The modular multilevel converter(MMC)is a promising topology for medium-voltage drive applications due to its high-quality output waveforms,low device switching frequency and voltage rating.However,the large cell capa...The modular multilevel converter(MMC)is a promising topology for medium-voltage drive applications due to its high-quality output waveforms,low device switching frequency and voltage rating.However,the large cell capacitor voltage ripple is a severe challenge faced by MMC at low motor speeds.Recently,a hybrid MMC(HMMC)topology is proven to be a competitive solution because of its lower cell capacitor voltage ripple and not demonstrating a common-mode voltage(CMV)problem compared with other methods.However,the DC-link switch with IGBT limits HMMC from being applied in highvoltage applications.This paper uses a thyristor instead of IGBT as the DC-link switch.To ensure the thyristor can be softly turned on and safely turned off,a new control scheme is proposed.When using this proposed scheme,HMMC can also tolerate the failure of the thyristor being turned-off without shutting down the system,effectively improving its reliability.The cell capacitor voltage ripple analysis is presented considering the effects of the thyristor switching process.In addition,a decoupled energy balancing control is utilized to suppress the fluctuation of the DC current.Experimental results obtained from a 380 V/7.5 kW downscaled prototype validate the effectiveness of starting up a motor from the standby mode to rated speed applying full-torque.展开更多
基金This work was supported by the National Natural Science Foundation of China under Grant 51720105008 and 52177173。
文摘The modular multilevel converter(MMC)is a promising topology for medium-voltage drive applications due to its high-quality output waveforms,low device switching frequency and voltage rating.However,the large cell capacitor voltage ripple is a severe challenge faced by MMC at low motor speeds.Recently,a hybrid MMC(HMMC)topology is proven to be a competitive solution because of its lower cell capacitor voltage ripple and not demonstrating a common-mode voltage(CMV)problem compared with other methods.However,the DC-link switch with IGBT limits HMMC from being applied in highvoltage applications.This paper uses a thyristor instead of IGBT as the DC-link switch.To ensure the thyristor can be softly turned on and safely turned off,a new control scheme is proposed.When using this proposed scheme,HMMC can also tolerate the failure of the thyristor being turned-off without shutting down the system,effectively improving its reliability.The cell capacitor voltage ripple analysis is presented considering the effects of the thyristor switching process.In addition,a decoupled energy balancing control is utilized to suppress the fluctuation of the DC current.Experimental results obtained from a 380 V/7.5 kW downscaled prototype validate the effectiveness of starting up a motor from the standby mode to rated speed applying full-torque.
