A current feedback control strategy for parallel-connected single-phase inverters using a third-order general-integrator crossover cancellation method

Authors: YUAN HUANG, AN LUO

Abstract: Virtual impedance is usually introduced to the control system of parallel inverters in order to change the inverter equivalent output impedance and to enhance control accuracy and power sharing. In this paper, a current feedback control strategy using a third-order general-integrator crossover-cancellation method that can be implemented in a virtual impedance loop is proposed. This method consists of 2 parts: a crossover-cancellation feedback network, which achieves the band-pass effect, and a multilevel TOGI-OSG link, which acts as a filter. Compared with the conventional virtual impedance method, the proposed method can avoid derivation of output current, reduce system calculating burden, and enhance dynamic response. Additionally, this method can reduce the THD of output voltage in the case of nonlinear load and can also drastically restrain the impact of DC component on output voltage. A prototype consisting of 2 sets of 2-kW photovoltaic inverters operating in parallel was built in the laboratory. Simulated and experimental results are examined to verify the effectiveness and feasibility of this method.

Keywords: Microgrid, island mode, parallel inverter, droop control, virtual impedance

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