Analysis and improvement of the control strategy of LCL grid-connected inverter based on split-capacitor

Among the existing current control methods of LCL grid-connected inverter, the split-capacitor method is a single current feedback control approach, which can achieve low steady error and THD of grid current. However, the resonant problem of LCL filter still exists in the traditional splitting capacitor method. Through analysis of the deflation progress of the splitting capacitor method, the cancelled poles are proven to be critical steady poles. The characteristic make the close-loop system incompletely controllable because the signal component at resonant frequency is not included in the current feedback signal. By introducing the equal-ratio passive resistors in series with capacitor branch, deflation is satisfied while the resonant problem of the LCL filter is solved. For better attenuation of the grid voltage disturbances, the voltage feed-forward strategy is derived. The result of simulation and experiment verifies the theoretical analysis and effectiveness of the proposed method. ©, 2015, The editorial office of Transaction of China Electrotechnical Society. All right reserved.