JP2006254624A - Controller of ac-ac converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller of an AC-AC converter for preventing control performance from being degraded during a normal operation, and reducing an inrush current when instantaneous power interruption is restored. <P>SOLUTION: The AC-AC converter for converting an AC voltage into an AC voltage with an arbitrary magnitude and a frequency using a plurality of semiconductor switches and supplying it to a load is provided with detection means 604, 605 each detecting an input voltage of a matrix converter 200, an operation monitoring means 606 as a means for comparing the magnitude of the input voltage with an operable level, monitoring the operation and outputting a voltage restoring signal when the input voltage is restored and the converter 200 restarts after the magnitude of the input voltage is reduced to the operable level or less and the operation is stopped, a q-axis voltage instruction calculating means 608 for calculating an output voltage instruction changed with a predetermined time constant from the voltage restoring signal, and means 611, 602 and 603 for switching the converter 200 based on the output voltage instruction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a control device for an AC / AC converter that converts an AC voltage into an AC voltage having an arbitrary magnitude and frequency, and in particular, restarts the operation after temporarily stopping the operation of the AC / AC converter due to an instantaneous power failure or the like. The present invention relates to a technique for reducing the inrush current.

A matrix converter is known as an example of an AC / AC converter.
This matrix converter is a power converter that can directly obtain an AC voltage having an arbitrary magnitude and frequency from an AC power supply voltage without using a large energy buffer, and has a long life, space saving, and input current. Since it can be controlled, it can regenerate power and can suppress power harmonics.

On the other hand, since there is no energy buffer, the matrix converter can output only a voltage corresponding to the magnitude of the input voltage. For this reason, when the input voltage decreases due to a power failure or the like, the voltage that can be output also decreases, so that it is difficult to continue the operation.
Therefore, conventionally, the input voltage of the matrix converter is monitored, and if the input voltage drops below the operable level, all the semiconductor switches in the converter are turned off (hereinafter referred to as all gate cutoff), and the input voltage exceeds the operable level. When returning, an operation method is adopted in which the semiconductor switch is switched again to resume operation.

Here, Patent Document 1 describes an operation operation after power recovery from the occurrence of a power failure in a PWM cycloconverter.
FIG. 7 shows a control block diagram in Patent Document 1. First, in the main circuit, 100 is a three-phase AC power source, 200 is a matrix converter (cycloconverter), 300 is an electric motor, and 400 is a load.

The configuration and operation of the control device in FIG. 7 are as follows.
The voltage phase detection means 501 and the instantaneous voltage phase detection means 502 obtain the phase angles θ ₁ and θ ₂ of the power supply voltage, respectively. The phase angle selection unit 503 selects which _{one of} the phase angles θ ₁ and θ ₂ to use from the output information of the abnormality detection unit 504 and the timer 505.
The matrix converter control means 506 calculates an output voltage command in order to control the matrix converter 200 according to the phase angle θ ₁ or θ ₂ of the selected power supply voltage. The PWM generation unit 507 calculates a PWM pulse pattern based on the output voltage command, and switches the semiconductor switches constituting the matrix converter 200. Thereby, matrix converter 200 supplies voltage corresponding to the output voltage command to electric motor 300.

FIG. 8 shows a time chart when a power supply abnormality occurs in the configuration of FIG. First, when a power supply abnormality such as a power failure occurs at time t1, the abnormality detection means 504 outputs an operation stop signal, shuts down all gates via the PWM generation means 507, and stops the operation. At this time, the phase angle is switched from the normal phase angle θ ₁ to the instantaneous phase angle θ ₂ by the instantaneous voltage phase detection means 502.
Thereafter, when the power supply is recovered from the power supply abnormality at the time t2, the gate cutoff is released after the time T1 has elapsed from the time t2, and the instantaneous phase angle θ ₂ is continuously set during this period in order to prevent abnormal operation due to the unstable power supply voltage. used to resume operation, then, when the time T2 has elapsed from time t2, is switched to a normal phase angle theta ₁ which is detected by the voltage phase detecting means 501.

JP 2003-309974 A ([0005] to [0008], FIG. 1, FIG. 6 to FIG. 9 etc.)

