Control Strategy For Microgrid Distributed Power With Different Load

Traditional energy plays an important role on the development of humansociety. However, the traditional energy reserve is limited and non-renewable. It isestimated that the fossil energy will run out in the middle of the21st century. Withthe rapid development of the global economy, the energy demand is increasing yearby year, so the worlds are seeking to develop renewable energy. The Doubly-FedWind Turbines which have outstanding advantages become an important direction ofwind power field. The control technology of Doubly-Fed Wind Turbines is more andmatures. In this thesis, I research two questions, how to make the double-fed windgenerator (DFIG) and photovoltaic generator operate in the Micro-grid with the oddharmonic component which interfere the wind turbine and Micro-grid powerdistribution.The non-linear loads accessing the Micro-grid system will introduce the oddharmonic currents to the Micro-grid systems. The harmonic component destroysother user loads on the Micro-grid and Micro-grid system itself, which need to besuppressed. In this worst scenario by controlling the rotor side DFIG andphotovoltaic inverter output corresponding odd harmonics to suppress Micro-gridharmonic elements. So the harmonic current falls within the normal range in theMicro-grid. This control method uses a proportional-resonant (PR) instead of thetraditional PI control method to achieve harmonic attenuation. The PR controller canbe implemented in αβ coordinates to adjust sinusoidal signals without static erroradjustment. Which reduces the number of the signal coordinate transformat ion andremove cross-coupling term related with surrounding in the PI control a algorithm.In the Micro-grid power system the frequency and amplitude of grid voltagehave a certain mathematical relationships with the power in the Micro-grid, thusensuring a balance of system power can make the grid voltage amplitude andfrequency remain stable to improve power quality and assurance the doubly-fedwind turbines operating smoothly in the Micro-grid. But the user loads will berandom access or removal from Micro-grid.The total power will change in theMicro-grid, thus the allocation of distributed power will generate an impa ct for theMicro-grid system stability. Depending on the characteristics of the distributedgenerators, the droop control algorithm can be used to ensure all of the distributedgenerator output power equal to the sum of the power required by the load.