中点箝位型光伏并网逆变器调制策略及效率对比

传统三电平中点箝位(Three-level neutral point clamped,3L-NPC)半桥逆变器在高压大功率条件下,由于开关器件损耗不均衡而使其容量受限,因此衍生了多种NPC型三电平半桥拓扑。为了优化选取NPC型拓扑及调制策略,对4种3L-NPC型拓扑(二极管NPC、有源式NPC、层叠式NPC及有源层叠式NPC)的调制策略及开关器件损耗分布进行了对比分析,并研制了一台5kW的NPC型统一实验平台,进行了效率测试。理论分析与实验结果表明:(1)根据零电平续流路径的配置不同,NPC型拓扑主要有4种调制策略;(2)选取合理的NPC型拓扑及调制策略,不仅可以均衡器件损耗,而且系统效率基本不变,为逆变器的扩容奠定了基础。

Modulation Strategies and Efficiency Comparison of NPC Grid-Tied PV Inverters

Under the condition of high input voltage and high power, the switch losses are unbalanced for three-level neutral point clamped(3L-NPC). It causes that the power of 3L-NPC is limited and many NPC topologies are derivated. In order to optimally select NPC topologies and modulation strategies, modulation strategies and switch loss distribution of four 3L-NPC topologies (Diode-clamped NPC, active NPC, stacked NPC and active-stacked NPC) are analyzed. A 5 kW unified prototype of NPC topologies is developed for efficiency tests. Theoretical analysis and experimental results indicate that there are mainly four modulation strategies for NPC topologies with different configuration of zero-level freewheeling path. Appropriate NPC topologies and modulation strategies can not only balance the switch losses, but also keep the same efficiency, which lays the foundation for improving the capacity of inverters.