  When the electric motor is operated by a power converter such as a matrix converter, an inrush current flows through the power converter and the electric motor when the operation is recovered from an instantaneous power failure or the like. This is because the motor continues to rotate due to inertia even during a power failure, and a speed electromotive force is generated according to the rotational speed. This speed electromotive force is applied to the power converter in a stepped state, resulting in a transient state. It is to do. Even when the motor is driven at a low speed and the speed electromotive force is small, if the power converter applies a step-wise voltage to respond the torque at a high speed, a transient state occurs and the inrush current flows from the power converter to the motor. May also flow.

In the prior art described in Patent Document 1, an inrush current may flow even if the operation is resumed after the phase of the power supply voltage is established at the phase angle θ ₁ .
In order to prevent the inrush current, there is a method of delaying the change in the supply voltage to the electric motor 300 by providing a filter on the output side of the matrix converter 200. However, according to this method, the inrush current after the instantaneous power failure recovery is prevented. Although it is possible, control performance during normal operation is deteriorated.
Therefore, the problem to be solved by the present invention is to provide a control device that reduces the inrush current at the time of instantaneous power failure recovery without deteriorating the control performance during normal operation.

In order to solve the above-mentioned problem, an invention according to claim 1 is an AC / AC converter that converts an AC voltage into an AC voltage having an arbitrary magnitude and frequency by a plurality of semiconductor switches and supplies the AC voltage to a load.
Means for detecting an input voltage of the converter;
A means for monitoring the operation of the converter by comparing the magnitude of the input voltage with an operable level, and after the operation is stopped when the magnitude of the input voltage falls below the operable level, the input Operation monitoring means for outputting a voltage return signal when the voltage is restored and the converter resumes operation; and
Voltage command calculation means for calculating an output voltage command that changes with a predetermined time constant by the voltage return signal;
Means for generating a drive pulse for switching the semiconductor switch based on the output voltage command.

The invention according to claim 2 is an AC / AC converter that converts an AC voltage into an AC voltage having an arbitrary magnitude and frequency by a plurality of semiconductor switches and supplies the AC voltage to a load.
Means for detecting an input voltage of the converter;
A means for monitoring the operation of the converter by comparing the magnitude of the input voltage with an operable level, and after the operation is stopped when the magnitude of the input voltage falls below the operable level, the input Operation monitoring means for outputting a voltage return signal when the voltage is restored and the converter resumes operation; and
Current command calculation means for calculating an output current command that changes with a predetermined time constant by the voltage return signal;
Voltage command calculation means for calculating an output voltage command of the converter from the output current command;
Means for generating a drive pulse for switching the semiconductor switch based on the output voltage command.

The invention according to claim 3 is the invention according to claim 1 or 2,
Calculation means for calculating the speed electromotive force of the electric motor as the load;
Means for adding the speed electromotive force to the output voltage command to generate a final output voltage command.

According to the first and third aspects of the invention, when the power supply voltage is restored after the operation is stopped due to a power failure or the like and the operation is resumed, the output voltage command is smoothly changed using the voltage restoration signal. By using the output voltage command obtained by adding the speed electromotive force according to the speed of the load, the inrush current flowing through the converter and the load can be suppressed.
According to the second aspect of the present invention, when vector control is performed, the torque current command and the time constant for obtaining the torque command are adjusted, and the output voltage command is generated based on these current commands. Thus, the inrush current can be suppressed as in the first aspect of the invention.
Thus, in the present invention, since the inrush current can be suppressed without depending on the method of providing a filter or the like on the output side of the converter, the control performance during normal operation is not impaired. Furthermore, the present invention can be configured by only a switch means for switching the time constant based on the voltage return signal and a simple calculation, and smooth restart after power return can be realized at low cost.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a first embodiment of the present invention. In FIG. 1, the configuration of the main circuit is the same as that in FIG.
Note that the phases on the three-phase input side of the matrix converter 200 are R, S, and T, and the phases on the three-phase output side are U, V, and W. The matrix converter 200 is connected between the R, S, T phase on the three-phase input side and the U, V, W phase on the three-phase output side in the same manner as the PWM cycloconverter described in Patent Document 1. Each of the three phases is composed of a total of nine bidirectional semiconductor switches, and one semiconductor switch is composed of, for example, two IGBTs connected in reverse parallel.

