多电平变换器直流侧电压平衡控制电路

为解决二极管箝位型多电平变换器直流侧电容电压不平衡的问题，设计了一种带二级辅助电感的平衡控制电路，通过简单控制可以平衡多电平变换器直流侧所有电容的电压.在分析电路结构和控制原理的基础上，从能量转换的角度出发，给出了辅助电感参数选择的范围.以五电平变换器为研究对象，建立了Matlab/Simulink仿真模型，搭建了实验样机，对比分析了本文平衡电路与传统一级平衡控制电路的电容电压平衡特性.实验结果表明，当二级辅助电路工作时，所有直流侧电容电压在20 ms内达到平衡，电容电压的纹波小于3%. 

DC Bus Capacitor Voltage Balancing Circuits in Diode-Clamped Multilevel Converter

In order to solve the imbalance of DC bus capacitor voltages in the diode-clamped multilevel converter, a balancing circuit with two-layer auxiliary inductors was designed. With this circuit, the voltages of all the DC-side capacitors in the multilevel converter can be balanced by a simple control. On the basis of analysis of the circuit structure and control principle, the ranges of inductor parameters were analyzed from the viewpoint of energy conversion. Taking a five-level converter as an example, a Matlab/Simulink simulation model and an experimental prototype were built, and the balance characteristics of DC bus capacitor voltages were compared between the proposed two-layer auxiliary circuit and the traditional one-layer circuit. Experimental results verify that the proposed two-layer circuit could effectively balance all the DC bus capacitor voltages within 20 ms, and the capacitor voltage ripple was less than 3%.