Abstract
Distributed energy sources are usually interfaced to the grid using power electronic converters, and lack of inertia in inverter dominated microgrids can affect the system stability. This paper presents a new method for virtual synchronous generator (VSG) control in order to solve the low system inertia and support the grid frequency problem. In this paper, the VSG based on electromagnetic transient characteristics is improved and an adaptive command filter back-stepping controller is designed. Firstly, the rotor swing equation and power part are modeled to complete the controller design for achieving system stability in the islanded, grid-connected and transition modes. In addition, a limited-amplitude command filter is used to deal with computational complexity and nonlinear saturation problems in the design process. Secondly, projection operator, and adaptive inertia and damping control are introduced to reduce the modeling error and disturbance caused by changing parameters. This ensures the boundedness of the estimated value and further improves the frequency response, especially in the transition mode. Finally, simulation results show that the proposed controller is more effective than the traditional control method for achieving power stability and frequency improvement.
Highlights
The development of wind turbines, photovoltaic cells and other renewable energy sources has increased the importance of implementing optimal control, operation and grid-connection of distributed generation (DG) units [1,2,3]
In order to improve the frequency response of virtual synchronous generator (VSG) in the transition process, this paper focuses on the adaptive adjustment of virtual inertia and damping
Suitable parameters can be selected, which cannot be achieved in synchronous generator (SG), because the mechanical inertia is a constant related to the physical properties of the rotor
Summary
The development of wind turbines, photovoltaic cells and other renewable energy sources has increased the importance of implementing optimal control, operation and grid-connection of distributed generation (DG) units [1,2,3]. To deal with the instability in power grid operations in a system consisting of distributed energy sources, the concept of a virtual synchronous generator (VSG) was first proposed in [5]. To further improve the grid frequency response, virtual inertia and damping can be used for parameter design. In [14], the inertia response of a synchronous motor was simulated by the energy storage system, and the frequency and power changes were reduced based on an optimal parameter selection algorithm. It mimics synchronous generator and realizes the smooth change of system frequency with virtual damping and inertia. In order to improve the frequency response of VSG in the transition process, this paper focuses on the adaptive adjustment of virtual inertia and damping.
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