Abstract
Aiming at the problem of power coupling and complicated decoupling in the d-q coordinate system of a three-phase grid-connected inverter, a current closed-loop control strategy based on an improved QPIR (quasi-proportional integral resonant) controller in the α-β two-phase static coordinate system is proposed. Firstly, the mathematical model of an LCL three-phase grid-connected inverter is established, and its instantaneous power calculation equation is deduced. Secondly, the frequency method is applied to compare and analyze the proportional resonant, quasi-proportional resonant, and improved current controller, and the appropriate improved controller parameters are obtained according to the traditional proportional integral controller parameter design method and the weight coefficient. Finally, the improved controller is compared with the traditional controller in the simulation model of the LCL three-phase grid-connected inverter based on active damping. The results show that the proposed improved current control strategy has good dynamic response characteristics, can realize the non-static error control of grid-connected current, and realizes the decoupling control of active power and reactive power when the load jumps. At the same time, the results also prove the superiority of the proposed control strategy and verify its effectiveness.
Highlights
High power factor and low grid-connected current total harmonic distortion are common requirements for grid-connected inverters [1,2,3]
This paper studies the controller of the three-phase LCL grid-connected inverter in the α-β coordinate system
An improved current control strategy (QPIR) for a three-phase LCL grid-connected inverter based on active damping is proposed, and the simulation and example analysis were carried out using MATLAB/Simulink software
Summary
High power factor and low grid-connected current total harmonic distortion are common requirements for grid-connected inverters [1,2,3]. In the d-q coordinate system, all control variables are DC flow, the classical PI controller can be used to realize the non-static error control of grid-connected current, and the implementation method is flexible and simple, so it has been widely used. For three-phase LCL grid-connected inverters, few studies consider the steady-state error of grid-connected current and the power grid frequency fluctuation at the same time, and relevant control technologies need further research. This paper consists of the following parts: In Section 2, the mathematical model of the LCL three-phase grid-connected inverter is established, and the advantages of independent power control in the α-β coordinate system are pointed out. MMaatthheemmaattiiccaall MMooddeell ooff tthhee TThhrreeee--PPhhaassee LLCCLL--TTyyppee GGrriidd--CCoonnnneecctteeddIInnvveerrtteerr. As can be seen from Equation (3), there is no coupling in the two-phase static coordinate system three-phase LCL grid-connected inverter This advantage can be fully utilized to decouple the active power and reactive power. The LCL type three-phase grid-connected inverter will be directly controlled in a two-phase stationary coordinate system
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
