PLL employed in distributed generation systems: controller design and comparative analysis of the use of moving average and Butterworth filters for its phase detector

Abstract

Distributed generation systems (wind, photovoltaic, etc.) require the injection of sinusoidal currents into the grid, that must be synchronized with fundamental component of the grid voltage in spite its distortion, or even in the presence of sags, swells and frequency deviations. This project proposes the study, the design and the implementation of one-phase digital synchronism systems known as phase locked loops (PLL), using a multiplier type phase detector. The performance of two commonly employed phase detector filters, including the moving average (MAV) and the Butterworth ones will be evaluated. The controller design will be carried out by using classical control in continuous time. The phase detector filter will be taken into account in the controller design, that specially in the MAV case is usually discarded. All the studied strategies will be numerically simulated and implemented in a Digital Signal Processor (DSP). This project objective is to show that the classical PLL with multiplier type phase detector and an adaptive MAV filter is a simple, computationally efficient and good performance implementation alternative not only for steady state but also for transient operation. (AU)