基于功率开关-二极管基本单元多电平逆变器及其功率均衡调制策略研究

Multilevel inverter based on power switch-diode basic unit and its power balance modulation strategy

针对级联H桥型多电平逆变器开关器件随逆变器输出电平数增加显著增多的问题,提出一种以功率开关器件-二极管为基本单元的新型多电平逆变器。该逆变器仅使用较少开关器件即可实现高质量电平输出,且该拓扑开关损耗低、效率高,不仅易于扩展还能有效避免级联单元间电流倒灌等问题。针对传统正负反向层叠载波调制策略调制下逆变器存在级联单元间输出功率不均衡的问题,在传统调制策略基础上推导分析区域功率,提出了一种基于部分载波循环的功率均衡调制策略,并验证了载波循环规律的普适性,所提调制策略能在保持输出电压波形质量不变的情况下,载波仅变换2(n-1)次即可在nT_(o)/2内实现级联单元输出功率均衡以及开关损耗平均分配,并提高电源利用率。最后搭建两单元七电平逆变器实验平台对所提调制策略进行了实验验证。

To solve the problem that the switching devices of cascaded H-bridge multilevel inverter increase significantly with the increase of inverter output levels,a new type of multilevel inverter based on power switching device-diode was proposed.The proposed inverter can achieve high quality level output with only a few switching devices,and the topology has low switching loss and high efficiency,which is not only easy to expand,but also effectively avoids problems such as current backflow between cascaded units.Under the pulse opposite disposition PWM,the inverter has the problem of unbalanced output power between units.Based on this modulation strategy and through the derivation and analysis of regional power,a power balance modulation strategy based on partial carrier cycle was proposed,and the universality of the carrier cycle law was verified.The proposed modulation strategy can achieve the output power balance of cascaded units and the average distribution of switching losses within nT_(o)/2 after the carrier is transformed 2(n-1)times while keeping the output voltage waveform quality unchanged,and the power utilization is improved.Finally,the proposed modulation strategy is experimentally verified on the experimental platform of the two-unit seven-level inverter.