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A New Adaptive Phase-locked Loop for Synchronization of a Grid-Connected Voltage Source Converter: Simulation and Experimental Results

Wei He, Jiachen Yan, Romeo Ortega, Daniele Zonetti

TL;DR

The paper tackles grid synchronization for grid-connected VSCs in weak-grid conditions where grid voltage parameters are unknown. It introduces an observer-based adaptive PLL that integrates a generalized parameter-based estimation observer (GPEBO) with a least-squares estimator (LS) and forgetting factor to reconstruct the grid-side dq voltage behind the grid impedance, feeding this into a phase detector of SRF-PLL or ATAN-PLL form. Under a persistently exciting input, the approach guarantees almost global synchronization and bounded signals, confirmed by both simulations and hardware experiments. The results demonstrate fast, robust angle tracking and dq-current regulation under active-power, frequency, and voltage perturbations, offering a practical path to reliable VSC synchronization and renewable energy integration in weak grids.

Abstract

In [1] a new adaptive phase-locked loop scheme for synchronization of a grid connected voltage source converter with guaranteed (almost) global stability properties was reported. To guarantee a suitable synchronization with the angle of the three-phase grid voltage we design an adaptive observer for such a signal requiring measurements only at the point of common coupling. In this paper we present some simulation and experimental illustration of the excellent performance of the proposed solution.

A New Adaptive Phase-locked Loop for Synchronization of a Grid-Connected Voltage Source Converter: Simulation and Experimental Results

TL;DR

The paper tackles grid synchronization for grid-connected VSCs in weak-grid conditions where grid voltage parameters are unknown. It introduces an observer-based adaptive PLL that integrates a generalized parameter-based estimation observer (GPEBO) with a least-squares estimator (LS) and forgetting factor to reconstruct the grid-side dq voltage behind the grid impedance, feeding this into a phase detector of SRF-PLL or ATAN-PLL form. Under a persistently exciting input, the approach guarantees almost global synchronization and bounded signals, confirmed by both simulations and hardware experiments. The results demonstrate fast, robust angle tracking and dq-current regulation under active-power, frequency, and voltage perturbations, offering a practical path to reliable VSC synchronization and renewable energy integration in weak grids.

Abstract

In [1] a new adaptive phase-locked loop scheme for synchronization of a grid connected voltage source converter with guaranteed (almost) global stability properties was reported. To guarantee a suitable synchronization with the angle of the three-phase grid voltage we design an adaptive observer for such a signal requiring measurements only at the point of common coupling. In this paper we present some simulation and experimental illustration of the excellent performance of the proposed solution.
Paper Structure (7 sections, 1 theorem, 24 equations, 16 figures, 2 tables)

This paper contains 7 sections, 1 theorem, 24 equations, 16 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Grid Synchronization Problem and Standard PLL Solutions
  3. An Observer-based Synchronization Method
  4. Simulation and experimental results
  5. Simulation results
  6. Experimental results
  7. Concluding Remarks

Key Result

Proposition 1

Consider the grid-connected VSC system sys_abc and its $\tt dq$ representation sys, sysx. Define the dynamic extension and introduce the signals where $F({\bf p})={\lambda \over {\bf p}+\lambda},\;\lambda>0$, is an LTI filter. Define the estimate of the state $x$ as where $\hat{{\boldsymbol\theta}}$ is generated by the least-squares parameter estimator with $F(0)={1 \over f_0} I_3$ and tuning

Figures (16)

  • Figure 1: Block diagram representation of the SRF- and ATAN-PLL schemes.
  • Figure 2: The structure of the proposed estimation method.
  • Figure 3: Block diagram representation of the system \ref{['sys']} and the proposed control scheme.
  • Figure 4: Responses of $\tt{dq}$ currents and angle $\varphi$, facing an active power step variation from $P_1^\mathrm{ref}$ to $P_2^\mathrm{ref}$.
  • Figure 5: Responses of $\tt{dq}$ currents and angle $\varphi$, facing an active power step variation from $P_1^\mathrm{ref}$ to $P_2^\mathrm{ref}$ and a step change in $V_g$ under both proposed PEBO-PLL and conventional PLL schemes.
  • ...and 11 more figures

Theorems & Definitions (1)

  • Proposition 1