Inverter high and low voltage ride-through test system and method

Abstract

The present invention relates to a high and low voltage ride-through test system and method for a frequency converter, wherein a test system includes: a multi-tap transformer, a contactor module, a PLC controller, a data acquisition unit and a simulated load, the contactor module includes a first contactor group and a second contactor group, the first contactor group includes a first contactor and a second contactor, the input ends of the first contactor and the second contactor are both connected to the rated voltage output end of the multi-tap transformer, the output end of the former is connected to the frequency converter, and the output end of the latter is connected to the frequency converter through a power resistor, the second contactor group includes a third contactor, the input end of which is connected to the other output end of the multi-tap transformer, and the output end is connected to the frequency converter. Compared with the prior art, the present invention can obtain accurate sag test data during the low voltage ride-through test by adding a second contactor and a power resistor, thereby obtaining more accurate test data of the low voltage ride-through capability.

Description

Technical Field

[0001] The present invention relates to a frequency converter test system, and in particular to a frequency converter high and low voltage ride through test system and method. Background Art

[0002] Low voltage ride-through means that when an external fault or disturbance causes the power supply voltage of an electrical equipment to rise or fall instantaneously, for a short time or for a long time, the relevant electrical equipment should adopt a reliable working mode within the specified voltage variation range and time interval to ensure the safe operation of the electrical equipment.

[0003] High and low voltage ride-through tests are used to verify equipment's ability to withstand high and low voltages. These tests require specialized testing equipment. By simulating power supply voltage drops, they verify the safe operation of related electrical equipment under certain conditions.

[0004] A voltage sag generator is one of the specialized test equipment required for low voltage ride-through testing. Currently, there are four types of voltage sag generators (VSGs): amplifier-based, switch-impedance-based, inverter-based, and voltage regulator-based. Amplifier-based VSGs are primarily implemented using power electronic devices operating in the linear region. They feature rich waveforms and good dynamic characteristics, but are expensive, consume large amounts of power, and have low efficiency. Switch-impedance-based VSGs are simple in structure and easy to implement, but suffer from high energy loss. Inverter-based VSGs are primarily implemented using power electronic devices operating in the switching state. They can handle a variety of voltage faults, but their output requires capacitor filtering, which affects their speed. Voltage regulator-based VSGs are primarily based on auto-regulators and are controlled by AC switches. They offer fast response and high efficiency, but AC switch failures can adversely affect the power supply. Summary of the Invention

[0005] The purpose of the present invention is to provide a high and low voltage ride through test system and method for an inverter in order to overcome the defects of the above-mentioned prior art.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A high and low voltage ride-through test system for an inverter, comprising:

[0008] The multi-tap transformer is a three-phase transformer with the input end connected to the power supply and each secondary winding symmetrically provided with multiple taps;

[0009] There are three contactor modules, with the input end connected to the output end of the multi-tap transformer and the output end connected to the inverter to be tested;

[0010] The PLC controller has an input end connected to the host computer and an output end connected to the contactor module for controlling the on and off of each contactor in the contactor module;

[0011] The data acquisition unit is connected to the frequency converter at one end and the host computer at the other end, and is used to collect test data;

[0012] Simulate the load and connect the inverter;

[0013] The contactor module includes a first contactor group and a second contactor group. The first contactor group includes a first contactor and a second contactor. The input ends of the first contactor and the second contactor are both connected to the rated voltage output end of the multi-tap transformer, the output end of the first contactor is connected to the frequency converter, and the output end of the second contactor is connected to the frequency converter through a power resistor. The second contactor group includes a third contactor. The input end of the third contactor is connected to one or more other output ends of the multi-tap transformer, and one of the third contactors is turned on, and the output end is connected to the frequency converter, wherein the other output ends are output ends other than the rated voltage output end.

[0014] There are multiple second contactors and multiple power resistors, each second contactor corresponds to each power resistor, and the resistance values ​​of each power resistor are different from each other.

[0015] Each output end of the multi-tap transformer is provided with a switch, and the input end of the third contactor is connected to the switches of each other output end of the multi-tap transformer.

[0016] The input terminal of the third contactor is connected to switches at all other output terminals of the multi-tap transformer.

[0017] A start-stop switch is provided between the input end of the multi-tap transformer and the power supply.

[0018] The simulated load is an adjustable simulated load.

[0019] The second contactor and power resistor are each provided with 6.

[0020] The host computer is a computer.

