The Research For Mismatched PV Modules In A Household PV Generation System

As a new way to solve the energy issues, the PV generation is growing fast in the whole world. With the popularity of the PV generation system, the problem of mismatch has attracted increasing attentions. In a household PV generation system, when PV modules are mismatched, it will lead to a wrong maximum power point tracking (MPPT) to all modules and a power decreasing of the whole system. Aiming at this problem, this paper presents a new idea that, based on the structure of conventional system, adding a DC-DC converter for MPPT control behind each module. The advantage of the system is low transforming cost and high increasing power generation when mismatch.The study is as follows:1、By the PSIM software, the mismatch problem of the conventional household PV generation system is studied. First, Circuit parameters of the conventional system are designed, and then a simulation model of the conventional system is built. By simulating the output voltage of PV array covered by shadow, a wrong tracking of maximum power point under the mismatch condition is proved. By simulating the system’s output power, the connection between mismatch and mismatch losses is presented.2、According to the mismatch problem, a improved system is proposed in the paper. Based on the type of the DC-DC converter, the idea can be divided into two schemes which uses boost converter and buck converter. After the circuit design of improved system, the two schemes are simulated by PSIM. By simulating the improved system’s output power under the mismatch condition, verify the feasibility of the schemes. The output power of two schemes increased108.2%and112.2%respectively comparing with the simulation result of the conventional system.3、The boost converter and buck converter are made. The experimental models of conventional system and improved system are set up by the equipments such as PV modules and electronic load. Under the mismatch condition of covering by shadow, the important data such as output voltage of maximum power point, output power, the power generation in a day is sampled in the experiment. After analyzing the data, considering the power loss of added converters, the power generation of two schemes in a day is improved68.3%and72.2%compared with conventional system. The improved system’s advantage in dealing with the mismatch problem is proved.