Research On Parallel Circulation Suppression Control Method Of Three Phase Current Source Rectifier

With the increasing demand for power supply equipment,it is urgent to study the technology to improve the capacity and reliability of power supply.Pulse width modulation(PWM)converters have a wide range of applications in the industrial field due to their high power factor,bidirectional flow of energy,and low harmonic content.According to the types of energy storage elements on the DC side of PWM converters,PWM converters can be divided into voltage source converters and current source converters.Current source converters have the advantages of relatively better performance than voltage source converters,such as fast dynamic response,high reliability,and wide output voltage range.In order to improve the capacity and redundancy of power supply equipment,PWM converters can be connected in parallel.The parallel PWM converter technology is widely used in electric vehicles,uninterruptible power supplies and other occasions,and has broader application prospects.However,due to the difference in hardware parameters of parallel modules and the asynchronism of working state,the current circulating between parallel modules will be generated.The current circulation will affect the stability of the system operation,reduce the power quality of the parallel system,and pollute the power grid.Therefore,it is of great significance to study the current circulation technology of suppressing the parallel current source PWM converter.This paper first analyzes the working principle of the three-phase current source rectifier,obtains the switching function of the three-phase current source rectifier,and obtains the three-phase current source in the three-phase static coordinate system.The mathematical models of the three-phase current source rectifier under the three-phase stationary coordinate system,the two-phase stationary coordinate system,and the two-phase rotating coordinate system are obtained.According to the mathematical model of the three-phase current source rectifier in the two-phase rotating coordinate system,the double closed-loop control scheme of the three-phase current source rectifier is designed,and the passive damping method is used to suppress the resonance generated by the LC filter on the AC side.The space vector modulation strategy of the current source rectifier is analyzed in detail.Next,a mathematical model is established for the parallel system of three-phase current source rectifiers,the DC side equivalent circuit of the parallel system is established,the positive and negative DC bus circulating current expressions of the parallel system are obtained,and the factors affecting the size of the circulating current are analyzed.In order to solve the circulation problem of parallel three-phase current source rectifier,a current suppression scheme without communication line based on virtual impedance was proposed,which reduced the circulation by changing the external characteristics of parallel module.The simulation of parallel system by MATLAB/Simulink proves the effectiveness of the proposed circulation suppression scheme.Finally,the main circuit of the three-phase current source rectifier is designed,and the control circuit with TMS320F28335 DSP and Xilinx XC6SLX9-2TQG144 C FPGA as the core control chip is designed.The experimental study on a three-phase current source rectifier verifies the effectiveness of the designed double closed-loop control method and space vector modulation strategy.