级联H桥五电平变流器工况分析与验证

以单相两功率单元级联为例,阐述了级联H桥五电平变流器的拓扑结构和载波相移SPWM(CPS-SPWM)调制策略.从该变流器的运行工况着手,给出了这种变流器在CPS-SPWM调制方法下的工作原理,并从数学角度推导了变流器开关切换、输出电压、电流流向以及均衡电压等情况,理论推导表明CPS-SPWM调制方法应用在级联多电平逆变器上的可行性、可靠性和控制的简易性,为实现调制方法的优化和拓扑结构的改进提供了理论基础.同时对五电平变流器的运行工况进行了详尽的分析,推导出了五电平变流器的数学模型,并进行了仿真和实验验证.基于DSP与FPGA,研制了多路PWM脉冲发生器,既简化了电路的设计,提高了系统的可靠性,又可保证整个系统功率元件驱动信号的同步.实验结果表明,这种变流器能在较低的器件开关频率下实现较高等效开关频率的效果,运行工况稳定,在高压、大功率场合有一定的工程应用前景.

Analysis and Validation of Cascade H-Bridge Five-Level Converter Operating Condition

Taking two power cells cascaded per phase as an example, the topology of cascaded Hbridge multilevel converter and carrier phase-shifted SPWM (CPS-SPWM) modulation strategy are introduced. The operation principle of the converter under the SPWM modulation is described in detail through the analysis of operating condition The power devices switching, output voltage, current circulation and balance voltage are analyzed. According to the analysis, the feasibility, reliability and convenience of the PWM strategy for the cascaded converter are proved, the theoretical basis for the modulation optimization and topology improvement is also provided. Operating mode of five-level converter is described in detail in the paper. Mathematicl model of five-level converter is deduced and validated by computer simulation. Cascade H-bridge five-level converter pulse generator is implemented by DSP and FPGA, which has the feature of simplifying circuit-design, guaranteeing reliability of system and concurrent triggering of power devices. Cascade multilevel converter based on carrier phase shifted PWM can achieve high equivalent switching frequency at low switching frequency devices, which is of perfect prospect in high voltage and power industry application.