Study On Photovoltaic Grid-Connected System Based On Biological Network

With the advantages of non-pollution, non-noise, abundant resources and easy management, photovoltaic technology has a broad horizonand bright prospect for development.In this paper, an intensive study of major control problems in PGCS (Photovoltaic Grid-Connected System) is made, such as model of photovoltaic array, MPPT (Maximum Power Point Tracking) methods, DC/DC converter, advanced control strategies of inverter and so on.Accordingly the contents of this paper include as follows. First of all, introduction of basic structure and principle of photoltaic cell and testing output character is a foundation of whole solar generator system. A mathematic model of photovoltaic array at any temperature and solar intensity was established by analyzing nameplate parameter of solar panels. Secondly, the technology of tracing and control of maximum power point can greatly improve the efficiency of photovoltaic system. After analyzing the merits and demerits of useful method, such as perturb and observe algorithms, increment conductance and constant voltage tracking, a novel control strategy which used the ideas of fuzzy control and regulating immunity feedback rule is introducd. MPPT is achieved by controlling the duty cycle of PWM signal in boost DC/DC circuit. Thirdly, it is urgent and very significant to develop control strategy for photovoltaic grid-connected inverter to improve its stability. In this paper, a new control strategy based on NEI (Neuroendocrine-Immune) network is proposed for single-phase photovoltaic grid-connected inverter. Two-way hormone regulating mechanism of human NEI system makes various physiological indicators in a highly stable by the carrier of cytokines, hormones and neurotransmitte. Compared with conventional control method, NEI controller has a high performance of rejecting the load disturbance, repressing the AC current distortion, reducing the interference of noise, and improving the shape of current wave. Also, it has very well dynamic performance and steady precision.Finally, a summation is made to generalize the work in this paper. Theoretical analysis and computer simulation results demonstrate that bio-network-based intelligent control theory have broad application prospect in photovoltaic grid-connected system. In addition, suggestions are proposed for further research and improvement of photovoltaic grid-connected system performance.