This work discusses the feasibility of series/parallel switching circuits with power MOSFETs to minimize the reduction in the output power of photovoltaic power systems due to the partial shading problems by connecting shaded panels and adjacent panels in parallel. The following observations were made on the basis of the experimental results: 1) When at least one of the photovoltaic panels is shaded, 50% of the reduction ratio of the solar radiation intensity becomes the lower limit of the threshold value for the series/parallel switching control. 2) The effect of the series/parallel switching control can be expected to be higher when more than two of the photovoltaic panels are shaded. However, the sum of the solar radiation intensities applied to the panels in the parallel circuit should be less than 150% of the maximum intensity of the photovoltaic power system. 3) The shaded panel, which should be connected to the adjacent panel in parallel, can be detected using bypass current measurements rather than direct measurements of the solar radiation intensity. The authors developed a prototype of a switching circuit module and performed the operation tests by using three photovoltaic panels. The results showed that the switching circuit module successfully detects the partial shading conditions and switches from the series operation mode to the parallel operation mode.
- Partial shading detection
- Photovoltaic power system
- Power MOSFET
- Series/parallel switching control