Based On Dividing The Sample-and-hold Type Of Maximum Power Point Tracking Principle

The solar photovoltaic power generation is the most promising new power generation technology, but the solar battery is expensive and in the process of power generation there are kinds of energy losses. the method of maximum power point tracking makes photovoltaic cells working in the maximum power point. this method improves the utilization rate of solar cells effectively and reduces energy losses. This has great practical significance on many occasions. The existed MPPT technologies have good ways to develop the absorption rate of solar energy, but all of them have different faults.On this basis, according to the output characteristic of solar cells and the working characteristic of constant pressure load, this paper proposes a solution to MPPT and achieves the best effect on the circuit type of sampling and holding/maximum power detecting and tracking based on the time division, which is based on the comprehensive analysis of the advantages and disadvantages of existed technologies. Its characteristics are as follows: separate maximum power analysis and power conversion process by the way of time division. In each conversion cycle, use one over one thousand or one percent of the time to judge the maximum power, and lock the maximum power point through the way of sampling. In the interval of power conversion, it uses the data locked as a given value of conversion control circuit, and control the duty cycle of pulse duration of the main switching element in the transform main loop, so as to achieve the maximum power generation power (largest efficiency) control on photovoltaic battery. This method can realize using pure hardware, the circuit is simple and don't need sensor, the measuring parameters is few. When the system is working, there is no need to disconnect circuit, the test is real-time dynamic current and voltage open, each cycle is independent, so it can rapidly and accurately work and won't appear oscillation and miscarriage of justice. There is no algorithm intervention, and it has low cost. It is easy to maintain at the same time. This scheme can solve the problem of energy losses in the case that the maximum power point tracking is bad in the photovoltaic system, fundamentally improve the quality and efficiency of tracking system.This paper briefly introduced the topic of background of the subject, the technology at home and abroad, research significance, the research direction and main work of this subject. The paper discusses the power electronic technology which involved in this design briefly, at the same time analyses the chips and components whose function is more important, internal principle is more complex, also discusses the basic principle. Then this paper gives the idea of the maximum power detection, and divided into two parts to elaborate:the first one, carries out a detailed analysis and design for maximum power detection analog circuit. and discusses the principle, parameter calculation, and choice of chips for multiplier circuit, differential circuit, and the comparison of circuit in detail. the second one, discusses the main circuit of power conversion and the design of related circuit. This chapter analyses the generation circuit of PWM pulse signal in this design and the principle of work for DC/DC step-down circuit on detailed. Chapter5is for the system commissioning and waveform analysis. Through the test of complete system, we prove the design achieve the anticipate goal.