A Novel Frequency Control Scheme for Autonomous Microgrid Using Cooperative Application of Supercapacitor-Battery HESS, Photovoltaics, LED Lighting Loads and TCLs

The supercapacitor-battery hybrid energy storage system (SBHESS) has been commonly used to reduce the stress of fast power variations on the battery, and hence, prolong its lifetime. However, the utilization of the supercapacitor (SC) significantly increases the cost of energy storage system. Considering the potentials of the photovoltaic systems, the smart LED lighting loads and the thermostatically controlled loads in primary frequency control (PFC), three novel PFC schemes are proposed for each of them. They are enabled to cooperatively participate in the PFC of islanded MG alongside the SBHESS. Their cooperative application alongside the SBHESS decreases the participation share of the SC in the PFC and hence, reduces the size and the cost of the SC and its converter which consequently decreases the SBHESS cost. In this regard, the genetic algorithm is employed to tune the controller coefficients of the PFC schemes and the distributed generators to limit and minimize frequency deviations within an acceptable range, and also minimize the size of SC and its converter. The results show that the proposed cooperative application considerably decreases the size and the cost of the SC and its converter. This is while the SBHESS battery life is still extended the same as the case in which the SBHESS is used alone. As the frequency control results are similar with and without the proposed cooperative application and the imposed cost is much higher in the latter case, the proposed cooperative application increases the cost-effectiveness of the SBHESS.