Network construction type PCS test power supply

Abstract

The invention discloses a network construction type PCS test power supply, which comprises an impedance network superposition module and a main power distribution module, and is characterized in that the impedance network superposition module comprises a waveform injection unit, and the main power distribution module comprises a circuit breaker and a plurality of contactors; each phase of the power grid or the power grid simulator is connected with each phase of the grid-forming type energy storage converter through a circuit breaker and a plurality of contactors in sequence, and each phase of one contactor is connected with a waveform injection unit in parallel; by controlling the start and stop of the waveform injection units connected with each phase and outputting voltages with different frequencies and amplitudes, the harmonic wave, oscillation and impedance change conditions of each phase of a power grid are simulated, and the grid-forming type energy storage converter is tested. The method has the advantages that accurate simulation of power grid characteristics and flexible adaptation to different test scenes are realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of networked energy storage converter testing, in particular to a networked PCS test power supply. BACKGROUND

[0002] As a key device in new energy power systems, networked energy storage converters (PCSs) need to be verified for their grid support capability, dynamic response characteristics and fault ride-through capability through rigorous performance testing. The existing test power supply topology has the following shortcomings: 1) Traditional test power supplies mostly use simple voltage source inverter topologies, which lack precise impedance modeling capabilities and cannot accurately reflect the line impedance characteristics of the grid, leading to control conflicts between the virtual synchronous control of the networked PCS and the test power supply.

[0003] 2) Lack of flexible topology configuration capabilities, making it difficult to adapt to the testing needs of networked PCSs of different power levels and different voltage levels. For example, Chinese Patent No. CN217112528U discloses a new type of energy storage converter grid-connected and off-grid test system, which directly connects the energy storage converter to the grid through a transformer, and the test voltage is single, which cannot adapt to the testing needs of networked PCSs of different power levels and different voltage levels.

[0004] Therefore, a new networked PCS test power supply topology is needed to solve the above problems and achieve accurate simulation of grid characteristics and flexible adaptation to different test scenarios. SUMMARY

[0005] The technical problem to be solved by the present application is how to set up a networked PCS test power supply to achieve accurate simulation of grid characteristics and flexible adaptation to different test scenarios.

[0006] The present application solves the above technical problems by the following technical means: a networked PCS test power supply, comprising an impedance network superposition module and a main distribution module, the impedance network superposition module comprising a waveform injection unit, the main distribution module comprising a circuit breaker and a plurality of contactors, each phase of the grid or grid simulator being connected to each phase of the networked energy storage converter in turn through the circuit breaker and the plurality of contactors, each phase of one of the contactors being connected in parallel to one of the waveform injection units; by controlling the start and stop of the waveform injection units connected to each phase and outputting voltages of different frequencies and amplitudes, the harmonics, oscillations and impedance changes of each phase of the grid are simulated, and the networked energy storage converter is tested.

[0007] The application simulates various harmonics, oscillations, impedance changes and the like that may occur in the power grid by controlling the start and stop of the waveform injection unit and outputting voltages of different frequencies and amplitudes to each phase of the grid side, and analyzes the grid impedance characteristics and harmonics by detecting the voltage and current signals of the grid-connected energy storage converter, so as to determine the actual grid-connected characteristics of the grid-connected energy storage converter. Through precise control of the output voltage of the waveform injection unit, the grid characteristics can be accurately simulated, and each phase of the grid is connected to the waveform injection unit. By controlling the start and stop of each waveform injection unit, the single-phase voltage injection condition, the voltage injection condition of any two phases of the three-phase, and the voltage injection condition of the three-phase can be met, thereby adapting to different power levels and different voltage levels of the grid-connected PCS test requirements, and realizing flexible adaptation of different test scenarios.

[0008] Further, the grid-connected PCS test power supply further comprises a plurality of transformers, and the output end of each waveform injection unit is connected to the primary side of a transformer.

[0009] Further, the waveform injection unit of the impedance network superposition module has three, which are A-phase waveform injection unit, B-phase waveform injection unit and C-phase waveform injection unit, and the output end of the A-phase waveform injection unit, the B-phase waveform injection unit and the C-phase waveform injection unit is connected to the primary side of a transformer.

[0010] Further, the impedance network superposition module further comprises an alternating current source and a 2-level three-phase PWM rectifier circuit, and the three-phase output end of the alternating current source is connected to the three-phase input end of the 2-level three-phase PWM rectifier circuit, and the three-phase output end of the 2-level three-phase PWM rectifier circuit is connected to the A-phase waveform injection unit, the B-phase waveform injection unit and the C-phase waveform injection unit.

[0011] Further, the voltage level of the alternating current source is 400V.

