JP2009153248A - Pwm cyclone converter and control method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control method of a PWM cyclone converter for preventing an operational failure even if a power capacity and a wiring distance are unknown. <P>SOLUTION: Each phase of a three-phase AC power supply and each phase of three-phase outputs of the power converter are directly connected by a combination of two unidirectional semiconductor switches for unidirectionally flowing a current and a bidirectional semiconductor switch 6 independently turned on/off. A to-be-driven object of the power converter is a motor. In the control method of the PWM cyclone converter having a speed controller and a current controller for operating the motor at a predetermined speed, a gain of the current controller is adjusted by an output from a power-supply-side impedance calculator for calculating a power-supply-side impedance before the motor is actually operated. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to control of a PWM cycloconverter (also referred to as a matrix converter) that is an AC / AC converter that can directly convert an AC power source to an arbitrary frequency and voltage, and in particular, the capacity of the power source and the state of the wiring distance are unknown. In particular, the present invention relates to a PWM cycloconverter and a control method thereof.

  PWM cycloconverters that can be directly converted to any frequency and voltage from the AC power supply side have been applied as a means of regenerative energy processing such as cranes and elevators, and power supply side harmonic suppression. It is expected to be applied as a countermeasure in the future. However, depending on the power supply capacity on the connected power supply side and the power supply side impedance such as the wiring distance to the power supply, the amount of rise and fall of the power supply side voltage may change due to electric and regenerative operations, causing various adverse effects. Countermeasures have been considered.

  FIG. 3 is a block diagram of a prior art PWM converter device disclosed in Patent Document 1. In FIG. The purpose is to convert a variable frequency / variable AC power supply voltage to DC by on / off control of a plurality of switching elements and to supply power to the load via the battery. The maximum power is taken out from the power source, and it is intended to enable proper charge / discharge of the battery.

  In FIG. 3, ACSP has an internal impedance and generates a three-phase AC voltage of variable frequency / variable voltage. CONV converts an AC power supply voltage into DC by ON / OFF control of switching elements constituting the main circuit. It is a power converter. DCC is a DC capacitor, DCL is a DC reactor, DCD is a current backflow prevention diode, BAT is a battery, and LOAD is a load device.

  MAVE is a voltage control circuit that controls the DC output voltage ed of the power converter CONV to a predetermined value, and EUCL is an input voltage that controls the power converter CONV according to the amplitude command iu * and the phase command φ * of the power supply current iu. Control circuit, DETC is a voltage detection circuit for detecting the effective voltage value Euo of the AC power supply ACSP, and LMIO is a voltage control circuit so as not to exceed the limit value Im of the converter input current set according to the output of the voltage detection circuit DETC A current limiting circuit that limits the output of MAVR, and LMER is a common-mode component limiting circuit that limits the common-mode component Eur * of the converter input voltage to the power supply voltage to a predetermined value.

  The BTCL is a battery control circuit that creates a DC voltage command Ed * so that the battery current Ib becomes a predetermined value, and manages the battery current so that it is always equal to or lower than the rated charging current. By the operation of the battery control circuit BTCL, proper charging can be performed within the range of the rated charging current of the battery, and battery deterioration due to an excessive charging current can be prevented.

  FIG. 4 is a block diagram of a prior art PWM converter device disclosed in Patent Document 2. In FIG. The purpose is the same as that of the prior art of Patent Document 1. The multiplier 137 receives the q-axis current component 116 obtained by the coordinate converter 115 as a first input, and inputs a coefficient corresponding to a power supply side impedance, for example, a coefficient corresponding to a power supply reactance L, as a second input thereto. The product of both inputs is obtained and output as a correction amount for the d-axis current reference 120. The adder is provided at the input end of the d-axis current reference 120 of the d-axis current control arithmetic unit 121. The d-axis current reference 120 is input to the first input end, and the second input end is multiplied. When the load current increases and the q-axis current component 116 increases, the d-axis current reference 120 is changed to q through the multiplier and adder 138. It is possible to suppress the situation in which the converter input voltage 132 fluctuates due to a voltage drop caused according to the power source impedance and the input current by increasing the axial current component 116 according to the shaft current component 116.

Both of these are capable of electric operation to extract energy from the AC power source side to the DC side, and regenerative operation to return energy from the DC side to the AC power source side, and the power source side input / output current flows as a pseudo sine wave by PWM control. The present invention relates to a PWM converter that can be applied to a PWM cycloconverter.
Patent Document 3 relates to a protection device for a PWM cycloconverter by the present applicant.
Japanese Patent No. 2633950 JP 2002-369533 A JP 2001-86751 A

However, depending on the power supply capacity on the connected power supply side and the power supply side impedance such as the wiring distance to the power supply, the amount of rise and fall of the power supply side voltage may change due to electric and regenerative operations, causing various adverse effects. Countermeasures have been considered.
According to the prior art, when the impedance and power capacity on the power source side are not known, voltage drop is performed by limiting the current or compensating the voltage by dropping the voltage. However, the PWM cycloconverter performs voltage control on the DC side and current control on the power supply side. If the impedance on the power supply side changes, the current loop that controls the motor is affected.

