CN-121983983-A - Transient synchronization stability judging method for multi-wind power grid-connected system in asymmetric short circuit scene

Abstract

The invention discloses a method for judging transient synchronous stability of a multi-wind power grid-connected system under an asymmetric short circuit scene, firstly, calculating positive and negative sequence components of the voltage of the machine end of the doubly-fed wind turbine under the asymmetric short circuit fault of the power grid, and then calculating positive and negative sequence q-axis components of the voltage of the machine end of each doubly-fed wind turbine. If positive and negative sequence components of output current of each unit in the system can be reasonably distributed, and the q-axis components of voltage at the motor end of all doubly-fed wind turbines are corrected to be zero, the system is stable under the asymmetric short circuit fault of the power grid, otherwise, the system is unstable in transient synchronization. The method comprehensively considers the coupling effect between positive and negative sequence networks of the system due to the control performance and response characteristics of different doubly-fed machines in the asymmetric short circuit scene of the power grid, and the criterion provided by the method can intuitively judge whether the transient state of the system is synchronous and stable.

Inventors

• GAO YONGQIANG
• ZHANG JIE
• LI JIALU
• MA JIAN
• TAO WENWEI
• LEI AOYU
• HUANG MEIYING
• ZHONG XINGLI
• HUANG FANGNENG
• JIN YUECHAO

Assignees

• 中国南方电网有限责任公司

Dates

Publication Date

20260505

Application Date

20260127

Claims (2)

1. 1. A method for judging transient state synchronous stability of a multi-wind power grid-connected system in an asymmetric short circuit scene is characterized by comprising the following specific steps: a1 Calculating positive and negative sequence components of the voltage at the machine end of the doubly-fed wind turbine generator under the asymmetric short circuit fault of the power grid: ; Wherein U+sj and U-sj are positive and negative sequence components of a voltage vector at a motor end of a j-th doubly-fed wind turbine generator, U+gf and U-gf are positive and negative sequence components of a voltage vector at a fault point, I+j and I-j are positive and negative sequence components of an output current vector of the j-th doubly-fed wind turbine generator, Z+Lj and Z-Lj are positive and negative sequence components of line impedance from the j-th doubly-fed wind turbine generator to the fault point, and Z+p and Z-p are positive and negative sequence components of impedance of a public line; a2 Calculating positive and negative sequence q-axis components of the voltages of the motor ends of the double-fed wind turbine generator, wherein the calculation expression is as follows: ; Wherein u+sqn+, U-sqn-are positive and negative sequence q-axis components of motor end voltage of the nth doubly-fed wind turbine generator, U+gf, U-gf are positive and negative sequence component amplitudes of fault point voltage, delta+n, delta-n are positive and negative sequence equivalent power angles of the nth doubly-fed wind turbine generator, I+n, I-n, theta+n, theta-n are positive and negative sequence component amplitudes and phase angles of output current of the nth doubly-fed wind turbine generator, Z+Ln, Z-Ln, phi+Ln, phi-Ln are positive and negative sequence component module values and impedance angles of line impedance from the nth doubly-fed wind turbine generator to the fault point, Z+p, phi-p are positive and negative sequence component module values and impedance angles of common line impedance; a3 Transient state synchronous stability criterion of the doubly-fed wind power multi-motor grid-connected system is as follows: ; If the transient state synchronization stability criterion of the doubly-fed wind power multi-machine grid-connected system is solved, the positive and negative sequence components of the output currents of all the units in the system can be reasonably distributed, and the q-axis components of the voltages at the motor ends of all the doubly-fed wind power units are corrected to be zero, so that the transient state stability under the asymmetric short circuit fault of the power grid is realized, otherwise, if the transient state synchronization stability criterion is not solved, the system has no stable balance point, and the transient state synchronization instability of the system occurs.
2. 2. The method for judging transient state synchronization stability of the multi-wind grid-connected system in the asymmetric short circuit scene according to claim 1 is characterized in that positive and negative equivalent power angles of each doubly-fed wind turbine generator are solved according to the following expression: Wherein U+sj and U-sj are respectively the positive and negative sequence component amplitude values of the voltage at the motor end of the j-th doubly-fed wind turbine generator.

