or the inverse converter 21 is operated and controlled.

As will be described with reference to the flow chart of FIG. 5, the memory circuit (MEM) 12 judges that the change of the polarity of the current reference Iref is detected by the switching judgment circuit 13 (steps S21, S22, S24). At the time point, the initial phase of the operation of the forward converter 20 or the inverse converter 21 to which the control is transferred by the switching operation is determined from the DC voltage detection value Vfbk and held. During the period of the control switching operation from the forward converter 20 to the inverse converter 21 (step S25) or the control switching operation from the inverse converter 21 to the forward converter 20 (step S23), the initial period held in the memory circuit 12 is held. An inverse converter 21 or a forward converter 20 converts a gate signal having an ignition phase corresponding to the phase.
(Step S26).

[0008]

When the thyristor converter has a load that frequently repeats the operation of powering / regeneration, overvoltage and overcurrent may occur due to the dead time when the thyristor converter is switched. In FIG. 6, the switching operation of the thyristor converter 2 is performed due to a slight increase in the DC voltage detection value Vfbk, as shown in part A, and as a result, the DC voltage detection value Vfbk and the current reference signal Iref fluctuate. However, this shows that the detected current value Ifbk also fluctuates.

Therefore, an object of the present invention is to provide a power conversion device which can continue stable control even in the case of a load in which power running / regeneration is frequently repeated.

[0010]

In order to solve the above-mentioned problems, the invention according to claim 1 is an order in which AC power from an AC power supply is converted into DC voltage and DC power is supplied to a voltage source inverter as a load. Equipped with a thyristor converter consisting of a converter and an inverse converter that regenerates regenerative power from a voltage source inverter into an AC power supply, and eliminates the deviation of the DC side main circuit voltage of the thyristor converter from a given voltage reference. To generate a phase control signal based on the result of comparison between the current reference and the current value of the thyristor converter, and forward conversion using the gate signal of the ignition phase according to the phase control signal. In a power converter in which operation of either the power converter or the inverse converter is controlled, when the DC side main circuit voltage drops, the DC side main circuit voltage controls the voltage source inverter. Time to reach a predetermined level does not hinder upon is characterized in that it comprises means for limiting the switching operation between the forward converter and the inverter. According to the present invention, for the switching operation between the forward converter and the inverse converter, the switching operation is limited until the DC voltage reaches a level that does not hinder the control of the load inverter. It is possible to prevent the thyristor converter from reacting to a transient change in the output of the load inverter, and it is possible to stably control the thyristor converter.

According to a second aspect of the present invention, a forward converter for converting the AC power from the AC power supply into a DC voltage and supplying the DC power to the voltage source inverter as a load, and the regenerative power from the voltage source inverter to the AC source. It is equipped with a thyristor converter consisting of an inverse converter that regenerates the power supply, and generates a current reference for zeroing the deviation of the main circuit voltage on the DC side of the thyristor converter from the given voltage reference. A phase control signal is generated based on the result of comparison with the current value of the converter, and one of the forward converter and the inverse converter is operation-controlled using the gate signal of the ignition phase corresponding to the phase control signal. In such a power converter, when the voltage deviation obtained as the difference between the voltage reference and the DC main circuit voltage decreases, the voltage deviation hinders the control of the voltage source inverter. No period to reach a predetermined level, characterized by comprising means for limiting the switching operation between the forward converter and the inverter. During the period until the voltage deviation related to the difference of the DC voltage with respect to the voltage reference reaches a predetermined level that does not hinder the control of the load inverter, the switching operation of the thyristor converter is limited to limit the thyristor converter. It can be controlled stably.

According to the third aspect of the present invention, a forward converter for converting the AC power from the AC power supply into a DC voltage and supplying the DC power to the voltage type inverter as a load, and the regenerative power from the voltage type inverter are converted into AC. It is equipped with a thyristor converter consisting of an inverse converter that regenerates the power supply, and generates a current reference for zeroing the deviation of the main circuit voltage on the DC side of the thyristor converter from the given voltage reference. A phase control signal is generated based on the result of comparison with the current value of the converter, and one of the forward converter and the inverse converter is operation-controlled using the gate signal of the ignition phase corresponding to the phase control signal. In such a power conversion device, when the current-based time integrated value decreases, the current-based time integrated value becomes a predetermined level that does not hinder the control of the voltage-source inverter. Time to reach is characterized in that it comprises means for limiting the switching between the forward converter and the inverter. According to the present invention, the thyristor converter can be stably controlled by limiting the switching operation of the thyristor converter until the current reference integrated value reaches the predetermined level.

