JP6575252B2 - Load simulator - Google Patents

Description

  The present invention relates to an inverter testing technique, and more particularly, to a load simulation apparatus that applies a desired load to an inverter that is a target of an inverter test.

  FIG. 2 is a block diagram showing the configuration of a general inverter test system. In this test system, the test inverter 202 converts AC power supplied from the AC power supply 201 into DC power using a built-in AC-DC converter, and further converts this DC power into AC power. The motor 203 is a motor to be driven by the test inverter 202, and is supplied with AC power from the test inverter 202. A torque meter, a speed meter, and the like are attached to the mechanical shaft of the motor 203, and a mechanical shaft of the load motor 204 is connected. The drive voltage input terminal of the load motor 204 is connected to the AC voltage output terminal of the load control inverter 205. The torque and rotation speed of the load motor 204 are controlled by the load control inverter 205. The regenerative converter 206 converts the AC power supplied from the AC power source 201 into DC power and supplies it to the load control inverter 205. On the other hand, if excessive DC power is generated in the load control inverter 205, the DC power Is converted into AC power and regenerated in the AC power source 201.

  According to this test system, various loads applied from the load motor 204 to the motor 203 are changed by the load control inverter 205, thereby changing various states of the motor 203 that is a load for the test inverter 202. 202 tests can be performed.

  However, the test system shown in FIG. 2 requires a load motor 204 as a load of the motor 203 and a load control inverter 205 for controlling the drive in addition to the test inverter 202 and the motor 203 to be driven. . For this reason, there is a problem that the scale of the test system becomes very large. For example, when the test inverter 202 and the motor 203 are produced and delivered by different manufacturers, the test can be performed by supplying an actual current to the test inverter 202 until the motor 203 is completed. Therefore, the development period may be long.

  Therefore, a technique for testing the test inverter 202 by providing a simulation circuit on the output side of the test inverter 202 so that the electrical characteristics viewed from the test inverter 202 side is the same as that of the motor 203 is disclosed in Patent Document 1, for example. Is disclosed. FIG. 3 is a block diagram showing the configuration of the test system disclosed in Patent Document 1. In FIG. FIG. 4 is a circuit diagram showing a configuration of the main circuit 303M of the test inverter 303 and the main circuit 305M of the PWM converter 305 in the test system.

In FIG. 3, the rectifier 302 rectifies the AC power supplied from the AC power supply 301 and supplies it to the test inverter 303 as DC power. As shown in FIG. 4, the test inverter 303 includes a main circuit 303M including three-phase upper arm switching elements 3031 to 3033 and three-phase lower arm switching elements 3034 to 3036. In the test inverter 303, the upper arm switching elements 3031 to 3033 and the three-phase lower arm switching elements 3034 to 3036 are switched, so that the DC power supplied from the rectifier 302 is changed to the three-phase AC voltage v _u , v _v and v _w are generated. The voltage detection unit 306 is means for detecting the three-phase AC voltages v _u , v _v , and v _w . The three-phase AC voltages v _u , v _v , and v _w are supplied to the three-phase AC terminals of the PWM converter 305 through the three-phase insulating transformer 304 and the three-phase inductors L _u , L _v , and L _w , respectively. Is done.

As shown in FIG. 4, the PWM converter 305 includes a main circuit 305 </ b> M including three-phase upper arm switching elements 3051 to 3053 and three-phase lower arm switching elements 3054 to 3056. The PWM converter 305 generates a three-phase AC voltage corresponding to the counter electromotive force generated by the simulation target motor from the rectifier 302 by switching operations of the upper arm switching elements 3031 to 3033 and the three-phase lower arm switching elements 3034 to 3036. It is generated from the DC power and supplied to the test inverter 303 via the three-phase inductors L _u , L _v , L _w and the three-phase insulating transformer 304. The PWM converter 305 converts surplus AC power into DC power and regenerates it at the output terminal of the rectifier 302. The current detection unit 307 detects the three-phase currents i _u , i _v , and i _w that enter and leave the three-phase AC terminals of the PWM converter 305 through the three-phase inductors L _u , L _v , and L _w , respectively. It is.

