Active power control using an alternative series connection scheme between the utility grid and Microgrid

In the context of microgrids, most of the research has concentrated on developing new control strategies for integration of DG sources into the power grid and seamless transition techniques between grid-connected and islanded modes. However, a few research work has focused on the power control at the point of common coupling (PCC) between utility grid and microgrid. This paper presents alternative connection scheme and control method at PCC between the utility grid and microgrid. A series voltage source converter (S-VSC) which emulates the operation of a series H-bridge has been introduced at PCC to control the active power exchange. This connection scheme gives the advantage that it has low losses and cost compared to other configurations beside that it is less bulky. The main utility grid interacts only with the S-VSC instead of the whole microgrid generating units. In order to make the active power controllable, this connection scheme provides a controlled voltage that can change the microgrid DGs voltage. The voltage provided by the S-VSC is in agreement with the voltage based droop control of the microgrid DGs. Thus, the DG units will spontaneously be adopted with changes of S-VSC voltage. The effectiveness of the proposed connection scheme and control strategy was validated through simulations using SimPower Systems toolbox of Matlab/Simulink.