一种三电平全桥直流变换器新型控制策略研究

Research on a Novel Control Scheme for Three-level Full-bridge Converter

三电平全桥变换器的移相控制策略中,不能使所有开关管实现软开关条件;斩波加移相控制策略中,隔离变压器原边绕组电压谐波总畸变率(total harmonic distortion,THD)高。针对这一问题,提出一种新的对称双移相控制策略。将对称双移相控制策略与斩波加移相控制策略进行对比研究。通过对对称双移相控制策略下开关过程进行分析,得出所有开关管均能实现软开关条件;通过对变压器原边电压进行傅里叶分析,得出该控制策略下变压器原边绕组电压谐波总畸变率低。通过分析谐波总畸变率随斩控角的变化规律,得出该控制策略下变换器的最优稳态工作点。制作一台三电平全桥直流变换器科研样机,对该文的分析进行验证。

In the phase-shift control scheme of three-level full-bridge converter, some switches can＇t implement soft switching. In the chop plus phase-shift（CPS） control, the total harmonic distortion（THD） of the transformer primary side voltage is high. To resolve this issue, a new symmetrical double phase-shift（SDPS） control scheme was proposed. A comparative study was done between CPS and SDPS control.Through analysis of one switching cycle, we can see that all switches can implement soft switching in SDPS control.Fourier analysis of the voltage showed that THD of the transformer primary side voltage was low in SDPS control. By analyzing how the THD varied with chopping angle, the optimal steady state operating point of this control scheme was got in SDPS control. A three-level full-bridge device was made and the analysis was verified by experiments.