The invention according to claim 4 relates to claims 1 to 3.
In the power converter according to any one of paragraphs (1) to (7), when the switching restriction is released while the switching to the forward converter is being restricted, the current reference operated on the positive polarity side is When the switching limit is released to the minimum possible value and while switching to the inverse converter is being limited, the current reference operating on the negative polarity side is the minimum value at which operation in the inverse converter is possible, Furthermore, by resetting the phase control signal to a predetermined memory value,
It is characterized in that it is provided with means for suppressing fluctuations in the output voltage of the thyristor converter due to overshoot of the control system. When the polarity of the voltage deviation was switched, the current reference that operated on the positive side during the switching limit of the forward converter was set to the minimum value at which the inverter can operate, and the negative side during the switching limit of the inverse converter. The current reference that operates in the above manner is reset to the minimum value that allows operation in the forward converter, and the phase control signal is reset to a predetermined memory value to suppress fluctuations in the output voltage of the thyristor converter due to overshoot of the control system. However, the thyristor converter can be controlled stably.

The invention according to claim 5 relates to claims 1 to 3.
In the power converter according to any one of paragraphs (1) to (5), the current reference is reset to zero and the phase control signal outputs a predetermined memory value while switching between the forward converter and the inverse converter is limited. It is characterized by comprising means for suppressing the fluctuation of the output voltage of the thyristor converter due to the overshoot of the control system when the switching limitation is released by continuing to output. When the switching limit of the thyristor converter is reset, the current reference is reset to zero, and the phase control signal continues to output the specified memory value, so that the overshoot of the control system when the switching limit of the thyristor converter is released. It is possible to suppress the fluctuation of the output voltage of the thyristor converter due to and to stably control the thyristor converter.

The invention according to claim 6 is the invention according to claims 1 to 3.
In the power converter according to any one of the items 1 to 3, even if a voltage deviation obtained as a deviation of a DC main circuit voltage with respect to a voltage reference or a current reference reaches a switching level of a thyristor converter, a polarity of a current flowing through a smoothing capacitor is a voltage. When the deviation is canceled, a means for limiting switching between the forward converter and the inverse converter is provided. The current of the smoothing capacitor connected to the DC side main circuit is detected, and even if the voltage deviation related to the difference of the DC voltage from the voltage reference or the current reference reaches the switching level of the thyristor converter, the polarity of the current of the smoothing capacitor is the voltage. If the deviation is canceled, the thyristor converter can be stably controlled by limiting the switching operation of the thyristor converter.

[0016]

1 and 2 show an embodiment of the present invention. In FIG. 1, the same circuit elements as those in FIG. 4 are designated by the same reference numerals, and their individual description will be omitted.

The control device of FIG. 1 is provided with an integrating circuit 14 and a switching condition circuit 15. Further, a memory circuit (MEM) 16 is provided instead of the memory circuit 12 of FIG. 4, and a switching determination circuit (CH) is provided instead of the switching determination circuit 13.
G) 17 is provided. The device of FIG.
A current detector 22 for detecting the current Idc of the smoothing capacitor 4 in the main circuit of FIG. 1 is provided.

The integrating circuit 14 integrates the current reference signal Iref output from the current control circuit 9 and outputs the integrated value ΣIref. The switching condition circuit 15 inputs the capacitor current Idc detected by the current detector 22 and the voltage deviation signal Vdev in addition to the current reference integrated value ΣIref obtained by the integration circuit 14, and will be described with reference to FIG. When the three conditions are satisfied by OR logic, the switching disapproval signal S1 is output.

The memory circuit 16 receives the DC voltage detection value Vfbk detected by the voltage detector 7 and the switching non-permission signal S1 output from the switching condition circuit 15, and receives the switching non-permission signal from the switching condition circuit 15. When the change of S1 is determined, from the DC voltage detection value Vfbk at that time,
The initial phase of the operation of the forward converter 20 or the inverse converter 21 to which the control is transferred by the switching operation is determined and held.

The switching determination circuit 17 receives the current reference Iref from the current control circuit 9 and the switching non-permission signal S1 from the switching condition circuit 15, and the switching non-permission signal S1 is inactive (S1 = 0). Only when the polarity of the current reference Iref is positive, the discrimination signal A is output to permit the output of the gate signal G1 for controlling the operation of the forward converter 20, and when the polarity of the current reference Iref is negative, Gate signal G2 for outputting the discrimination signal B and controlling the operation of the inverse converter 21
Output is allowed. During the period when the switching disapproval signal S1 is active (S1 = 1), switching of the determination signal A or B is disapproved, and the thyristor converter 2 is restricted from switching.

As shown in FIG. 2, the switching condition circuit 15 includes
The voltage deviation Vdev, the current reference integrated value ΣIref obtained by the integrating circuit 14, and the capacitor current Idc detected by the current detector 22 are input, and when the three conditions are satisfied by the OR logic, the switching disapproval signal S1 is output. . The switching condition circuit 15 includes an absolute value conversion circuit 23, a switching condition determination circuit 24,
An absolute value conversion circuit 25, a switching condition determination circuit 26, a polarity determination device 27, and OR gates 28 and 29.

