Research On Dynamic Phasor Model And Cooperative Control Strategy Of Microgrid

With the aggravation of the global energy crisis, the development and utilization of clean and renewable energy has become the focus of attention, thus the microgrid technology has been developed rapidly, it has become an effective way for grid-connected and local consumption of distributed energy. With the research of the microgrid gradually, new problems continue to emerge. Such as, the modeling and stability analysis of microgrid electromagnetic transient process is very difficult, the voltage unbalance at the point of common coupling(PCC) caused by the unbalanced load, the deviation of frequency and volt age amplitude caused by droop control, and the reactive power is difficult to share caused by voltage variation in AC island microgrid. Therefore, these problems should be studied and solved.Focus on the problem of complex microgrid model, established a d ynamic phasors model of grid-connected microgrid in this paper, in order to verify the correctness of dynamic phasor model, the electromagnetic transient model and dynamic phasor model of the microgrid is established on the Matlab/Simulink platform, and the simulation results show that the dynamic phasor model can quickly and accurately reflect the dynamic characteristics of the microgrid. According to the problem of the stability analysis of the islanded microgrid, established a dynamic phasors model of islanded microgrid in this dissertation, the singular perturbation theory is used to reduce the order of the model, and the Lyapunov direct method is also used to analyze the changes of different parameters in the system is how to affect the stability of the system, and the method is very effective to the microgrid system of nonlinear strong coupling. The simulation verifies the correctness of the theoretical analysis, determined the range of each parameter in the system. Meanwhile, the distributed hierarchical control method based on consensus algorithm is proposed. The average value of global variable is obtained by using the consensus algorithm and used to generate correction terms to adjust the primary control. Thus, the good control performance of the mic rogrid can be obtained even when the initial state of distributed generation(DG) is different. Finally, the impact on the communication delay is analyzed in detail. The Matlab/Simulink is used to simulate and verify the proposed control strategy in a low voltage AC microgrid system. Results show that the distributed hierarchical control based on consensus algorithm can compensate the unbalanced voltage of point of common coupling(PCC), restore frequency and voltage amplitude, ensures effectively sharing r eactive power of system. The system is still stable when there is a proper communication delay.