摘要：電力電子變壓器(power electronic transformer,PET)在給不平衡或非線性負荷供電時,可能會出現PET裝置輸出側電壓幅值和頻率不穩定的現象,甚至影響PET的供電可靠性.針對PET輸出容量大、容量模塊化可調、高電能質量供電等需求,避免單臺逆變器輸出模塊在處理不對稱或非線性負荷時的局限性,本文提出了PET輸出側(逆變級)雙模塊并聯的高電能質量控制策略.主要思路為:輸出側中的一個逆變器模塊采用電壓電流雙閉環控制策略,可視為電壓源,負責提供穩定的PET輸出側電壓,起到穩定其他輸出側逆變器模塊的電壓基準值的作用,既可以補償所有負序、諧波及無功電流以降低對PET輸出電壓的不利影響,同時還按照既定的輸出側模塊功率分配策略輸出有功功率和無功功率.輸出側的其他逆變器模塊則采用電流補償控制策略,可視為電流源,用于增大輸出電流,提升PET裝置的容量.以兩個輸出側逆變器模塊并聯輸出為例進行理論分析,認為所提控制策略既可以提高PET裝置的輸出容量,又可以極大降低非對稱負荷對PET輸出電壓穩定的不利影響,有效地提升了PET的負載適應性、容量擴展性及供電可靠性.仿真結果驗證了本文所提出控制策略的有效性.%When power electronic transformer (PET) supplies power to the unbalanced or non-linear loads,the voltage amplitude and frequency of the output-side in PET may be unstable,and even affect the power supply reliability of the PET.Aiming at demands of large output capacity,adjustable capacity modules,and high-quality power supply of PET,and for avoiding the limitations of single inverter output module in handling asymmetric or non-linear loads,a dual-module control strategy with high power quality for parallel output sides (inverters) of PET is proposed.In which,one of the inverter modules in output side is regarded as a voltage source and adopts double closed-loop control strategy of voltage and current,it provides stable output voltage of PET and stabilizes the voltage reference values of the output sides for other inverter modules,which can not only compensate for negative sequence current,harmonics and reactive current to reduce the negative impacts on the output voltage of PET,but also provide active power and reactive power in accordance with established power distribution strategy for output side modules.Other output-side inverter modules treated as current sources adopt the current compensation control strategy.They are used to enlargc the output current and enhance the capacity of PET.Taking two parallel output-side inverter modules as an example,the proposed high power quality control strategy is analyzed theoretically.It is concluded that the proposed strategy can improve the output capacity of the PET,greatly reduce the adverse effects of asymmetric loads on the output voltage stability of PET and effectively enhance the adaptability,capacity expansion and power supply reliability of PET.The simulation results verify the effectiveness of the proposed control strategy.
