Analysis of photovoltaic modules with protection diodes in presence of mismatching

Simulation was used to investigate the electrical status of photovoltaic (PV) array components in mismatching conditions, leading to general rules for shaded PV array modules with bypass diodes. In particular, it is shown that, for a given PV array, load, and shading ratio (SR), there is a critical load point that identifies a load current (or load voltage) beyond (or below) which the diode securely goes into operation. The values of dissipated power and reverse voltage of shaded cell are lower when the diode does not go into operation. With the diode in operation the worst condition for the shaded cell occurs for minimum SR, there is a current split between diode and module, and the diode current increases with increasing SR. If the array is short circuited, the diode goes into operation with minimum SR. With the diode in operation, the electrical state of the shaded module is practically independent of array configuration