T型逆变器中点电压全范围精确平衡研究

Research on Full Range Accurate Balance of Neutral Point Voltage for T-Type Inverter

中点电压不平衡是T型逆变器的固有缺点。分别建立空间矢量脉宽调制(SVPWM)算法和虚拟空间矢量脉宽调制(VSVPWM)算法的中点电压偏移量数学模型,得到两种算法的中点电压不可平衡区域与负载功率因数角、调制比之间的关系,提出一种中点电压全范围精确平衡算法。该算法通过计算和修正小矢量作用时间的平衡因子来实现中点电压的精确平衡,通过判断平衡因子的取值来确定控制算法,以确保在保持中点电压精确平衡的基础上有效减小输出谐波和开关损耗,仿真和实验验证了所提算法的有效性。

The unbalance of neutral point voltage is the inherent shortcoming of T-type inverter.The neutral point voltage offset models of space vector pulse width modulation(SVPWM)algorithm and virtual space vector pulse width modulation(VSVPWM)algorithm are established respectively.The relationship of the unbalanced region of neutral point voltage with the load power factor angle and modulation ratio is obtained.A full range accurate balance algorithm of neutral point voltage is proposed.In this algorithm,the precise balance of neutral point voltage is achieved by calculating and correcting the balance factor of the time of positive small vector.The algorithm is selected by judging the balance factor to reduce harmonics and switching losses effectively while maintaining accurate balance of neutral point voltage.Simulation and experimental results verify the proposed algorithm.