Impedance-based Analysis of Grid-connected Inverter in high Impedance Grids

Distributed Generation may be located far away from load centers due to their use of new energy resource distribution characteristics. In this case, Long distance transmission lines will introduce an equivalent impedance to the grid. In this paper, the interaction between grid-connected inverter and high impedance grid is studied by means of impedance-based analysis method. A distributed generation system test-bed was built to evaluate the interaction between grid-connected inverter and high impedance grid from impedance-base analysis an. The high impedance grid can result in a small stability margin of impedances ration. The paper also presents a kind of active damping method to improve the stability of the grid-connected inverter. The active damping design with a virtual resistor in parallel with the capacitor is described, and the control scheme without differential factor has a simple algorithm. The experimental results are depicted to demonstrate the feasibility of the active damping algorithm.