[0012] Further, the waveform injection unit comprises a dual active bridge (DAB) isolation DC / DC conversion circuit, an H-bridge DC / AC inverter circuit and a filter circuit, and the DAB isolation DC / DC conversion circuit, the H-bridge DC / AC inverter circuit and the filter circuit are sequentially connected, and the output end of the filter circuit is the output end of the waveform injection unit.

[0013] Further, a waveform start-stop protection switch is arranged on the line between the output end of each filter circuit and the primary side of the corresponding transformer, the waveform start-stop protection switch is connected in parallel with the primary side of the transformer, and when the waveform start-stop protection switch is closed, the waveform injection unit on the line is short-circuited, and vice versa.

[0014] Furthermore, by controlling the start and stop of each switching transistor in the waveform injection unit and the 2-level three-phase PWM rectifier circuit through PWM signal control, the waveform injection unit can output voltages of different frequencies and amplitudes to simulate the harmonic and oscillation changes of each phase of the power grid.

[0015] Furthermore, by controlling the start and stop of each switching transistor in the waveform injection unit and the 2-level three-phase PWM rectifier circuit through PWM signal control, the output voltage and output current of the waveform injection unit are adjusted to simulate the different impedance changes of each phase of the power grid. The ratio of output voltage to output current is the impedance.

[0016] Furthermore, the testing of the grid-type energy storage converter refers to simulating the harmonics, oscillations, and impedance changes of each phase of the power grid, and testing whether the preset indicators of the grid-type energy storage converter meet the power grid operation requirements. If they meet the requirements, the performance of the grid-type energy storage converter is qualified under the corresponding harmonics, oscillations, and impedance changes; otherwise, it is unqualified.

[0017] The advantages of this invention are: This invention controls the start and stop of waveform injection units to output voltages of different frequencies and amplitudes, which are then applied to each phase of the grid side. This simulates various harmonics, oscillations, impedance changes, etc., that may occur in the grid. By detecting the voltage and current signals of the grid-connected energy storage converter, grid-side impedance characteristics and harmonic analysis are performed to determine the actual grid-connected characteristics of the grid-connected energy storage converter. Precise control of the output voltage of the waveform injection units enables accurate simulation of grid characteristics. Each phase of the grid is connected to a waveform injection unit. By controlling the start and stop of each waveform injection unit, single-phase voltage injection, voltage injection of any two phases out of three, and voltage injection of all three phases can be achieved. This adapts to the testing requirements of grid-connected PCS with different power levels and voltage levels, enabling flexible adaptation to different testing scenarios. Attached Figure Description

[0018] Figure 1 This is a circuit schematic diagram of a network-type PCS test power supply disclosed in an embodiment of the present invention; Figure 2 The schematic diagram of the AC source and the 2-level three-phase PWM rectifier circuit in the circuit schematic diagram of a grid-type PCS test power supply disclosed in the embodiment of the present invention is shown. Figure 3 The schematic diagram of the waveform injection unit in the circuit schematic diagram of a network-type PCS test power supply disclosed in the embodiment of the present invention is shown. Figure 4 The circuit diagram shown is for the side where the grid-type energy storage converter is located in the circuit schematic diagram of a grid-type PCS test power supply disclosed in an embodiment of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] like Figure 1 As shown, this embodiment of the invention provides a network-type PCS test power supply, including an impedance network superposition module and a main power distribution module. The impedance network superposition module includes an AC source 1, a 2-level three-phase PWM rectifier circuit 2, and waveform injection units 3. There are three waveform injection units 3: phase A waveform injection unit 3, phase B waveform injection unit 3, and phase C waveform injection unit 3. The voltage level of the AC source 1 is 400V. The three-phase output terminals of the AC source 1 are respectively connected to the three-phase input terminals of the 2-level three-phase PWM rectifier circuit 2, and the three-phase output terminals of the 2-level three-phase PWM rectifier circuit 2 are respectively connected to phase A waveform injection unit 3, phase B waveform injection unit 3, and phase C waveform injection unit 3. The output terminals of phase A waveform injection unit 3, phase B waveform injection unit 3, and phase C waveform injection unit 3 are respectively connected to the primary side of a transformer. To clearly illustrate the structure of each circuit module, this invention will... Figure 1 Split into Figures 2 to 4 Several subgraphs.

[0021] See Figures 1 to 4 Each waveform injection unit 3 includes a dual active bridge DAB isolated DC / DC converter circuit 31, an H-bridge DC / AC inverter circuit 32, and a filter circuit 33. These circuits are connected sequentially, with the output of the filter circuit 33 serving as the output of the waveform injection unit 3. For detailed circuit principles of the 2-level three-phase PWM rectifier circuit 2, the dual active bridge DAB isolated DC / DC converter circuit 31, the H-bridge DC / AC inverter circuit 32, and the filter circuit 33, please refer to [link to relevant documentation]. Figure 1 , can be adopted Figure 1 The circuit structure shown can also be used in Figure 1 Based on the circuit structure shown, capacitors, resistors, inductors, and switching devices are added to fine-tune it. This embodiment does not impose special limitations on the specific structure of each circuit unit, as long as the corresponding circuit unit function can be achieved.

