Research On The Engineering Simulation Model And The MPPT Algorithm Of PV Cells

With increasing contradiction between demand of energy and environmental protection due to rapid development of global economic, the technology of photovoltaic(PV) power generation has been widely concerned. And a practical simulation model of PV cells as well as an efficient maximum power point tracking(MPPT) algorithm are significant in the popularization and application of the PV power generation. To this end, this paper mainly investigated the simulation model of the PV cells and the MPPT algorithm.In the conventional 4-parameter behavior model and modifier formulas of performance parameters, the simulation curves are not in agreement with the temperature characteristic of PV cells when the compensation coefficient is set as typical recommended value. To resolve it, an advice for setting temperature compensation coefficient has been proposed combined with simulation results, after summarizing the coefficient measured values from the data sheets of the actual PV cells and the adjustment results of the compensation coefficient in literature. In view of the shortage of existing simulation model of the PV cells, a practical simulation model encapsulated into a hardcover subsystem has been developed in Matlab/Simulink. The simulation model has good portability and convenience. And the simulation results indicate that the model can simulate the physical characteristics of PV cells accurately under different environment conditions by setting the compensation coefficient correctly according to the advice.Tracking the maximum power point(MPP) in varying irradiation, the power prediction method can avoid misjudgment successfully. However, the single tracking scheme may cause unnecessary power oscillation around the MPP when the tracker is closely following the changing MPP in varying irradiation. At the same time, the oscillation makes the work point deviate from the MPP, resulting in unnecessary power loss. To counter this problem, this paper improves the power prediction method. The criterions of changes in the irradiation and the work point position have been added into the modified method. In the proposed algorithm, two kinds of tracking schemes are employed to track the changing MPP in varying irradiation according to the change intensity of the irradiation and the work point position. In the work point position criterion, a threshold is set to divide the ranging of work point into two areas which are named ‘near MPP’ and ‘away from MPP’. And the calculation formula of the threshold is derived in order to popularize the modified method. The modified algorithm is characterized by easy implementation in engineering, attributing to its essence of no extra difficulties aroused. The simulation results demonstrate that the proposed algorithm is able to avoid unnecessary power oscillation, and improve the efficiency and economic benefits of PV power generation system.