全控型电力电子器件取代半控型器件，变换技术由相位控制转变成脉宽调制 模拟电子控制已基本上让位于数字电子控制 交流可调拖动系统逐步取代直流拖动系统已经成为不争的事实，而且交流拖动控制技术本身也有不小的进展。-Full-controlled power electronic devices to replace semi-controlled devices, transform into the phase control pulse width modulation　analog electronic control has largely given way to digital electronic control　AC adjustable drag system is gradually replacing the current system has become a drag indisputable fact, and the exchange of drag control technology itself has no small progress.