电网电压不平衡下采用串联网侧变换器的双馈感应风电系统改进控制

为进一步提高电网电压不平衡下采用串联网侧变换器的双馈感应发电机(doubly fed induction generator,DFIG)风电系统的运行性能,研究了适用于该系统的改进运行控制策略。提出电网电压不平衡下采用串联网侧变换器的DFIG系统的3种可选运行方案,以此为基础提出串联网侧变换器与并联网侧变换器的协调控制策略,并建立了在双同步dq旋转坐标轴系下两者的控制模型。所提系统协调控制方案无需改变电网电压不平衡下转子侧变换器的控制策略,在实现发电机输出功率无二倍频波动、电磁转矩无二倍频波动以及定、转子三相电流平衡的同时,可实现电网电压不平衡下整个系统或总输出有功功率无二倍频波动(同时可实现直流链电压无二倍频波动)或总输出无功功率无二倍频波动或整个系统无负序电流注入电网的不同运行功能,进一步增强了不平衡电压下DFIG风电系统的运行能力。对一台采用串联网侧变换器的DFIG风电模拟系统在不平衡电压条件下的运行进行了相关实验,实验结果验证了该文所提改进控制策略的可行性。

Improved Control of a Doubly Fed Induction Generator Wind Turbines With a Series Grid-side Converter Under Unbalanced Grid Voltage Conditions

In order to improve the operational performance of the doubly fed induction generator(DFIG) wind turbine with a series grid-side converter(SGSC) under unbalanced grid voltage conditions,the improved control strategies for the system were investigated in this paper.According to the different operation commands,three selective control schemes for the DFIG system with SGSC were proposed.Furthermore,the coordinated control strategies for the SGSC and parallel grid-side converter(GSC) were proposed,and the control models for the two converters were established under dual synchronous dq rotating frames respectively.With the proposed control scheme,the control strategy of the rotor-side converter(RSC) would not be changed during network unbalance conditions.While achieving the goal that eliminating the double supply frequency oscillations in generator’s power output and electromagnetic torque and balancing the stator and rotor currents,the pulsations of the total active power output(also the pulsations of the DC-link voltage) or the pulsations of the total reactive power output or the total negative sequence currents of the system could be restrained.The operational performance of the DFIG system can be further improved with the proposed scheme.The experimental results of a DFIG test rig with SGSC under unbalanced voltage conditions are used to verify the proposed improved control strategies.