[0022] The main power distribution module includes a circuit breaker 4 and multiple contactors 5. Each phase of the power grid or power grid simulator is connected to each phase of the grid-type energy storage converter through the circuit breaker 4 and multiple contactors 5. Each phase of one of the contactors 5 is connected to the secondary side of each transformer.

[0023] A waveform start / stop protection switch (e.g., ...) is installed on the line between the output terminal of each filter circuit 33 and the primary side of its corresponding transformer. Figure 1 (K4B, K7B, and K12B shown are all waveform start-stop protection switches). These switches are connected in parallel with the primary side of the transformer. When a waveform start-stop protection switch is closed, the waveform injection unit 3 on its corresponding line is short-circuited; conversely, when it is open, the waveform injection unit 3 on its corresponding line is connected. The waveform start-stop protection switches are designed to prevent voltage spikes from the grid side, amplified by the transformer, from damaging the switching transistors in the waveform injection unit 3. They also control the start and stop of the waveform injection unit 3. Before the waveform injection unit 3 starts operating, closing the waveform start-stop protection switch short-circuits it, preventing the grid voltage from affecting the switching transistors and burning them out. When different frequencies and amplitudes of voltage output are required from the waveform injection unit 3, the start and stop of each switching transistor in the waveform injection unit 3 are controlled by a PWM signal. Then, the waveform start-stop protection switch is opened, allowing the voltage output from the waveform injection unit 3 to be transmitted to the grid side through the transformer, simulating the harmonics and oscillations of each phase on the grid side.

[0024] Specifically, the waveform injection unit 3 and the switching transistors in the 2-level three-phase PWM rectifier circuit 2 are controlled by PWM signals to start and stop, thereby controlling the output voltage of the waveform injection unit 3 to have different frequencies and amplitudes. This injects corresponding voltages into the power grid and the lines where the grid-connected energy storage converter is located, generating corresponding interference and simulating the harmonic and oscillation variations of each phase of the power grid. Furthermore, by controlling the start and stop of the switching transistors in the waveform injection unit 3 and the 2-level three-phase PWM rectifier circuit 2 with PWM signals, the output voltage and output current of the waveform injection unit are adjusted to simulate the different impedance variations of each phase of the power grid. The ratio of the output voltage to the output current is the impedance. Thus, the overall circuit can simulate the harmonics, oscillations, and impedance variations of each phase on the power grid side, and is used to test the grid-connected characteristics of the grid-connected energy storage converter under different harmonic, oscillation, and impedance variation conditions. For example, it can test whether the preset indicators of the grid-connected energy storage converter meet the power grid operation requirements. If they do, the performance of the grid-connected energy storage converter is qualified under the corresponding harmonic, oscillation, and impedance variation conditions; otherwise, it is unqualified.

[0025] The main power distribution module of this invention mainly consists of circuit breakers 4, contactors 5, grid-side or grid simulators, and grid-type energy storage converters (PCS). Depending on the power of the PCS, the corresponding grid-side power or grid simulator power is adapted, along with circuit breakers 4 and contactors 5 of appropriate capacity. Under normal conditions, circuit breaker 4 is closed first, and each contactor 5 is engaged. Simultaneously, the waveform injection unit 3 of the impedance network superposition module is opened as needed to perform PCS functional testing. Different power and voltage levels of grid-type energy storage converters (PCS) can meet their testing requirements by adapting to the corresponding grid-side power, circuit breakers 4, contactors 5, and other power distribution devices. The main topology of the impedance network superposition module adopts a three-level structure, including a 2-level three-phase PWM rectifier circuit 2, a dual active bridge DAB isolated DC / DC converter circuit 31, and an H-bridge DC / AC inverter circuit 32. The power switching transistors involved are all SiC MOSFET devices, enabling high-frequency control with a switching frequency of 20kHz-50kHz. They are small in size, have a high control frequency of up to 25kHz, a control cycle of 50µs, an output voltage and current response speed of 3ms, and low output voltage and current distortion, with a total harmonic distortion (THD) of less than 3%. The inverter output of the H-bridge DC / AC inverter circuit 32 is connected to the main distribution module via a power frequency transformer. By controlling the voltage amplitude, frequency, and phase of the inverter output, the voltage is superimposed onto the A, B, and C phases of the grid side of the main distribution module through the power frequency transformer to simulate various harmonics, oscillations, impedance changes, etc., that may occur in the grid. Then, by detecting the voltage and current signals of the grid-connected energy storage converter, grid-side impedance characteristic analysis and harmonic analysis are performed to determine the actual grid-connected characteristics of the grid-connected energy storage converter. The above process also involves PWM drive control conditioning circuit, voltage sampling conditioning circuit, current sampling conditioning circuit, and external communication conditioning circuit, which are used for PWM signal generation, voltage sampling, current sampling and communication transmission, respectively. When performing test performance analysis, a high-speed DSP or FPGA is used as the main control chip. It is fast, has high sampling accuracy, and is suitable for high-speed processing of various voltage and current signals and rapid analysis and calculation of the signals.

