Research On The Control Strategy Of Parallel Micro-sources

The technology of micro-grids is an efficient and feasible way for the utilization ofdistributed energy. However, the using of power electronic converters increases theinterface control flexibility of distributed resources and decreases parallel system’sinertia, what will cause difficulty on achieving micro-grids’ energy and frequencybalance. Thus, the micro-grids must solve the problem that how to controldifferent-capacity parallel micro-sources. The safe and steady operation ofdifferent-capacity parallel micro-resources is a burning question and this paper will putemphasis on it.In order to achieve the stable operation of different-capacity parallel micro-sources,the existing control strategies for parallel micro-sources are comprehensively introduced,and the operating principle is studied through building the parallel micro-sources’simulation model. Then the paper proposes an improved droop control strategy imitatingthe control method of different-capacity synchronous generators. By adopting theimproved control strategy, the active power and reactive power can be automaticallyallocated by ratio of micro-source capacity, and the micro-source in micro-grids has thefunction of plug and play. In that way, the flexibility of distributed generator’sinterconnection is improved, and the technological problem of different-capacitydistributed resources’ interconnection is solved. To verify the proposed droop controlstrategy, simulation system based on MATLAB/SIMULINK and hardware circuit basedon DSP TMS320F2812are designed. The simulation and experimental results show thatthe modified control strategy can effectively keep inverter output voltage stable, improvethe following performance of inverter current, reduce the current harmonic distortion rateand make the different-capacity parallel micro-sources work stably under Static andtransient operation condition.