| Power demand increases continuously, fossil energy is slowly depleted, energycrisis and environmental issues have become increasingly serious, the worldwideelectric power industry faces severe challenges, and microgrid technology has derivedfrom the distributed generation. The flexible operation mode and high quality powersupply service of microgrid must have perfect control system.Therefore,it has greatsignificance to research the control strategy of microgrid.The State Grid Corporation of Henan province microgrid pilot project as the basisenabled the research of photovoltaic and energy-storage hybrid microgrid integratedcontrol strategy theory and simulation analysis, and it is successfully applied to theactual power system. The project is the first domestic contain photovoltaic powergeneration and energy storage microgrid pilot project, and has made effective attempt tothe operation and control and laid the important foundation for microgrid’s furtherstudy.Based on PV principle,its mathematical model is established,and PV powergeneration of operation characteristic is researched. After the analysis of perturbationand observation, incremental conductance algorithm, constant voltage tracking,quadratic interpolation and fuzzy control algorithm, a MPPT control of combiningconstant voltage tracking with perturbation and observation is proposed. According tothe principle of inverter, current control is used to real time controlling the inverteroutput current and achieving the goal of power grid. Energy storage battery has theadvantages of fast response characteristics. It can use constant PQ control when paralleloperation, but also be used for constant V/f control when island operation,and play thefunction of charging and discharging.The simulation model of photovoltaic and energy-storage hybrid microgrid is builtunder Simulink software, whose characteristics is studied. On the basis of master-slaveoperation and peer-to-peer control, the coordination control strategy of photovoltaic andenergy-storage hybrid microgrid is proposed. Based on the control strategy, microgridcan effectively control the grid-connected inverter and output specified power when ingrid-connected operation, and can provide voltage and frequency support when underisland operation. And then, the control strategy is tested to be correct through differentexamples in simulation software. Considering microgrid in two typical operating mode between frequent switching,the thesis has studied the function and implementation of the principle of microgridsystem controller which includes automatic parallel and islanding detection isolation.Analysising the influence of voltage amplitude difference, phase difference andfrequency difference on the system when paralleling grid, comparing comprehensivelyof multiple islanding detection method features, the logic diagram and related criteria ofcontroller are summarized.Last, the overall survey of microgrid pilot project is described. After a period oftwo months of trial operation as well as several times online test, microgrid systemusing integrated control strategy can achieve PV and energy storage complementary,island stable operation and smooth switch, and certain practical experience formicrogrid control technology further research is accumulated. |
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