Buck变流器级联系统直流母线电压补偿控制策略

Compensation Methodology for DC Bus Voltage of Cascaded System Formed by Buck Converters

在直流分布式电源系统的设计过程中,稳定性设计是最核心但最复杂的部分。随着系统规模日益庞大,若想将其作为整体进行稳定性设计几乎是不可能的。由于级联是分布式结构中最基本的连接形式,故深入研究、改善级联系统的稳定性对于确保整个系统的稳定运行非常重要。除优化设计变流器参数外,增加母线补偿装置(VBC)也是改善级联系统直流母线电压稳定性的一种有效途径,目前针对DC-DC级联系统母线补偿策略及补偿容量的研究已取得了一定的成果,其中一些研究还可以应用于大信号扰动的场合。但总体而言仍有进一步探索和发展的空间。本文从大信号的研究角度出发,基于混合势函数理论和回转器大信号模型,提出了一种直流母线电压补偿控制策略。该控制策略可根据级联系统中源、负载变流器的具体特性参数进行有针对性的补偿;同时,该策略由混合势函数理论的稳定性定理推导得出,从理论上保证了加入VBC后整个系统在大信号扰动下的稳定性。仿真和实验以峰值电流模式控制型Buck变流器级联系统为例对该补偿控制策略的有效性和补偿效果进行了验证。

For the design of DC distributed power system(DPS), stability analysis is the most important but complex issue. As the size of system gets increasingly larger, it is almost impossible to take the DC DPS as a whole for stability analysis. Since cascade connection is one of the most popular connection forms of distributed architecture, investigating and improving the stability of cascaded system is very important to ensure stable operation of DC DPS. In addition to optimizing the parameters of converters, the voltage bus conditioner(VBC) is also an effective way to improve the stability of DC bus voltage in DC-DC cascaded system. Many research results were proposed in the control method and compensation capacity of VBC. Some of them can be applied to large-signal disturbance occasions. Overall, there is still room for further investigation. From the point of view of large-signal stability, this paper proposes a novel compensation control method for VBC based on the mixed potential theory and gyrator large signal model. With the proposed control method, effective compensation can be achieved according to the parameters of source and load converters. Meanwhile, this control method is derived from the stability theorem of mixed potential theory, so the large-signal stability of cascaded system with VBC is guaranteed theoretically. A cascaded system formed by two peak current-mode controlled Buck converters is adopted for simulation and experiments. The effectiveness of the proposed control method are verified by the experimental results.