微电网并网逆变器的改进下垂控制策略研究

采用下垂法下垂系数的确定是个很大的难题。下垂系数很小，动态响应速度变慢；增大下垂系数可以改善动态响应，但是频率和电压幅值会大幅度偏离设定值，造成系统的不稳定，这种矛盾很难调和。本文提出了分段滞环的下垂控制策略，用三条斜率较大的下垂曲线代替一条斜率较小下垂曲线，使用此方法既可以解决动态响应的问题又可以增加功率输出范围而保持输出幅频不会变化太大。最后让此控制策略与传统的下垂控制策略相比较，比较结果证明了该策略的可行性和优越性。

Research of improved droop control strategy for grid connected inverters in microgrids

It is a big problem to determine the droop coefficient when using the droop method.The droop coefficient is small and dynamic response speed is slow;increasing the droop coefficient can improve the dynamic response,but the amplitude of the frequency and the voltage can deviate significantly from the setting value,resulting in the instability of the system,so it is difficult to reconcile the contradictions.This paper presents the droop control strategy of piecewise hysteresis,instead of a sag curve with three sag curve,using this method can not only solve the problem of dynamic response but also can increase the power output range and keep the output of the voltage amplitude and frequency not changing too much.Finally let the subsection hysteresis droop control strategy compared with the traditional droop control strategy,the comparison results prove the feasibility and superiority of this strategy.