The Study Of Mismatch In PV Array

As the result of lacking traditional energy and the people of all counties in the world pay more attention to environment protection, as a clean and potential new power source, a great many of countries have supported the development of PV system. So the study of PV system becomes more and more important.Now the low efficiency convert and high price of PV cells makes a long cycle of cost recovery and has baffled the development and application of photovoltaic system. The main reason that causes the low efficiency convert of photovoltaic system is mismatch. This paper has analyzed the main reasons that caused mismatch, and put forward some corresponding methods to reduce the mismatch losses.Firstly, we have analyzed the parasitic resistances, reverse saturation current of the equal diode on the performance of PV cell and module. Then have analyzed the mismatch losses due to the variance of PV cell parameters. The results show that the variance of PV cells in one module will bring some bad effects, not only causes mismatch losses but also short circuit, and makes the module out of work. In order to reduce the mismatch losses of the module that the PV cells have variance parameters we suggest the manufactures should classify the PV cells before module encapsulation.Then by finding the reasons that causes hot spots and the mismatch losses due to hotspots, we have summarized some solution to reduce the mismatch losses. This part also has analyzed the effects of PV modules that the bypass diode overlapped and none overlapped on the mismatch losses.The degradation of PV cells in the module affects the module's efficiency convert. The mismatch losses become seriously with the degradation of PV cells. So the study on the mismatch losses of module due to degradation is very important. By simulation find the TCT connection in the PV module with least mismatch losses. If the number of PV cells in the module is certain,the mismatch losses of the TCT network are least.When the PV array or parts of it were shaded, it will cause lots of mismatch losses. We have analyzed six kinds of PV array networks, the results of simulation show that 2×4TCT PV array network has least mismatch losses, least wave crests that tends to track the maximum power points, and the highest reliability compare with other PV array networks.