Research And Development Of 3kW Photovoltaic Power Generation System Based On Fuzzy Control

Nowadays,the shortage of fossil fuels and the pollution of the ecological environment have become an important factor limiting the sustainable development of society,with the rapid increase of the world is population and the rapid growth of the social economy.These have become urgent problems to be solved that we vigorously promote renewable energy,reduce the use of traditional fossil fuels,and improve the natural environment.On the other hand,the solar energy,which is extensive distribution,non-pollution and never exhausted,which has been widely used and studied and developed into the important way of achieving sustainable development in today's society.According to remote areas using electricity with the difficulty,this paper established the two-stage structure of a independent photovoltaic power system,introduce the working principle of DC level and inverter level of independent photovoltaic power generation system,established switching cycle average model for DC and inverter stages,the MPPT control algorithm and voltage regulator control algorithm are studied.The stability of the constant voltage zone and the constant current zone is analyzed and compared.The correctness of the theoretical analysis was verified through simulation and experiments.The specific research content is as follows:This paper introduced the principle of photovoltaic cells,deduced mathematical models and engineering models.In Matlab/simulink,according to its engineering model,the simulation model of the photovoltaic cell is built,the P-U and I-U curves were obtained.The working principle of MPPT technology is studied,the three commonly used MPPT methods are introduced and simulated to compare the dynamic performance and stability accuracy.Theexisting problems in MPPT technology are clarified and the main research contents of this paper are determined.A mixed control strategy based on ?-Parameter is proposed in this paper according to the photovoltaic cell mathematical model in order to reduce misjudgment and oscillation at maximum power points(MPP)under traditional power prediction algorithm when illumination changes suddenly.The tracking process is divided into two phases with the value of ?.At different phases,the variable step perturbation method and the fuzzy control method are used to track the MPP accurately so as to avoid the misjudgment when the light is not uniformly changing.Through theoretical analysis,simulation and experimental verification.The proposed strategy can avoid power misjudgment,improve system steady-state performance and reduce output power and voltage fluctuations.The tracking time is shortened to 40 ms,and the voltage fluctuation rate is reduced to 1.67%,which effectively improves the accuracy and stability of the MPPT algorithm.Introduced the topological structure of the inverter stage and established its mathematical model.A double closed-loop PI control system with capacitor voltage and inductor current as the control volume was designed to perform system simulation.The results show that the double closed-loop PI control cannot follow the given value after the load mutation and the output voltage is unstable.Then the single-phase dq decoupling control is studied,and the switching cycle average model of the inverter stage in dq coordinates is established.Decouple the coupled power in the system,design the decoupled double closed PI loop controller and perform system simulation and experiment.The results show that the single-phase dq decoupling control can achieve no-deviation tracking after system disturbance,and meet the system index requirements.The topological structure of the independent photovoltaic power generation system was designed and the mathematical relationship between the DC bus voltage and the system energy was deduced,the control strategy of the DC level using the MPPT mode and the constant voltage mode was determined.ADC-level mathematical model was established to analyze the stability of the constant current zone and the constant voltage zone.The stability of the system in the constant voltage zone was obtained,and the steady-state simulation and experiment of the traditional PI control was performed.The results show that after the load is cut,the system will oscillate,when the power and voltage levels increase,the oscillation will cause serious system shutdown.It is difficult to make the independent photovoltaic power generation system have good dynamic response and steady-state accuracy.According to the D-V curve of photovoltaic cells,a duty cycle disturbance voltage stabilization method is proposed.Through the perturbation of the duty cycle,the working point of the photovoltaic cell is changed,make the system energy become balancing,and the DC bus voltage is stabilized.Finally,experiments were conducted in the constant current zone and the constant voltage zone.The results show that:(1)In constant voltage mode,the stability of the system in the constant pressure zone is better than that of the constant current zone.(2)Using the duty cycle disturbance voltage regulation method can effectively solve the system oscillation problem after loading,and improve the dynamic performance and anti-interference ability of the independent photovoltaic power generation system.