KR101889361B1 - Motor emulator - Google Patents

Abstract

Embodiments of the present invention relate to a motor emulator for an inverter under test (IUT) for driving a motor. The motor emulator includes a voltage following inverter for at least partially attenuating an output voltage of the IUT, and an output current control unit for controlling an output current of the IUT based on an estimated current of the motor to be emulated and the output voltage of the IUT. Accordingly, the present invention can secure a wider voltage modulation area.

Description

MOTOR EMULATOR [0002]

The present invention relates to an electric motor simulation apparatus, and more particularly to an electric motor simulation apparatus comprising an inverter for canceling an output voltage of an inverter for driving a motor, and a circuit for synthesizing a current to a simulated electric motor.

A real-time motor simulation device (Real-Time Motor Emulator) is a device that is connected to an inverter under-test (IUT) to output a current similar to a real AC motor from an inverter. 1 shows a conventional motor simulation apparatus. The motor simulator shown in Fig. 1 is designed to boost the primary side DC voltage and output it to the secondary side as shown in Patent Document 1 below. This structure makes it possible to equalize the neutral point of the primary side voltage and the neutral point of the secondary side voltage, and as a result, it is possible to secure a wider voltage modulation area of the motor simulation apparatus. However, when the secondary side DC voltage is stepped up to simulate the high-speed operation region of the motor, the secondary side voltage becomes excessively large, so that there is a problem that the withstand voltage of a device used in the motor simulator becomes very large.

The current that the motor simulator should simulate can be divided into the operating frequency band of the motor and the switching frequency band current. The fundamental frequency of the motor of the simulated motor is usually about 1kHz, but the harmonic currents of 5 and 7 may affect the control. Therefore, in order to accurately simulate the control performance, the current in the frequency range of 0Hz ~ 7kHz should be simulated .

The following technical limitations exist for accurate current simulation including switching bandwidth.

- The motor simulator should have a sufficiently high switching frequency to synthesize the current in the IUT's switching frequency (typically 5-10 kHz).

- Appropriate circuit topology and high performance control techniques should be used to synthesize the harmonic currents due to spatial harmonics of the actual motor flux and the switching frequency current of the IUT.

However, the conventional motor simulation device has a relatively low switching frequency of about 20 kHz, and the practical current simulatable band has been limited to a maximum of about 4 kHz due to limitation of the circuit method and control technique. Therefore, the use of the conventional motor simulator is limited mainly to the durability verification of the IUT, and there is a limit to the simulation of the transient response of the harmonic current and the control of the motor.

The limitation of the switching frequency of 20kHz has recently been overcome by the development of SiC (Silicon Carbide) device technology. If a high-voltage, high-current SiC device capable of high-speed switching is applied to a motor simulation device, the switching frequency can be increased to 100 kHz or more according to heat radiation conditions.

However, even if the switching elements are changed, the technical problem of the existing motor simulator still exists. In order to simulate the high-frequency current of the motor simulator, it is desirable to use a value (0.9 pu ~ 1.1 pu) similar to the inductance of the simulated motor to the motor simulator in terms of the inductance. However, Becomes larger. Therefore, in order to simulate medium-speed operation conditions, the DC voltage needs to be further increased through the booster circuit. As described above, the DC voltage is limited by the limit of the breakdown voltage. If the dc voltage is limited by the device breakdown voltage, it is impossible to simulate all operating conditions of the simulated motor.

If the inductance of the motor simulation apparatus is small (0.1 pu to 0.3 pu), the voltage shortage problem is solved, but the problem as shown in Fig. 2 occurs at this time. FIG. 2 shows the current of the motor simulation apparatus and the actual motor current when the output voltage of the IUT is switched (on-off). Referring to FIG. 2, a time delay of 2 samples occurs due to the digital signal processing until the motor simulator synthesizes the voltage, and a large current ripple occurs during the time. Since the size of the ripple is inversely proportional to the magnitude of the inductance, the smaller the inductance of the motor simulation apparatus, the larger the current ripple due to the conduction. For this reason, the use of conventional circuit schemes can not reduce the inductance of the motor simulator, which limits the simulatable operating speed.

US registered patent US8587322 B2

In order to overcome the above problems, the present invention proposes a method of reducing the current pulsation generated by the digital control without shorting the DC short voltage at the time of medium speed operation of the motor.

The technical problem of the present invention is not limited to those mentioned above, and another technical problem which is not mentioned can be clearly understood by those skilled in the art from the following description.

An electric motor simulation apparatus for an inverter under test (IUT) according to an embodiment of the present invention includes a voltage follower inverter for at least partially canceling an output voltage of the IUT and an output voltage And an output current controller for controlling the output current of the IUT based on the estimated current of the motor to be simulated.