  For example, when the wiring distance to the power source is short and the power source capacity is large, the impedance on the power source side is extremely smaller than the impedance of the reactor between the voltage detection and the power converter in FIG. 1, and the wiring distance to the power source Is long, the power supply capacity is small, and the impedance on the power supply side is equivalent to the impedance of the reactor between the voltage detection and the power converter, even if the load such as the motor connected to the output side is the same, speed control, current The amount of change in control differs greatly, and the same control loop gain and time constant may cause the control to not catch up and become unstable. In addition, there is a problem that the impedance on the power source side is usually unknown, such as the power source capacity and the wiring distance.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a PWM cycloconverter and a control method thereof that do not cause an operation failure even if the power source capacity and the wiring distance are unknown.

In order to solve the above problem, the present invention is configured as follows.
The invention according to claim 1 is a configuration in which two unidirectional semiconductor switches that allow current to flow in only one direction each phase of the three-phase AC power source and each phase of the power converter of the three-phase output are combined, and each is independent. A power converter directly connected by a bidirectional semiconductor switch configured to be able to be turned on and off, wherein the power converter is driven by an electric motor, and a speed controller and a current controller are installed to operate the electric motor at a predetermined speed. In the PWM cycloconverter control method, the power supply side impedance calculator for calculating the impedance on the power supply side before the actual operation of the electric motor and the gain of the current controller are adjusted by the output of the power supply side impedance calculator.

  The power supply side impedance computing unit measures the impedance of the power supply in advance and stores the measured value, and the current corresponding to the stored measured value of the impedance of the power supply. The controller gain is set to a value that does not deteriorate the motor characteristics, current controller gain data for power supply impedance is stored in advance, and the current controller gain for power supply impedance measured during actual operation is stored. The gain of the current controller is determined from data stored in advance and the gain of the current controller is set.

  The invention according to claim 3 is a configuration in which two unidirectional semiconductor switches that allow current to flow in only one direction each phase of the three-phase AC power source and each phase of the three-phase output power converter are combined. A power converter that is directly connected by a bidirectional semiconductor switch that can be turned on and off independently. The power converter is driven by an electric motor, and a speed controller and a current controller are installed to operate the electric motor at a predetermined speed. The PWM cycloconverter includes a power supply side impedance calculator that calculates the power supply side impedance before the actual operation of the electric motor, and adjusts the gain of the current controller based on the output of the power supply side impedance calculator.

    According to a fourth aspect of the present invention, in the third aspect, the power source side impedance computing unit measures the impedance of the power source in advance and stores the measured value, and the current corresponding to the stored measured value of the impedance of the power source. The controller gain is set to a value that does not deteriorate the motor characteristics, the current controller gain data for the power supply side impedance is stored in advance, and the current controller gain for the power supply side impedance measured during actual operation is set. Means are provided for determining the gain of the current controller from data stored in advance and setting the gain of the current controller.

  According to the present invention, it is possible to provide a PWM cycloconverter and its control method that do not cause an operation failure even if the power source capacity and the wiring distance are unknown.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Hereinafter, the control method of the cycloconverter will be described in detail using embodiments.
FIG. 1 shows a block diagram of a PWM converter device to which the present invention is applied. In FIG. 1, 1 is a commercial power source, 2 is a power source side impedance (reactance component), 3 is a power source side impedance (resistance component), 4 is an input filter for a PWM cycloconverter generally composed of a reactor and a capacitor, 6 Is a bidirectional switch, and constitutes a group of five bidirectional switches in which inputs and outputs are connected in a matrix. 7 is an electric motor. The bidirectional switch 6 has a function of allowing a current to flow in both directions, and in order to realize it at present, a self-extinguishing element is used, for example, a diode 61 and an IGBT 62 connected in series as shown in FIG. They may be connected in parallel, or may be a reverse-blocking IGBT 63 that is reverse-parallel.

The PWM cycloconverter can convert the AC power supplied from the commercial power source 1 into an arbitrary frequency and voltage using the bidirectional switch group 6 and operate the motor 7 at an arbitrary frequency.
The PWM cycloconverter is controlled by a voltage detector 9 that detects the phase (θin) and magnitude (Er, Es, Et) of the input voltage and a current detector 8 that detects the current (Iu, Iw) flowing through the motor 7. Have. A speed command (Fref) for operating the motor 7 at a desired number of revolutions is input to the speed controller 10, compared with the current values (Iu, Iw) detected by the current detector 8, and input to the current detector 11. Is done. The output of the current detector 11 is input to the PWM calculator 12 and drives the nine bidirectional switches 6 of the bidirectional switch group 5.