  In the test system shown in FIG. 3, an insulating transformer 304 is interposed between the main circuit 303M of the test inverter 303 and the main circuit 305M of the PWM converter 305 shown in FIG. This insulation transformer 304 is galvanically insulated from the AC output terminal of the main circuit 303M and the AC output terminal of the main circuit 305M, that is, only enables transmission of AC power between them, and cuts off transmission of DC power. Is provided. If this insulation transformer 304 is not provided, as illustrated by a broken line in FIG. 4, the high-potential power line of one main circuit flows through the upper arm switching element, and the lower arm switching element of the other main circuit There is a possibility that a short-circuit current passing through and flowing into the low potential power supply line may occur. The insulating transformer 304 plays a role in preventing such a short-circuit current between the high potential power line and the low potential power line.

  In FIG. 3, a control unit 340 including a current command calculation circuit 310, a rotation speed calculation circuit 320, and a gate signal generation unit 330 performs control for realizing the electrical characteristics of the simulation target motor by the PWM converter 305. . In this example, the simulation target motor is an induction motor.

The current command calculation circuit 310 takes in the voltage values of the three-phase AC voltages v _u , v _v , and v _w from the voltage detection unit 306 at a predetermined sampling time interval, and is simulated by a rotation speed calculation circuit 320 described later. The calculated electric angular velocity ω _r of the target motor is taken in, and the predicted d-axis current value i _ds (n + 1) and the predicted q-axis current value i _qs (n + 1) flowing in the stator of the simulation target motor, and flowing in the rotor of the simulation target motor. The predicted d-axis current value i _dr (n + 1), predicted q-axis current value i _qr (n + 1), and phase current command values i _u ^* , i _v ^* , i _w ^* are calculated. Then, the current command calculation circuit 310 includes the stator d-axis current prediction value i _ds (n + 1) and the q-axis current prediction value i _qs (n + 1), and the rotor d-axis current prediction value i _dr (n + 1) and q. The shaft current predicted value i _qr (n + 1) is supplied to the rotation speed calculation circuit 320 and the phase current command values i _u ^* , i _v ^* , i _w ^* are supplied to the gate signal generation unit 330. The rotation speed calculation circuit 320 calculates the calculated electrical angular velocity ω _r of the simulation target motor based on the rotor d-axis current predicted value i _dr (n + 1) and the q-axis current predicted value i _qr (n + 1). The gate signal generation unit 330 performs PWM control of the gate signal supplied to the upper arm switching elements 3051 to 3053 and the lower arm switching elements 3054 to 3056 of the main circuit 305M of the PWM converter 305, thereby causing the inductor L _u to be supplied to the PWM converter 305. , L _v , L _w , and the currents i _u , i _v , i _w that enter and exit are made to coincide with the phase current command values i _u ^* , i _v ^* , i _w ^* .

The calculated electrical angular velocity ω _r of the simulation target motor calculated by the rotation speed calculation circuit 320 is supplied to the current command calculation circuit 310 and the test inverter 303. A control circuit (not shown) in the test inverter 303 drives the simulation target motor based on the calculated electrical angular velocity ω _r of the simulation target motor and the current value of the three-phase output current of the test inverter 303. The same PWM control as in the case of the above is performed on the gate signal for the main circuit 303M.

JP 2000-224866 A

  By the way, in the technique disclosed in Patent Document 1 described above, the current command calculation circuit 310 and the rotation speed calculation circuit 320 perform calculation to determine the behavior of the equivalent circuit of the simulation target motor. In order to perform this calculation, a high-speed calculation device is required, which increases the cost. On the other hand, with respect to the test inverter, for example, only the efficiency of the test inverter when driving the simulation target motor, the amount of heat generation, and the like may be evaluated, and it is not appropriate that high cost is required for such evaluation.

  The present invention has been made in view of the circumstances described above, and an object thereof is to provide a load simulation device that can evaluate a test inverter with a simple configuration that does not require high costs.

  The present invention relates to an inverter main circuit in which an AC terminal is connected to an AC terminal of a test inverter via an inductor, and has an amplitude indicated by a current amplitude command and a phase with respect to an output voltage of the test inverter. Provided is a load simulation device comprising: an inverter control unit that controls the inverter main circuit that causes an alternating current having a phase angle specified by an angle command to flow from the test inverter to the inverter main circuit. .

  According to the present invention, under the control of the inverter control unit, the alternating current having the amplitude specified by the current amplitude command and having the phase angle specified by the phase angle command with respect to the output voltage of the test inverter is used for the test. Output from the inverter to the inverter main circuit. The control by the inverter control unit can be realized by a low-cost simple arithmetic means. Therefore, according to the present invention, it is possible to evaluate the efficiency of the test inverter, the heat generation amount, and the like with a simple configuration that does not require high costs.

