The Research Of Power Quality Real Time Monitor Based On FFT And Wpt

For the power quality monitoring and harmonic pollution problems, a power quality real-time monitor is developed on the technique embedded ARM and virtual instrument, which can achieve the real-time monitoring for three-phase power phase/line voltage, current, active power, reactive power, apparent power, frequency, power factor, active energy, reactive energy and harmonic of three-phase voltage and current.The thesis mainly includes the analysis of the theory, hardware design and software design. Firstly, the principle of various energy parameters is introduced in the theory. Especially, the joint method for FFT and WPT which is used to deal with the harmonic is simulated by matlab in order to confirme the feasibility of this method.Secondly, the hardware which is designed using ARM7 LPC2132 as the core processing chips includes signal sampling circuit, filter circuit, the frequency measurement circuit, communications circuit and so on. The 10-bit A/D, UART, Timer Counter, I2C, real-time clock and other functional modules integrated in LPC2132 are fully used to improve the circuit integration. In the communication module design, two communication ports based on the two UART interface integrated in LPC2132 are designed, which not only can communicate with external devices simultaneously, but also each communication port can selecte CAN bus or RS485 bus in the physical protocol. This design brings convenience to the on-site monitoring and remote monitoring and enhances the compatibility with other devices.Software programming is divided into two parts of host computer program and client computer program. In the client computer program, the signal sampling and the calculation of various energy parameters are realized. The harmonic component of 0 to 30 times is acquired by using the FFT. Host computer program is developd on the virtual instrument platform of Lab Windows/CVI to fulfill data processing and the display of the power parameter. In the data processing program, the joint method of FFT and WPT is used to get more then 30 times harmonics through the Lab Windows/CVI and matlab interface. At the same time, in order to enhance the real-time quality, the multithreading technology is used to keep the independence of each function. The communication program follows the MODBUS protocol to enhance the universal of the monitor in the industry.According to the above specification, the prototype is produced. After three times circuit modification and software debugging, the comparison test with the outsourcing power data management module is carried out in the laboratory. The result of the test shows that the monitoring accuracy of power parameters meets the design requirement and the monitoring performance with a load is stable. The industrial test of the monitor is being carried out in the harmonic control system.