Research On Output Characteristics And Strategy Of PV Module Under Partial Shading

As a kind of clean and abundant renewable energy, the use of solar energy is currently the focus of attention. Using the photovoltaic cell is the best way to use solar energy. However, due to the uncertainty of the weather environment, photovoltaic power generation will often be affected by shadow shielding.In the actual production, in order to obtain enough power and voltage, photovoltaic cells are often connected in series to form a photovoltaic module. However the impact of the shadow will cause the PV module mismatch phenomenon, and then hot spots will be generated, the entire component will be burnt. Although the parallel bypass diode can effectively avoid hot spot phenomenon for photovoltaic components, the output characteristics of PV module impact in the two aspects:one is the reduction of the PV module overall power output, the second is multiple peak output power of photovoltaic module curve, the effect of photovoltaic module maximum power control. The purpose of this paper is to solve these problems above, the specific work is as follows:Firstly, this paper analyzes the loss mechanism with photovoltaic cells in detail, and establishes the simulation model of photovoltaic cell under the shading conditions, then simulates the power output of photovoltaic cells under shading. To illustrate how to solve the mismatch problem through the bypass diode paralleled with photovoltaic cells, it will lead to the ladder type of the volt ampere characteristic curve the ladder type, which also leads to the decline in output power of photovoltaic module.Through the analysis of the shading PV modules output power, for the current lack of photovoltaic component connection, this paper presents a new photovoltaic module connection, "door" connection, which can reduce the shadow effect of the output power of the photovoltaic component. From multiple directions of shadow simulation, the output power of photovoltaic module with normal connection and door connection are compared, the advantages and disadvantages of these two connection way are pointed out. It proved that the door connection can improve the rate of output power of the PV modules under the shadow.For the shortcoming of "door" connection at the time of the shadow moving from the upper and lower two direction, the reconstruction method of "door" connection is proposed to improve the output power, which can convert the PV modules gantry between the door connection and normal connection according to the different shadow. Then the photovoltaic component reconstruction of detection methods and the realization of the way are explained in detail, which maximize the PV modules output power in the affected by the shadow.Finally, aiming at the problem of multi peak output power of photovoltaic module, this paper analyzes the cause of multi peak output power curve, and simulates a variety of output power curve under different light, and finds that the photovoltaic module front peak point is a fixed value. It proved that the fixed value is associated with the number of bypass diodes connected in parallel with photovoltaic modules in the theory. Then the multi peak problem is changed into single peak problem, the post peak is found by perturbation and observation method, which compares with the front peak to find out the maximum power point of PV modules.