It is a block diagram which shows the structure of the test system using the load simulation apparatus by one Embodiment of this invention. It is a block diagram which shows the structure of the test system of the conventional inverter. It is a block diagram which shows the structure of the test system using the conventional load simulation apparatus. It is a circuit diagram which shows the structure of the main circuit of the test inverter and PWM converter in the test system.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing the configuration of an inverter test system using a load simulator 10 according to an embodiment of the present invention. In FIG. 1, three-phase AC power output from an AC power source 1 is applied to a test inverter 3 via an insulating transformer 2. The test inverter 3 converts AC power supplied via the insulating transformer 2 into DC power by a built-in converter, converts this DC power into three-phase AC power, and outputs the DC power.

The three-phase AC power output from the test inverter 3 is supplied to the three-phase AC terminal of the inverter main circuit 4 through the inductors L _u , L _v , and L _w . Here, the inductors L _u , L _v and L _w simulate the inductors interposed in the stator windings of the simulation target motor. The simulation target motor in the present embodiment may be an induction motor or a synchronous motor.

  The inverter main circuit 4 switches the DC power supplied from the regenerative converter 5 under the control of the inverter control unit 100, and applies a three-phase AC voltage corresponding to the counter electromotive force generated by the simulation target motor to the three-phase AC terminal. Occurs. The regenerative converter 5 converts the three-phase AC power supplied from the AC power source 1 into DC power and supplies it to the inverter main circuit 4, while regenerating surplus AC power generated in the inverter main circuit 4 to the AC power source 1. .

The voltage detector 6 is a circuit that detects the voltage values v _u , v _v , and v _w of the three-phase AC voltage output from the test inverter 3. Further, the current detection unit 7 obtains the current values i _u , i _v , i _w of the three-phase alternating current supplied to the three-phase alternating current terminal of the inverter main circuit 4 via the inductors L _u , L _v , L _w. It is a circuit to detect.

  The test inverter 3 has a main circuit similar to the main circuit 303M of the test inverter shown in FIG. The inverter main circuit 4 is a main circuit having the same configuration as the main circuit 305M in FIG.

  In the test system shown in FIG. 3, an insulating transformer 304 is provided between the test inverter 303 and the PWM converter 305 in order to electrically insulate the main circuit 303M of the test inverter 303 from the main circuit 305M of the PWM converter 305. It was provided. However, in this embodiment, no insulating transformer is provided between the test inverter 3 and the inverter main circuit 4. Instead, in this embodiment, an insulating transformer 2 is provided that electrically insulates the AC power supply 1 and the regenerative converter 5 from the test inverter 3.

  In this embodiment, by providing an insulating transformer 2 that electrically insulates the AC power supply 1 and the regenerative converter 5 from the test inverter 3, power is supplied to the high potential power line and the low potential power line of the main circuit of the test inverter 3. Both the DC power supply that supplies power and the DC power supply that supplies power to the high potential power line and the low potential power line of the inverter main circuit 4 are in a floating state. Therefore, the short-circuit current described above does not occur. The insulating transformer 2 may be provided between the three-phase AC terminal of the regenerative converter 5 and the three-phase AC terminal of the AC power supply 1 as indicated by a broken line in FIG.

In FIG. 1, an inverter main circuit 4, inductors L _u , L _v , L _w , a voltage detection unit 6, a current detection unit 7, and an inverter control unit 100 constitute a load simulation device 10 according to the present embodiment. Here, the inverter control unit 100 is means for controlling the inverter main circuit 4 for realizing the electrical characteristics of the simulation target motor by the inverter main circuit 4 and the inductors L _u , L _v , and L _w . Details of the inverter control unit 100 will be described below.

A current amplitude command I ^* and a phase angle command φ ^* are input to the inverter control unit 100 from an external controller or the like (not shown). Here, the current amplitude command I ^* is a command value that indicates the current value of the three-phase alternating current flowing into the three-phase alternating current terminal of the inverter main circuit 4. The phase angle command φ ^* indicates the phase angle between the three-phase AC voltage generated at the three-phase AC terminal of the inverter main circuit 4 and the three-phase AC current flowing into the three-phase AC terminal of the inverter main circuit 4. It is a command value. The inverter control unit 100 generates an alternating current from the test inverter 3 having an amplitude indicated by the current amplitude command I ^* and having a phase angle indicated by the phase angle command φ ^{* with} respect to the output voltage of the test inverter 3. Control of the inverter main circuit 4 for flowing through the inverter main circuit 4 is performed.

