CN-121984082-A - Photovoltaic asymmetric low voltage ride through control method, device and control equipment

CN121984082ACN 121984082 ACN121984082 ACN 121984082ACN-121984082-A

Abstract

The application provides a photovoltaic asymmetric low-voltage ride through control method, a device and control equipment, and relates to the technical field of photovoltaic grid connection. The method comprises the steps of obtaining voltage of a photovoltaic grid-connected point, determining whether an asymmetric low-voltage fault occurs according to the voltage of the photovoltaic grid-connected point, determining a positive sequence reactive current reference value, a negative sequence reactive current reference value and a positive sequence active current reference value based on distribution sequences of positive sequence reactive current, negative sequence reactive current and positive sequence active current from large to small when the asymmetric low-voltage fault is detected, setting the negative sequence active current reference value to be 0, and controlling the photovoltaic inverter according to the positive sequence reactive current reference value, the negative sequence reactive current reference value, the positive sequence active current reference value and the negative sequence active current reference value. According to the priority distribution strategy, the grid-connected point positive sequence voltage is rapidly supported, the grid asymmetry is restrained, and the compatibility of the photovoltaic grid-connected system and the grid is improved.

Inventors

Liang Guandi
FENG TENG
LIU WENXUAN
HAN LIU
ZHU SHIJIA
ZHANG HAIMING
LIU YANG
AN JIAKUN
FAN HUICONG
LI WENXIAO
QIN YING
LI HONGTAO

Assignees

国网河北省电力有限公司经济技术研究院
国网经济技术研究院有限公司
国家电网有限公司

Dates

Publication Date: 20260505
Application Date: 20251223

Claims (10)

