Circulating Current Suppression Method with Adaptive Virtual Impedance for Multi-bidirectional Power Converters Under Unbalanced Conditions

卷:9

Article

关键词: 3-PHASE PWM CONVERTER;    CONTROL STRATEGY;    AUTONOMOUS OPERATION;    COORDINATION CONTROL;    PARALLEL INVERTERS;    COMPLEX IMPEDANCE;    AC;    DC;   

DOI  :  10.17775/CSEEJPES.2020.01980

来源: SCIE

【 摘 要 】

Multi-paralleled bidirectional power converters (BPCs) are commonly used to improve the power capacity and reliability in an AC/DC hybrid microgrid. However, circulating current through multi-BPCs has been one of the challenges and it can be aggravated in the presence of non-ideal operating conditions, such as unbalanced AC voltages, and the mismatch of hardware parameters. In order to suppress the circulating current, this paper proposes a distributed method based on adaptive virtual impedance, which also employs positive sequence power droop control and voltage deviation compensation control. The traditional positive sequence power droop control is adopted to only regulate the positive components of the BPCs output voltage. The negative sequence power term is fed to an adaptive virtual impedance generator to modify the damping characteristics of the BPCs. Also, an adaptive virtual impedance-based voltage deviation compensation method is proposed to recover the fluctuated output voltage of the BPCs due to droop action and the power fluctuations. The fully distributed regulation of adaptive virtual impedance enables the load power to be shared accurately among BPC modules and thus the circulating current can be effectively suppressed. The proposed control strategy does not require an additional communication system and the precise parameters of hardware equipment and line impedance. Furthermore, the effectiveness of the proposed method is verified by the experimental results.