Daily operation cost minimization of photovoltaic-diesel-battery hybrid systems using different control strategies

In this work, an optimal scheduling model is developed to minimize the operation cost of solar photovoltaic-diesel-battery hybrid systems. Furthermore, two operation modes of the diesel generator, namely the "ON-OFF" and the "CONTINUOUS", are modeled and integrated in the hybrid system operation mode. The principal objective of these developed models is to minimize the hybrid system´s daily fuel expenses while optimizing the power flow from the different power sources and from the storage system. The variable character of the load demand, the efficient operation zone of the diesel generator as well as the charging and discharging constraints have been taken into account in the development of the models. These models have been applied to two test examples in South Africa; and the results are analyzed and compared to the case where the diesel generator is the only alternative of providing the load with electricity. Sensitivity analyses have been conducted on the diesel generator´s size, and the battery control setting as key parameters. The results show that using the developed models, the daily operation cost can be significantly reduced compared to the case where the diesel is the only alternative of providing the load.