1. The photovoltaic asymmetric low voltage ride through control method is characterized by comprising the following steps of: acquiring the voltage of a photovoltaic grid-connected point, and determining whether an asymmetric low-voltage fault occurs according to the voltage of the photovoltaic grid-connected point; when an asymmetric low-voltage fault is detected, determining a positive sequence reactive current reference value, a negative sequence reactive current reference value and a positive sequence active current reference value based on the distribution sequence of positive sequence reactive current, negative sequence reactive current and positive sequence active current with priority from large to small, and setting the negative sequence active current reference value to 0; And controlling the photovoltaic inverter according to the positive sequence reactive current reference value, the negative sequence reactive current reference value, the positive sequence active current reference value and the negative sequence active current reference value.
2. The method for controlling photovoltaic asymmetric low voltage ride through according to claim 1, wherein determining the positive sequence reactive current reference value, the negative sequence reactive current reference value and the positive sequence active current reference value based on the distribution sequence of the positive sequence reactive current, the negative sequence reactive current and the positive sequence active current from the large to the small of the priority comprises: Acquiring the voltage of the photovoltaic grid-connected point; Determining the positive sequence reactive current reference value according to the voltage of the photovoltaic grid-connected point; Determining the negative sequence reactive current reference value according to the positive sequence reactive current reference value; and determining the positive sequence active current reference value according to the positive sequence reactive current reference value and the negative sequence reactive current reference value.
3. The method of claim 1, wherein determining the positive sequence reactive current reference value from the voltage of the photovoltaic grid-connected point comprises: determining the positive sequence voltage of the photovoltaic grid-connected point according to the voltage of the photovoltaic grid-connected point; And determining the positive sequence reactive current reference value according to the positive sequence voltage of the photovoltaic grid-connected point.
4. The method of claim 3, wherein determining the positive sequence reactive current reference value according to the positive sequence voltage of the photovoltaic grid-connected point comprises: determining the positive sequence reactive current reference value according to the positive sequence voltage of the photovoltaic grid-connected point by combining a first formula; The first formula includes: Wherein, the For the positive sequence reactive current reference value, For the rated current of the photovoltaic, Is the upper limit of the reactive current of the positive sequence, Is a positive sequence reactive current lower limit, Is the per unit value of the positive sequence voltage, For the positive sequence voltage of the photovoltaic grid-connected point, The phase voltages are rated for the photovoltaic grid-tie points.
5. The method of claim 2, wherein determining the negative sequence reactive current reference value from the positive sequence reactive current reference value comprises: Determining the negative sequence voltage of the photovoltaic grid-connected point according to the voltage of the photovoltaic grid-connected point; And determining the negative sequence reactive current reference value according to the negative sequence voltage of the photovoltaic grid-connected point and the positive sequence reactive current reference value.
6. The method of claim 5, wherein determining the negative sequence reactive current reference value based on the negative sequence voltage of the photovoltaic grid-tie point and the positive sequence reactive current reference value comprises: determining the negative sequence reactive current reference value according to the negative sequence voltage of the photovoltaic grid-connected point and the positive sequence reactive current reference value by combining a second formula; The second formula includes: Wherein, the For the negative sequence reactive current reference value, Is a negative sequence reactive current amplitude reference value, For the rated current of the photovoltaic, For the positive sequence reactive current, In order to correct the coefficient of the coefficient, Is the phase difference between the positive and negative sequence currents, Is the per unit value of the negative sequence voltage, For the photovoltaic grid-connected point negative sequence voltage, Rated phase voltages for the photovoltaic grid-tie points; And The photovoltaic positive sequence current phase and the photovoltaic negative sequence current phase are respectively; And And the dq axis components of the negative sequence voltage of the photovoltaic grid-connected point are respectively.
7. The method of claim 2, wherein determining the positive sequence active current reference value from the positive sequence reactive current reference value and the negative sequence reactive current reference value comprises: Performing park inverse transformation on the positive sequence reactive current reference value and the negative sequence reactive current amplitude reference value to obtain three phases of equivalent reactive current and three-phase equivalent reactive current amplitude values; determining the positive sequence voltage and the phase of the photovoltaic grid-connected point according to the voltage of the photovoltaic grid-connected point; And determining the positive sequence active current reference value according to the positive sequence voltage of the photovoltaic grid-connected point, the positive sequence voltage phase of the photovoltaic grid-connected point, the three phases of the equivalent reactive current and the three-phase equivalent reactive current amplitude.
8. The method of claim 7, wherein determining the positive-sequence active current reference value according to the positive-sequence voltage of the photovoltaic grid-connected point, the positive-sequence voltage phase of the photovoltaic grid-connected point, the three phases of the equivalent reactive current, and the three-phase equivalent reactive current amplitude comprises: Determining the positive sequence active current reference value according to the positive sequence voltage of the photovoltaic grid-connected point, the positive sequence voltage phase of the photovoltaic grid-connected point, the three phases of the equivalent reactive current and the three-phase equivalent reactive current amplitude by combining a third formula; the third formula includes: Wherein, the For the positive sequence active current reference value, 、 And The correction coefficients are three-phase correction coefficients respectively, Positive sequence voltage phase of the photovoltaic grid-connected point, 、 And Three phases of the equivalent reactive current respectively; for the active power of the photovoltaic, For the rated current of the photovoltaic, 、 And The three-phase equivalent reactive current amplitude values are respectively; is the per unit value of the positive sequence voltage, For the positive sequence voltage of the photovoltaic grid-connected point, The phase voltages are rated for the photovoltaic grid-tie points.
9. A photovoltaic asymmetric low voltage ride through control device, comprising: The fault determining module is used for obtaining the voltage of the photovoltaic grid-connected point and determining whether an asymmetric low-voltage fault occurs according to the voltage of the photovoltaic grid-connected point; The reference value determining module is used for determining a positive sequence reactive current reference value, a negative sequence reactive current reference value and a positive sequence active current reference value based on the distribution sequence of positive sequence reactive current, negative sequence reactive current and positive sequence active current from the large to the small of priority when the occurrence of the asymmetric low-voltage fault is detected, and setting the negative sequence active current reference value to 0; and the low-pass control module is used for controlling the photovoltaic inverter according to the positive sequence reactive current reference value, the negative sequence reactive current reference value, the positive sequence active current reference value and the negative sequence active current reference value.
10. A control device comprising a memory storing a computer program and a processor implementing the photovoltaic asymmetric low voltage ride through control method according to any one of claims 1 to 8 when the computer program is executed by the processor.

