基于MPPT切换的VSC-HVDC低电压穿越控制策略

Low Voltage Ride-through Strategy for VSC-HVDC by Switching MPPT Lines

在分析电压源型高压直流输电(VSC-HVDC)风电并网系统稳态控制策略的基础上,针对交流电网发生电压跌落的情况,提出了一种基于双馈感应发电机(DFIG)最大功率跟踪(MPPT)曲线切换的VSC-HVDC低电压穿越控制策略。该策略将VSC-HVDC直流侧电容存储的有功不平衡信息反映为风电场的频率变化指令,同时切换发电机MPPT曲线,桨距角控制辅助调节,使风机有功输出响应频率变化,增大转子转速,存储动能。基于Matlab/Simulink搭建了VSC-HVDC风电并网仿真系统,验证了其有效性。在不同风速下发生电网电压跌落时,该策略均能迅速响应,限制VSC-HVDC直流过电压幅值,支持系统低电压穿越。

Based on the analysis of the steady-state control strategy for the voltage source converter-high voltage direct current （VSC-HVDC）in wind power integrated system, a low voltage ride-through strategy was proposed by switching the maximum power point tracking （MPPT） lines of doubly-fed induction generators （DFIGs） when the DC grid voltage dip occured. The proposed method adjusted the wind farm frequency change orders according to the unbalanced active power information of the VSC-HVDC DC capacitor. At the same time, the DFIG convertors switched the MPPT lines and used the pitch control as an aid. And then,the DFIGs output power was changed and increased the rotor speed to temporarily store the kinetic energy. The VSC-HVDC based wind power integrated system was modeled by the Matlab/Simulink, and the effectiveness of the strategy was proved. The simulation result shows that the strategy can response to prevent DC over-voltage quickly when the grid voltage dip occurs under different wind speed, which will support the low voltage ride-through of the system.