MPPT constraint conditions based on four-parameter cell model for some usual photovoltaic systems

Hitherto there is no work to specially analyze in detail the question when the maximum power point (MPP) of the photovoltaic (PV) system exists and when it disappears. It has caused the difficulty in the hardware and software designs of the PV system when the maximum power point tracking (MPPT) control must be implemented all the time. To solve this question, in this paper, the MPPT constraint conditions (MPPTCC) of the 12 usual PV systems are proposed under ideal conditions and expressed by the model parameters of the four-parameter cell model in the engineering application. They are the necessary and sufficient conditions to guarantee the existence of the MPPs of these 12 PV systems. Meanwhile, they also disclose the inherent relationships between load (or bus voltage) and cell parameters when the MPP of the PV system always exists. In addition, to apply them in practice, their expressions in practical application are also presented. Finally, some simulation experiments verify the reasonableness and accuracy of these MPPTCC in practical application, and test the influence of the varying weather to the MPPT range. By this work, the possible failure of the MPPT control arising from the occasional disappearance of the MPP of the PV system can be completely avoided. Therefore, the findings in this work can be used as the theory foundation for the hardware design, theoretical research and product installation of the PV system.