Maximum Power Point Tracking Control Research For Independent Photovoltaic Power Generation System

The independent photovoltaic power generation system not only solves the electricity problem of self-sufficiency, but also makes the remote users such as in plateau and desert regions can use electricity without the difficulty of transmission.This paper studied the MPPT(Maximum Power Point Tracking) method in the independent photovoltaic system to improve the optical energy efficiency.This paper analyzed the research condition of the maximum power point tracking in the independent photovoltaic system in the first place, which makes the purpose and significance of the paper more clearly. Then, it studied the important parts of the system in detail, such as the equivalent circuit and mathematical model of the solar cell, the I-U and P-U curves of the solar cell in changing environment. It also studied the working principles and characteristics of several common DC/DC converter switch are used for MPPT control and battery charge-discharge control in photovoltaic power generation system. And this paper studied the SPWM technology of the DC/AC inverter which can supply steady sinusoidal voltage for ac loads. Once more, it introduced the function of the energy storage device and its charge-discharge control methods in the independent photovoltaic system. Next, this paper researched the principle and progress of MPPT and introduced the Perturbation and Observation algorithm and the Incremental Conductance algorithm. It also built a MPPT model by using Matlab/Simulink module, analyzed and compared the simulation results between the two methods above and improved the Perturbation and Observation algorithm on the oscillation problem. This paper also came up with a new MPPT method based on the Perturbation and Observation algorithm which can be used in uneven illumination condition. On the basis of the above research, this paper proposed an scheme which can realize the MPPT control by controlling the charge and discharge current of the battery which includes the overall design and analysis of the scheme, the charge-discharge control circuit design, the grouping design of the battery and the fuzzy control design for controlling the battery current. This scheme can realize the MPPT function and guarantee the power utilization of the users in the independent photovoltaic power generation system.The study of the MPPT in the independent photovoltaic system not only can use the sunlight more efficiently and make the remote users can use electricity by self-sufficiency, but also reduce the dependence on non-renewable energy. And what is more, it can reduce the long transmission costs.