单一直流源的七电平混合级联逆变器

摘要

Traditional two-unit H-bridge hybrid inverters need two different voltage sources. This paper adopts capacitances instead of low voltage source, accordingly only high voltage source is needed to achieve 7-level output. With the multi-carrier stacked PWM modulation, the charge status of the capacitance can be controlled by choosing different combination levels. This paper analyses the conditions that control the capacitance voltage to the half value of the high voltage source. Consequently, two factors that determine whether the capacitance voltage is stable are achieved. By comparing the power loss, the optimum scheme is obtained to realize the purpose of holding the capacitance voltage to the half value of the high voltage source. Last, system simulation and experiments verify the proposed strategy.%针对传统的两单元H桥混合级联逆变器需要两个独立的直流源问题，采用电容来代替低压单元直流源，只需高压单元直流源就可实现级联逆变器七电平输出。在载波层叠 PWM 调制方式下，可以通过选择输出电平的不同组合方式来控制电容充放电，分析了电容电压稳定到高压单元直流源二分之一电压所需满足的条件，得到决定电容电压能否稳定到目标值的两个因素。通过损耗分析比较，得到电容电压稳定控制的最优方案。最后系统仿真与实验结果验证了理论分析的正确性。