孤岛微电网电压及频率双重优化控制策略研究

RESEARCH OF VOLTAGE AND FREQUENCY DUAL OPTIMIZATION CONTROL STRATEGY FOR ISLANDED MICROGRID

采用下垂控制的微电网系统在孤岛运行时因负荷波动与发电源功率容量限制会导致系统在PCC点产生实际电压与额定电压偏差及实际频率与50 Hz之间的偏差,并且下垂系数的取值会影响系统稳定裕度。为了保证微电网系统在具有良好稳定裕度的前提下减小微电网系统PCC点的电压偏差及频率偏差,提出一种以下垂系数为一次被控量、以下垂控制环电压及频率给定为二次被控量、以下垂控制环稳定裕度为约束条件的双重优化控制策略。通过采用双重优化控制策略,可以保证系统在具有良好稳定裕度的前提下使PCC点电压偏差及频率偏差为零。该优化控制方案分别在系统带额定负载及重载情况下进行仿真和实验,验证该双重优化控制方案的可行性和正确性。

The microgrid system using droop control will lead to deviation between actual voltage and rated voltage and deviation between actual frequency and 50 Hz at the PCC point due to fluctuation of the load and limitation of supplying power in island operation. Also, droop coefficient will affect stability marg!n of system. In order to ensure reducing frequency deviation and voltage deviation at the PCC point of the microgrid system with a good stability margin, a doubly optimized control strategy was proposed, which considered the droop coefficient as the first controlled variable, the voltage and frequency of droop control hoop as the second controlled variable, the droop control stability margin as the restriction conditions. The proposed method can be used to ensure the frequency deviation and the voltage deviation at the PCC point of the microgrid system with a good stability margin to be zero. The simulations and experiments of the optimized control strategy were performed in the rated load and overload conditions, respectively to verify the feasibility and correctness of the doubly optimized control strategy.