Optimal Scheduled Power Flow for the Distributed Photovoltaic-Wind Turbine-Diesel Generator with Battery Storage System

Abstract

The high cost of the transportation of power from the grid to rural areas is a great concern for most of the countries in the world and the above results in many remote areas not being able to have electricity. To overcome the challenges of electrification of rural areas, some generate their own energy by continuous or prime power diesel generators (DGs) or by producing energy using different small-scale renewable energy sources (Photovoltaic, Wind, hydroelectric and others). Despite their advantages of being easy to transport, easy to install and of low initial cost, diesel generators present many disadvantages when they are used as continuous or prime power sources due to the high requirement of fuels and non-linearity of daily load demand profile. Beside the cost, diesel generators are detrimental to the environment and cause global warming. To overcome the issues of costs and global warming, diesel generators can be used in combination with renewable energy such as photovoltaic as a backup to form a hybrid power generation system. The stand-alone photovoltaic (PV) and wind turbine (WT) power generators have drawbacks as the power produced depends on the sun and wind, which means that if there is no sun or wind, no electricity can be produced. The non-linearity of solar and wind resources makes the stand-alone photovoltaic and wind operation non-reliable. The combination of photovoltaic-wind turbine–diesel-battery power generation ensures that the energy produced is reliable and efficient. The diesel generator is used as back up to the system and is used only when the renewable energy sources are insufficient and the battery banks are low. The PV-WT-Diesel-Battery hybrid power system reduces the consumption of fuel hence minimizes fuel costs. The system also presents the advantage of less pollution to the environment due to the short running time of the generator, a low generator maintenance requirement and long life expectancy of the generator. As indicated above, the hybrid systems have the advantage of saving costs compare to a standalone diesel generator operation, but the system requires proper control to minimize the operation costs while ensuring optimum power flow considering the intermittent solar and wind resources, the batteries state of charge and the fluctuating load demand. The aim of this research is to develop two different control strategies to minimize the daily operational cost of hybrid systems involving PV/WT/DG and batteries by finding the optimal schedules for running the diesel generator while in the meantime responding to the power required by the load. The two control strategies developed are “Continuous operational mode” and “ON/OFF” operational mode. The developed mathematical models of the two control strategies are simulated using MatLab functions, with “fmincon solver” for continuous operational mode and “Intlinprog solver” for ON/OFF operational mode.