级联变换器改进功率平衡控制策略

Improved Power Balance Control Strategy for Cascaded Converters

针对传统功率平衡控制存在控制偏差而难以实现准确功率补偿的问题,以单相整流器与双有源桥(dual active bridge, DAB)变换器级联的功率变换系统为例,提出了一种改进功率平衡控制策略。首先,在整流级利用中间直流电压闭环调节功率平衡系数,利用功率平衡系数直接在功率平衡计算式中对变换器功率损耗以及采样偏差等控制误差进行补偿。其次,在DAB级将输出电压闭环的输出信号引入功率平衡系数的调节,具备了两条产生移相比的路径,在前馈路径故障缺失时仍可产生移相比。最后,实验结果表明,所提策略具备更高的功率平衡计算精度,并且对电流传感器故障导致的负载信息缺失或采样偏差大的故障工况也具备一定的容错性。

For traditional power balance control strategy, the power compensation is inaccurate due to the power loss and sampling deviation of converters. In this paper, an improved power balance control strategy is proposed for cascaded converters. The cascaded converter is comprised of a rectifier and a dual active bridge(DAB) converter. In the rectifier,the proposed strategy generates the power balance coefficient by intermediate voltage loop. Then, control errors caused by power loss and sampling deviation can be directly compensated in calculation equations by adjusting the power balance coefficient. Meanwhile, the proposed strategy introduces the output signal of output voltage loop to another PI controller to generate the power balance coefficient in DAB converter, which provides two phase-shift generation paths. Therefore,phase-shift generation can be guaranteed even if the compensated path fails. Finally, experimental results show that the proposed control strategy has higher power balance calculation accuracy, and has a fault tolerance for the fault condition of missing load information or large sampling deviation.