Synthesis of Active Damping for Grid-Connected Inverters with an LCL Filter

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LCL filter characterized with high harmonic current attenuating and low bulk is preferable for medium and high power grid-connected inverters, but the resonance poles of filter endanger the safety of operation. Active damping (AD) is an effective measure to increase the system stability, but various AD structures were developed with no explanation as to how they were generated. The objective of this paper is to propose a general approach for developing AD technology of grid-connected inverter with LCL-filter. Firstly, the unified analytical model and systematical synthesis method for AD are proposed, the AD structures are listed based on single-state-variable single-compensator (SSVSC), and the effective AD structures are identified by root locus. Accordingly, a family of AD structures included some of the existing AD structures and a new one has been generated systematically. In order to verify the feasibility of the synthesis method, the properties of the deduced new AD structure are analyzed and compared with the existing AD structures by theoretic and simulation. Finally, a 3kw prototype is implemented and tested to show the effectiveness of the deduced AD structures by synthesis method. Furthermore, the AD structures are developed based on multi-state-variables multi-compensators (MSVMC) to deduce another family of AD structures, and an AD table is drew. One of the main contributions of this paper is that a clear picture is made on the systematical synthesis method to generate AD structures