| With the development of the human society, the shortage of energy is becomingcritical. Solar energy is being popular nowadays for its clean and renewable characteristics.Due to the non-linear function of the operating voltage and power of the PV array, a PVinverter with the MPPT controller is essential in a PV system. The well known MPPTalgorithms are: Constant voltage, Perturb and observe, Incremental conductance, Fuzzylogic control, Neural network and the Partially Shadowed MPPT algorithm.An equivalent circuit model of the PV cell is founded by analyzing its principle. Thesimulation result under the Matlab/Simulink of the PV cell, presents the P-V and I-V curveunder varying solar irradiation and temperature. The model of the PV array under partiallyshadowed situation is built to optimize the distribution scheme which provides strongsupport for the engineering design of PV systems.A wide range input voltage MPPT algorithm is proposed because the MPPTalgorithm loses its effect when the PV input voltage is higher than the bus-bar voltage.Under low voltage situation, the duty circle of Boost circuit is perturbed, and under highvoltage situation the reference voltage of the bus-bar voltage is perturbed, also a hysteresisis introduced to avoid the frequent switch of the controller algorithm at the critical voltage.No matter under which situation this method is proved to be effective. Take the partiallyshadowed situation into consideration, an improved method is essential. Throughcomparing the equivalent output powerS pvi, the global MPPT interval is obtained. Thenthe MPPT algorithm is performed in the interval to find the global MPP.To verify the effectiveness of the improved MPPT algorithm, a PV inverter model isbuilt in the Matlab/Simulink; also a real3KW PV inverter is designed for experiment. Theresults of the simulation and the experiments demonstrate its advantages on the validity,stability and efficiency under high voltage, low voltage and dynamic situation. |
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