Harmonic Control Architectures for Virtual Synchronous Generator-based Distributed Generation Systems

The virtual synchronous generator (VSG) control has been widely used in wind power generation, solar power generation, and other aspects. At present, research on VSG mostly 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 caused by power generations, converters, and nonlinear loads. 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. The VSG should therefore play a more important role in injecting high-quality power into the grid. Although some research has been done to develop harmonic suppression methods for VSG, the reduction of the output impedance in most of the voltage-controlled harmonic suppression methods will result in an increase of the inrush fault current of VSG, which impairs the low voltage ride-through capability of the system.
In this sense, a harmonic suppression control architecture for VSG-based DG systems will be developed in this project to suppress both harmonic current and inrush fault current. The VSG control algorithm will be discussed in detail. The VSG-based hierarchical control strategy for DG systems will be developed to enhance the stability of the system. The power quality and component harmonic contribution of the VSG-controlled system will be analyzed, the harmonics and inrush fault current model of the system in both time and frequency domain will be developed. The harmonic and inrush fault current coordinated suppression approach of VSG will be proposed. System performance will be validated in the stand-alone mode as well as grid-connected mode, the simulation will be carried out in the professional software MATLAB and Digsilent, and experimental verification will also be implemented.