Single-stage Energy Storage System With Parameter Adaptive VSG Control Technology

With the increasing proportion of renewable energy represented by wind power and photovoltaic in the global energy structure,how to use renewable energy reasonably and efficiently has become an urgent problem to be solved.Energy storage system can absorb and release energy according to the instructions,so it becomes an important link to cooperate with the application of renewable energy.However,the sharp increase of installed capacity of renewable energy has put forward higher requirements for the voltage and capacity level of energy storage system.In view of this situation,this paper has researched on the single-stage H-bridge battery energy storage system.In order to improve the grid-connected friendliness of energy storage system and reduce the impact of power electronic devices on the stability of traditional power system,virtual synchronous generator control strategy(VSG for short),which simulates external characteristics of synchronous generator,has become an ideal choice for energy storage system control strategy.In this paper,the traditional VSG control strategy has been improved to improve the practical application of VSG such as parameter setting difficulties.Due to the inherent lowfrequency ripple current at the DC side of single-stage H-bridge when AC-DC power transformation is realized,long-term operation will lead to the battery heating and thus shorten the battery life.Therefore,this paper adopts Energy Spring(ES)at the DC side of single-stage Hbridge to absorb low-frequency ripple current.In this paper,the MATLAB/Simulink simulation model and experimental prototype of the three-phase eight-stage 380V/10 kVA single-stage Hbridge system are built,and research on the energy storage system is carried out.Firstly,the mathematical models of the AC side and the DC side of the single-stage H-bridge system are established and analyzed.Energy spring(ES)is used to absorb the low-frequency ripple current generated by AC-DC transformation on the DC side of single-stage H-bridge,and four working modes of ES are introduced.Secondly,on the basis of the traditional VSG control strategy,this paper introduces the firstorder inertia link in the reactive power-voltage control link,so that the output voltage of the energy storage system has inertia and is closer to the voltage characteristics of the synchronous generator.The energy storage system under VSG control can realize the switch between off-grid modes and grid-connected modes without changing the control strategy.In this paper,the pre-synchronization control method without phase-locked loop is adopted,which not only saves the phase-locked loop parameter design process,but also saves the controller resources.Then,for the core parameters of VSG,the of inertia J and the damping coefficient D,this paper presents a dual-parameter adaptive control method,as well as a dual-closed-loop control method of AC side and a phase-in-equalizing control method.Finally,the design process of main circuit parameters and controller of energy storage system is given,and the simulation model and experimental platform are built.Simulation and experimental results verify the effectiveness and accuracy of the energy storage system topology and control strategy.