CN-121984332-A - Current limiting method and device for grid-structured grid-connected converter

CN121984332ACN 121984332 ACN121984332 ACN 121984332ACN-121984332-A

Abstract

The application provides a current limiting method and device for a grid-connected converter, which are used for carrying out current limiting control on the grid-connected converter according to a current reference value of a filter inductor under a two-phase static coordinate system and an output voltage stable value of the grid-connected converter under a two-phase rotating coordinate system. The application can realize the feedback control of the grid-connected converter, further realize the current limiting control, and is not easy to damage the power devices in the grid-connected converter, thereby ensuring the stable operation of the grid-connected converter. According to the application, the actual voltage value of the primary winding under the two-phase static coordinate system and the actual current value of the filter inductor under the two-phase static coordinate system are used as feedback quantities, so that the calculation of the actual output voltage value of the grid-connected converter under the two-phase static coordinate system is realized, the transient impulse current can be restrained, and the stability of the grid-connected converter is further improved.

Inventors

JI FENG
KOU LONGZE
YAN HEMING
GAO YUQIN
GUO JIAN
MA TING

Assignees

中国电力科学研究院有限公司
国家电网有限公司
国网宁夏电力有限公司经济技术研究院

Dates

Publication Date: 20260505
Application Date: 20251222

Claims (20)