In the present embodiment, description will be made assuming that a virtual AC / DC / AC conversion method is used as an example of control of the matrix converter 200.
Briefly describing the virtual AC / DC / AC conversion method, this method virtually controls a rectifier and an inverter in a matrix converter and independently controls them. As shown in FIG. In this method, the PWM pulses obtained by the rectifier PWM generation means 601 and the virtual inverter PWM generation means 602 are finally synthesized by the PWM pulse synthesis means 603 to obtain the switching pattern of the matrix converter 200. Note that the PWM pulse synthesizing unit 603 can block all the gates by an operation stop signal described later.

In the control device according to the present embodiment using the virtual AC / DC / AC conversion method described above, the voltage detection unit 604 detects the input voltages v _r , v _s , and v _t of the matrix converter 200. Size calculating means 605 of the input voltage, calculates the magnitude of the input voltage vector _{v i} from the detected value _{v r, v s, v t} .
FIG. 2 is a functional block diagram of the calculation means 605. The detected values v _r , v _s , and v _t are converted into three-phase / two-phase by the following formula 1 to obtain AC biaxial components v _α and v _β . Next, the magnitude of the voltage vector v _{i is} obtained by the calculation of Equation 2.

In addition to the above calculation, the input voltage magnitude calculation means 605 may be realized by full-wave rectifying the three-phase input voltage and obtaining an average value thereof. The voltage detecting means 604, without detecting all three phases of voltage, calculates the voltage v _s of the remaining one phase based on the equation 3 by detecting the two-phase voltage _{(v r,} v _t) Alternatively, the voltage of each phase can be substituted into Equation 1 thereafter.
[Equation 3]
From v _r + v _s + v _t = 0, v _s = v _r −v _t

The magnitude of the input voltage vector obtained by Expression 2 is input to the operation monitoring unit 606.
FIG. 3 is a flowchart showing the operation of the operation monitoring unit 606. It is determined whether or not the magnitude of the input voltage vector has decreased below the operable level of the matrix converter 200 (step S1). As a result, if it is determined that the voltage has decreased, a decrease flag is set (S1 YES, S2). . Then, an operation stop signal is output (S3), and all gates are cut off via the PWM pulse synthesizing means 603.

If no decrease in input voltage is detected (S1 NO) and there is no operation stop signal (S4 YES), it is determined whether or not a decrease flag is being set (S5). Here, if the decrease flag is being set (S5 YES), it can be determined that the input voltage has once decreased, but the operation stop signal has subsequently disappeared, so that the input voltage has recovered and exceeded the operable level. Then, a voltage return signal is output (S6), the lowering flag is further reset (S7), and the operation is restarted.
Thereafter, in step S5, when it is detected that the lowering flag is in the reset state (S5 NO), the process proceeds to normal operation and the voltage return signal is cleared (S8).
If there is an operation stop signal even though there is no decrease in input voltage (S4 NO), it is judged that there is another cause of abnormality and an emergency stop signal is output (S9), all gates are shut off or an alarm is generated. Etc.

In FIG. 1 again, the voltage return signal output from the operation monitoring unit 606 is input to the q-axis voltage command calculation unit 608.
Here, FIG. 4 is a block diagram showing the configuration of the q-axis voltage command calculation means 608 and the operation pattern creation means 607 in the preceding stage.

As represented by the V / f control, the operation pattern creating means 607 uses the frequency voltage conversion means 621 and the low-pass filter 622 in FIG. 4 to generate a voltage command v on the rotation coordinates of two orthogonal axes proportional to the speed command ω ^*. _q ^* is calculated. When the voltage return signal output from the operation monitoring unit 606 is on, the q-axis voltage command calculation unit 608 sets the time constant τ of the low-pass filter 622 through the switch 623 in FIG. When τ ^* is set and the voltage return signal is off, the normal operation is performed by setting the time constant τ of the low-pass filter 622 to a reference value by shortening.

