Power Flow Control Of Interconnected Ac-dc Microgrids In Grid-connected Hybrid Microgrids Using Modified Uipc

This paper introduces a new approach for power flow control of interconnected AC-DC micro-grids in grid-connected hybrid micro-grids based on implementing a modified unified interphase power controller (UIPC). A typical grid-connected hybrid micro-grid including one AC micro-grid and one DC micro-grid is considered as studied system. Instead of using the parallel-connected power converters, these micro-grids are interconnected using a modified UIPC. As the first contribution of this paper, the conventional structure of UIPC, which uses three power converters in each phase, is modified so that a reduced number of power converters is implemented for power exchange control between AC-DC micro-grids. The modified structure includes one power converter in each phase, named as line power converter (LPC), and a power converter which regulates the DC bus voltage, named as bus power converter (BPC) here. The AC micro-grid is connected to the main grid through the LPCs which their DC buses are linked and can operate in capacitance mode (CM) or inductance mode (IM). A fuzzy logic controller is used in the control structure of the LPCs. The fuzzy inference system is optimized based on H∞ filtering method to reduce the errors in membership functions design. Through the BPC, the DC voltage of LPCs is supplied by the DC micro-grid. However, since the DC micro-grid voltage is provided here by a PV system, the DC link voltage of the LPCs is fluctuating. Thus, as the second contribution, to stabilize the DC link fluctuations, a new nonlinear disturbance observer based robust multiple-surface sliding mode control (NDO-MS-SMC) strategy is presented for DC side control of the BPC.