Research On Predictive Control Of Power Decoupling For A New Single-phase Voltage Source Inverter

Single-phase inverters are widely used in small and medium distributed grid-connected power generation systems.However,single-phase systems have an inherent second-order ripple problem,which poses a huge threat to the stable and reliable operation of the converter.This problem can be effectively resolved by connecting large-capacity electrolytic capacitors in parallel on the dc side,but the short lifetime and low reliability of electrolytic capacitors restrict the development of single-phase converters.Therefore,power decoupling technology without electrolytic capacitors has been a hot area of research in solving the problem of low-order ripple.Based on the single-phase voltage source inverter with the fucntions of voltage-boosting and power decoupling proposed by the research group,this dissertation carries out research on the power decoupling control algorithm.The specific research contents and results are as follows:1.Firstly,the principle of the new single-phase inverter topology to achieve voltage boosting and power decoupling is analyzed.Based on this,a power decoupling control method based on the input current prediction model is proposed.This method eliminates the low-order ripple on the dc side by directly predicting the input current of the inverter’s front-end stage,thereby realizing the power decoupling function.At the same time,a moving average filter and a voltage ripple compensation unit are introduced in the double closed-loop control which includes an inner current loop and an outer voltage loop,thereby eliminating the impact of the dc-link voltage ripple caused by power decoupling on the output current quality,and satisfying THD design requirements.2.The corresponding robustness and stability analysis of the proposed control algorithm is discussed,which provides a basis for the parameter design of the controller.Simulation results verify the effectiveness of the proposed control strategy under the conditions of ±50% change in inductance and ±20% change in capacitance.3.Furthermore,the harmonic transmission mechanism under power grid with background harmonics is investigated,and the result shows that under the double closedloop control the transmission mechanism of the background harmonics is the same as the one caused by the dc-link voltage ripple.Therefore,it proves that the proposed control algorithm is still robust under the condition of power grid with background harmonics.Simulation and experiment results prove the correctness of the theoretical analysis.4.Physical experimental platform and the RT-LAB-based hardware-in-the-loop experimental platform are built,respectively,and the control method proposed in this dissertation is experimentally verified.The experimental results show that the pulsating component of the input current is almost totally eliminated,and the setting time of power decoupling control during transients is less than 1ms.5.Comparison between the proposed control algorithm and the PMR-control-based power decoupling method is conducted both in the simulation and the experiment.The corresponding results show that the proposed method has a better power decoupling performance in both steady-state and transient-state.