NPC三电平逆变器PWM时降低损耗的研究

Research on Reduce Loss of PWM Strategy for Three-level Inverter

在大功率应用场合中,逆变器开关器件的损耗问题一直是制约其性能提高的因素之一。其损耗可分为通态损耗和开关损耗。讨论了这两种损耗的计算方法,并提出一种降低开关损耗的PWM方法,即SLMPWM。给出了调制度和功率因数角变化时,传统SPWM和SLMPWM策略的损耗分布区面。可见,在很大范围内,PWM策略能将开关损耗降低约一半。最后,给出了这两种调制策略谐波特性的比较,可见,SLMPWM调制策略的谐波特性与SPWM基本一致,不会由于等效开关次数降低而导致谐波特性变差。

The loss of switch device of three-level inverter is a disadvantage that restricts the application of three-level inverter in high power,high voltage environment.The loss of switch device can be grouped to conduction loss and switch loss.The calculation methods of these two losses are proposed.A novel PWM strategy is proposed that the switch loss can be reduced.Aiming to traditional SPWM and SLMPWM strategy, the surfaces of loss are carried out as modulation index and power angle varying.This SLMPWM strategy can reduce the half of switch loss compared with SPWM strategy in a wide range.At last, the spectrum characteristics of these two PWM strategies are investigated and compared, the spectrum of these two PWM is identical approximately.The spectrum characteristic of SLMPWM strategy is not deteriorated due to the reduction of equivalent switch frequencies of switch device.