Nonlinear PID (N-PID) Controller for SSSP Grid Connected Inverter Control of Photovoltaic Systems

Abstract

In this work, a Nonlinear Proportional Integral Derivative (N-PID) controller based on Popov's stability criterion is applied for retaining the power quality of single stage single phase grid connected photovoltaic systems. Popov's stability criterion based nonlinear gain is added with conventional PID controller design which is termed as N-PID. Here, Nonlinear gain is designed with the approach of the controller to provide a nonlinear relationship with the error for the accuracy in reference tracking as conventional PID controller shows a linear relationship with the error. Thus, the N-PID controller joins the benefits of conventional PID controller and also reduces the complexity of tuning of PID gains as tuning of PID gains is the most challenging process of the conventional PID controller to achieve the accuracy on set point tracking. N-PID is designed in such a way to control the duty cycle of DC-AC converter for obtaining the maximum power without any harmonics, also for achieving unity power factor and achieving the efficiency with 96%-99% of the system. The proposed topology with N-PID controller ensures fast tracking of maximum power point, reducing harmonics considerably and improving the efficiency further with the wide investigation of error over the responses.