| The shortage of the energy and the disadvantage of the traditional centralized generation system make the micro-grid technique be concerned. However, the realization of the function of the micro-grid system should base on the appropriate control strategy of the converters.In this thesis, the control strategies of converters connecting in parallel are analyzed and the advantages and disadvantages of the strategies are compared. In allusion to the operation requirements of the micro-grid system, the peer-to-peer control is selected as the key point of the study. The thesis analyzes the droop control particularly and illustrates the confirmation method of the droop parameters.By comparing and improving, the droop control strategy based on P-f and Q-V droop principle (the active power to the frequency, the reactive power to the amplitude) is selected. The control scheme which is appropriate for practical project is designed combined with decoupling control strategy of the practical converter. In theory, the converters connected in parallel with the droop control strategy can realized peer-to-peer operation and the stable operation in both grid-connected and islanding modes. The converters also can switch between grid-connected mode and islanding mode seamlessly and the output of the converters can follow the active power and reactive power of the load. The feasibility of the control scheme is analyzed by simulation in Matlab/simulink. The improved method considering the influences of the line impedance and the unbalance load and is simulated in Matlab.Because of the peer-to-peer control strategy of the converters connected in parallel is applied in micro-grid system, the thesis does the further deep going studies based on the systematic level. The platform of connecting system is constructed using King View6.53and CAN communication as the monitoring and controlling system. The program of droop control is realized based on DSP28335and the experimental study are done in the platform. |
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