Effect of Eddy Current for Photovoltaic Module on Lightning-Induced Overvoltage Caused by Electromagnetic Coupling

Lightning electromagnetic field will induce a high voltage on the photovoltaic (PV) farm and also generate the eddy current. To study the effect of eddy current inside a PV module, the mechanism of the eddy current is elucidated. The density of eddy current is derived and it is solved by the method of moments. The eddy current produces a magnetic field to weaken the original field, which can reduce the lightning-induced voltage. The eddy current is mainly distributed on the outside surface of both aluminum-back surface field solar cells and aluminum foil. Moreover, the lightning transient of a PV array is computed. It is concluded that the PV backsheet cored with aluminum foil can greatly reduce the differential-mode-induced voltage of PV module. Several crucial factors, including foil material, foil thickness, and the distance to solar cells, are discussed. In order to minimize the induced voltages of PV modules, the PV module with aluminum foil on backsheet is proposed and the suitable range of the foil thickness is determined.