基于移相控制的三相交错并联LLC谐振变换器均流控制策略

Current sharing control strategy of three-phase interleaved paralleled LLC resonant converter based on phase-shifting control

为了适应大功率应用场合,多相LLC谐振变换器的交错并联结构得到了广泛关注和研究。由于并联各相LLC谐振变换器谐振参数(励磁电感L_(m)、谐振电容C_(r)和谐振电感L_(r))的差异,各相的电压增益互不相同,进而导致各相电流不平衡。为了解决这一问题,基于原副边星形连接的三相交错并联LLC谐振变换器电路拓扑,详细分析了各谐振参数对并联LLC谐振回路均流的影响程度;提出了一种基于移相控制的均流控制策略,运用余弦定理求出谐振电流相位的关系,转化为开关管的相位驱动信号,在不增加任何附加电路的情况下,实现并联各相LLC谐振回路的自动均流,提高了系统整体运行的可靠性。最后通过仿真和实验分析了所提控制方法的有效性和准确性。

In order to adapt to high-power application situations,the interleaved parallelled structure of multiphase LLC resonant converter has been widely concerned and studied.However,due to the difference of resonant parameters(excitation inductance L_(m),resonant capacitor C_(r),resonant inductance L_(r))of each phase LLC resonant converters in parallel,the voltage gain of each phase is different,resulting in the unbalance of current of each phase.In order to solve this problem,based on the circuit topology of three-phase interleaved paralleled LLC resonant converter with star connection of primary and secondary sides,the influence of resonance parameters on current sharing of paralleled LLC resonant circuit is analyzed in detail;a current sharing control strategy based on phase-shifting control is proposed.The relationship of resonant current phase angle is obtained by using cosine theorem,which is transformed into the driving signal phase angle of the switch tube.Without adding any additional circuit,the LLC resonant circuit of each phase in parallel is balanced,which improves the overall operation reliability of the system.Finally,the effectiveness and accuracy of the proposed control method are analyzed by simulative and experimental results.