  The power supply side impedance calculator 13 obtains the impedance of the commercial power supply side by calculation based on the current and voltage detection value between the commercial power supply 1 and the PWM cycloconverter. That is, as a method of measuring the power supply impedance by the power supply side impedance calculator 13, for example, at the stage of trial operation adjustment, the PWM cycloconverter device is driven by changing the load, the current and voltage flowing through the PWM cycloconverter device are detected, and the power supply Measure the impedance.

  Before the actual operation of the PWM cycloconverter, the impedance of the power supply is measured in advance and the measured value is stored. The gain of the current controller 11 corresponding to the stored measured value of the power supply impedance is set in advance. The gain setting of the current controller 11 is determined to be a value within a range that does not deteriorate the motor characteristics. In this way, gain data of the current controller 11 with respect to the power supply side impedance is stored in advance. Even when the power supply side impedance changes when the motor is driven, the power supply side impedance is measured during the actual operation of the motor, and the current controller 11 is obtained from data in which the gain of the current controller 11 with respect to the measured power supply side impedance is stored in advance. The motor drive characteristics can be kept constant by determining the gain of the current controller 11 and setting the gain of the current controller 11.

  In the present invention, correction by the power supply side impedance calculator 13 is performed in the calculation of the current controller 11. For example, when the power source capacity of the commercial power source 1 is small and the power source impedance is large, the current flowing through the electric motor 7 is difficult to flow, and therefore the power source impedance calculator 13 is adjusted so that the gain of the current controller 11 is increased. When the power supply capacity of the commercial power supply 1 is large, the reverse adjustment is performed by the power supply side impedance calculator 13. As a result, when the electric motor 7 is operated, control following the speed command (Fref) can be performed regardless of the capacity of the commercial power source 1. The power supply side impedance calculator 13 needs information on the power supply capacity, but a transformer name board value of the commercial power supply 1 can be used. Further, when the commercial power supply 1 and the PWM cycloconverter are connected by long-distance wiring, the same effect can be obtained by using power supply information in consideration of wiring impedance.

  According to the present invention, it is possible to provide a PWM cycloconverter control method that does not cause an operation failure even if the power supply capacity and the wiring distance are unknown. Application can be expected.

1 is a block diagram of a PWM cycloconverter showing an embodiment of the present invention. Configuration diagram of bidirectional switch of cycloconverter of the present invention Block diagram showing the configuration of a conventional PWM converter device Block diagram showing the configuration of a conventional PWM converter device

Explanation of symbols

1 Commercial power supply 2 Power supply impedance (reactance)
3 Power supply impedance (resistance)
4 Input Filter 5 Bidirectional Switch Group 6 Bidirectional Switch 7 Motor 8 Current Detector 9 Voltage Detector 10 Speed Controller 11 Current Controller 12 PWM Calculator 13 Power Supply Impedance Calculator 14 Control Unit

Claims (4)

Bi-directional configuration that combines two one-way semiconductor switches that allow each phase of a three-phase AC power supply and each phase of a three-phase output power converter to flow in only one direction, and each can be turned on and off independently. A power converter directly connected by a semiconductor switch, wherein the power converter is a motor to be driven, and a PWM cycloconverter control method having a speed controller and a current controller for operating the motor at a predetermined speed ,
A control method for a PWM cycloconverter, comprising: a power supply side impedance calculator for calculating a power supply side impedance before actual operation of the electric motor; and adjusting a gain of a current controller according to an output of the power supply side impedance calculator.   The power supply side impedance calculator measures the impedance of the power supply in advance and stores the measured value so that the motor characteristic does not deteriorate the gain of the current controller corresponding to the stored measured value of the power supply impedance. The current controller gain data for the power supply side impedance is determined in advance and stored in advance, and the current controller gain for the power supply side impedance measured during actual operation is stored in advance. 2. The method of controlling a PWM cycloconverter according to claim 1, wherein the gain is determined and the gain of the current controller is set. Bi-directional configuration that combines two one-way semiconductor switches that allow each phase of a three-phase AC power supply and each phase of a three-phase output power converter to flow in only one direction, and each can be turned on and off independently. A power converter directly connected by a semiconductor switch, wherein the power converter is a motor to be driven, and a PWM cycloconverter having a speed controller and a current controller for operating the motor at a predetermined speed.
A PWM cycloconverter characterized in that a power source side impedance calculator for calculating a power source side impedance before actual operation of the electric motor, and a gain of a current controller is adjusted by an output of the power source side impedance calculator.   The power supply side impedance calculator measures the impedance of the power supply in advance and stores the measured value so that the motor characteristic does not deteriorate the gain of the current controller corresponding to the stored measured value of the power supply impedance. The current controller gain data for the power supply side impedance is determined in advance and stored in advance, and the current controller gain for the power supply side impedance measured during actual operation is stored in advance. 4. A PWM cycloconverter according to claim 3, further comprising means for determining and setting the gain of the current controller.

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