有源中点箝位式(ANPC)五电平逆变器调制方法和飞跨电容电压控制策略研究

分析了ANPC型五电平逆变器开关状态和输出电平的关系,并提出单周期SPWM调制方法。该调制方法在一个开关周期内实现有效电平且包含飞跨电容充电、放电两个状态。针对控制飞跨电容电压的问题,提出了在调制策略中增加充电因子,通过检测飞跨电容电压和实时调节充电因子实现飞跨电容电压闭环可控。最后对单周期SPWM调制方法和飞跨电容电压控制策略进行了仿真和实验,验证了其正确性。

Research on Modulation Method of ANPC Five-level Inverter and Control Strategy of Flying Capacitor Voltage

Due to the low harmonic content of its output voltage and low withstanding voltage of its power switches, the five-level inverter is especially suitable for high voltage and electrical power situation. However, owing to the shortage of the conventional five-level inverter topologies, an ANPC (active neutral point clamped) five-level inverter is adopted in this paper. Nevertheless, the traditional multi-carrier SPWM (sinusoidal pulse width modulation) method cannot be utilized in this topology. Additionally, the stable and controlled voltage of flying capacitor makes a major contribution to the output voltage waveforms of this ANPC inverter. The relationship between the on-off state and output level of this inverter is researched in this paper. Furthermore, the relationship among the charging-discharging of flying capacitor, the current direction and redundant switching state of this five-level inverter is also analyzed. Then, a single-cycle modulation method concerning with accomplishing effective level and the charging-discharging of flying capacitor during one switching period is raised. A charging factor that can be used to adjust the operating time of charging-discharging state is proposed to add into the modulation strategy of this paper. Hence, the closed loop control of flying capacitor voltage is achieved via detecting the voltage of flying capacitor and regulating the charging factor in real time. Finally, the single-cycle SPWM method and the control tactic of flying capacitor voltage are simulated and researched; the validity of this SPWM means and control strategy is verified simultaneously.