To determine the first switching condition, the absolute value conversion circuit 23 obtains the absolute value | Vdev | of the voltage deviation Vdev,
This is compared with the switching limit set value A in the switching condition determination circuit 24, and when A> | Vdev |, the switching disapproval signal S1 = 1 is output via the OR gate 28. Switching limit setting value A
Is set as the amount of DC voltage fluctuation in which the absolute value of the voltage deviation Vdev is allowed with respect to the voltage reference Vref. For the second switching condition determination, the absolute value conversion circuit 25 determines the absolute value | ΣIref | of the current reference integrated value ΣIref, and the switching condition determination circuit 24 compares this with the switching limit set value B, and B> | Σ
When Iref |, the switching prohibition signal S1 = 1 is output via the OR gates 29 and 28. The switching limit set value B is set as a variation of the DC voltage in which the absolute value of the current reference integrated value ΣIref is allowed with respect to the voltage reference Vref. In order to determine the third switching condition, the polarity determiner 27 determines whether the polarity of the capacitor current Idc acts in a direction to cancel the voltage deviation Vdev, and if it does, the OR gates 29, 28. The switch disapproval signal S1 = 1 is output via. In this way, the switching non-permission signal S1 = 1 is output when any one of the three switching condition determinations is satisfied.

As shown in FIG. 3, as a basic operation of the apparatus of FIG. 1, when the switching non-permission signal S1 is inactive, that is, S = 0, when the load inverter 5 performs the power running operation, the current reference Iref is , Iref> 0 and the voltage reference V
Forward converter 2 in operation according to ref via gate signal G1
0 is continuously operated as it is (steps S10, S11,
S12), or if the reverse converter 21 is in operation, the forward converter 2
Switching to 0 is executed (steps S12 and S13). At that time, the memory 16 stores the phase of the DC voltage detection value Vfbk at the time when the switching prohibition signal S1 changes from 0 to 1 as an initial phase and holds it. When the load inverter 5 performs regenerative operation, the current reference Iref is
Iref <0 and the gate signal G2 according to the voltage reference Vref.
The inverse converter 21 which is in operation is continuously operated as it is (steps S10, S11, S14) or the forward converter 20.
If is running, switching to the inverse converter 21 is executed (steps S14 and S15). The operation of the memory 16 at that time is similar to that in the case of the forward converter operation.

One of the reasons why the thyristor converter frequently repeats the power running operation and the regenerative operation is that it responds faithfully to the polarity change of the voltage control signal or the current control signal near zero. Therefore, in the present invention, in order to eliminate such inconvenience, in order not to follow the polarity change of the control signal near zero very faithfully, the switching condition circuit 1
5 is provided, and if any of the above three conditions is satisfied here, the switching non-permission signal S1 is made active, that is, S1 = 1, and the discrimination signal A / B is switched through the switching discrimination circuit 17. Is not allowed and gate signal G1 /
Disable G2 switching. Then, the current reference Iref output from the voltage control circuit 9 is preset to the minimum value that allows regenerative operation (steps S10 and S17). As a result, the phase control signal PH is similarly preset to the corresponding value. In this way, the overshoot of the converter current immediately after the restriction of the switching operation to the inverse converter 21 is released can be suppressed.

As another method of suppressing the converter current overshoot, the current reference Iref is set while the switching prohibition signal S1 output from the switching condition circuit 15 is active and the switching operation of the thyristor converter 2 is limited. Means may be provided for resetting to zero and continuing to output the phase control signal PH to the memory location. This also makes it possible to suppress the overshoot of the converter output immediately after the restriction on the switching operation of the thyristor converter 2 is released.

[0026]

According to the present invention, it is possible to minimize the switching of the converter within a range that does not hinder the control of the inverter, and the dead of control caused by the switching operation of the converter. It is possible to provide a power conversion device that hardly causes control instability during time.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a block diagram showing details of a switching condition circuit in the device of FIG.

FIG. 3 is a flowchart showing a switching process of the present invention.

FIG. 4 is a block diagram showing a circuit configuration of a conventional device.

5 is a flowchart showing a conventional switching process executed by the apparatus of FIG.

FIG. 6 is a time chart showing an example of a DC side voltage detection value and an AC side current detection value in a conventional device.