In a preferred embodiment, the voltage follower inverter comprises a DC step voltage source, a first switching unit connected in parallel with the DC step voltage source, the first switching unit being electrically connected to the output terminal of the IUT, And a first switching control unit for controlling switching of the switching unit.

In a preferred embodiment, the first switching unit includes an upper-side switch and a lower-side switch connected in series, wherein the first switching control unit compares the output voltage of the IUT with a predetermined threshold voltage, The switch can be switched.

In one preferred embodiment, the first switching control unit may include an electronic circuit receiving the output voltage of the IUT and the predetermined threshold voltage. The electronic circuit may be an analog circuit.

In a preferred embodiment, the output current control section estimates the current of the simulated motor based on the switching circuit electrically connected to the output terminal of the IUT and the output voltage of the IUT and the characteristics of the simulated motor, And a second switching control unit for controlling the switching of the switching circuit.

In a preferred embodiment, the switching circuit may be composed of a SiC MOSFET.

In a preferred embodiment, the switching circuit may be composed of at least one of a full bridge circuit, a half bridge circuit, and a linear power amplifier circuit.

In a preferred embodiment, the characteristic of the simulated electric motor may include at least one of a flux linkage, a magnetic saturation, and a spatial harmonic of the electric motor.

In a preferred embodiment, the switching circuit further comprises an independent DC voltage source for providing a DC voltage to the switching circuit, wherein the independent DC voltage sources of each phase may be insulated from each other.

In a preferred embodiment, the filter further includes at least one of a single-phase inductor, a three-phase inductor, and a Zero Sequence Filter, the filter portion being disposed between the output terminal of the IUT and the voltage follower inverter .

The motor simulator according to the embodiment of the present invention can secure a wider voltage modulation area than that of the prior art with the same direct current voltage and can increase the simulated operation speed and realize accurate simulation up to the current in the higher switching frequency range There is a possible advantage.

Therefore, it is possible to simulate the steady state and transient state even under difficult or difficult operating conditions. Therefore, it is necessary to verify the durability of the IUT as well as the IUT Motor control performance, and safety verification.

The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by those skilled in the art from the description of the claims.

1 shows a conventional motor simulation apparatus.
Fig. 2 shows the current of the conventional motor simulation apparatus and the actual motor current when the output voltage of the IUT is switched (on-off).
3 is a block diagram of an electric motor simulation apparatus for an inverter under test (IUT) according to an embodiment of the present invention.
4 shows a voltage-follower inverter 100 according to an embodiment of the present invention.
Figure 5 shows an example of generating a gating signal at any one phase (x) of the voltage-tracking inverter.
6 is a detailed circuit diagram of an output current controller 200 according to an embodiment of the present invention.
7 is a simplified circuit diagram of an electric motor simulation apparatus 100 according to an embodiment of the present invention.
8A and 8B show switching characteristics of the voltage follower inverter 100 and the IUT according to an embodiment of the present invention.
9A and 9B show the capacity curves of the electric motors used in the simulation.
10 to 14 show simulation results of the motor simulation apparatus 1000 according to an embodiment of the present invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, the terms "comprises" or "having", etc. are intended to specify the presence of stated features, integers, steps, operations, elements, parts or combinations thereof, But do not preclude the presence or addition of steps, operations, elements, parts, or combinations thereof.

Embodiments described herein may be wholly hardware, partially hardware, partially software, or entirely software. A "unit," "module," "device," or "system" or the like in this specification refers to a computer-related entity such as a hardware, a combination of hardware and software, or software. A processor, an object, an executable, a thread of execution, a program, and / or a computer, for example, a computer, but is not limited to, a computer. For example, both an application running on a computer and a computer may correspond to a part, module, device or system of the present specification.

The following detailed description of the invention refers to the accompanying drawings, which illustrate, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It should be understood that the various embodiments of the present invention are different, but need not be mutually exclusive. For example, certain features, structures, and characteristics described herein may be implemented in other embodiments without departing from the spirit and scope of the invention in connection with one embodiment.

It is also to be understood that the position or arrangement of the individual components within each disclosed embodiment may be varied without departing from the spirit and scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is to be limited only by the appended claims, along with the full scope of equivalents to which such claims are entitled, if properly explained. In the drawings, like reference numerals refer to the same or similar functions throughout the several views.

