Research On Three-level Rectifier With Active Neutral Point Clamped

With the rapid development of modern power electronics technology,multilevel converter has become a hot research topic of power electronics technology in high-voltage and high-power field,because of the advantages of its little voltage stress afford by power device,high equivalent switch frequency,low switching loss and good output waveform,and has been widely used in medium and high voltage frequency conversion speed regulation system,AC and DC power conversion system,new energy power generation system,power quality analysis and other fields.Based on NPC topology of diode clamped three-level PWM rectifier,this paper constructs ANPC topology of active neutral clamped three-level PWM rectifier from the perspective of power tube loss balance.Firstly,this paper analyzes and compares the topological structure and working principle of the two,establishes the mathematical model of three-level PWM rectifier in three-phase static coordinate system and synchronous rotation coordinate system,which provides the theoretical basis for the design of the control system.In this paper,the voltage and current double closed-loop control strategy based on direct current control adopted by three-level PWM rectifier is described in detail.Aiming at the problem of neutral point potential fluctuation,a space vector modulation algorithm with small positive and negative vectors is adopted.For the control of power tube loss balance,a special power tube conduction sequence is adopted in this paper,which makes the current flowing through each power tube more balanced,thus realizing the purpose of loss balance of each power tube when the total loss is almost the same.The control strategy,modulation algorithm and neutral point potential balancing method of three-level PWM rectifier are all simulated by Matlab/Simulink,and results of simulation verify the correctness and feasibility of these control methods in theory.On the basis of theoretical analysis and simulation verification,experimental platform of diode-clamped three-level PWM rectifier based on TMS320F28377 has been constructed,and the hardware circuit and software program of the experimental prototype are designed.Experimental results verify the feasibility and effectiveness of the designed experimental prototype,which shows that the prototype has achieved the design requirements.