Effect of Errors in Maximum Power on Reliability Evaluation for Photovoltaic Modules

In this work, impact of maximum power errors on photovoltaic module reliability evaluation was studied through MATLAB simulation. In order to illustrate effect of power errors more clearly, the assumed measurement error values of power are -10%, -5%, -3%, 0, 3%, 5% and 10%. It is concluded that the smaller the error in maximum power, the more unreliability the photovoltaic modules. This can be proved by the changing trend of reliability function and failure probability density function. It is interesting to find that change of module failure rate includes two stages. In the first stage, failure rate increases as exposure time increases. Also, the smaller the error, the earlier failure occurs and the more drastic the increase in failure rate. However, in the second stage, failure rate decreases with time increasing. Meanwhile, after a certain year, the smaller the error, the smaller the failure rate. In addition, when the errors are -10% and 10% respectively, the difference of the mean time to failure can reach 69.6%, which may cause huge economic disputes for photovoltaic modules stakeholders. The obtained results in this paper indicate that more attention should be given to measurement error control in maximum power so as to carry out more effective reliability evaluation for photovoltaic modules.