双有源桥直流储能系统软开关优化控制

Soft-switching Optimal Control for Dual Active Bridge DC Energy Storage System

传统直流储能系统中电容器荷电状态SOC(state of charge)的变化会导致直流变换器两端电压不匹配,使得功率器件无法处在软开关状态,从而增加了开关损耗。通过分析软开关控制与电容器SOC之间的关系,提出一种双有源桥DAB(dual active bridge)直流储能系统软开关优化控制,实现储能系统在充放电过程中,各功率器件始终处在软开关状态,维持直流母线电压稳定,降低功率损耗。该方法将储能电容SOC变化引入DAB移相控制,确定SOC与移相角的定量关系,使直流变换器功率器件满足软开关条件。根据直流母线电压及储能系统充放电特性,设计恒压、恒流充电和恒压及恒功率放电控制方法。仿真与实验验证了所设计软开关优化控制方法的有效性。

The changes in the state-of-charge(SOC)of a capacitor in the traditional DC energy storage system may lead to voltage mismatch of the DC converter,which makes the power device unable to be kept in a soft-switching state and further increases switching losses.By analyzing the relation between the soft-switching control and capacitor SOC,a soft-switching optimal control method for a dual active bridge(DAB)DC energy storage system is proposed in this paper,by which the soft-switching states of power devices can be always kept in the charging and discharging process of the DC energy storage system,thereby maintaining the voltage stability of DC bus and reducing power losses.Moreover,the SOC changes in the energy storage capacitor are introduced into the phase shifting control of DAB to determine the relation between SOC and phase shifting angles,which makes the DC converter power devices satisfy the soft-switching conditions.According to the DC bus voltage and the charging and discharging characteristics of the energy storage system,a control method of constant voltage and constant current charging and constant voltage and constant power discharging is designed.Simulation and experimental results verified the effectiveness of the proposed soft-switching optimal control method.