Optimal automatic tuning of PID controllers applied to Grid Converters

A systematic automatic tuning method for PID-type controllers in SISO systems is proposed. The method is inspired from the Magnitude Optimum design criterion and considers 1) the existence of a poor process model and 2) access to the output of the process and not to its states, as it frequently happens in many industry applications. For applying the method, an open-loop experiment of the process is carried out which serves for initializing the algorithm. The method proceeds by identifying on line the dominant time constants of the plant and the ‘parasitic’ one of the closed-loop system. The potential of the proposed method is justified on the vector control loop of a grid power converter via simulation results.