Three-port isolated dc–dc converter, as an active exploration and trial of photovoltaic access to dc distribution system, has the advantages of superior control flexibility and high reliability. Due to the changes in the phase-shift (PS) angle, the conventional PS control method cause transient dc bias in inductor current and magnetisation current, further increasing the current stress of switches and threatening the safe operation of the converter. Based on superposition theorem analysis, this study discusses the formation mechanism of transient dc bias, constructs a mathematical model of drive signals, and proposes two typical combination strategies of drive signals. The proposed method can simultaneously suppress the dc bias of port inductor and transformer magnetisation inductor in one switching cycle by changing the duty ratio of square wave voltage or adding the zero-voltage phase related to the PS angle. By simulating the PS angle change and output power fluctuation, the dynamic characteristics under conventional PS control and the proposed strategy are compared and discussed. The simulation and experimental waveforms show that the proposed method is not only suitable for the multi-step step change of PS angle, but also sufficient for the continuous evolution of the PS angle.

中文翻译：

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三端口隔离式DC-DC转换器的瞬态DC偏置抑制

三端口隔离式dc-dc转换器作为光伏接入直流配电系统的积极探索和尝试，具有优越的控制灵活性和高可靠性的优势。由于相移（PS）角的变化，传统的PS控制方法会在电感器电流和磁化电流中造成瞬态dc偏置，从而进一步增加开关的电流应力并威胁转换器的安全运行。在叠加定理分析的基础上，探讨了瞬态直流偏置的形成机理，构建了驱动信号的数学模型，并提出了两种典型的驱动信号组合策略。通过改变方波电压的占空比或增加与PS角相关的零电压相位，该方法可以在一个开关周期内同时抑制端口电感和变压器磁化电感的直流偏置。通过模拟PS角度变化和输出功率波动，比较和讨论了传统PS控制下的动态特性和所提出的策略。仿真和实验波形表明，该方法不仅适用于PS角的多步阶跃变化，而且对于PS角的连续演化是足够的。比较和讨论了常规PS控制下的动态特性和所提出的策略。仿真和实验波形表明，该方法不仅适用于PS角的多步阶跃变化，而且对于PS角的连续演化是足够的。比较和讨论了常规PS控制下的动态特性和所提出的策略。仿真和实验波形表明，该方法不仅适用于PS角的多步阶跃变化，而且对于PS角的连续演化是足够的。