Description

Transient synchronization stability judging method for multi-wind power grid-connected system in asymmetric short circuit scene Technical Field The invention relates to a method for judging transient state synchronous stability of a multi-wind power grid-connected system under an asymmetric short circuit scene, which judges the instability risk of the multi-doubly-fed wind power system through the constraint condition of existence of a positive and negative system balance point, realizes rapid and accurate evaluation of transient state stability of the doubly-fed wind power multi-motor parallel system under an asymmetric short circuit fault of a power grid, improves the reliability of the renewable energy source grid-connected system and belongs to the technical field of new energy power generation. Background In the global energy transformation large background, renewable energy power generation technologies represented by wind power generation and the like have been developed in great extent to solve the problems of energy shortage, climate change and the like in order to realize economic sustainable development. However, as the large-scale wind turbine generator is connected to the power system, the control coupling effect among different equipment is aggravated, and the interaction characteristic among the source networks is complex, which can have multiple effects on the stability of the system, especially the transient synchronization stability during the asymmetric short-circuit fault of the power network. Therefore, how to evaluate the transient state synchronous stability and the instability risk of the double-fed wind power multi-motor parallel system under the asymmetric short circuit fault of the power grid is a key problem of wind power development at present. At present, related researches developed by domestic and foreign scholars mainly aim at judging transient synchronous stability of a multi-wind power system, such as the following published documents: [1] FU X K, HUANG M, PAN S Z, et al. Cascading synchronization instability in multi-VSC grid-connected system[J]. IEEE Transactions on Power Electronics, 2022, 37(7): 7572-7576. [2] SUN H, WANG S, XU S, et al. Synchronization stability analysis of PLL-based grid-connected VSC system by voltage space vectors[J]. CSEE Journal of Power and Energy Systems, 2024, 10(5): 2055-2064. The literature [1] establishes a nonlinear model containing interaction items of a multi-machine parallel system, analyzes a transient instability mechanism of the system by utilizing an equal-area criterion, and verifies that multi-machine dynamic interaction can cause the problem that a head-swing stabilizing unit is out of step in a subsequent process through simulation and experiment. The document [2] discloses an action mechanism of the phase-locked loop dynamic to the synchronous stability of the multi-machine grid-connected system, and analyzes the influence of grid parameters, controller parameters and the like on the transient synchronous stability of the system. However, the research is mainly aimed at dynamic interaction mechanism between the new energy power generation equipment and the power grid and transient state synchronization instability risk assessment thereof when the power grid is in three-phase short-circuit fault. However, when an asymmetric short-circuit fault occurs in the power grid, the cross coupling characteristic between the positive and negative sequence networks brings a new form of transient state synchronization stability, the control mode of the multi-new energy station can aggravate the coupling effect between the positive and negative sequence networks, the applicability of the transient state synchronization stability criterion in the symmetric short-circuit fault scene of the power grid is limited, and the method is difficult to popularize and apply further. Disclosure of Invention Aiming at the defects existing in the prior art, the invention aims to provide a method for judging the transient state synchronous stability of a multi-wind power grid-connected system under an asymmetric short circuit scene, which comprehensively considers the situation of asymmetric short circuit of a power grid, the method can provide a criterion for judging whether the transient state of the system is synchronous or not intuitively due to the coupling effect caused by the control performance and response characteristics of different doubly-fed machines. The technical scheme of the invention is realized as follows: A method for judging transient state synchronous stability of a multi-wind power grid-connected system under an asymmetric short circuit scene comprises the following specific steps: a1 Calculating positive and negative sequence components of the voltage at the machine end of the doubly-fed wind turbine generator under the asymmetric short circuit fault of the power grid: ; Wherein U+sj and U-sj are positive and negative sequence componen