[0021] A low voltage ride-through test method for a test system according to claim 4, comprising:

[0022] Step S1: Turning on switches of the rated voltage output terminal and the low voltage output terminal, wherein the low voltage output terminal is an output terminal with a voltage lower than the rated voltage;

[0023] Step S2: Turning on the first contactor for a first set time, and collecting voltage, current, power, frequency and waveform data of the inverter by the data acquisition unit;

[0024] Step S3: closing the designated second contactor;

[0025] Step S4: opening the first contactor, closing the third contactor, and opening the second contactor in the closed state after the third contactor is fully closed for a second set time, and the data acquisition unit continuously collects the voltage, current, power, frequency and waveform data of the inverter during the entire process;

[0026] Step S5: Close the designated second contactor, open the third contactor, close the first contactor, and continuously collect the voltage, current, power, frequency and waveform data of the inverter during the entire process by the data acquisition unit.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1) By adding a second contactor and a power resistor, accurate sag test data can be obtained during the low voltage ride-through test, thereby obtaining more accurate low voltage ride-through capability test data.

[0029] 2) The second contactor and power resistor. When the first contactor is disconnected and the third contactor is not yet closed, the rated voltage is supplied to the inverter through the power resistor. Different resistance values ​​can be used to simulate different sag processes, thereby improving the comprehensiveness and credibility of the test data.

[0030] 3) The use of adjustable simulated load has a wider range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a structural schematic diagram of the present invention;

[0032] Figure 2 It is a single-phase schematic diagram;

[0033] Among them: 1. Host computer, 2. PLC controller, 3. Data acquisition unit, 4. Multi-tap transformer, 5. Contactor module, 6. Frequency converter, 7. Simulated load. DETAILED DESCRIPTION

[0034] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0035] A high and low voltage ride through test system for frequency converters, such as Figure 1 As shown, including:

[0036] The multi-tap transformer 4 is a three-phase transformer, the input end of which is connected to the power supply, and each secondary winding is symmetrically provided with multiple taps;

[0037] There are three contactor modules 5, with the input end connected to the output end of the multi-tap transformer 4 and the output end connected to the frequency converter 6 to be tested;

[0038] The PLC controller 2 has an input end connected to the host computer 1 and an output end connected to the contactor module 5 for controlling the on and off of each contactor in the contactor module 5, wherein the host computer 1 is generally a computer;

[0039] The data acquisition unit 3 has one end connected to the frequency converter 6 and the other end connected to the host computer 1 for collecting test data;

[0040] Simulated load 7, connected to inverter 6;

[0041] like Figure 2 As shown, the contactor module 5 includes a first contactor group and a second contactor group, the first contactor group includes a first contactor and a second contactor, the input ends of the first contactor and the second contactor are both connected to the rated voltage output end of the multi-tap transformer 4, the output end of the first contactor is connected to the frequency converter, and the output end of the second contactor is connected to the frequency converter through a power resistor, the second contactor group includes a third contactor, the input end of the third contactor is connected to one or more other output ends of the multi-tap transformer 4, and one of them is turned on, and the output end is connected to the frequency converter 6, wherein the other output ends are output ends other than the rated voltage output end. Figure 2 In the figure, KM1 is the first contactor, KM2~KM6 are the second contactors, KM7 is the third contactor, R1~R5 are power resistors, K0 is the start-stop switch, K1~K5 are switches corresponding to the four output terminals of the multi-tap transformer, and the size of U is 6KV.

[0042] like Figure 2 As shown, there are multiple second contactors and multiple power resistors, each second contactor corresponds to each power resistor, and the resistance values ​​of each power resistor are different.

[0043] Each output end of the multi-tap transformer 4 is provided with a switch, and the input end of the third contactor is connected to the switches of each other output end of the multi-tap transformer 4 .

[0044] In another embodiment of the present application, the input terminal of the third contactor is connected to switches of all other output terminals of the multi-tap transformer 4 .

[0045] Preferably, a start-stop switch is provided between the input end of the multi-tap transformer 4 and the power supply, the simulated load 7 is an adjustable simulated load, and the second contactor and the power resistor are both provided with 6.

[0046] The low voltage ride-through test method of the test system includes:

[0047] Step S1: Before the test begins, connect the power supply K0, then turn on the switches K5 at the rated voltage output terminal K2 and the low voltage output terminal, where the low voltage output terminal is an output terminal with a voltage lower than the rated voltage. Then, adjust the adjustable simulated load according to the test requirements.