3 is a block diagram of an electric motor simulation apparatus for an inverter under test (IUT) according to an embodiment of the present invention. Referring to Figure 1 the electric motor simulation apparatus 1000, the output voltage of the IUT v _a, v _b, v _c at least the output voltage of the voltage follower inverter 100 and IUT to partially offset v _a, v _b, v _c and the simulated target And an output current controller 200 for controlling the output currents i _a , i _b , and i _c of the IUT based on the estimated current of the motor 1000.

Although FIG. 3 illustrates a three-phase motor and a three-phase inverter, the motor simulator of the present invention is not limited to a three-phase circuit, but may be applied to a single-phase or other multi-phase (5-phase, 6-phase, have.

4 and 5 illustrate a voltage-follower inverter 100 according to an embodiment of the present invention. Specifically, FIG. 4 shows a state in which the output terminals of the respective phases are connected to each other, and FIG. 5 shows a specific circuit diagram for one phase. In Fig. 5, x may be any one of abc.

The voltage follower inverter 100 may at least partially cancel the output voltage of the IUT.

In one embodiment the voltage follower inverter 100, the DC stage voltage source 100 (v2) and direct current stage being parallel connected with a voltage source 100, a first switching unit connected to the IUT output terminal and electrical _{120 (120 a, 120 b,} 120 c) And a first switching control unit 130 for controlling switching of the switching unit 120 based on an output voltage of the IUT and a predetermined threshold voltage.

Referring to FIG. 4, the DC voltage source 110 shares both ends with the DC voltage source v1 of the IUT. The first switching unit 120 may include a pair of switches 120 _a, 120 _b, 120 _c, including the two switches for each phase. Two switches constituting each switch pair herein is represented by witsang switch 121 _a, 121 _b, 121 _c and the lower switch _{122 a, 122 b, 122 c} .

As shown in Figure 4, and _a pair of switches 120, on each of the 120 _b, 120 _c are parallel, witsang switch and the lower switch may be connected in series. The output of each phase of the IUT can be connected between the upper and lower switches.

A first switch control unit 130 includes a first switch control unit 130 may switch the output voltage v _x and predetermined by comparing the threshold voltage v _th witsang switch 121 _x 122 _x switch and the bottom of the IUT.

Referring to FIG. 5, when the x-phase output voltage of the IUT exceeds an arbitrary threshold voltage v _th set between 0 and v1, the upper-side switch 121 _x of the switch pair is turned on, and the lower switch 122 _x is turned off. Anti-x when the output voltage of the IUT is smaller than the v _th, witsang turned off and the switch 121 _x, 122 _x lower phase switch is turned on. At this time, the voltage follower inverter 100 can at least partially cancel the output voltage of the IUT, since the voltage follower inverter 100 and the IUT share a DC stage (if only switching is performed).

In one preferred embodiment, the voltage follower inverter 100 may operate to cancel all of the output voltage of the IUT, but the present invention is not limited thereto and may be operative to offset only an arbitrary fraction of the output voltage of the IUT. The above arbitrary ratio can be determined according to the operating characteristics of the output current control unit 200. [ For example, the voltage follower inverter 100 may offset 80% of the output voltage of the IUT, and the remaining 20% may be canceled by the operation of the output current controller 200.

As shown in FIG. 5, the first switching controller 130 may be an analog circuit, but the present invention is not limited thereto. However, in the performance of the motor simulation apparatus, it is important to minimize the delay time that occurs until the switching signal is transmitted to the voltage follower 100. Therefore, it is preferable that the switching signal of the voltage-follower inverter 100 is transmitted without digital delay through an analog circuit without being subjected to arithmetic processing by a CPU or a DSP.

8A and 8B show switching characteristics of the voltage follower inverter 100 and the IUT according to an embodiment of the present invention. 8A, the DC terminal voltage of the IUT and the voltage follower inverter 100 is 310 V, and FIG. 8B is a view obtained by enlarging the time axis of FIG. 8A by 10 times.

Referring to FIGS. 8A and 8B, the voltage follower inverter 100 follows the switching of the IUT 400 ns and completely cancels the output voltage of the IUT. Therefore, when the voltage follower inverter 100 operates normally, it can be seen that the influence of the output current of the IUT is negligible regardless of the voltage of the IUT.

As described above, when the voltage follower inverter 100 completely cancels the voltage of the IUT, the output current of the IUT can be determined by the voltage synthesized by the output current controller 200. [

6 is a detailed circuit diagram of an output current controller 200 according to an embodiment of the present invention. The output current control unit 200 synthesizes the current of the simulation target motor and can control the output current of the IUT based on the output voltage of the IUT and the estimated current of the simulation target motor.

