A phase-compensated harmonic suppression method for virtual synchronous generator system in distorted grid

Power quality issues are challenging to deal with by conventional harmonic suppression methods in a virtual synchronous generator-based system connected to the distorted grid. To address this issue, a phase-compensated harmonic suppression method is proposed to effectively suppress the grid harmonic current for the virtual synchronous generator in the distorted grid. The phase-compensated harmonic suppression method is developed according to the Nyquist diagram to improve the harmonic control bandwidth and the system stability. With this method, the grid harmonic component is effectively suppressed, the Nyquist sensitivity distance of the system is maximized, the total harmonic distortion (THD) of the grid current is reduced from 8.53% to 2.97%, and the harmonic suppression response time is reduced from 10 cycles to 2 cycles, showing a better harmonic suppression performance.

I. Introduction

With the increase of the distributed generation (DG) integration, the virtual synchronous generator (VSG) has been extensively investigated. The VSG adds inertia and damping to the conventional droop control, providing effective frequency and voltage support for the power systems. Currently, research on VSG mainly focuses on inertia, damping, and other dynamic characteristics. Little research has been done regarding the power quality issues of VSG-based systems. For distributed power generation system, the grid current can be easily distorted by harmonic problems. These harmonics can create complex interaction problems between distributed generation networks and control systems, and even cause unpredictable equipment trips, especially in weak-grid situations [1]. The VSG should therefore take more responsibility in injecting high-quality power into the grid.