Optimal transient droop compensator and PID tuning for load frequency control in hydro power systems

This paper presents an optimal method to tune the Proportional, Integral and Derivative (PID) controller for a hydraulic turbine coupled with the corresponding Transient Droop Compensator (TDC). The proposed methodology is based on the Desired Time Response Specification (DTRS) of the input guide vane servomotor that includes typical rate limiters and gain saturation in power plants. Therefore, the problem consists of adjusting both the parameters of the controller and compensator such as the time response remains close to the specified one. To avoid suboptimal solutions at local minimum points, it is necessary to solve the resulting non linear problem in two steps: (i) firstly, solve a linear programming (LP) to determine the values of PID&TDC block using state space representation to match the input and output time responses specifications and (ii) determine the final values of the PID and TDC parameters using the previous results in a new non linear programming. The proposed methodology has presented the advantage of tuning the PID coordinated with the TDC spending low computational time. The results show that the performance of the method covers a wide range of operating conditions of the system. Comparisons were also made with existing methods in the literature to show the effectiveness of the proposed methodology. 2014 Elsevier Ltd. All rights reserved.