[0026] The entire circuit topology solves the problem of traditional test power supplies being unable to simulate grid impedance and avoids conflicts with the control strategy of grid-connected PCS. The power conversion circuit, constructed using SiC MOSFET devices, achieves a high switching frequency of 20kHz-50kHz while ensuring a total harmonic distortion (THD) of ≤3% for the output voltage, balancing fast dynamic response and high output accuracy. The main power distribution module is flexibly configurable, adapting appropriate power distribution devices to grid-connected energy storage converter PCS of different power and voltage levels to meet diverse testing requirements.

[0027] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A network-type PCS test power supply, characterized in that, The system includes an impedance network superposition module and a main power distribution module. The impedance network superposition module includes a waveform injection unit, and the main power distribution module includes a circuit breaker and multiple contactors. Each phase of the power grid or power grid simulator is connected to each phase of the grid-type energy storage converter in sequence through the circuit breaker and multiple contactors. Each phase of one of the contactors is connected in parallel with a waveform injection unit. By controlling the start and stop of the waveform injection units connected to each phase and outputting voltages of different frequencies and amplitudes, the system simulates the harmonics, oscillations, and impedance changes of each phase of the power grid, and tests the grid-type energy storage converter.

2. The network-type PCS test power supply according to claim 1, characterized in that, It also includes multiple transformers, with the output of each waveform injection unit connected to the primary side of a transformer, and the secondary side of each transformer connected in parallel with the three phases of one of the multiple contactors in the main power distribution module.

3. The network-type PCS test power supply according to claim 2, characterized in that, The impedance network superposition module has three waveform injection units: phase A waveform injection unit, phase B waveform injection unit, and phase C waveform injection unit. The output terminals of phase A waveform injection unit, phase B waveform injection unit, and phase C waveform injection unit are respectively connected to the primary side of a transformer.

4. The network-type PCS test power supply according to claim 3, characterized in that, The impedance network superposition module also includes an AC source and a 2-level three-phase PWM rectifier circuit. The three-phase output terminals of the AC source are connected to the three-phase input terminals of the 2-level three-phase PWM rectifier circuit, and the three-phase output terminals of the 2-level three-phase PWM rectifier circuit are connected to the A-phase waveform injection unit, the B-phase waveform injection unit, and the C-phase waveform injection unit, respectively.

5. A grid-type PCS test power supply according to claim 4, characterized in that, The voltage level of the AC source is 400V.

6. A grid-type PCS test power supply according to claim 3, characterized in that, The waveform injection unit includes a dual active bridge DAB isolated DC / DC converter circuit, an H-bridge DC / AC inverter circuit, and a filter circuit. The dual active bridge DAB isolated DC / DC converter circuit, the H-bridge DC / AC inverter circuit, and the filter circuit are connected in sequence, and the output terminal of the filter circuit serves as the output terminal of the waveform injection unit.

7. A grid-type PCS test power supply according to claim 6, characterized in that, A waveform start / stop protection switch is installed on the line between the output terminal of each filter circuit and the primary side of its corresponding transformer. The waveform start / stop protection switch is connected in parallel with the primary side of the transformer. When the waveform start / stop protection switch is closed, the waveform injection unit on its line is short-circuited; otherwise, the waveform injection unit on its line is connected.

8. A grid-type PCS test power supply according to claim 7, characterized in that, By controlling the waveform injection unit and the start / stop of each switching transistor in the 2-level three-phase PWM rectifier circuit with PWM signals, the waveform injection unit outputs voltages of different frequencies and amplitudes, simulating the harmonic and oscillation changes of each phase of the power grid.

9. A grid-type PCS test power supply according to claim 7, characterized in that, By controlling the start and stop of each switching transistor in the waveform injection unit and the 2-level three-phase PWM rectifier circuit through PWM signal control, the output voltage and output current of the waveform injection unit are adjusted to simulate the different impedance changes of each phase of the power grid. The ratio of output voltage to output current is the impedance.

10. A grid-type PCS test power supply according to claim 7, characterized in that, The testing of the grid-type energy storage converter refers to simulating the harmonics, oscillations, and impedance changes of each phase of the power grid, and testing whether the preset indicators of the grid-type energy storage converter meet the power grid operation requirements. If they meet the requirements, the performance of the grid-type energy storage converter is qualified under the corresponding harmonics, oscillations, and impedance changes; otherwise, it is unqualified.

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