1. The current limiting method of the grid-structured grid-connected converter is characterized in that the grid-structured grid-connected converter is connected with a transformer through a filter, and comprises the following steps: determining a current reference value of a filter inductor in the filter under a two-phase stationary coordinate system according to the actual voltage amplitude value and the actual current value of an original winding in the transformer; Calculating an output voltage stable value of the grid-connected converter under a two-phase rotating coordinate system according to the current actual value of the primary winding; And performing current limiting control on the grid-structured grid-connected converter according to the current reference value of the filter inductor under the two-phase static coordinate system and the output voltage stable value of the grid-structured grid-connected converter under the two-phase rotating coordinate system.
2. The current limiting method according to claim 1, wherein determining the current reference value of the filter inductor in the filter under the two-phase stationary coordinate system according to the actual voltage amplitude value and the actual current value of the primary winding in the transformer comprises: Calculating a voltage reference value of the primary winding according to the actual voltage amplitude value of the primary winding; Determining a current limiting value of the primary winding according to the current actual value of the primary winding; And determining the current reference value of the filter inductor under a two-phase stationary coordinate system according to the voltage reference value of the primary winding and the current amplitude limiting value of the primary winding.
3. The current limiting method according to claim 2, wherein the calculating the voltage reference value of the primary winding according to the actual voltage amplitude value of the primary winding comprises: And performing proportional integral control and amplitude limiting on the difference value between the voltage amplitude reference value of the primary winding and the voltage amplitude actual value of the primary winding to obtain the voltage reference value of the primary winding.
4. The current limiting method according to claim 2, wherein said determining a current limiting value of said primary winding based on an actual value of a current of said primary winding comprises: Performing park transformation on the current actual value of the primary winding to obtain the current actual value of the primary winding under a two-phase rotating coordinate system; And limiting the current actual value of the primary winding under a two-phase rotating coordinate system to obtain the current limiting value of the primary winding.
5. The current limiting method according to claim 2, wherein said determining the current reference value of the filter inductor in the two-phase stationary coordinate system based on the voltage reference value of the primary winding and the current limited value of the primary winding comprises: Calculating a current reference value of the filter inductor under a two-phase rotation coordinate system according to the voltage reference value of the primary winding and the current amplitude limiting value of the primary winding; And performing inverse Peak conversion on the current reference value of the filter inductor under the two-phase rotating coordinate system to obtain the current reference value of the filter inductor under the two-phase stationary coordinate system.
6. The current limiting method according to claim 5, wherein the current reference value of the filter inductor in the two-phase rotation coordinate system is as follows: Wherein, the Representing the d-axis current reference value of the filter inductor under a two-phase rotation coordinate system, Representing the q-axis current reference value of the filter inductor in a two-phase rotation coordinate system, Representing the d-axis current limiting value of the primary winding under a two-phase rotating coordinate system, Representing the q-axis current clipping value of the primary winding in a two-phase rotating coordinate system, Representing the d-axis voltage reference value of the primary winding under a two-phase rotating coordinate system, Representing the q-axis voltage reference value of the primary winding in a two-phase rotating coordinate system, Indicating the rated angular frequency of the ac power network, Representing the capacitance of the filter capacitor in the filter.
7. The current limiting method according to claim 2, wherein the output voltage stabilizing value of the grid-connected inverter in the two-phase rotation coordinate system is as follows: Wherein, the The d-axis output voltage stable value of the grid-structured grid-connected converter under a two-phase rotation coordinate system is represented, The q-axis output voltage stable value of the grid-structured grid-connected converter under a two-phase rotation coordinate system is represented; Representing the d-axis voltage reference value of the primary winding under a two-phase rotating coordinate system, Representing a q-axis voltage reference value of the primary winding under a two-phase rotating coordinate system; Representing the d-axis current limiting value of the primary winding under a two-phase rotating coordinate system, Representing the q-axis current limiting value of the primary winding under a two-phase rotating coordinate system; Indicating the rated angular frequency of the ac power network, Representing the capacitance of the filter capacitor in the filter, Representing the inductance of the filter inductance.
8. The current limiting method according to claim 2, wherein the current limiting control of the grid-connected converter according to the current reference value of the filter inductor in the two-phase stationary coordinate system and the output voltage stable value of the grid-connected converter in the two-phase rotating coordinate system includes: Performing inverse Peak transformation on the output voltage stable value of the grid-structured grid-connected converter under a two-phase rotating coordinate system to obtain the output voltage stable value of the grid-structured grid-connected converter under a two-phase static coordinate system; Calculating the actual value of the output voltage of the grid-structured grid-connected converter under the two-phase static coordinate system according to the stable value of the output voltage of the grid-structured grid-connected converter under the two-phase static coordinate system and the current reference value of the filter inductor under the two-phase static coordinate system; modulating the actual value of the output voltage of the grid-structured grid-connected converter under a two-phase static coordinate system to obtain a control signal; and carrying out current limiting control on the grid-structured grid-connected converter according to the control signal.
