Design And Experimental Research Of Photovoltaic Pump System

With the advantages of no pollution, no fuel consumption, unattended, the photovoltaic pump system can ease the agriculture and life water shortage in arid regions in western China, remote mountain areas without electricity and promote the people's living standards. However, the PV pump system is difficult to achieve large-scale application because of its expense, complexity and other factors. In this thesis, the photovoltaic pump system is used as an object of this research. A optimized system was designed and tested.This is a beneficial exploration to develop the PV pump system with low cost, high performance and simple structure.The main research contents and conclusion are as following.(1) The battery array output characteristic was analyzed. The relationship between array output and radiation intensity, environmental temperature and light incident angle was studied. The principle of constructing array was discussed.(2) The flow characteristics near the entrance of the pump impeller was studied. Formula of the impact loss near the entrance of the impeller was derived using speed triangle, refering to the design conditions. As the speed reducing, the impact loss increase first and then decrease. Then, the position and scope of the secondary flow loss was discussed under different radiation.(3) The software of Pro/E was used to build the three-dimension passage model and the meshes of impeller, diversion slot inlet and outlet was created using unstructured grid technology in the software of Gambit.Based on the Reynolds-averaged N-S equation and standard k-εturbulence model, a self-designed photovoltaic pump was simulated by using SIMPLEC method in Fluent software. Four different kinds of radiation conditions were considered during the simulation. The calculation and analysis results have a good agreement.(4) For the weak point of the Perturb-and-Observe Method (PAO), the study proposed an improved Double Criterion, Five-zone Perturb-and-Observe Method (DCFPO). The tracking algorithm can find the right tracking direction and take the tracking speed and tracking accuracy into account to achieve a higher performance-price ratio. Then, the Maximum Power Point Tracking hardware circuis was designed using NI Multisim 10.0, based on SCM.(5) In order to improve the efficiency of the battery, and prolong its life, a kind of intelligent charge and discharge control strategy of lead-acid batteries was researched in this paper.The principle of the strategy and the circuit structure was analyzed detailedly.Then, the charge and discharge hardware circuit were designed using NI Multisim 10.0 based on SCM. These circuit included voltage testing circuit, data conversion circuit, power valve driver circuit, instructions and protection circuit, etc.(6) A set of photovoltaic pumping test system was trial-manufacted. And the corresponding tests was carried out on pump performance test platform in good weather conditions. The result shows that the MPPT method achieves good practical result and high performance-price ratio.The charge and discharge experiment indicates that this method can solve the phenomenon of over charge, less charge and charge each other of the lead-acid batteries. So, it extends the life of those batteries.