负载电流前馈闭环控制的快速动态响应双有源桥式变换器的输出阻抗分析

提出了一种基于前馈控制的双有源桥DAB(dual active bridge)变换器的控制策略,并通过小信号模型分析了DAB变换器的输出阻抗及其对电路动态特性的影响。DAB变换器的输出阻抗不仅取决于输出电容,还与控制回路的增益有关。由于传输延迟和零阶保持器的存在,控制回路的交叉频率和增益不能选得过高。如果输出电容非常低,变换器无法实现快速动态响应。为了提高动态性能,根据期望的输出电流,提出了一种新的前馈控制策略。前馈路径只与负载电流有关,而对于输出电压是独立的,且前馈控制在实时计算中易于实现。这种具有前馈控制策略的闭环增益与单电压闭环控制的比较结果表明,采用前馈控制的控制回路具有较好的动态性能。最后,搭建了1 kW的实验样机,验证了所提控制策略的有效性。

Output Impedance Analysis of Dual Active Bridge Converter with Load Current Feedforward Closed-loop Control for Fast Dynamic Response

This paper presents a control strategy of dual active bridge (DAB) converter with feedforward control. By analyzing the small-signal modeling, the output impedance of the DAB converter is analyzed. The output impedance has an impact on dynamic performance. It is associated not only with the output capacitor but also with the gain of the control loop. Because of the transport delay and zero-order holder, the crossover frequency and the gain of the control loop can not be selected too much high. If the output capacitance is very low, the converter can not achieve fast dynamic response. To improve the dynamic performance, a new feedforward control strategy is proposed according to the desired output current. The feedforward path is only associated with the load current, and it is inde-pendent of the output voltage. Furthermore, the feedforward control is easy to be implemented in the real-time calculation. The loop gain of the control strategy with the feedforward is compared with the single voltage loop control, which demonstrates that the control loop with the proposed feedforward control has better dynamic performance. Finally, a 1kW experimental prototype has been built to verify the effectiveness of the proposed control strategy.