矩阵变换器两种调制策略的比较与分析

Comparison between two modulation methods of matrix converter

对矩阵变换器的两种调制策略进行了分析比较,证明了两者占空比之间的相等关系,指出双电压调制法只是零矢量中置空间矢量调制法调换导通次序的另一种形式。两种调制法均能实现在输入电压不平衡时的控制,且占空比计算都较为简单,但是采用空间矢量调制法可以完全消除窄脉冲,且能够较为方便地进行电压补偿操作。分析了两种方法对开关损耗的影响。由于空间矢量调制法为了消除窄脉冲、提高输出波形质量,在换流时的输出电压在大压差之间反复变化,造成了开关损耗大大上升,而双电压调制法在选通输入电压时均是按电压高低依次排列,因此双电压调制法的开关损耗较小。故在选择消除窄脉冲和降低开关损耗之间,必须折衷考虑具体选择哪种调制顺序,也可以交替使用,兼有两者的优点。

The space vector modulation （SVM） and double line voltage modulation （DLVM） for matrix converter are compared. The two modulations are proved to have the same duty-cycle. DLVM is a special modulation sequence of SVM which has one zero-vector in the middle of modulation sequence. Both two modulations can detect unbalanced input voltage real-time and generate balanced output voltage. But SVM with suitable zero vectors can further eliminate short PWM pulses and compensate output voltage at low modulation index. The switching loss of the two modulations is analyzed. The high differential voltage consists in the middle of the SVM modulation subsequence which will cause high switching loss in the commutation before or after the high differential voltage. However, DLVM has lower switching loss than SVM because DLVM modulates according to the order of the magnitude of the input voltages. The choice between SVM and DLVM depends on request of eliminating short PWM pulses or reducing switching loss. The two modulations can be alternatively used to show both merits.