New Enhanced Droop Controller for Seamless Load Sharing in AC Microgrids in Presence of Wind Turbine and Photovoltaic Source

Abstract

Load sharing, as an important challenge in microgrids (MGs), is realized commonly via a droop control method. Conventional droop control methods are not applicable in unpredictable renewable energy sources (RESs) like photovoltaic (PV) and wind turbines (WT) because their output power depends on the weather conditions and can be extracted only if these free sources are available. This paper, considers two operating modes for these types of sources as Maximum Power Point Tracking (MPPT) and DC-link Voltage Control (DCLVC). These power sources usually operate in the MPPT mode unless the load of the MG drops to a lower level compared to the maximum power generation by RESs, in which case the sources switch to the DCLVC operating mode. This study proposed a method based on enhanced droop control, which helps RESs to choose its control mode locally without communication and share the demand of the AC MG with other dispatchable sources besides supplying its maximum power. The proposed method focused on supplying MG load from RESs as much as possible and simplicity in implementation. MG frequency helps the proposed controller to select its operation mode. Enhanced control for DC link voltage control is offered for inverter based RESs. The validity of the proposed method is approved by simulations in the MATLAB/SIMULINK environment.

Keywords

• droop method
• load sharing
• microgrid (mg)
• photovoltaic (pv)
• wind turbine (wt)