微网中多逆变器并联系统下垂控制策略研究

Research of droop control strategy for parallel operation of multi-inverters in microgrid

在低压微网多逆变器并联系统中,由于输出线路阻抗比相对较高,若线路阻抗与逆变器等效输出阻抗之和成阻性,则无法使用传统的应用于高压系统中的下垂控制方法,针对这一问题,分析研究了下垂控制方法以及逆变器输出阻抗对系统性能的影响,提出在电感电流处引入虚拟阻抗的方法,使其等效输出阻抗为感性,设计出了适合低压微电网多逆变器并联系统的电压电流双环下垂控制器.最后建立了微网的仿真模型,进行了微网多逆变器并联系统的负荷波动及分布式电源的离并网情况下的微网运行特性仿真分析,结果证明了上述控制方法及控制器的可行性和有效性.

For parallel operation of multi-inverters in microgrid, the line impedance ratio between the inverters is relatively high. If the result of the line impedance and the output impedance of inverters is resistive, it is not appropriate to use droop control strategy used in HV power systems. To solve this problem, droop control strategy and the influence of output impedance of the inverters are analyzed, and a droop control strategy based on voltage and current double-loop for distributed generator of microgrid is proposed by introduction of virtual impedance. Finally the simulation model of microgrid with distributed generators is established, and the operation variation of the microgrid are analyzed, respectively. It is found that when it runs with load changes in islanding mode and runs with the generated power source varied suddenly. The simulation results demonstrate that the control strategy is correct and effective.