Abstract:
Aiming at the problem of DC bus voltage fluctuation caused by the instability of input and output power of distributed power supply in DC microgrid, and considering the characteristics of dual active bridge(DAB) energy storage converter with bidirectional energy flow, a dual closed-loop model predictive control strategy based on internal model principle is proposed in this paper. Based on the analysis of extended phase-shifting modulation principle and characteristics of the DAB converter, external voltage closed-loop model predictive control strategy and internal current closed-loop model predictive control strategy are emphatically studied. In order to solve the problem that the performance of model predictive control depends on the accuracy of circuit parameters, the sensitivity of model parameters is analyzed from two aspects: the influence of the mismatch of circuit main parameters on power transmission and DC-bus voltage stabilization. Finally, the steady-state error sensitivity area of DC-bus voltage is set. Outside the error sensitivity area, only double closed-loop model predictive control is used to ensure the dynamic response performance of the system. Within the error sensitivity area, double closed-loop model predictive control and PI compensation control is used to eliminate the steady-state error of the system. An experimental platform is built. The experimental results show that when the system is disturbed, the charging and discharging modes of the DAB energy storage converter can achieve smooth switching, and the hybrid control strategy can quickly stabilize the DC-bus voltage, achieve system power balance, and enhance the system anti-interference ability.