基于微分平坦理论的直流微电网母线电压控制

Bus Voltage Control of DC Microgrid Based on Differential Flatness Theory

含恒功率负荷和阻性负荷的混合型负载接入直流微电网中,具有负阻抗特性的恒功率负荷会降低直流微电网系统稳定性。以并联型Buck变换器为研究对象,设计了基于扩张状态观测器的微分平坦控制系统。首先,将直流系统经坐标变换转化为双闭环结构的微分平坦系统,并对平坦系统中的微分项进行误差反馈控制。其次,通过扩张状态观测器对外环中的负载电流进行观测和补偿,从而抑制负载侧波动对系统的冲击。最后,在PSIM平台中搭建了仿真模型。仿真结果表明,基于扩张状态观测器的双闭环微分平坦控制策略应用于带混合型负载的并联型Buck变换器,在保证各相均流的同时显著地提高了系统的稳定性和抵抗内外扰动的能力。

When a hybrid load containing constant power loads and resistive loads is connected to a DC microgrid,the constant power loads with negative impedance characteristics will reduce the stability of the DC microgrid system.In this paper,a differential flatness control system based on an extended state observer(ESO)is designed for a parallel Buck converter.First,the DC system is transformed into a differential flatness system with a double closed-loop structure through coordinate transformation,and the differential terms in the flatness system are controlled by error feedback.Second,the load current in the external loop is observed and compensated by the ESO,so as to suppress the impact of load-side fluctuations on the system.Finally,a simulation model is built on the PSIM platform.Simulation results show that the ESO-based double closed-loop differential flatness control strategy which is applied to the parallel Buck converter with hybrid load significantly improves the stability of the system and its resistance to internal and external disturbances while ensuring current sharing in each phase.