Design And Research On Power Quality Monitoring System Based On Virtual Instrumentation

In recent years, the power load that make up the emergence of new trends, the influence on power quality caused by non-linear, high-power impacting, unbalanced load can not be ignored. At the same time a large number of very sensitive to power quality emerging industries, such as micro-electronics, computer, IT, CNC automation production line, and etc.develop rapidly and bring forward a more rigorous request on transient power quality. In order to solve this problem, it is necessary to research on power quality in depth and monitor the power quality parameters in real time.First of all, introduces the definition of power quality, and according to the characteristics of power quality and the operating status of power system, power quality is divided into two kinds of steady-state and transient. The steady-state power quality includes voltage deviation, power frequency deviation, three-phase unbalance, voltage fluctuation and flicker, and harmonics; transient power quality includes voltage sags, swells and short voltage interruption as the main object of study. The cause, hazards and national standards of power quality problems have made a derailed analysis, and as the basis for the design of on-line power quality monitoring system.Then, for the problems of leak and fence effect due to FFT to the harmonic detection, Windowed Bimodal Interpolation Correction Algorithm was used in this paper to improve detection accuracy, and by using wavelet transformation of the singularity detection principle to achieve the disturbance of transient recognition and positioning. An effective method through combination of Wavelet Transform and FFT is putting forward. In this way, transient and steady-state signal are de-noised by wavelet method and segregated through Wavelet multi-resolution function firstly, then transient signal is analyzed in the disturbing surroundings and harmonic analysis uses the stead-state signal.Last, combined with the concept of virtual instrument "software is the instrument", the outstanding developing platform of Lab VIEW is used to the development of the functional module, for its flexible dataflow programming ability and abundant functions, and to adopt MicroSoftwara Access database technology for data storage, inquires and delete. Through laboratory testing, the design of the monitoring system has high precision and will be able to achieve the ideal power quality monitoring.