Study Of Multi-channel Data Acquisition System For The Application Of PV Module Measurement

Data acquisition(DAQ) systems are widely used in different fields. Along with the development of science and technology, the requirements of their performance are becoming higher and higher. In terms of applications with harsh environments, such as aviation, marine and so on, there are specific requirements for DAQ systems, in which case a customized DAQ system rather than the universal ones is needed.During the operation of photovoltaic(PV) power plants, the conversion efficiency of PV modules continuously decreases, which in turn heavily affects the power generation of PV plants. Currently, the PV modules can only be measured at the factory before delivered, and for outdoor conditions there is still no feasible method and system to characterize their performance. In order to solve the above problem, this thesis designs a cost-effective DAQ system and proposes two different solutions for outdoor testing of PV modules.The thesis starts with the fundamentals of data sampling theory, and designs a DAQ system based on it. The DAQ system has eight single-ended analog inputs, two differential analog inputs and two analog outputs. The minimum resolution for input is 38 uV and the minimum resolution for output for 5mV. The most important part of this work is the design of communication system, including both USB mode and wireless mode which adopts ZigBee protocol. In the meantime, the data interface and processing are provided for the acquisition of module temperature and sun radiation.Then this work investigates the software architecture of the DAQ system, including the upper-computer program and the micro-chip program. The data acquisition control program on the upper-computer is designed using Labview graphical programming technique. This platform is responsible for the management of several important tasks, such as machine communication, user-machine interaction, data storage, processing, and sharing. On the other side, the micro-chip program is developed using C language. This part of software is mainly used to drive the machine, which needs a few steps to complete the task, such as receiving and decoding of commands, driving of chips and processing of acquired data.At the last part of this thesis, two possible applications are proposed for the previously designed DAQ system. One of them is a novel method for the yield estimation of PV power plants, which is based on the real-time IV curve measurement. The advantage of this method have been proved by outdoor field contrast experiment. In addition, this work also proposes a new design of the real-time testing system for PV plants. The basic principle of this system is explained in detail, particularly for the connection topology between the tester and the PV modules, and the control logic of the intelligent switch.