Research On Neutral-Point Potential Balance Of Bidirectional Inverter In 50kW Energy Storage System

With the continuous improvement of voltage levels in the power industry,three-phase invertersare widely used in power transmission and distribution systems,as AC-DC converters.Among them,the T-type threelevel main circuit topology is the most common.This article mainly studies the control strategy and neutral point potential balance of the T-type threelevel inverter.In line with the construction and operating principle of T-type threelevel inverter,this article recommended the basic theories of SVPWM and VSVPWM control strategies.The 50 k W inverter systems under the two control strategies were simulated respectively.On this basis,10 k W energy storage system test platform based on SVPWM controlled bidirectional inverter was built.The simulation results prove that voltage and current waveforms of the point of common coupling of the inverters under the two control strategies are ideal,but have the problem of potential fluctuation at the midpoint of the DC side.The test results prove that the inverter has fairly good steady-state and dynamic response.However,the DC voltage fluctuation is close to the critical value of the specified range and still needs improvement.Aiming at the DC bus mid-point voltage imbalance problem that appears in the simulation and test of the T-type inverter,this paper proposed an optimized fuzzy VSVPWM control strategy based on the ant colony algorithm.Firstly,based on the traditional VSVPWM modulation strategy,this new control strategy refined the sector distribution,redistributed the time sequence of output voltage vector,and increased fuzzy control factor D to control the action time of vector.Then,the three memberships of triangular membership function,fuzzy control rules,as well as quantization and scale factors are simultaneously optimized by ant colony algorithm.Finally,in the path construction,the algorithm optimized the probability transition function and effectively prevented the ant colony from falling into the local optimal state.The simulation results prove that the parameters of the fuzzy controller optimized by the ant colony algorithm are applied to the T-type inverter system,so that the point potential fluctuation difference in the system is controlled within the allowable range,and the optimized system prove to be great in dynamic response and static properties.