9. The current limiting method according to claim 8, wherein the calculating the actual output voltage value of the grid-connected converter in the two-phase stationary coordinate system according to the output voltage stable value of the grid-connected converter in the two-phase stationary coordinate system and the current reference value of the filter inductor in the two-phase stationary coordinate system includes: performing Clark transformation on the actual voltage amplitude value of the primary winding to obtain an actual alpha-axis voltage value and an actual beta-axis voltage value of the primary winding under a two-phase static coordinate system; Performing Clark transformation on the actual current value of the filter inductor to obtain an actual alpha-axis current value and an actual beta-axis current value of the filter inductor under a two-phase static coordinate system; performing inverse Peak conversion on the voltage reference value of the primary winding to obtain an alpha-axis voltage reference value and a beta-axis voltage reference value of the primary winding under a two-phase static coordinate system; And calculating the alpha-axis output voltage actual value and the beta-axis output voltage actual value of the grid-structured grid-connected converter under the two-phase static coordinate system according to the alpha-axis output voltage stable value and the beta-axis output voltage stable value of the grid-structured grid-connected converter under the two-phase static coordinate system, the alpha-axis voltage reference value and the beta-axis voltage reference value of the primary winding under the two-phase static coordinate system, the alpha-axis voltage actual value and the beta-axis voltage actual value of the primary winding under the two-phase static coordinate system, the alpha-axis current actual value and the beta-axis current actual value of the filter inductor under the two-phase static coordinate system and the alpha-axis current reference value and the beta-axis current reference value of the filter inductor under the two-phase static coordinate system.
10. The method of current limiting according to claim 9, wherein, The actual value of the alpha-axis output voltage of the grid-structured grid-connected converter under a two-phase static coordinate system meets the following conditions: ; Wherein, the The actual value of the alpha-axis output voltage of the grid-structured grid-connected converter under a two-phase static coordinate system is represented, The alpha-axis output voltage stable value of the grid-structured grid-connected converter under a two-phase static coordinate system is represented, Representing the alpha-axis voltage reference value of the primary winding in a two-phase stationary coordinate system, Representing the actual value of the alpha-axis voltage of the primary winding in a two-phase stationary coordinate system, Representing the alpha-axis current reference value of the filter inductor in a two-phase stationary coordinate system, Representing the actual value of the alpha-axis current of the filter inductor in a two-phase stationary coordinate system, A first state feedback coefficient is represented and, Representing a second state feedback coefficient; the actual value of the beta-axis output voltage of the grid-structured grid-connected converter under a two-phase static coordinate system meets the following conditions: ; Wherein, the The actual value of the beta-axis output voltage of the grid-structured grid-connected converter under a two-phase static coordinate system is represented, The beta-axis output voltage stable value of the grid-structured grid-connected converter under a two-phase static coordinate system is represented, Representing the beta-axis voltage reference value of the primary winding under a two-phase stationary coordinate system, Representing the actual value of the beta-axis voltage of the primary winding in a two-phase stationary coordinate system, Representing the beta-axis current reference value of the filter inductor under a two-phase static coordinate system, Representing the actual value of the beta-axis current of the filter inductor in a two-phase static coordinate system.
11. The current limiting device of the grid-structured grid-connected converter is characterized in that the grid-structured grid-connected converter is connected with a transformer through a filter, and the current limiting device comprises: the determining module is used for determining a current reference value of the filter inductor in the filter under a two-phase static coordinate system according to the actual voltage amplitude value and the actual current value of the primary winding in the transformer; the calculation module is used for calculating the output voltage stable value of the grid-connected converter under a two-phase rotation coordinate system according to the actual value of the primary winding current; The control module is used for carrying out current limiting control on the grid-structured grid-connected converter according to the current reference value of the filter inductor under the two-phase static coordinate system and the output voltage stable value of the grid-structured grid-connected converter under the two-phase rotating coordinate system.
12. The flow limiting device according to claim 11, wherein the determining module is specifically configured to: Calculating a voltage reference value of the primary winding according to the actual voltage amplitude value of the primary winding; Determining a current limiting value of the primary winding according to the current actual value of the primary winding; And determining the current reference value of the filter inductor under a two-phase stationary coordinate system according to the voltage reference value of the primary winding and the current amplitude limiting value of the primary winding.
13. The flow limiting device according to claim 12, wherein the determining module is specifically configured to: And performing proportional integral control and amplitude limiting on the difference value between the voltage amplitude reference value of the primary winding and the voltage amplitude actual value of the primary winding to obtain the voltage reference value of the primary winding.
14. The flow limiting device according to claim 12, wherein the determining module is specifically configured to: Performing park transformation on the current actual value of the primary winding to obtain the current actual value of the primary winding under a two-phase rotating coordinate system; And limiting the current actual value of the primary winding under a two-phase rotating coordinate system to obtain the current limiting value of the primary winding.
15. The flow limiting device according to claim 12, wherein the determining module is specifically configured to: Calculating a current reference value of the filter inductor under a two-phase rotation coordinate system according to the voltage reference value of the primary winding and the current amplitude limiting value of the primary winding; And performing inverse Peak conversion on the current reference value of the filter inductor under the two-phase rotating coordinate system to obtain the current reference value of the filter inductor under the two-phase stationary coordinate system.
