下垂控制逆变器中并网功率控制策略

下垂控制策略广泛应用于交流微电网中,可以实现并网模式和孤岛模式的无缝切换以及不同逆变器之间的功率均流。然而,在目前的研究工作中,并网模式下的工作性能却很少被考虑到。实际上,并网模式下的功率控制会受到电网频率以及电网电压幅值波动的影响,并且传统下垂控制中无功功率控制本身就存在静态误差。因此提出了电网频率和电网电压幅值前馈控制来抑制电网波动对功率控制的影响,另外基于此提出公共耦合点电压幅值控制实现无功功率的无静差跟踪。基于提出的控制策略实现了下垂控制逆变器并网功率的精确稳定控制。

Power Flow Control Strategy for Droop-Controlled Inverters

Droop control strategy is widely applied in AC microgrid to realize the seamless transition between grid-connected (GC) mode and islanding (IS) mode, and to achieve average power sharing among different inverters. However, there is a lack of analysis about the operation of droop control strategy in GC mode. Actually, the power flow control in GC mode may be influenced by the fluctuation of grid frequency and voltage magnitude. Moreover, tracking error also exists in the reactive power control loop. The feedforward of grid frequency and voltage magnitude is proposed to suppress the grid fluctuation impacts in this paper. The voltage magnitude control of PCC voltage is added to realize the precise reactive power control. With the implementation of the proposed control scheme, accurate power flow control is guaranteed for droop-controlled inverters in GC mode.