Abstract
The virtual synchronous generator (VSG), which emulates the essential behavior of the conventional synchronous generator, has attracted great attention. This paper proposes to analyze the harmonic resonance characteristics in VSG using the state-space model. The analysis is based on a full-order state-space small-signal model that fully considers the dynamic of the inner loops and the VSG-based outer power control loop. Participation analysis is used to point out the contributions of different states to the eigenvalues. Moreover, eigenvalue locus and singular value decomposition (SVD) are applied together to evaluate the impact of the inner loop parameters on the harmonic resonance characteristics around the LCL filter resonance frequency. The analysis indicates that the harmonic resonance instability is mainly caused by decreasing the proportional gains of the current loop and the voltage loop. Finally, extensive numerical simulation and experimental results are given to verify the validity of the theoretical analysis. Both the simulation and experimental results indicate that the voltage of the common coupling point is unstable after decreasing the proportional gains of the current and voltage controllers. As Kpc decreases from 5 to 0.4 or Kpv decreases from 0.6 to 0.2, the harmonic distortion factor (HDF) around the LCL filter resonance frequency increases. Furthermore, the consistency of simulation results, experimental results, and the theoretical analysis results is validated.
Highlights
The increasing integration of renewable energy sources (RESs) has received significant attention [1]
The rest of this paper is organized as follows: Section 2 provides the state-space model that fully considers the dynamic of the inner loops and the virtual synchronous generator (VSG)-based outer power control loop
The VSG control in References [27,28] contains inner loops, but only the outer power loops are taken into consideration when building the small-signal model and conducting the small-signal analysis
Summary
The increasing integration of renewable energy sources (RESs) has received significant attention [1]. The influence of VSG numbers and outer loop parameters on the VSG-based multi-terminal direct current (VSG-MTDC) systems is intensively studied by SVD and modal analysis in [26] This method has not been presented for VSG to uncover the constraints in inner parameters. The rest of this paper is organized as follows: Section 2 provides the state-space model that fully considers the dynamic of the inner loops and the VSG-based outer power control loop.
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