| The rapid development of modern power electronic technology promotes the continuous innovation and change of power electronic devices.PWM rectification technology is a new type of rectification technology based on fully controlled devices.Compared with traditional rectification technology,PWM rectification technology not only achieves controllable AC/DC conversion performance,but also realizes unit power factor operation,sinusoidal current control and energy bidirectional transmission.Based on the theory of three-phase voltage source PWM rectifier,the traditional direct power control system(DPC)of three-phase voltage source PWM rectifier is studied more deeply in this paper.Firstly,according to the topological structure of three-phase voltage-source PWM rectifier,the specific working principle and state of three-phase voltage-source PWM rectifier are analyzed.The mathematical model of three-phase voltage-source PWM rectifier in three-phase static ABC coordinate system is deduced by using Kirchhoff theorem,and the transformation matrix of the mathematical model in three-phase static ABC coordinate system to two-phase static de coordinate system and two-phase synchronous rotating FG coordinate system is given.According to the instantaneous power theory,the calculation method of instantaneous power is given and the power flow problem of three-phase voltage source PWM rectifier is analyzed in two-phase static de coordinate system.Then the traditional direct power control system is studied and analyzed.Based on the two-phase synchronous rotating FG coordinate system,this paper innovatively improves the traditional direct power control system,studies the relative magnitude of the influence of each switching vector on the power change rate in more detail,summarizes the fast switching table for fast power regulation and the slow switching table for slow power regulation,and re-divides a dynamic eighteen sectors.By introducing a three-state hysteresis comparator,a dual switching table direct power control system is developed,which can select appropriate switching table and switching vector according to specific power difference.The traditional direct power control system model of three-phase voltage source PWM rectifier and the improved model of double switching meter direct power control system are built in Matlab/Simulink.The results show that the improved double switching meter direct power control system improves the output characteristics of three-phase voltage source PWM rectifier and reduces reactive power ripple.Considering the difference between experiment and theory,this paper chooses the power module IPM model PS22A76 according to the actual conditions,and builds the experimental system platform of three-phase voltage source PWM rectifier.The experimental results show that the improved double switch meter direct power control system studied in this paper is effective and correct. |
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