混合钳位型四电平和五电平逆变器拓扑结构和控制策略

The Topologies and Control of Hybrid-Clamped Four-Level and Five-Level Inverters

为了提高传统二极管钳位和飞跨电容多电平变换器的电平数并减少钳位器件的数量,同时避免五电平有源中点钳位拓扑中开关器件的直接串联,提出一种混合钳位四电平逆变器拓扑及其扩展五电平拓扑结构。为实现悬浮电容和母线中点电压的平衡控制,提出一种改进的载波移相PWM策略,通过微调PWM脉冲占空比实现悬浮电容和母线中间电容的平衡控制。在此基础上为实现上、下母线电容电压的平衡控制,提出一种基于最优零序电压注入的平衡控制策略。研制了一台实验样机并通过实验验证了该拓扑及控制策略的有效性和可行性。

A novel hybrid-clamped four-level inverter topology and its derived five-level topology are presented in this paper. The proposed topologies can improve the voltage levels, reduce the number of devices in the diode-clamped and flying capacitor multilevel converters, and avoid the series connection of switches in the five-level active-neutral-point-clamped converter. To achieve the voltage balancing of DC-link capacitors and flying capacitors, a modified PWM method is proposed. This PWM method can regulate the central DC-link capacitor and flying capacitor voltages by adjusting the duty cycles of PWM signals slightly. The upper and lower DC-link capacitor voltages are balanced by zero-sequence voltage injection. An experimental prototype is built up, and the experimental results verify this topology.