If the q-axis voltage command v _q ^* calculated by the operation pattern creation means 607 is used as the voltage command after return, the speed electromotive force of the motor 300 is generated when the motor 300 is rotating by inertia. Therefore, an inrush current flows from the load 400 to the matrix converter 200 side. Therefore, the speed electromotive force e _q ^* is calculated by multiplying the speed command ω ^* and the magnetic flux command φ ^* by the multiplication means 624 in FIG. 4, and this is added to the original q-axis voltage command v _q ^* by the addition means 625. Thus, the final q-axis voltage command v _q ^** is obtained.
The time constant set in the low-pass filter 622 may be other than the electric time constant of the electric motor 300 as long as it can prevent the inrush current at the time of return. In this embodiment, the speed electromotive force e _q ^* is simply obtained by multiplying the speed command ω ^* and the magnetic flux command φ ^* (using the rated value). You may calculate using a value etc.

As shown in FIG. 1, the q-axis voltage command v _q ^** is input to the virtual inverter command calculation means 611 together with the d-axis voltage command v _d ^* (usually set to v _d ^* = 0), and further integrated. Based on the phase angle θ from the means 609, an output voltage command for the virtual inverter is generated. The virtual inverter PWM generation means 602 generates a PWM pulse for outputting a voltage corresponding to the output voltage command, and outputs it as a PWM pulse for the virtual inverter.
On the other hand, the virtual rectifier command calculating unit 610 calculates a virtual rectifier current command based on the detected voltage values v _r , v _s , and v _t , and the virtual rectifier PWM generating unit 601 calculates an input current corresponding to the current command. A PWM pulse for flowing is generated and output as a PWM pulse for the virtual rectifier.
The PWM pulse synthesizing unit 603 generates drive pulses for the 18 semiconductor switches of the matrix converter 200 by synthesizing output pulses of the generating units 601 and 602 (that is, switching functions for the virtual rectifier and the virtual inverter). Output.

Next, FIG. 5 shows an operation time chart of the present embodiment.
When the magnitude of the input voltage vector | v _i | falls below the operable level at time t11, the operation stop signal is set in steps S1 to S3 in FIG. 3 described above, the speed command ω ^* becomes zero, and all gates Is cut off, and the q-axis voltage command v _q ^{* and} thus the output voltage becomes zero. Next, when the magnitude of the input voltage vector | v _i | returns to the operable level or higher at time t12, the voltage return signal is set in steps S4 to S6 in FIG.

Thereby, the time constant of the low-pass filter 622 of FIG. 4 constituting the operation pattern creating means 607 is set to the time constant τ ^* of the electric motor 300, and the q-axis voltage command v _q ^* increases smoothly. Then, by adding the the q-axis voltage command v _q ^* and the speed electromotive force corresponding to the rotational speed (speed command omega ^*) when the e _q ^*, q-axis voltage command v _q ^** are determined, An output voltage command for the matrix converter 200 is obtained by the virtual inverter command calculation means 611.
With the above operation, even when the power supply is restored after the power failure while the electric motor 300 is rotating with inertia, the matrix converter 200 can output a smooth voltage corresponding to the torque required for the electric motor 300, and the operation can be restored. It becomes possible to suppress the inrush current at the time.

  Next, FIG. 6 is a block diagram showing a second embodiment of the present invention. The same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted. The following description will focus on the parts different from those in FIG.

In this embodiment, vector control is used to control the virtual inverter.
That is, the speed information from the speed detector 632 and the speed command ω ^* are input to the adding means 633 to obtain the speed deviation, and the speed adjusting means 631 calculates the torque command T ^* so that the deviation becomes zero. To do. The q-axis current command calculation means 634 calculates a q-axis current command i _q ^* proportional to the torque command T ^* .
From this q-axis current command i _q ^* , the time constant of the low-pass filter 635 is adjusted according to the voltage return signal in the same manner as in the first embodiment to obtain the final q-axis current command i _q ^** .

A deviation between the q-axis current command i _q ^** and the q-axis current detection value i _q obtained by the current detection means 638, the phase detector 639 and the coordinate conversion means 640 is calculated by the addition means 636, and this deviation is calculated. The q-axis current control means 637 calculates the q-axis voltage command v _q ^* so as to make it zero. In addition, the q-axis current control means 637 adds the speed electromotive force e _q ^* obtained from the product of the speed command ω ^* and the magnetic flux command to the q-axis voltage command v _q ^* in the same manner as described above to obtain the final q The shaft voltage command v _q ^** is obtained.
On the other hand, the d-axis current control unit 642, the deviation between the d-axis current command _i ^{d *} and the d-axis current detection value _{i d} obtained by adding means 641 to zero, calculating a d-axis voltage command _v ^{d *} To do. Then, the coordinate conversion unit 643 performs two-phase / three-phase conversion using the d-axis voltage command v _d ^* , the q-axis voltage command v _q ^**, and the phase angle θ, and generates an output voltage command of the virtual inverter.
Subsequent operations are the same as those in the first embodiment.

