Research On The Control Algorithm Of Three-Level PWM Rectifier Based On The IGCT Device

The multilevel topology structure, high power electronics device and high performance control strategy are the key factors for the development of high power converter. This paper compared three multilevel topological structures and chose three-level NPC PWM rectifier based on the IGCT device as the object of study. It studied the characteristic of IGCT, modulation methods and control strategies of three-level rectifier.This paper introduced the structure and working principle of IGCT device. It is pointed the existing problems and the solution of the control on three-level rectifier based on IGCT device by analysis of NPC three-level rectifier.It is emphatically analyzed the three-level SVPWM and SHEPWM methods. It derived the realization process of three-level N3V SVPWM method. For the neutral-point balance problem of three-level clamping rectifier, we analyzed the causes and proposed a kind of neutral-point control method basic on distribution factor. It optimized the space voltage vector switch sequence and derived three-level SVPWM N style switch sequence algorithm. By introducing the principle of three-level SHEPWM method, we list the three-level SHEPWM nonlinear equation and solved the equation with Newton iterative and "impulse quivalent" methods. It got the root locus of three-level SHEPWM equation when N=11and put forward to optimize the result of the equation with the function FSOLVE of Matlab, then introduced small vector substitution method to control the neutral-point voltage. Finally, we built the NPC three-level rectifier SVPWM and SHEPWM simulation modelings and proved the feasibility of the methods.Grid connected control strategy is an important technology in three-level PWM converter application. This paper respectively introduced two common grid connected control strategies—VOC and DPC. It analyzed the principle and realization schemes of the two control strategies. On one hand, it combined VOC and three-level SVPWM method. On the other hand, it optimized three-level DPC space voltage vector switch table. It compared two control strategies. Finally, we built NPC three-level PWM converter VOC and DPC simulation modelings and by analysis of the waveforms it demonstrated the features of the two grid connected control strategies. The simulation verified the feasibility of the scheme. We built25kW three-level converter experimental platform and verified the correctness of the simulation and calculation of three-level SVPWM and SHEPWM methods. We also completed the experiment on3MW IGCT three-level converter and verified the feasibility.