16. The current limiting device according to claim 15, wherein the current reference value of the filter inductor in a two-phase rotation coordinate system satisfies: Wherein, the Representing the d-axis current reference value of the filter inductor under a two-phase rotation coordinate system, Representing the q-axis current reference value of the filter inductor in a two-phase rotation coordinate system, Representing the d-axis current limiting value of the primary winding under a two-phase rotating coordinate system, Representing the q-axis current clipping value of the primary winding in a two-phase rotating coordinate system, Representing the d-axis voltage reference value of the primary winding under a two-phase rotating coordinate system, Representing the q-axis voltage reference value of the primary winding in a two-phase rotating coordinate system, Indicating the rated angular frequency of the ac power network, Representing the capacitance of the filter capacitor in the filter.
17. The current limiting device according to claim 12, wherein the output voltage stabilizing value of the grid-connected inverter in the two-phase rotation coordinate system satisfies: Wherein, the The d-axis output voltage stable value of the grid-structured grid-connected converter under a two-phase rotation coordinate system is represented, The q-axis output voltage stable value of the grid-structured grid-connected converter under a two-phase rotation coordinate system is represented; Representing the d-axis voltage reference value of the primary winding under a two-phase rotating coordinate system, Representing a q-axis voltage reference value of the primary winding under a two-phase rotating coordinate system; Representing the d-axis current limiting value of the primary winding under a two-phase rotating coordinate system, Representing the q-axis current limiting value of the primary winding under a two-phase rotating coordinate system; Indicating the rated angular frequency of the ac power network, Representing the capacitance of the filter capacitor in the filter, Representing the inductance of the filter inductance.
18. The current limiting device according to claim 11, wherein the control module is specifically configured to: Performing inverse Peak transformation on the output voltage stable value of the grid-structured grid-connected converter under a two-phase rotating coordinate system to obtain the output voltage stable value of the grid-structured grid-connected converter under a two-phase static coordinate system; Calculating the actual value of the output voltage of the grid-structured grid-connected converter under the two-phase static coordinate system according to the stable value of the output voltage of the grid-structured grid-connected converter under the two-phase static coordinate system and the current reference value of the filter inductor under the two-phase static coordinate system; modulating the actual value of the output voltage of the grid-structured grid-connected converter under a two-phase static coordinate system to obtain a control signal; and carrying out current limiting control on the grid-structured grid-connected converter according to the control signal.
19. The current limiting device according to claim 18, wherein the control module is specifically configured to: performing Clark transformation on the actual voltage amplitude value of the primary winding to obtain an actual alpha-axis voltage value and an actual beta-axis voltage value of the primary winding under a two-phase static coordinate system; Performing Clark transformation on the actual current value of the filter inductor to obtain an actual alpha-axis current value and an actual beta-axis current value of the filter inductor under a two-phase static coordinate system; performing inverse Peak conversion on the voltage reference value of the primary winding to obtain an alpha-axis voltage reference value and a beta-axis voltage reference value of the primary winding under a two-phase static coordinate system; And calculating the alpha-axis output voltage actual value and the beta-axis output voltage actual value of the grid-structured grid-connected converter under the two-phase static coordinate system according to the alpha-axis output voltage stable value and the beta-axis output voltage stable value of the grid-structured grid-connected converter under the two-phase static coordinate system, the alpha-axis voltage reference value and the beta-axis voltage reference value of the primary winding under the two-phase static coordinate system, the alpha-axis voltage actual value and the beta-axis voltage actual value of the primary winding under the two-phase static coordinate system, the alpha-axis current actual value and the beta-axis current actual value of the filter inductor under the two-phase static coordinate system and the alpha-axis current reference value and the beta-axis current reference value of the filter inductor under the two-phase static coordinate system.
20. The flow restrictor device of claim 19, wherein the flow restrictor device, The actual value of the alpha-axis output voltage of the grid-structured grid-connected converter under a two-phase static coordinate system meets the following conditions: ; Wherein, the The actual value of the alpha-axis output voltage of the grid-structured grid-connected converter under a two-phase static coordinate system is represented, The alpha-axis output voltage stable value of the grid-structured grid-connected converter under a two-phase static coordinate system is represented, Representing the alpha-axis voltage reference value of the primary winding in a two-phase stationary coordinate system, Representing the actual value of the alpha-axis voltage of the primary winding in a two-phase stationary coordinate system, Representing the alpha-axis current reference value of the filter inductor in a two-phase stationary coordinate system, Representing the actual value of the alpha-axis current of the filter inductor in a two-phase stationary coordinate system, A first state feedback coefficient is represented and, Representing a second state feedback coefficient; the actual value of the beta-axis output voltage of the grid-structured grid-connected converter under a two-phase static coordinate system meets the following conditions: ; Wherein, the The actual value of the beta-axis output voltage of the grid-structured grid-connected converter under a two-phase static coordinate system is represented, The beta-axis output voltage stable value of the grid-structured grid-connected converter under a two-phase static coordinate system is represented, Representing the beta-axis voltage reference value of the primary winding under a two-phase stationary coordinate system, Representing the actual value of the beta-axis voltage of the primary winding in a two-phase stationary coordinate system, Representing the beta-axis current reference value of the filter inductor under a two-phase static coordinate system, Representing the actual value of the beta-axis current of the filter inductor in a two-phase static coordinate system.

