针对单相NPC型H桥级联逆变器并联时环流与电容电压不均的相互关系进行研究。通过环流等效电路推导了一个开关周期内环流与电容电压不均之间的数学关系，发现电容电压不均差异是环流的激励源之一；同时环流会改善一台并联逆变器的电容电压不均，恶化另一台逆变器的电容电压不均。为建立周期稳态条件下的环流-电容电压不均数学模型，提出采用“假设—建模—求解—检验—校正”的建模思路建立了基于阻滞的环流作用模型，有效避免了多因素建模的复杂性，同时提高了模型的准确性，仿真和试验结果表明，基于阻滞的环流作用模型拟合决定系数可达0.963 8和0.945 0，证明了环流模型的准确性。

The relationship between circulating current and capacitor voltage unbalance is studied when single-phase NPC H-bridge cascaded inverters are connected in parallel. Through the equivalent circuit of circulating current, the mathematical relationship between the circulating current and the unbalanced capacitor voltage in a switching cycle is derived, and it is found that the difference of the unbalanced capacitor voltage is one of the excitation sources of the circulating current. Meanwhile, the circulating current will improve the capacitor voltage balance of a parallel inverter and worsen the capacitor voltage balance of another inverter. In order to establish a mathematical model of circulating current-capacitor voltage unbalance under periodic steady-state conditions, a modelling idea of “hypothesis-modeling-solving-checking-correction” is proposed to establish a circulation effect model based on blockage, which effectively avoids multiple factors. The complexity of modelling also improves the accuracy of the model. Simulation and experimental results show that the coefficient of determination for the fitting of the block-based circulation model can reach 0.963 8 and 0.945 0, which proves the accuracy of the circulation model.

国家自然科学基金项目(51977218)