海上风电场与柔性直流输电系统的新型协调控制策略

提出了一种适用于采用双馈机型的海上风电场与柔直输电系统的新型协调控制策略。接入风电场的送端换流站采用基于锁相环的定功率控制,根据风电场的有功参考值控制其有功功率输入,并且在送端换流站的有功功率控制外环中加入有功功率与直流电压平方的下垂特性来加强直流电压暂态稳定性;双馈风电机组采用同步控制,调节海上风电场交流电网的电压幅值和角度。相对于经典协调控制策略,该控制策略可以加强柔直输电系统的直流电压稳定性,对通信延时不敏感,通信成本较低。该控制策略还实现了送端交流电网故障下系统的故障穿越。文中以风电场接入基于多电平的两端柔直输电系统作为仿真研究对象,通过仿真分析验证了该协调控制策略的有效性和优越性。

Coordinated Control Strategy of Offshore Wind Farms and VSC-based HVDC Transmission Systems

A novel coordinated control strategy for wind farms based on offshore doubly-fed induction generator(DFIG)type integrated into voltage source converter based(VSC-based)high voltage direct current(HVDC)transmission system is proposed. The constant power control strategy based on phase locking loop(PLL)is applied to the sending converter station, which regulates the active power according to the reference from the wind farm. Meanwhile, the droop of the active power and the squared DC voltage is added to active power control loop of the sending converter station to enhance the transient stability of the DC voltage. The synchronized control is applied to the offshore DFIG wind turbines, which can control the amplitude and angle for the offshore AC grid voltage. Compared with the classical fault ride-through(FRT)coordinated control strategy, this novel control strategy can enhance the DC voltage transient stability and is insensitive to communication delay. Meanwhile, the novel control strategy can also achieve low-voltage ride-through in the case of a 3-phase short-circuit at the sending converter station. This paper uses the example of an offshore wind farm integrated into a two-terminal multilevel modular converter(MMC)VSC-based HVDC transmission system as simulation cases to validate the effectiveness and advantages of the novel FRT coordinated control strategy. This work is supported by National Key Research and Development Program of China(No. 2016YFB0900100).