The International Journal Of Engineering And Science (IJES) || Volume || 4 || Issue || 9 || Pages || PP -43-52|| 2015 || ISSN (e): 2319 – 1813 ISSN (p): 2319 – 1805 www.theijes.com The IJES Page 43 Electric Power Management for a Grid Connected Renewable Energy Sources Felix N. C. Anyaegbunam (Ph.D.) Department of Electrical/Electronic/Computer Engineering, Federal University Ndufu-Alike-Ikwo, Nigeria --------------------------------------------------------ABSTRACT-------------------------------------------------------------- Operation of a grid connected hybrid system for renewable energy sources has been presented. The hybrid system composed of a photovoltaic (PV) array and a proton exchange membrane fuel cell (PEMFC) is considered. The operation modes used in the hybrid system are unit-power control (UPC) and the feeder-flow control (FFC) modes. In the UPC mode, variations of load demand are compensated by the main grid because the hybrid source output is regulated to reference power. Renewable energy is currently widely used because fossils are known to endanger the environment. One of these resources is solar energy. The photovoltaic (PV) array normally uses a maximum power point tracking (MPPT) technique to continuously deliver the highest power to the load when there are variations in temperature. The disadvantage of PV energy is that the PV output power depends on weather conditions and cell irradiation and temperature, making it an uncontrollable source. Moreover, the sun is not available during the night. In order to overcome these inherent drawbacks, alternative sources, such as PEMFC in the hybrid system are used. By changing FC output power, the hybrid source output becomes controllable. Therefore, the reference value of the hybrid source output is determined. In the FFC mode, the feeder flow is regulated to a constant, the extra load demand is picked up by the hybrid source, and, hence, the feeder reference power must be known. Thus the hybrid system can maximize the generated power when load is heavy and minimizes the load shedding area. Key Words: Fuel cell, hybrid system, micro grid, photovoltaic, unit power control, power management. ---------------------------------------------------------------------------------------------------------------------------------------- Date of Submission: 08 September 2015 Date of Accepted : 30 September 2015 ---------------------------------------------------------------------------------------------------------------------------------------- I. INTRODUCTION Although the conventional fossil fuel energy sources meet most of the world’s energy demand today, they are being depleted rapidly and are not renewable. In addition, their combustion products are causing the greenhouse effect and pollution which are posing great danger to our environment and eventually endangering the entire planet. The renewable energy sources (solar, wind, tidal, plasma-wte, geothermal etc.) are gaining more attention as alternative energy sources. Among the renewable energy sources, the photovoltaic (PV) energy has been widely utilized in low power applications. It is also the most promising candidate for research and development for large scale users as the fabrication of low cost PV devices become a reality. Photovoltaic generators which directly convert solar radiation into electricity have a lot of significant advantages such as being inexhaustible and pollution free, silent, with no rotating parts, and with size- independent electric conversion efficiency. Due to harmless environmental effect of PV generators, they are replacing electricity generated by other polluting methods and even more popular for electricity generation in rural areas. With increasing penetration of solar photovoltaic devices, various anti-pollution apparatus can be operated by solar PV power. From an operational point of view, a PV power generation experiences large variations in its output power due to intermittent weather conditions. Those phenomena may cause operational problems at the power station, such as excessive frequency deviations. In many regions of the world, the fluctuating nature of solar radiation means that purely PV power generators for off grid applications must be large and thus expensive. One method to overcome this problem is to integrate the photovoltaic plant with other power sources such as diesel, fuel cell (FC), or battery back-up.