低共模电压三相准单级逆变器空间矢量调制策略

由于部分光伏功率可单级传输馈入电网,三相准单级逆变器的变换效率高于传统三相两级式逆变器,但共模电压幅值和频率变化量较高.提出一种适用于三相准单级逆变器的低共模电压空间矢量调制(LCSVPWM)策略,通过舍弃部分小矢量和替换零矢量,降低了共模电压幅值和频率的变化量.此外,通过理论计算,比较了三相准单级逆变器分别采用传统空...

SVPWM scheme for low common-mode voltage of three-phase quasi-single-stage inverter

Since part of the photovoltaic power can be fed to the grid with single-stage power conversion, three-phase quasi-single-stage inverter has higher efficiency than that of conventional three-phase two-stage inverter. However, it still has the issue of high variation of amplitude and frequency of common-mode voltage. A LCSVPWM(Low Common-mode voltage Space Vector Pulse Width Modulation) scheme is proposed to reduce the variation of amplitude and frequency of common-mode voltage by omitting part of small voltage vectors and replacing zero voltage vectors. In addition, by calculating theoretically, the power losses of switching devices in three cases are compared, including the three-phase quasi-single-stage inverter adopting the CSVPWM(Conventional Space Vector Pulse Width Modulation) scheme and LCSVPWM scheme, and the three-phase two-stage inverter adopting seven-segment SVPWM scheme. A prototype of a 3 kW three-phase quasi-single-stage inverter is built. Experimental results show that when the input voltage is low, the variation of amplitude and frequency of common-mode voltage of inverter adopting LCSVPWM scheme is lower than that adopting CSVPWM scheme. In addition, the efficiency of the three-phase quasi-single-stage inverter adopting LCSVPWM scheme is slightly lower than that adopting CSVPWM scheme, but higher than that of the three-phase two-stage inverter. Thus, LCSVPWM scheme has advantages in improving both efficiency and common-mode performance.