电力电子变压器的内部能量流动协调控制策略

Coordination Control Strategy for Energy Flow Inside Power Electronic Transformer

在电力电子变压器(PET)中,当级联H桥(CHB)和双有源桥(DAB)变换器的动态响应特性差异较大时,高、低压直流母线电压容易出现大幅波动。为解决此问题,文中提出了一种基于PET内部能量流动的协调控制策略。该策略由基于直流母线能量总和调节的CHB控制和基于直流母线能量协调的DAB模型预测控制这2个部分组成,能够将PET直流母线储能总量的波动定量地分配给高、低压直流母线共同承担,以使所有直流母线能量的相对偏差的平方和达到最小。该策略简化了PET闭环控制系统和控制参数设计的复杂性,能够提升直流电压的动态响应性能,并且通过补偿控制的方法有效抑制了DAB中的二次功率传输。理论分析表明,所提控制策略对于电路参数的不一致有较强的鲁棒性。仿真结果验证了所提控制方法的正确性和有效性。

In the power electronic transformer(PET), when the dynamic response of cascaded H-bridge(CHB) and dual active bridge(DAB) converters is quite different, the voltages of the high and low voltage DC buses will have large fluctuations. To solve this problem, this paper proposes a coordination control strategy for energy flow inside PET. The proposed strategy consists of the CHB control based on total DC bus energy adjustment and the model predictive control of DAB based on DC bus energy coordination. The fluctuations of total DC bus energy are quantitatively assigned to the DC bus on both high and low voltage sides.As a result, the quadratic sum of the relative deviation of DC bus energy on both sides can be minimized. The proposed strategy simplifies the closed-loop control system and the design method of control parameters while improves the dynamic response of DC voltage. Moreover, a compensation control method is presented to suppress second-order power transmission in DAB. The theoretical analysis shows that the proposed control strategy has strong robustness against the inconsistent circuit parameters. The correctness and effectiveness of the proposed method have been validated by simulations.