Coordinate Control Strategy for Multiple Distributed Generations with PV in a Microgrid

A coordinated control strategy will be presented to realize efficient power management in a microgrid which is connected to 12-node distribution system and consists of photovoltaic (PV) array, solid-oxide fuel cell (SOFC) and an ultra-capacitor (UC). The output power of a PV array is intermittent due to the variations of irradiation and temperature, causing a power imbalance in the power system, while SOFC is not only able to generate power to its own local load, but also to compensate the power imbalance caused by the intermittency of PV array. A power management is implemented by fuzzy logic control to coordinate the operations of SOFC and UC, maximizing the lifetime of SOFC and improving the transient response by ultra-capacitor as supplementary energy source. Therefore, the fuel utilization rate should be in the safe operation range, and the state-of-charge of UC should be maintained in the normal range to enhance the lifetime of UC. The proposed operating strategy always operates the PV array at the maximum power point and the SOFC in high efficiency and safe performance range, hence, to enhance the system stability and improve the performance of system operation.