Research On Key Technologies Of Power Conversion System Based On Chain Energy Storage

With the rapid development of clean energy power generation technologies such as wind power and solar energy,energy storage power stations,as places for energy storage,participating in energy regulation of the power system,have become an important part of the power system and played an increasingly important role in the safe operation of the power system.Taking the power generation side for example,wind power generation and solar power generation are greatly restricted by environmental factors such as wind and light condition.In order to ensure the effective consumption of power generation and reduce the wind and light curtailment,it is particularly necessary to set up corresponding energy storage facilities for power supply.When the load of the power grid is low,the energy storage battery can store the electric energy that cannot be absorbed temporarily.When the network load is large,then the stored electricity is transferred to the power grid.The energy storage battery of the energy storage power station has the characteristics of modularity,which is more suitable for the use of chain energy storage technology.Therefore,it is of great practical significance to study the key technologies of power control systems based on chain energy storage.This paper researches the structural topology and grid-connected control technology of the electric vehicle battery replacement station chain energy storage system.Simulation and experimental results verify the correctness of theoretical analysis.1.The structure of the chain energy storage system is given and its basic AC/DC conversion unit is analyzed.The problems of the most common full-bridge AC/DC converter unit is analyzed.A new no dead-time AC/DC converter unit is proposed.The working principle is discussed and the detailed working models are given.Harmonic analysis proves that the proposed no dead-time AC/DC converter unit can effectively reduce the current harmonics during grid connection.The harmonics can be improved by 1.8%.2.The traditional Space Vector Pulse Width Modulation(SVPWM)grid-connected control technology is improved.A corresponding semi-period control method is given for the proposed dead zone AC/DC conversion unit.Considering the influence of non-ideal power grid,a reactive power closed-loop frequency tracking technique is proposed.Automatic tracking of grid frequency is achieved by closed-loop control of active and reactive power in a rotating coordinate system.It can effectively avoid the phase-locking error caused by non-ideal power grid,so that low-harmonic grid connection can still be realized under non-ideal grid conditions.In the condition of non-ideal power grid presented in this paper,the harmonic improvement effect can be increased by 5.2%.3.In order to solve the problem that the impact of grid connection of power electronic systems,the virtual synchronous motor control technology is presented.The chain energy storage system is equivalent to synchronous generator.The mathematical model of the system is established,and the control strategy of the synchronous motor is simulated to carry out the chain energy storage system.The inertia of the system can be effectively increased.Flexible grid connection of the system can be realized.System stability analysis are given to prove the reliability and effectiveness of the system.On the basis of theoretical analysis,a simulation model based on MATLAB/Simulink and a prototype of small power in the laboratory conditions are built to verify the theoretical analysis.The simulation and experimental results show that the power control system based on chain energy storage studied in this paper can achieve high performance and reliable grid connection.