[0048] Step S2: Turning on the first contactor for a first set time. The first set time should be selected so that the data can be relatively stable. The data acquisition unit 3 collects the voltage, current, power, frequency and waveform data of the inverter.

[0049] Step S3: Select the required power resistance by calculation, and then close the designated second contactor;

[0050] Step S4: Open the first contactor and close the third contactor. If the third contactor is not fully closed, a voltage sag process may be initiated. After the third contactor is fully closed, the closed second contactor is opened and the process is continued for a second set time. The second set time is determined in the same manner as the first set time. The data acquisition unit 3 continuously collects the voltage, current, power, frequency, and waveform data of the inverter during the entire process.

[0051] Step S5: close the designated second contactor, open the third contactor, close the first contactor, and the data acquisition unit 3 continuously acquires the voltage, current, power, frequency and waveform data of the inverter during the entire process.

[0052] During the test, the data acquisition unit collects the changes in voltage, current, power, frequency and waveform on the power supply side and load side of the inverter during the entire process, and the computer completes the calculation and recording.

[0053] When conducting a test using the high voltage ride-through test system of the present application, by adjusting the taps of the multi-tap transformer, the inverter power supply line voltage can be adjusted to the voltage value and duration during the high voltage ride-through test, such as 110% of the rated voltage, so that the inverter 6 can be subjected to a high voltage ride-through test.

[0054] In addition, by selecting multi-tap transformers, AC contactors and power resistors of different voltage levels and using the same system structure, low voltage ride-through tests for inverters of corresponding voltage levels can be achieved.

Claims

1. A low voltage ride through test method for a frequency converter high and low voltage ride through test system, the test system comprising: A multi-tap transformer (4) is a three-phase transformer, the input end of which is connected to a power supply, and each secondary winding is symmetrically provided with multiple taps; There are three contactor modules (5), the input end of which is connected to the output end of the multi-tap transformer (4), and the output end of which is connected to the frequency converter (6) to be tested; A PLC controller (2), the input end of which is connected to the host computer (1), and the output end of which is connected to the contactor module (5) for controlling the on and off of each contactor in the contactor module (5); A data acquisition unit (3) is connected to the frequency converter (6) at one end and to the host computer (1) at the other end, and is used to collect test data; Simulated load (7), connected to the inverter (6); It is characterized by: The contactor module (5) includes a first contactor group and a second contactor group, the first contactor group includes a first contactor and a second contactor, the input ends of the first contactor and the second contactor are both connected to the rated voltage output end of the multi-tap transformer (4), the output end of the first contactor is connected to the frequency converter, the output end of the second contactor is connected to the frequency converter through a power resistor, the second contactor group includes a third contactor, the input end of the third contactor is connected to one or more other output ends of the multi-tap transformer (4), and one of the third contactors is turned on, and the output end is connected to the frequency converter (6), wherein the other output ends are output ends other than the rated voltage output end; There are multiple second contactors and multiple power resistors, each second contactor corresponds to each power resistor, and the resistance values ​​of the power resistors are different from each other; Each output end of the multi-tap transformer (4) is provided with a switch, and the input end of the third contactor is connected to the switches of each other output end of the multi-tap transformer (4); The input end of the third contactor is connected to switches of all other output ends of the multi-tap transformer (4); Test methods include: Step S1: Turning on switches of the rated voltage output terminal and the low voltage output terminal, wherein the low voltage output terminal is an output terminal with a voltage lower than the rated voltage; Step S2: turning on the first contactor for a first set time, and collecting voltage, current, power, frequency and waveform data of the inverter by the data acquisition unit (3); Step S3: Select the required power resistance by calculation, and then close the designated second contactor; Step S4: disconnecting the first contactor and closing the third contactor; starting the voltage sag process when the third contactor is not yet fully closed; and disconnecting the second contactor in the closed state after the third contactor is fully closed for a second set time; and continuously collecting the voltage, current, power, frequency and waveform data of the inverter during the entire process by the data acquisition unit (3); Step S5: close the designated second contactor, open the third contactor, close the first contactor, and the data acquisition unit (3) continuously acquires the voltage, current, power, frequency and waveform data of the inverter during the entire process.

2. The test method according to claim 1, characterized in that A start-stop switch is provided between the input end of the multi-tap transformer (4) and the power supply.

3. The test method according to claim 1, characterized in that The simulated load (7) is an adjustable simulated load.

4. The test method according to claim 1, characterized in that There are six second contactors and six power resistors.

5. The test method according to claim 1, characterized in that The host computer (1) is a computer.

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