四开关三相逆变器全调制度范围内两种等效PWM算法

Two Types of Equivalent PWM Algorithms in the Full Modulation Region for Four-Switch Three-Phase Inverter

为提高两电平逆变器单桥臂故障重构拓扑四开关三相逆变器(FSTPI)的直流电压利用率,提出了一种FSTPI的空间矢量脉宽调制(SVPWM)过调制算法,该算法根据调制度的大小将整个过调制区域划分为过调制模式Ⅰ区、过调制模式Ⅱ区和过调制模式Ⅲ区。为揭示全调制度范围内FSTPI的SVPWM算法和载波脉宽调制(CBPWM)算法的内在联系,从调制函数角度出发,基于PWM规则采样法,分别推导了与这三个过调制模式区SVPWM算法等效的CBPWM算法,并得到了随着调制度变化,全调制度范围内CBPWM相应等效调制函数的变化规律。理论研究表明,全调制度范围内,FSTPI的SVPWM算法是一种特殊形式的CBPWM算法。仿真和实验结果证明了理论分析的正确性和有效性。

The four-switch three-phase inverter(FSTPI)is the post-fault reconfigured topologyfor the two-level inverter with single-leg failure.In order to enhance the DC-link voltage of FSTPI,aspace vector pulse-width modulation(SVPWM)algorithm in the over-modulation region is proposed.Itdivides the over-modulation region of FSTPI into over-modulation modeⅠregion,over-modulationmodeⅡregion and over-modulation modeⅢregion depending on the modulation index.In order toreveal the relationship between SVPWM and carrier-based pulse-width modulation(CBPWM)algorithm of FSTPI,the equivalent carrier-based modulating functions of SVPWM in these threeover-modulation modes are derived respectively,based on the PWM regular sample method.Thechange rules of the equivalent carrier-based modulating functions in the full modulation region aresummarized with the modulation index changing afterwards.Theoretical analysis shows that theSVPWM of FSTPI is a special type of CBPWM algorithm in the full modulation region.Simulation andexperimental results verify the theoretical analysis.