The Research Of Three-phase Grid Inverter Current Control Technology

The inverter as the power eletronic device is a significant component for thephoto voltaic power system. However, in order to prevent the situation that the powerelectronic switches turn on in one bridge, we usually add a dead time in the drivingsignal which will control the power electronic switches. But with this method, therewill be the harmonic waves in the output side of the inverter, which can be thepollution to the power grid. So that in this paper, we improve the output power qualityof photovoltaic by using reduplicate shunt PI control method, Space Vector PulseWidth Modulation（SVPWM）.According to the coordinate transformation for the mathematic model at thestatic coordinate system for the two-step three-phase inverter, we obtained themathematic model at the rotating coordinate system. Then we accomplish theseparation of the control for active and reactive power by decoupling the current inthe rotating coordinate system in d as well as q axis. Besides we designed thereduplicate and PI controller. Reduplicate control theory is based on the internalmodel principle in control theory. It is based on periodic compensating control, so thatit has a lot of advantages for example: good capacity of stability and robust, littleperiodic disturbance caused by the switch dead time. However, it also has thedisadvantages, such as the bad capacity of dynamic state, so in this paper, we combinethe two control methods together, using the reduplicate control to compress theperiodic disturbance, using the PI control to improve the capacity of the dynamic stateof the system. At last, we use Matlab/Simulink to establish the control model for thethree-phase inverter system, simulate the two conditions with reduplicate control aswell as without duplicate control. The result indicates that the two control methods areas implement， they not only modify the dynamic state capacity, but also obtain themore accurate static state wave of the inverter.