In the inverter control unit 100, the trigonometric function calculation unit 101 calculates a cosine value cosφ ^* and a sine value sinφ ^* from the phase angle command φ ^* . The component separation unit 102 converts the current vector determined by the current amplitude command I ^* and the phase angle command φ ^* to a component in the d-axis (axis of the rotor magnetic pole direction) direction of the simulation target motor and the q-axis (perpendicular to the d-axis). And a d-axis current command i _d ^* indicating the d-axis direction component and a q-axis current command i _q ^* indicating the q-axis direction component are output.

Subtraction unit 103d subtracts the d-axis current value _{i d} of the coordinate conversion unit 108 to be described later from the d-axis current command _i ^{d *} is outputted, and outputs both the difference value. In addition, the subtracting unit 103q subtracts a q-axis current value i _q output from the coordinate conversion unit 108, which will be described later, from the q-axis current command i _q ^*, and outputs a difference value therebetween.

The current control unit 104 generates a d-axis voltage command v _d ^* and a q-axis voltage command v _q ^* that make each difference value output from the subtraction units 103 d and 103 q zero. Specifically, the current control unit 104 generates a d-axis voltage command v _d ^* and a q-axis voltage command v _q ^* from the difference values output from the subtraction units 103 d and 103 q by the PI controller.

The coordinate conversion unit 105 is supplied with an output voltage phase angle θ from an angle detection unit 107 described later. This output voltage phase angle θ is the phase angle of the output voltage of the three-phase AC terminal of the test inverter 3. In the present embodiment, it is assumed that the rotor of the simulation target motor rotates in synchronization with the phase of the output voltage of the three-phase AC terminal of the test inverter 3. Therefore, the output voltage phase angle θ serves as an estimated value of the rotor angle of the simulation target motor. Therefore, the coordinate conversion unit 105 performs a coordinate conversion process from the biaxial coordinate system having the d axis and the q axis to the triaxial coordinate system having the u axis, the v axis, and the w axis based on the output voltage phase angle θ. This is applied to the d-axis voltage command v _d ^* and the q-axis voltage command v _q ^* . By this coordinate conversion processing, phase voltage commands v _u ^* , v _v ^* , and v _w ^* are generated that indicate phase voltages to be supplied to the U-phase, V-phase, and W-phase windings of the stator of the simulation target motor. The

The gate signal generation unit 106 uses the phase voltage commands v _u ^* , v _v ^* , v _w ^* to supply the gate signals S _u1 , S _v1 , S _w1 to be supplied to the upper arm switching element of the inverter main circuit 4, Pulse width modulation of the gate signals S _u2 , S _v2 and S _w2 supplied to the arm switching element is performed.

The output voltage values v _u , v _v , v _{w of} the test inverter 3 detected by the voltage detector 6 are supplied to the angle detector 107. The angle detection unit 107 detects the above-described output voltage phase angle θ based on the output voltage values v _u , v _v , and v _w . Various methods are conceivable as a method for detecting the output voltage phase angle θ. For example, a periodic waveform such as a sawtooth wave synchronized with the zero cross point of the waveform of the U-phase output voltage value v _u is obtained by a PLL (phase locked loop). The output voltage phase angle θ may be calculated from the waveform value of the periodic waveform. Alternatively, a signal whose phase is advanced by π / 2 with respect to the U-phase output voltage v _u (corresponding to cos θ when the U-phase output voltage v _u is sin θ) is generated, and this signal and the U-phase output voltage v _u The output voltage phase angle θ may be calculated by calculating tan θ from the ratio and calculating θ = tan ⁻¹ (tan θ). The angle detection unit 107 supplies the output voltage phase angle θ thus obtained to the coordinate conversion unit 105 and the coordinate conversion unit 108 described above.

The coordinate conversion unit 108, an inductor _{L u, L v, L} U _{which w} is supplied to the inverter main circuit 4 through, V, the current value of each phase _i u of _W, i v, _{i w} are current detector 7 is supplied. Based on the output voltage phase angle θ, the coordinate conversion unit 108 performs coordinate conversion processing from a three-axis coordinate system having a U-axis, a V-axis, and a W-axis to a two-axis coordinate system having a d-axis and a q-axis. , W are applied to the current values i _u , i _v , i _w of each phase to generate a d-axis current value i _d and a q-axis current value i _q . The coordinate transformation unit 108, respectively supplies the d-axis current value _{i d} and the q-axis current value _{i q} to the subtraction unit 103d and 103q described above.
The details of the inverter control unit 100 have been described above.

