A Laboratory PMU Based on Third-Order Generalized Integrator Phase-Locked Loop

The dynamic monitoring and control of modern power systems require synchronized time-stamped electrical measurements to estimate the voltage and current phasors, as well as frequency and rate of change of frequency (ROCOF), under normal and abnormal conditions. Phasor measurement units (PMUs) are designed to perform this task by providing accurate, high-speed measurement data to the phasor data concentrator (PDC), while the time stamping is provided by a global positioning system (GPS) at the coordinated universal time (UTC). However, the cost of these devices remains high due to their complex infrastructure, and thus, low-cost PMU design is needed without sacrificing their accuracy and reliability. This article presents a complete development of a low-cost laboratory PMU based on the phase-locked loop (PLL) concept, employing the third-order generalized integrator (TOGI) PLL for the estimation of the positive sequence of the voltage and current phasors, synchronized with the UTC time given by a GPS module.