双低压单元混合级联逆变器的改进载波层叠调制策略

An improved carrier-stack modulation strategy for hybrid cascaded inverter with dual low-voltage cells

传统的载波层叠调制方法应用于双低压单元混合级联逆变器时,存在低压单元之间功率不平衡问题。为此,文中提出了一种改进的载波层叠调制策略。该策略首先通过传统的载波层叠调制方法产生开关管的初始驱动信号,然后再对开关管的驱动信号进行功率平衡优化后得到开关管的实际驱动信号。仿真结果表明:该策略能够在逆变器高压单元工作在基波频率的情况下,解决逆变器电流倒灌问题和实现两个低压单元的功率平衡;逆变器输出电压的谐波主要为以载波比mf为中心的边带谐波,且随着调制度ma的增大,输出电压THD(Total Harmonic Distortion)逐渐减小。

When the conventional carrier-stack modulation method is applied to a dual low-voltage cell hybrid cascade inverter, there is a power imbalance problem between the low voltage cells. Therefore, this paper proposes an improved carrier-stack modulation strategy. The strategy firstly generates the initial drive signal of the switch tube by the traditional carrier-stack modulation method, and then, the actual drive signal of the switch tube is obtained after power balance optimization of the drive signal of the switch tube. The simulation results show that this strategy can solve the reverse current problem and realize the power balance of the two low-voltage cells when the inverter high-voltage cell operates at the fundamental frequency. The harmonics of the inverter output voltage are mainly sideband harmonics centered on the carrier ratio m f. As the modulation degree ma increases, the output voltage THD (total harmonic distortion) gradually decreases.