降低直流母线电容的两级单相逆变器系统中DAB优化控制

In order to reduce the intermediate dc-bus capacitance while maintaining high efficiency in the two-stage single-phase inverter system, an optimized double line-frequency power control method of dual-active-bridge (DAB) is proposed under high dc-bus voltage ripple and reduced dc-bus capacitance. First, a general approximate analytical calculation method of the maximum allowable value of dc-bus voltage ripple is derived based on the analysis of positional relationship between dc-bus voltage and grid voltage. Next, both the double line-frequency power in DAB and the dc-bus voltage reference are optimized to reduce the rms current of DAB in a whole double line-frequency period. The optimal control combinations have been derived in analytical expressions. Then, considering the limitation of maximum voltage ripple and the optimization of DAB current, an optimized and coordinated control method is presented, so that the DAB rms current can be minimized while ensuring the stable operation of inverter system in both steady state and transient process. The dc-bus capacitance is also designed based on the tradeoff between capacitance reduction and DAB rms current reduction. Finally, the experimental results verify the feasibility and effectiveness of the proposed optimized control method. The high-efficiency operation of DAB can be achieved under reduced dc-bus capacitance.