基于可变系数的双馈风机虚拟惯量与超速控制协调的风光柴微电网频率调节技术

Frequency Regulation of the Wind/Photovoltaic/Diesel Microgrid Based on DFIG Cooperative Strategy with Variable Coefficients BetweenVirtual Inertia and Over-speed Control

为了提高风光柴微电网孤岛运行时的频率稳定性,将变速恒频双馈感应风力发电机(DFIG)和柴油机作为调频电源,通过DFIG的虚拟惯量、转速和桨距角的协调控制与柴油机的一次调频相配合,共同抑制负荷波动和风速变化引起的微电网频率变化。低于额定风速时,DFIG采用虚拟惯量控制和超速控制;高于额定风速时,采用虚拟惯量控制和自动桨距角控制。以此弥补虚拟惯量控制作用时转速恢复过程的功率跌落问题,并为微网提供持久的功率支撑。为保证此调频策略在时变风速中的有效性,通过不同风速下的参数分析制定了DFIG的虚拟惯量控制系数曲线与功频静特性系数曲线,实现了可变系数控制。并在DIgSILENT PowerFactory软件平台上搭建了包含柴油机、DFIG、光伏电池的微电网模型,验证了此策略的有效性。

To improve the frequency stability of the isolated islanding wind/photovoltaic/diesel microgrid,in this paper,the doubly fed induction generator(DFIG) and the diesel turbine are both utilized as the frequency regulation sources.Via coordinating virtual inertia control,rotor speed control,and automatic pitch control strategy,DFIG can cooperate with diesel turbine to restrain the frequency fluctuation caused by the change of the wind speed and the load.When operating at the below-rated wind speed,DFIG adoptsbothvirtual inertia control and over-speed control strategy.On the other hand,when at above-rated wind speed,DFIG utilizes virtual inertia control and automatic pitch control.Therefore,the output power drop during the recovery period of the rotor speed with virtual inertia control can be avoided.Moreover,this combined control strategy can provide permanent power support for the microgrid.In order to guarantee the efficiency of this strategy in a timevarying wind speed,an inertia coefficient curve and a droop control gain curve areplotted by analyzing parameter settings under different wind speeds,and as a result,the variable coefficient control is realized.This paper established the microgrid control model includes the diesel generator,photovoltaic power generator and DFIG using the software DIgSILENT PowerFactory.The simulation results show that this control strategy is valid.