Research On Adaptive Droop Control Strategy For AC Microgrid

Improving the consumption rate of renewable energy is the key problem to be solved urgently in the large-scale grid-connection of new energy,and microgrid is one of the important ways to solve this problem.A good operation control strategy is the basis for the stable operation of the microgrid,this thesis is based on the state grid corporation's scientific and technological research project "considering a variety of source-grid-load flexible matching experimental microgrid planning,operation and platform demonstration".This thesis makes an in-depth analysis of the unbalanced power distribution,control delay and harmonic problems of traditional droop control,and studies the improvement scheme of droop control strategy.The control parameters of the droop controller depend heavily on the system parameters of the microgrid,when the load fluctuation,line fault or serious imbalance between supply and demand produce the phenomenon of weak grid,the performance parameters of the microgrid will produce time-varying and nonlinear changes with different severity levels,resulting in unbalanced power distribution,in severe cases,it may even cause a chain reaction and cause system instability.In response to this,a microgrid and droop control simulation model are first established,the system dynamic characteristics of microgrid operation under various working conditions are analyzed,and simulated analyze the adverse effects of nonlinear changes in system parameters on inverter power distribution.On this basis,the adaptive droop control strategy is proposed,and the neural fuzzy inference algorithm is used to compensate the inverter output adaptively,so as to improve the accuracy of the inverter power distribution;Secondly,a large number of inverter power and nonlinear load are connected to the microgrid,serious harmonic problems and time-delay problems caused by complex algorithm for droop control,quasi-proportional resonance control is used to track the fundamental wave and the harmonic wave of AC respectively,and the time delay is improved by reducing the calculation amount,and harmonic droop control is used for harmonic suppression;Aiming at the complex control structure and coupling problem caused by the superposition control algorithm of different harmonic frequencies,the quasi-proportional resonance control and repetitive control are combined to improve the comprehensive suppression ability of harmonics.The algorithm is validated on the MATLAB platform and RT-LAB semi-physicalsimulation platform,and the experimental results verified the effectiveness of the algorithm.