风电场多端直流系统应用研究

Research on Multi-terminal DC System for Wind Farms

本文介绍了用于风电场组网的多端直流系统,研究了直流线路参数与系统稳定性的关系,并提出了一种网侧变流器的非线性PI控制方法。风电场多端直流系统由多个电压源变流器(VSC)并联组成,发电侧VSC控制风机向直流系统输送能量,再经网侧变流器并网。在不同控制模式下,需要在保证系统稳定性的前提下进行直流线路的参数匹配。本文根据小信号模型与大信号模型分别推导了稳定判据,并进行了仿真对比。本文利用以误差的非线性函数与传统PI环节构成的级联式控制器,实现了网侧变流器的高性能控制。仿真与实验表明该方法既提高了系统响应的快速性,又增强了抗扰能力。

This paper discusses the structure of the multi-terminal DC （MTDC） system consisting of several voltage source converters （VSC） in wind farms and researches the stability of the DC system and the control strategy of grid-interfacing inverter. The MTDC system aggregates the power of many wind-generator units into a dc grid. Then a grid-interfacing converter inverts the collected power into a three-phase ac electric utility grid. The stability criteria based on small signal model and large signal model is obtained and verified by simulations. The cascaded nonlinear controller for grid side converter, consisting of the nonlinear function of the error and the traditional PI regulator, improves the dynamic response as well as the robustness of the system.