Research And Design Of Power Multi-Parameter Test Instrument

With the development of national economy, more requirements are needed to power qulity of power department, while power network's measurement is the necessary condition of improving power qulity. Due to the broad application of electric power equipments, this problem has drawn much attention not only from power enterprises but also from management sectors as well, and promoted research and development of related products. In the mean time, the rapid progress in computer technology, signal processing theory and methods and the sharp decline in the prices of DSP chips and CPLD have led the application of DSP and CPLD to a more profound extent.In order to monitor power network and warrant the electric equipments to operate properly, this paper combined DSP and CPLD to design a general power parameter test instrument.It can measure three phase voltage, current and their harmonics, three disequilibrium, active power, reactive power, power factor, frequency, power.off time and power on time etc, the data are saved every one minute for 64 days,have real.time monitor and data acquisition, analysis, processing functions with PC software;have interface of RS232/485 and Modem,can communication remotely through public phone network.Emphasis of the paper are laid on following: the principle and methods of power parameter measurement; Design of hardware, including signal conditioning circuit, A/D transfer circuit, communication interface, data saving circuit, the logic circuit in CPLD; DSP code design, including the programming of A/D transfer, the programming of FFT, the programming of keyboard/LCD service etc;Development of PC software,including interface design, function modules design, database design, software packaging; then the paper shows hardware tests and software tests, the results are satisfied, the error of harmonic testing reaches national standard B, meanwhile we analysis the reasons of error and provide method to correct error. Finally the paper gives the summarization and prospects for the future trends.Different from other systems which often use dual cpu in their projects, the main feature of this system is that it combines CPLD with DSP together as a solution, thus it not only enhances the system's stability, but also use resources of DSP fully. More over,we combined software with virtual instrument control to make interface more friendly and enhance the function of software.