An Analysis of Modified Demodulation-Based Grid Voltage Parameter Estimator

The estimation of the grid voltage fundamental parameters, i.e., the phase, frequency, and amplitude, is required for a wide variety of applications, particularly for synchronization and control of grid-connected converters and for monitoring and protection purposes in power systems. To accomplish this task, many approaches have been proposed in the literature. Recently, a modified demodulation-based technique (MDT) has been presented, which aims to accurately extract the grid voltage fundamental parameters under harmonically distorted and frequency-varying conditions. In this letter, it is shown that the MDT is actually a phase-locked loop. The MDT small-signal modeling and stability analysis are then conducted, and some modifications to enhance its performance are suggested. The effectiveness of these modifications is finally confirmed using numerical results.