Research On Inverter Control Of Large Capacity Energy Storage System Based On VSG

The randomicity and volatility of clean energy makes energy storage systems be irreplaceable in the large-scale development of clean energy.However,energy storage systems are generally connected to the power grid through a power electronic interface,with quick response and poor anti-perturbation.This paper analyzes the mechanical characteristics of synchronous generator and the characteristics of rotation,uses the vanadium redox flow battery as energy storage unit and proposes the inverter control technology of large capacity energy storage system based on virtual synchronous generator.Then the effectiveness of the control method is verified by simulation.Major research contents of this paper are as follows:1)This paper analyzes the structure of high-capacity,as well as the VRB,bi-directional DC/DC converter and grid-connected inverter.Meanwhile,mathematical model is establishes to analyze the structural similarity of synchronous generator and inverter.On this basis,the inverter control strategy adopted in this paper is proposed.2)To ensure the energy storage system has a rotational inertia and high output impedance,this paper adopts a VSG-based inverter control strategy for the energy storage system.Mechanism of mechanical characteristic and electrical characteristic of the synchronous generator are analyzed,as well as its frequency active power and voltage reactive power,so as to design the VSG algorithm,power frequency controller and excitation controller.Distribution of load power is also analyzed for the parallel operation of VSG-based multi energy storage units.Finally,system model is created on the MATLAB/Simulink simulation platform to verify the effectiveness of control strategy.3)The functions of inertia time constant and camping coefficient are analyzed,their setting methods are also discussed.Meanwhile,the capacity,dynamic response time and energy requirements of energy storage unit are also studied when the energy storage system is in the state of over damping,under damping and critical damping under the disturbance of distributed generation.