Description

Photovoltaic asymmetric low voltage ride through control method, device and control equipment Technical Field The invention relates to the technical field of photovoltaic grid connection, in particular to a photovoltaic asymmetric low-voltage ride through control method, a device and control equipment. Background Photovoltaic power generation is used as a clean renewable energy source, and the installed capacity and the grid-connected scale of the photovoltaic power generation are continuously increased, so that the photovoltaic power generation becomes an important component of a modern power system. With the continuous improvement of the photovoltaic permeability, the operation characteristics and the control strategy of the photovoltaic power station have increasingly remarkable influence on the safety and stability of the power grid, which means that the grid connection requirement of the photovoltaic power station needs to be converted from the most basic grid connection capable to the higher-level grid support. Under the background, the low voltage ride through capability of the photovoltaic power station after the external system fails becomes a key link for supporting the power grid to stably pass through a failure stage, namely, when the voltage of the power grid is reduced due to failure or abnormal disturbance, the photovoltaic system still needs to keep grid-connected operation within a certain low voltage range, and reactive current is dynamically injected to help the voltage of the power grid to recover to be normal. In the prior art, under the working condition of low voltage ride through, a negative sequence current suppression mode is generally adopted. Firstly, the strategy maintains the grid-connected current balance degree by actively suppressing the negative sequence current, but simultaneously gives up the capability of injecting the negative sequence reactive current, and fails to fully utilize the capacity of the inverter to provide dynamic voltage support, secondly, the strategy adopts a simple priority distribution mechanism, and according to positive sequence reactive power priority and positive sequence active power order, the negative sequence current is suppressed to be in a distribution mode of 0, voltage asymmetry cannot be effectively suppressed, comprehensive dynamic support on the power grid voltage is not realized, and therefore, the conventional strategy lacks the capability of cooperatively guaranteeing safety and control performance, and optimal dynamic support is difficult to realize. Disclosure of Invention The embodiment of the invention provides a photovoltaic asymmetric low-voltage ride through control method, a device and control equipment, which are used for solving the problem that the optimal dynamic support is difficult to realize in a negative sequence current suppression mode adopted in the low-voltage ride through in the prior art. In a first aspect, an embodiment of the present invention provides a photovoltaic asymmetric low voltage ride through control method, including: Acquiring the voltage of the photovoltaic grid-connected point, and determining whether an asymmetric low-voltage fault occurs according to the voltage of the photovoltaic grid-connected point; when an asymmetric low-voltage fault is detected, determining a positive sequence reactive current reference value, a negative sequence reactive current reference value and a positive sequence active current reference value based on the distribution sequence of positive sequence reactive current, negative sequence reactive current and positive sequence active current with priority from large to small, and setting the negative sequence active current reference value to 0; And controlling the photovoltaic inverter according to the positive sequence reactive current reference value, the negative sequence reactive current reference value, the positive sequence active current reference value and the negative sequence active current reference value. In a second aspect, an embodiment of the present invention provides a photovoltaic asymmetric low voltage ride through control apparatus, including: The fault determining module is used for obtaining the voltage of the photovoltaic grid-connected point and determining whether an asymmetric low-voltage fault occurs according to the voltage of the photovoltaic grid-connected point; The reference value determining module is used for determining a positive sequence reactive current reference value, a negative sequence reactive current reference value and a positive sequence active current reference value based on the distribution sequence of positive sequence reactive current, negative sequence reactive current and positive sequence active current from the large to the small of priority when the occurrence of the asymmetric low-voltage fault is detected, and setting the negative sequence active current reference value to 0; And the low-pass control module is us