In the present embodiment, the current control performance of the load simulation device 10 is made higher than the current control performance of the test inverter 3. There are two reasons for this. The first reason is that the output current cannot follow the output voltage fluctuation of the test inverter 3 unless the output voltage phase angle θ used in the control is calculated at high speed. The second reason is that if the ripple of the current flowing through the inductors L _u , L _v and L _w becomes large, the control may become unstable. As a guide, when the switching frequency of the test inverter 3 is fi and the control cycle of the test inverter 3 is 1 / fi, the switching frequency of the inverter main circuit 4 of the load simulator 10 is set to 2 fi or more, and the control cycle is 1 / 2fi or less. In this way, by setting the switching frequency of the inverter main circuit 4 of the load simulation device 10 to be more than twice the switching frequency of the test inverter 3, the test system is not affected by aliasing noise due to the Nyquist frequency. And the influence of ripples of the current flowing in the inductors L _u , L _v , and L _w can be prevented.
The above is the details of the present embodiment.

According to the present embodiment, under the control of the inverter control unit 100, the phase angle indicated by the phase angle command φ ^* having the amplitude indicated by the current amplitude command I ^{* and} the output voltage of the test inverter 3 is indicated. Is output from the test inverter 3 to the inverter main circuit 4. The control by the inverter control unit 100 has a small amount of calculation for control, and can be realized by simple calculation means at low cost. Therefore, according to the present embodiment, it is possible to evaluate the efficiency and the amount of heat generated by the test inverter 3 with a simple configuration that does not require high costs.

In this embodiment, since the switching frequency of the load simulator 10 is set to be more than twice the switching frequency of the test inverter 3, the control system of the test system is stabilized and the currents flowing through the inductors L _u , L _v , L _w It is possible to prevent the influence of ripples and the like.

  In the present embodiment, since the insulating transformer 2 is provided between the AC power source 1 and the test inverter 3 or between the AC power source 1 and the regenerative converter 5, the insulating transformer 2 is provided near the alternating frequency of the AC power source 1. It is possible to use an inexpensive insulating transformer corresponding to the frequency band. Therefore, the test system can be made inexpensive.

DESCRIPTION OF SYMBOLS 1 ... AC power source, 2 ... Insulation transformer, 3 ... Test inverter, 4 ... Inverter main circuit, 5 ... Regenerative converter, 6 ... Voltage detection part, 7 ... Current detection part, _Lu , L _v , L _w …… Inductor, 10 …… Load simulation device, 100 …… Inverter control unit, 101 …… Trigonometric function calculation unit, 102 …… Component separation unit, 103 d, 103 q …… Subtraction unit, 104 …… Current control , 105, 108 ... coordinate conversion unit, 106 ... gate signal generation unit, 107 ... angle detection unit.

Claims (1)

An inverter main circuit in which the AC terminal is connected to the AC terminal of the test inverter via an inductor;
The inverter main circuit having an amplitude instructed by a current amplitude command and an alternating current having a phase angle instructed by a phase angle command with respect to an output voltage of the test inverter from the test inverter to the inverter main circuit an inverter control unit for controlling the,
A current detector for detecting a current flowing through the inductor;
A voltage detector for detecting the output voltage of the test inverter;
The inverter control unit
An angle detector for detecting a phase angle of the output voltage;
A component separation unit that separates a current having an amplitude instructed by the current amplitude command and a phase angle instructed by the phase angle command into orthogonal biaxial components;
A first coordinate conversion unit that converts the current detected by the current detection unit into the orthogonal biaxial component based on the phase angle detected by the angle detection unit;
A current control unit that generates the orthogonal biaxial voltage command based on the difference between the orthogonal biaxial component obtained by the component separation unit and the orthogonal biaxial component obtained by the first coordinate conversion unit. When,
A second coordinate converter that converts the orthogonal two-axis voltage command into a voltage command that indicates the output voltage of the inverter main circuit based on the phase angle detected by the angle detector;
A gate signal generation unit that generates a gate signal for switching and driving the inverter main circuit based on the voltage command obtained by the second coordinate conversion unit;
A load simulator for switching driving the inverter main circuit at a switching frequency higher than the switching frequency of the test inverter .

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