Description

Current limiting method and device for grid-structured grid-connected converter Technical Field The application relates to the technical field of power electronics, in particular to a current limiting method and device of a grid-connected converter. Background The distributed power generation system is suitable for new energy power generation with unbalanced distribution, so that the distributed power generation system is widely applied to new energy power generation. The grid-connected converter is used as a key link for connecting the distributed power generation and the alternating current power grid, and can convert direct current into high-quality alternating current and transmit the high-quality alternating current to the alternating current power grid. Therefore, the stable, safe and economical operation of the grid-connected converter is of great significance to the alternating current grid. Grid-connected converters are mainly divided into Grid-connected converters (Grid-Following Inverter) and Grid-connected converters (Grid-Forming Converter). With the gradual increase of the permeability of new energy, the grid-connected converter benefits from the simulation of the characteristics of the synchronous generator, can actively provide frequency and voltage support, has better stability under a weak power grid, and is widely applied. In practical applications, short circuits, overloads, equipment switching into and out of the grid, etc. may cause fluctuations in the ac grid voltage or even cause the ac grid to fail. Voltage drop, direct current bias, frequency offset, phase jump and the like easily bring great influence to the stability of the grid-connected converter. Under the condition that an alternating current power grid breaks down, the grid-connected converter often has an overcurrent phenomenon. When the overcurrent exceeds the maximum current allowed to pass by the filter inductor and the power device in the grid-connected converter, the power device is damaged, and the stable operation of the grid-connected converter is affected. Disclosure of Invention In order to solve the problem of damage to a power device caused by overcurrent in the prior art, the application provides a current limiting method and device for a grid-connected converter. In a first aspect, the present application provides a current limiting method for a grid-connected inverter, where the grid-connected inverter is connected to a transformer through a filter. The current limiting method may include: And determining a current reference value of the filter inductor in the filter under a two-phase static coordinate system according to the actual voltage amplitude value and the actual current value of the primary winding in the transformer. And calculating the output voltage stable value of the grid-connected converter under the two-phase rotation coordinate system according to the actual value of the primary winding current. And performing current limiting control on the grid-connected converter according to the current reference value of the filter inductor under the two-phase static coordinate system and the output voltage stable value of the grid-connected converter under the two-phase rotating coordinate system. In some possible implementations, determining a current reference value of a filter inductor in a filter under a two-phase stationary coordinate system according to a voltage amplitude actual value and a current actual value of an original winding in a transformer includes: And calculating a voltage reference value of the primary winding according to the actual value of the voltage amplitude of the primary winding. And determining the current limiting value of the primary winding according to the actual current value of the primary winding. And determining the current reference value of the filter inductor under the two-phase static coordinate system according to the voltage reference value of the primary winding and the current limiting value of the primary winding. Further, calculating the voltage reference value of the primary winding according to the actual voltage amplitude value of the primary winding includes: And performing proportional integral control and amplitude limiting on the difference value between the voltage amplitude reference value of the primary winding and the voltage amplitude actual value of the primary winding to obtain the voltage reference value of the primary winding. Optionally, determining the current limiting value of the primary winding according to the current actual value of the primary winding includes: And performing park transformation on the current actual value of the primary winding to obtain the current actual value of the primary winding under a two-phase rotating coordinate system. And limiting the current actual value of the primary winding under the two-phase rotation coordinate system to obtain the current limiting value of the primary winding. Illustratively, det