Referring to FIG. 6, the output current controller 200 estimates the current of the simulated motor based on the output voltages of the switching circuits 210 (210a, 210b, and 210c) and the IUT and the characteristic of the simulated motor, And a second switching control unit 220 for controlling the switching of the switching circuit based on the estimated current and the actually measured current.

Although the switching circuit 210 is shown as a full bridge circuit in FIG. 6, this is merely an example of various embodiments of the present invention, and the switching circuit 210 can be used for various circuits such as a half bridge circuit or a linear power amplifier circuit. Hereinafter, a case where the switching circuit 210 is configured as a full bridge circuit will be described as an example.

In an embodiment of the present invention, the switching circuit 210 may be composed of a SiC MOSFET. When the switching circuit 210 is operated at a switching frequency of 100 kHz which is ten times the IUT switching frequency, the output current controller 200 can synthesize up to the current of the IUT switching frequency band of 10 kHz. In addition, since the voltage applied to the actual load in the circuit method of the motor simulation apparatus 1000 is the same as that of a general three-level converter, the switching current ripple caused by the motor simulation apparatus becomes very small. Also, since the circuit method of the motor simulation apparatus 1000 has a voltage modulation range of about 2 to 3 times as much as that of a general three-phase converter using the same DC power source, the motor can be simulated with a much wider speed range than the conventional circuit method .

The second switching controller 220 estimates the current of the simulated subject motor based on the output voltage of the switching circuit 210 and the IUT and the characteristics of the simulated motor, The switching of the switching circuit can be controlled. Here, the characteristics of the motor to be simulated may include a link-up look-up table (LUT). The flux linkage reference table may include the magnetic properties of the motor, such as magnetic saturation and spatial harmonics of the motor.

For example, the second switching controller 220 can use the measured output voltage of the IUT as the state observer input of the motor, and apply it to the flux linkage reference table to estimate the current and torque of the motor. Also, the second switching controller 220 can control the output current so that the actual IUT current becomes equal to the current estimated in the motor model. Also, the second switching controller 220 can estimate the speed and position of the motor determined by inertia, friction coefficient, torsion coefficient, etc. using the torque of the virtual motor and the load torque.

6, the output current controller 200 may include an independent DC voltage source 230 (v _{3a, 3b} v, v _3c) for providing a DC voltage to the respective switching circuit _{210 a, 210 b, 210 c} . Here, the independent DC voltage sources 230 (v _3a , v _3b , v _3c ) are isolated from each other.

7 is a simplified circuit diagram of an electric motor simulation apparatus 100 according to an embodiment of the present invention. Referring to FIG. 7, independent DC voltage sources v _3a , v _3b , and v _3c are implemented as a DC / DC converter using a high frequency transformer.

In the motor simulation apparatus 100 as viewed from the output terminal of the switching circuit 210, there is a difference between the IUT output voltage and the voltage following inverter 100, that is, a voltage applied to the filter inductance and the line resistance. , The difference between the two output voltages will be very small.

Therefore, the effective power consumed by the switching circuit 210 from the motor simulation apparatus 1000 is very small. Therefore, the effective power supplied by the independent DC voltage source to the output current control unit is only a few percent of the motor power capacity simulated by the motor simulator. In addition, since the reactive power generation is absorbed by the DC capacitor c of the switching circuit, the DC / DC converter only needs to supply the active power generated by the loss of the switching circuit and the voltage difference due to the switching.

Therefore, since the input / output power of the DC / DC converter is less than a few% of the power capacity of the motor simulator device and there is no power regenerated through the DC / DC converter, the DC / DC converter of the motor simulator is implemented as a unidirectional power supply It is possible.

However, the converter type shown in Fig. 7 is merely exemplary, and various embodiments in which three isolated voltage sources can be stably obtained can be included here. That is, the independent DC voltage sources v _3a , v _3b , v _3c insulated from each other in the embodiments of the present invention can be implemented in various forms. For example, a commercial power source may be simply isolated by using a transformer to make an AC voltage of an appropriate size, and then a DC voltage may be obtained through a rectifying circuit.

Referring again to FIG. 3, the motor simulation apparatus 1000 may further include a filter unit 300 disposed between the output terminal of the IUT and the voltage follower inverter. When the filter unit 300 between the output terminal of the IUT and the voltage follower inverter 100 is constituted, the output current of the IUT can also be influenced by the filter unit 300. The filter unit 300 may include at least one of a single-phase inductor, a three-phase inductor, and a Zero Sequence Filter, but is not limited thereto. However, since the image minute current can flow, the filter unit 300 preferably includes an image minute filter.

