| With the development of economy and technology, the distributed energy system, which is directly oriented to the users, simplifies the energy transportation and improves the security of energy supply, gradually becomes a powerful complement for centralized power supply. The small residential photovoltaic power generation, which not only has the typical characteristics of distributed energy system, but also provides renewable and clean energy, will become the new direction of future energy development.The small and efficient photovoltaic grid-connected system with automatic tracking and concentrating system is studied as the research object in this paper, which includes solar panel tracking and concentrating system and grid-connected generation system.Tracking and concentrating part: for the problems of receiving low light intensity of fixed installation of solar panel or single-axis tracking mode, a kind of automatic tracking and concentrating system is designed in this paper, which use the plane mirrors to reflect the sunlight. Compare with the concentrating without plane mirrors, the automatic tracking and concentrating system designed in this paper can make photoelectric conversion efficiency increased by 30%. Its structure is simple, and it have low manufacturing cost. Photovoltaic grid-connected generation part: the two stage structures of photovoltaic grid-connected generation system with storage battery which is used as a power buffer is designed. The first stage circuit is DC/DC converter, which achieves maximum power output control and control for battery charging and discharging. The second stage circuit is DC/DC-DC/AC grid-connected converter, which is composed of push-pull DC/DC converter and DC/AC inverter, to realize conversion of electrical energy. For the strong nonlinear output characteristics of photovoltaic cells, the MPPT control algorithm based on fuzzy variable step is proposed with comparing and analyzing several conventional maximum power tracking algorithm. It enables the system to quickly track the maximum power point and improves the energy conversion efficiency of photovoltaic system. For the problems of nonlinear characteristics and resonant of single-phase photovoltaic grid-connected inverter with LCL filter, the three-closed loop control strategy which consists of DC side voltage outer loop, grid-connected current inner loop and capacitive current inner loop based on quasi-PR control is presented, and the discretization method of quasi-PR control are given. For the quasi-PR controller of fixed parameters are unable to adapt to changes in power network parameters, and the system control performance cannot be optimized. A quasi-PR control method based on DRNN of self-tuning is presented and its learning algorithm are given. For self-tuning the parameters of quasi-PR controller by DRNN, it realizes the grid-connected current with zero steady-state error. It makes the small harmonic distortion rate of grid-connected current and fast dynamic response. The grid-connected current is in the same frequency and phase with the grid voltage, and the power factor is improved. The feasibility and effectiveness of the above algorithms are verified by the simulating results.On the basis of theoretical research and system design, the experimental prototype which power is 300 W is designed. The hardware design and software programming are completed, and system integration and testing are carried out. The running situations and the test results of the experimental prototype show that the technical indicators are achieved the design standard. The test results of the prototype show that the proposed control strategies are feasible and effective. The researches of this topic provide the strong theoretical basis for solving the control problems of small photovoltaic gridconnected power generation system and play an active role in the promotion and utilization of distributed energy. |
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