In the above configuration, instead of obtaining the q-axis current command i _q ^** by the low-pass filter 635, the torque command output from the speed adjusting unit 631 by changing the position of the low-pass filter 635 to the output side of the speed adjusting unit 631. T ^* may be adjusted.
Further, although the q-axis current control system and the d-axis current control system are constituted by feedback control systems, the voltage command may be calculated in a feedforward manner from the current command of each axis.
In addition, the current detection means 638 does not need to detect the three phases, but detects the two phases, and replaces Equation 3 in the first embodiment with the currents i _u , i _v , i _w and the remaining one phase. Can also be calculated.

It is a block diagram which shows 1st Embodiment of this invention. It is a functional block diagram of the magnitude | size calculating means of the input voltage in FIG. It is a flowchart which shows operation | movement of the driving | running | working monitoring means in FIG. It is a block diagram which shows the structure of the driving | operation pattern creation means in FIG. 1, and a q-axis voltage command calculating means. It is an operation time chart of this embodiment. It is a block diagram which shows 2nd Embodiment of this invention. FIG. 11 is a control block diagram in Patent Document 1. 8 is a time chart when a power supply abnormality occurs in the configuration of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100: Three-phase alternating current power supply 200: Matrix converter 300: Electric motor 400: Load 601: Virtual rectifier PWM control means 602: Virtual inverter PWM control means 603: PWM pulse synthesis means 604: Voltage detection means 605: Input voltage magnitude calculation means 606: Operation monitoring means 607: Operation pattern creation means 608: q-axis voltage command calculation means 609: Integration means 610: Virtual rectifier command calculation means 611: Virtual inverter command calculation means 6211: Frequency voltage conversion means 622: Low-pass filter 623: Switch 624: multiplication means 625: addition means 631: speed adjustment means 632: speed detector 633: addition means 634: q-axis current command calculation means 635: low-pass filter 636: addition means 637: q-axis current control means 638: current detection means 639 : Phase detector 640: coordinate conversion means 641: addition means 642: d-axis current control means 643: coordinate conversion means

Claims (3)

In an AC / AC converter that converts an AC voltage to an AC voltage having an arbitrary magnitude and frequency by a plurality of semiconductor switches and supplies the AC voltage to a load,
Means for detecting an input voltage of the converter;
A means for monitoring the operation of the converter by comparing the magnitude of the input voltage with an operable level, and after the operation is stopped when the magnitude of the input voltage falls below the operable level, the input Operation monitoring means for outputting a voltage return signal when the voltage is restored and the converter resumes operation; and
Voltage command calculation means for calculating an output voltage command that changes with a predetermined time constant by the voltage return signal;
Means for generating a drive pulse for switching the semiconductor switch based on the output voltage command;
A control device for an AC / AC converter, comprising: In an AC / AC converter that converts an AC voltage to an AC voltage having an arbitrary magnitude and frequency by a plurality of semiconductor switches and supplies the AC voltage to a load,
Means for detecting an input voltage of the converter;
A means for monitoring the operation of the converter by comparing the magnitude of the input voltage with an operable level, and after the operation is stopped when the magnitude of the input voltage falls below the operable level, the input Operation monitoring means for outputting a voltage return signal when the voltage is restored and the converter resumes operation; and
Current command calculation means for calculating an output current command that changes with a predetermined time constant by the voltage return signal;
Voltage command calculation means for calculating an output voltage command of the converter from the output current command;
Means for generating a drive pulse for switching the semiconductor switch based on the output voltage command;
A control device for an AC / AC converter, comprising: In the control device according to claim 1 or 2,
Calculation means for calculating the speed electromotive force of the electric motor as the load;
Means for adding the speed electromotive force to the output voltage command to generate a final output voltage command;
A control device for an AC / AC converter, comprising:

Images