Research On AC-Link Based Energy Storage Converter

With the depletion of traditional chemical energy sources such as oil and natural gas,the environmental pollution problems,resource allocation problems,and structural aging problems it causes are becoming more and more serious.Domestic and foreign countries have paid sufficient attention and attention to the development and utilization of new energy.However,new energy power generation represented by wind energy,solar energy and other renewable energy sources is extremely intermittent and unstable,which has a certain impact on the safety and stability of power grid operation.Energy storage converters track charge changes in real time,Adjusting the charge and discharge power of the energy storage system can effectively suppress the power fluctuation of the new energy power generation system,reduce the impact on the power grid,and enable the new energy to be flexibly connected to the grid.This paper proposes a new energy storage converter based on high-frequency AC link technology(AC-Link),which has the power of two-way flow of traditional converter and adjustable power factor,with high switching frequency and high frequency isolation and harmony The advantages of low waves.First,the application status and topological structure of the energy storage converter are analyzed and researched.At the same time,the related development of the AC link technology used in this paper is briefly introduced.By comparing and analyzing the four types of converters based on AC link technology The topology and its characteristics finally select the series resonant high-frequency AC-Link converter as the main circuit topology.Then,according to the topology of the energy storage converter,its working principle is analyzed in detail,the corresponding equivalent circuit is established,and the main working waveform of the converter is given.On this basis,the control target of the energy storage converter in each operation mode is further analyzed,and a PWM strategy for modulating the instantaneous voltage is proposed according to the charge distribution idea,and combined with the control idea of the traditional energy storage converter The control system under each operation mode is designed reasonably.Finally,a simulation model is built through the Matlab / simulink software platform to verify the correctness of the topology and control strategy.The simulation results show that the converter can run stably under three conditions: grid-connected,off-grid and charging.Under grid-connected conditions,the power factor of the grid-side current is close to 1,and the harmonic content is 0.78%.In the case of grid dispatching,the current has completed 20 degrees of phase adjustment within 0.005 s,and the response is faster and the transition is smoother;under off-grid conditions,it can stably output 380 V 50Hz three-phase AC power,and the load voltage harmonic content 0.62%;under charging conditions,the output voltage is adjustable within a certain range,the grid-side power factor is close to 1,and the grid-side current harmonic content is about 2.2%.In addition,the control program of the converter is written based on the DSP chip TMS320F28377S.