frequency control and power balancing in a hybrid renewable energy system (hres): effective tuning of pi controllers in the secondary control level

With advent of the modern hybrid renewable energy system (hres), the application of different energy storage systems has increasingly expanded. when the solar radiation or wind speed has low values, the energy storage system (ess) injects the required energy to supply the load demand, continuously. due to large numbers of equipment and different control loops in the hres, effective contribution of ess needs an efficient control approach to coordinate the ess with other equipment within hres. to fulfil this gap, a proportional integral (pi)-based control synthesis approach is presented for the tuning of the pi controllers. in the proposed method, all pi controllers for different types of ess are designed based on root-locus trajectory, damping coefficient of dominant poles, and coordination among different equipment. finally, comparison among different types of ess based on presented control approach is performed. results show that the presented control technique has adequate capability to damp the frequency deviations against multiple disturbances and parameter variations.