基于故障录波的海上风电经柔直并网系统阻抗分析方法

Impedance Analysis of Offshore Wind Farms With VSC-HVDC Systems Based on Fault Record Data

宽频振荡问题是制约大规模海上风电经柔性直流并网系统大功率运行的关键难题,已有方法难以分析复杂工况下风电场与柔直系统的阻抗特性与宽频振荡模式,使得工程上振荡源定位与阻抗优化存在困难。提出一种基于故障录波的系统阻抗分析方法,首先,针对谐振工况下各端口电压与电流波形数据,应用窗口傅里叶分析与相序变换提取对应序分量;其次,在谐振频率下构建谐波序网络方程,将谐波源与端口阻抗作为未知量;最后,基于谐波序网络方程与端口电气量构造目标函数,结合系统拓扑参数与稳态物理特性确定变量初值与不等式约束。将阻抗分析抽象为一个非线性方程组的最优解问题,应用粒子群算法求解上述优化问题,获得风电集群与柔直系统的谐波阻抗。参考某实际工程参数,设计了6风电集群经柔直送出系统验证所提方法的有效性与准确性。

The application of large-scale offshore wind farms with Voltage Source Converter based High Voltage Direct Current transmission(VSC-HVDC)systems is severally restricted by broadband oscillations.The complicated conditions of an actual system make it challenging to analyze the impedance characteristics or oscillation modes of wind power clusters and VSC-HVDC systems.In this paper,a method is proposed to analyze the impedances of offshore wind farms and VSC-HVDC systems based on the fault record data.Firstly,the positive sequence components of the voltages and currents under the resonant condition are extracted by the Window Fourier Transform and Phase-Sequence Transform.Secondly,the equivalent harmonic network equation is constructed at the resonant frequency.The harmonic sources and the port impedances are defined as the unknown variables.Thirdly,the objective function is constructed from the harmonic network equation and port electric variables.The initial values and inequality constraints are derived by topology parameters and physical relations in the steady-state.Thus,the analysis of the port impedances are abstracted as an optimization problem.The Particle Swarm Optimization(PSO)is utilized to solve the impedances of wind power clusters and VSC-HVDC systems.Based on the actual engineering parameters,a system with six wind power clusters and a VSC-HVDC is designed to verify the accuracy and effectiveness of the proposed method.