基于超越方程极点分布间接判定的分布式电站谐波不稳定分析方法

Harmonic instability analysis method of distributed power plants based on indirect determination of pole distribution of transcendental equation

线路分布参数模型的引入导致系统极点方程为含复数双曲函数的超越方程,极点分布难以确定,且忽略dq轴耦合可能导致系统稳定性误判。建立并验证了同时计及dq轴耦合及线路分布参数的分布式电站阻抗模型。提出基于广义奈奎斯特稳定判据的极点分布间接判定方法,利用回率矩阵特性间接判定超越方程极点分布,解决了超越方程极点分布求解难题。给出稳定判据应用过程中回率矩阵构造和稳定条件判定的详细过程。分析结果表明忽略线路分布参数或dq轴耦合均可能造成稳定性误判,且忽略前者还将导致遗漏高频谐波放大点。所提方法能准确分析该系统稳定性,并可准确评估系统潜在谐波放大点。最后,仿真验证了所提方法的准确性和有效性。

The introduction of the line distribution parameter model leads to the system pole equation being a transcendental equation with complex hyperbolic function,which makes it hard to determine the pole distributions.Ignoring the dq axis coupling may cause misjudgment of the system stability.The impedance model of the distributed generation power plants by considering both dq axis coupling and line distribution parameters is established and verified.An indirect determination method for pole distribution based on the general Nyquist stability criterion is proposed,which determines the pole distribution of the transcendental equation using the characteristics of the return-ratio matrix.A detailed process of constructing the returnratio matrix and judging the stability condition in the application of the stability criterion is provided.The analysis results show that ignoring the line distributed parameters or dq axis coupling may lead to misjudgment of stability,and ignoring the former may also lead to omitting high-frequency harmonic amplification points.The proposed method can accurately evaluate the system stability and analyze the frequency of the potential harmonic amplification points.Finally,the performance and effectiveness of the proposed method are verified.