Enhanced Grid-Connected Phase-Locked Loop Based on a Moving Average Filter

Abstract

Moving average filter (MAF)-based phase-locked loops (PLLs) have received considerable attention in recent years due to their attractive features. Indeed, they are able to completely eliminate the unwanted effect of harmonics, dc offset, and unbalanced voltages. Unfortunately, these advantages come at the cost of open-loop bandwidth reduction, which worsens the system's dynamic response. The main challenge is to estimate the phase and frequency timely and precisely from an imbalanced and distorted voltage. In addition, optimized parameter design is also a difficult issue. The main aim of this paper is to present an enhanced PLL based on a moving average filter (EMAF-PLL) and a control method with a novel compensation algorithm. The EMAF-PLL can maintain high performance even under harsh grid conditions, and the novel control method enables the designer to set the controller parameters simply and effectively. The design method compensates the PLL small-signal model to form a type-II classic system and then optimizes the control-loop design by the rules of type-II systems. Finally, experimental investigations are performed to validate the effectiveness of the EMAF-PLL. The experimental results are also presented, and comparison with conventional PLLs verifies that the dynamic performance can be significantly improved. INDEX TERMS Moving average filter (MAF), phase-locked loops (PLLs), type-II classic system, utility grid synchronization.

Impedance Modeling and Stability Analysis of the IMAF-PLL-Based NPC Three-Level LCL Grid-Connected Inverter

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