Study On An Integrated Control Strategy Of Active And Reactive Power For The Grid-Connected Pv System

Facing with the world’s energy crisis and highlight global environmental issues, more and more attention had been paid on clean and renewable energy, represented as photovoltaic generation technology. Generally, grid-connected PV systemsonly provide active power to the grid. However, in case of insolation is weak or itis at night,thegrid-connected PV system will stop the power supply to the grid, which will lower equipment utilization. To solve this problem,this paper uses an integrated control of active and reactive strategy based on instantaneous reactive power theory of grid-connected PV systems, while achieving active power provide to the grid and reactive power compensation. Without an increase in special cases of reactive power compensation equipment and improve the economy of the PVsystemFirstly, according to the mathematical expression of photovoltaic cells, the simulation model was establishedin MATLAB/Simulink. The nonlinear characteristics of photovoltaic cell among the output voltage, current and power were analyzed,while the temperature and light conditions changing. The realization of the principle of maximum power point tracking (MPPT) method was introduced, and self-tuning fuzzy rules was applied to the photovoltaic power generation system MPPTbased on the traditional fuzzy control.Combined with several common MPPT methods, comparing simulation were carried out and verified the effectiveness of MPPT method based on self-tuning fuzzy rules. In responding to environmental catastrophe, the MPPT method also showed good adaptability. The PQ constant power control theory was introduced at the same timeand built a PQ control model to verify the operation characteristics of PQ control with a unity power factor.Secondly, the instantaneous reactive power theory and the inverter control method were introducedand analyzed,the realization of reactive power compensation for the photovoltaic generation system was theoretical discussed. On this basis, simulatedand verified the feasibility of harmonic and reactive current detection techniques based on instantaneous reactive power theory.The simulation result shows that the reactive power compensation realized effectively and responded quickly.A simulation model of grid-connectedPVpower conditioning system with active power supplied and reactive power compensation was established. The photovoltaic system affect to the power of distribution gridunder two operating conditionsof daytime and at night were simulated. Simulation results show that,atthe time of night,the grid-connected PV system with reactive power compensation function for reducing transport reactive power, increase system utilization, increase the load voltage level has a significant effect.Finally, the PV island phenomenonwas researched. Several commonly used active islanding detection methods for the grid-connected PV system were introduced and discussed theses’ principles, advantages and disadvantages. A model for islanding detection based on Slip-Mode Frequency Shift method was established to detect and simulation control the island phenomenon.