Study Of Decoupling Hysteresis Current Control For Three-Phase Grid-Connected Inverter Based On Lcl Filter

Nowadays,due to the depletion of fossil energy,research and development of renewable energy power generation system has been becoming urgent.Among them,converting renewable energy into electricity and injecting it into the grid are a major and effective way.In such renewable energy gridtied system,the grid-connected inverter is one essential part.Its performance directly affects the quality of injected current and the prospect of renewable energy.Nonlinear boundary control technique can offer superior dynamic behavior and eliminate the LCL-filter resonance in the three-phase three-wire grid-connected inverter.However,the chattering might be aroused by the distorted intracycle voltage information in the control law.Moreover,due to the coupling of three phase circuit variables,it becomes worse when the nonlinear boundary controller is directly applied in three-phase three-wire inverter configuration.A hybrid decoupled current control scheme utilizing the decoupled predictive hysteresis capacitor current controller integrated with the linear grid current controller is proposed in the paper.First,the article introduces the principle of 60° DPWM in detail.On this basis,combined with the state space equation of the three-phase two-level grid-connected inverter in the abc stationary coordinate system,the virtual dual-buck circuit structure is derived for the decoupling of three-phase current.Second,two sets of independent switching criteria are established to determine the switching states of the two half-bridge arms.Based on the research of hybrid current decoupling control strategy for three-phase grid-connected inverter,the ac small-signal model of hybrid double-closed loop control system is established.The feasibility of resonance suppression by controlling capacitor current is theoretically analyzed.At the same time,by designing the parameters of the PID compensator,the purpose of improving the control bandwidth and stability of the system is achieved,and the robustness requirements of the system are met.In order to verify the correctness of the above theoretical analysis,this paper uses PSIM simulation software to build a 10 k W inverter simulation platform.In the simulation,the response characteristics of the system under decoupling and coupling conditions,under balance and unbalance conditions,and grid-side inductance changes are compared.Finally,a 1.5k W experimental prototype was made in the laboratory and tested in various working conditions,including experimental comparison of decoupling control and coupling control;system startup performance,transient performance and steady state performance.At the same time,under the condition of grid voltage balance and unbalance,and under different grid conditions,the feasibility and superiority of the proposed hybrid current decoupling control algorithm are verified.The experimental results agree with the theoretical analysis and simulation results.The simulation and experimental results fully verify the superiority and reliability of the hybrid current decoupling control strategy based on threephase grid-connected inverter.