减小死区影响的准单极性PWM调制方法

Quasi-single-polarity PWM method for reducing the effect of dead time

通常在脉宽调制(PWM)信号中需要插入“死区”时间以防逆变器上下桥臂“直通”,但这也导致了输出性能的恶化。为此,该文提出了一种准单极性PWM调制方法。文中首先分析了逆变器带异步电机负载时的开关导通规律,然后根据电流的极性,在一个半波周期内封锁上下管驱动脉冲中的其中一路,使逆变器工作在“半控”状态下,因而可以消除死区。针对电流过零点极性检测问题和保证电机顺利启动的需要,文中也提出了相应措施。所述方法可以改善电流波形,提高电压利用率。仿真和试验表明该方法简单有效,有一定实用性。

The dead time is necessary to prevent the shoot-through phenomenon in a PWM （pulse-width modulation） inverter feeding an induction motor, but the dead time reduces the system performance. This paper presents a new method for dead time, the quasi-single-polarity PWM method. The method disables the drive pulse of one switching device based on the phase current polarity during one half of a cycle for the current. The bridge is in a half-controlled state so that the dead time can be reduced. The control scheme also includes measures to deal with zero-cross and motor startup. The method significantly improves the current wave and the inverter performance. Simulations and experimental results illustrate the effectiveness of the method.