基于模型预测控制的孤岛微电网频率二次控制策略

Secondary control strategy of microgrid frequency of isolated island based on model predictive control

在多逆变器并联的孤岛微电网系统中,由于线路阻抗以及负荷分布不均等因素的影响,采用传统的下垂控制会导致稳态下系统频率偏离额定值.为了消除频率偏差,通常采用分层控制方法,但二次层中采用PI控制无法解决不确定通信延时对系统稳定性的影响.为此,在分层控制的基础上,提出了一种基于模型预测控制的孤岛微电网频率二次控制策略,在二次控制系统设计中采用模型预测控制方法,以此解决不确定延时对系统频率的影响;并采用小信号模型和参与因子分析系统的稳定性.最后,通过Matlab/Simulink仿真验证采用所提控制方法的分层控制系统对不确定延时具有较强的鲁棒性,验证了所提控制方法的有效性和可行性.

Utilization of traditional droop control in a multi-inverter parallel system of microgrid on isolated island will lead a steady-state system frequency to deviate from its nominal value due to the effect of ununiform distribution of line impedance and load.In order to eliminate this frequency deviation,a hierarchical control method may be adopted generally;however,the PI control in secondary layer can not deal with the effect of uncertain communication delay on system stability.Therefore,based on the hierarchical control,a secondary control strategy for frequency restoration of microgrids on isolated island was proposed on the basis of model predictive control.The model predictive control method was adopted in the design of the secondary control system,so that the impact of uncertain communication delay on the system frequency was well dealt with and the system stability was analyzed based on small signal model and participation factor.Finally,by means of simulation with Matlab/Simulink,it was verified that the hierarchical control system adopting the proposed control method would have stronger robustness to the uncertain time delay and that the proposed control method would be effective and feasible.