Simulation result

The hardware characteristics of the motor used in this simulation are shown in Table 1 below, and the output curves and operating currents are shown in FIGS. 9A and 9B. 10 to 14 show simulation results of the motor simulation apparatus 1000 according to an embodiment of the present invention.

In this simulation, the DC inductor voltage was 310 V, the switching frequency of the IUT was selected to be 10 kHz, and the inductance of the filter inductor was selected to be 82 μH (0.3 pu) under the simulation condition of the motor simulator 1000, and the switching frequency of the motor simulator 1000 100kHz, and sampling is 200kHz double sampling.

10 is a simulation result of the torque control situation, which is a result of sequentially increasing the motor speed to 4200 r / min and the torque command to 0, 0.25, 0.5, 0.75, 1 (pu). It can be seen that the motor can be precisely simulated so that there is almost no difference between the actual motor drive waveform and the actual motor drive waveform when the motor simulator of the present invention is used.

Fig. 11 shows currents when the actual motor and the motor simulator are driven under the conditions shown in Fig. The middle graph is an enlarged view of the portion 11a, and the last graph is an enlarged view of the portion 11b. It can be seen that the current pulsation of the high frequency is accurately simulated by the motor simulation apparatus of the present invention.

12 is a simulation result of the speed control situation, wherein the load torque is 0.1p.u. and the speed command is a result of sequentially increasing the speed command to 0,1000,2000,3000,4000 (r / min). It can be seen that the virtual machine inertia system can be accurately simulated by the motor simulation apparatus of the present invention.

Fig. 13 is a simulation result of the signal injection sensorless situation. As a result, the motor speed is 200r / min and the torque command is increased from 0 to 3p.u with a slew rate of 20 pu / s. It can be understood that the estimation performance and the divergence condition can be accurately simulated in the sensorless operation by the motor simulation apparatus of the present invention.

Fig. 14 shows currents when the actual motor and the motor simulation apparatus are driven under the condition of Fig. 13, respectively. The middle graph is an enlarged view of portion 14a, and the last graph is an enlarged view of portion 14b.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, Those skilled in the art will appreciate that various modifications and changes may be made thereto without departing from the scope of the present invention.

Therefore, the spirit of the present invention should not be construed as being limited to the above-described embodiments, and all of the equivalents or equivalents of the claims, as well as the following claims, I will say.

1000: Motor simulator
100: Voltage follower inverter
110: DC voltage source
120: first switching unit, 121: up-and-down switch, 122:
130: a first switching control section
200: Output current control section
210: switching circuit
220: second switching control section
230: Independent DC voltage source

Claims (10)

An electric motor simulation apparatus for an inverter under test (IUT)
The motor simulator includes:
A voltage follower inverter for at least partially canceling the output voltage of the IUT; And
And an output current controller for controlling the output current of the IUT based on the output voltage of the IUT and the estimated current of the simulated motor,
Wherein the output current controller includes:
A switching circuit electrically connected to the output terminal of the IUT; And
And a second switching control unit for estimating the current of the simulated subject motor based on the output voltage of the IUT and the characteristics of the simulated motor, and controlling the switching of the switching circuit based on the estimated current. .
The method according to claim 1,
The voltage follower inverter includes:
DC voltage source;
A first switching unit connected in parallel to the DC voltage source and electrically connected to an output terminal of the IUT; And
And a first switching control unit for controlling the switching of the first switching unit based on an output voltage of the IUT and a predetermined threshold voltage.
3. The method of claim 2,
Wherein the first switching unit includes an upper-side switch and a lower-side switch connected in series,
Wherein the first switching control unit switches the upper-side switch and the lower-side switch by comparing an output voltage of the IUT with a predetermined threshold voltage.
The method of claim 3,
Wherein the first switching control unit comprises:
And an electronic circuit receiving the output voltage of the IUT and the predetermined threshold voltage.
delete The method according to claim 1,
Wherein the switching circuit comprises:
SiC < / RTI > MOSFET.
The method according to claim 1,
Wherein the switching circuit comprises:
A full-bridge circuit, a half-bridge circuit, and a linear power amplifier circuit.
The method according to claim 1,
The characteristic of the above-
Wherein the at least one of the at least one of the at least one of the at least one of the at least one of the at least one of the at least two types of electromagnetic induction motors is at least one of the following:
The method according to claim 1,
Further comprising an independent DC voltage source for providing a DC voltage to the switching circuit, wherein the independent DC voltage sources of each phase are insulated from each other.
The method according to claim 1,
Further comprising a filter portion disposed between the output terminal of the IUT and the voltage follower inverter,
Wherein the filter unit includes at least one of a single-phase inductor, a three-phase inductor, and a Zero Sequence Filter.

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