[Explanation of symbols]

1 AC power supply 2 Thyristor converter 3 smooth reactor 4 Smoothing capacitor 5 voltage source inverter 6 AC motor 7 Voltage detector 8 Current detector 9 Voltage control circuit (AVR) 10 Current control circuit (ACR) 11 Phase control circuit (PHC) 12 Memory circuit (MEM) 13 Switching discrimination circuit (CHG) 14 Integrator 15 Switching condition circuit (SEL) 16 Memory circuit (MEM) 17 Switching discrimination circuit (CHG) 20 Forward converter 21 Inverter 22 Current detector 23 Absolute value conversion circuit 24 Switching condition judgment circuit 25 Absolute value conversion circuit 26 Switching condition determination circuit 27 Polarity detector S1 switching non-permission signal A Forward converter operating discrimination signal B Inverter operation discrimination signal PH phase control signal G1 Forward converter gate signal Gate signal for G2 inverse converter

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroaki Matsumoto             1-24 East, 2-24 Harumi-cho, Fuchu-shi, Tokyo             Shiba IT Control System Co., Ltd.             In the company F-term (reference) 5H006 AA05 BB01 BB05 CA03 CB01                       CC06 DA04 DB02 DB07 DC02                       DC05 GA01 GA04                 5H007 AA06 BB01 CA03 CB02 DA06                       DB13 DC02 DC05 GA01 GA08

Claims (6)

[Claims] 1. A forward converter that converts AC power from an AC power supply into a DC voltage and supplies the DC power to a voltage source inverter as a load, and regenerative power from the voltage source inverter is regenerated by the AC power source. A thyristor converter including an inverse converter, and generates a current reference for zeroing a deviation of a DC side main circuit voltage of the thyristor converter with respect to a given voltage reference, and the current reference and the thyristor converter. A phase control signal is generated based on the result of comparison with the current value of, and one of the forward converter and the inverse converter is operated and controlled by using the gate signal of the ignition phase according to the phase control signal. In the power converter described above, when the DC side main circuit voltage drops, the DC side main circuit voltage reaches a predetermined level that does not hinder the control of the voltage source inverter. Period until the power conversion apparatus characterized by comprising means for restricting the switching operation between the forward converter and the inverter. 2. A forward converter that converts AC power from an AC power supply into a DC voltage and supplies the DC power to a voltage-type inverter as a load, and regenerative power from the voltage-type inverter is regenerated by the AC power supply. A thyristor converter including an inverse converter, and generates a current reference for zeroing a deviation of a DC side main circuit voltage of the thyristor converter with respect to a given voltage reference, and the current reference and the thyristor converter. A phase control signal is generated based on the result of comparison with the current value of, and one of the forward converter and the inverse converter is operated and controlled by using the gate signal of the ignition phase according to the phase control signal. In the power converter described above, when the voltage deviation obtained as the difference between the voltage reference and the DC main circuit voltage is reduced, the voltage deviation controls the voltage source inverter. Time to reach a predetermined level without Ede trouble, the power conversion apparatus characterized by comprising means for restricting the switching operation between the forward converter and the inverter. 3. A forward converter that converts AC power from an AC power supply into a DC voltage and supplies the DC power to a voltage-type inverter as a load, and regenerative power from the voltage-source inverter is regenerated by the AC power supply. A thyristor converter including an inverse converter, and generates a current reference for zeroing a deviation of a DC side main circuit voltage of the thyristor converter with respect to a given voltage reference, and the current reference and the thyristor converter. A phase control signal is generated based on the result of comparison with the current value of, and one of the forward converter and the inverse converter is operated and controlled by using the gate signal of the ignition phase according to the phase control signal. In the power conversion device described above, when the time-integrated value of the current reference decreases, the predetermined time-integrated value of the current reference does not interfere with the control of the voltage source inverter. A period until Le, the power conversion apparatus characterized by comprising means for limiting the switching between the forward converter and the inverter. 4. The power conversion device according to claim 1, wherein when the switching restriction is released while the switching to the forward converter is restricted, the power converter operates on the positive polarity side. The current reference is the minimum value that allows operation in the forward converter, and when the switching restriction is released while the switching to the reverse converter is restricted, the current reference operating on the negative polarity side is reversed. The phase control signal is reset to a predetermined memory value to a minimum value that allows operation in the converter, and means for suppressing fluctuation of the output voltage of the thyristor converter due to overshoot of the control system is provided. A power conversion device characterized by: 5. The electric power converter according to claim 1, wherein the current reference is set to zero while switching between the forward converter and the inverse converter is limited. By resetting and continuing to output a predetermined memory value as the phase control signal, there is provided means for suppressing fluctuation of the output voltage of the thyristor converter due to overshoot of the control system when the switching limitation is released. A power conversion device characterized by the above. 6. The power converter according to claim 1, wherein a voltage deviation obtained as a deviation of the DC main circuit voltage with respect to the voltage reference or the current reference is a switching of the thyristor converter. When the polarity of the current flowing through the smoothing capacitor is in the direction of canceling the voltage deviation even when the level is reached, a means for limiting switching between the forward converter and the inverse converter is provided. Power converter.