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In this paper control strategy of micro-grid, control system, system simulation areresearched deeply.Firstly, the control strategies of the grid-connected micro-grid system are researcheddeeply. In the introduction of droop control theory, this paper pointed out the differentpower distribution on linear load by using different droop Coefficient on the system ofmicro-grid; this paper realization on no differential regulation of paralleled DR micro-gridsystem on the control of variable frequency; this paper also compared all kinds of controlstrategies.Secondly, based on the operational principle of PV cells is analysised, the equivalentcircuit and performance characteristic are obtained. By comparising several traditionalMaximum Power Power Point Tracking (MPPT) control algorithms, gradual approximationcontrol algorithm is designed to achieve PV system of the maximum power output andimprove system performance and maximum power point tracking speed. Finally this paperused DDS technoloy to realize frequency tracking, phase tracking and MPPT of grid system.The structure and operational principle of PV grid-connected generate system are introducedin detail. Based on the requirement of PV grid-connected inverter, the best topology of PVgrid-connected system is chose.This paper designed a system of micro-grid, different control strategies were adoptedon different DRs, double closed loop control strategy of P/Q was adopted on DR1andmultiple loop control strategy on DR2. This paper completed the designing of SPWMcontroller, filter, phase detection, P/Q controller, f/P-V/Q controller, and switch parallelling.SPWM controlling is selected as the system control mode and method of equal precisionphase detection was also choosen, this papaer used DDS technoloy to realize frequencytracking and phase tracking in order to meet the requirements of grid.At the end of this paper, photovoltaic cells, single phase photovoltaic grid-connectedsystem, microgrid islanded mode in the control of constant power, system in f/P-V/Qcontrol were analyzed and simulated, the results showed that the control method andalgorithm meet the design requirements. Finally, this paper summarized the whole work,pointed out the deficiencies of the system, and prospected more work.