Monitoring And Control Of Power Quality In Distribution Network

With the rapid rise of non-linear loads in the power distribution network, with the large-scale access of distributed new energy and along with the increasingly higher requirements of the industrial customers, the issue of power quality has received more and more concern from both the suppliers and customers. The decline of power quality not only has a considerable negative impact upon the safe operation and economic benefits of the power-supply enterprises, upon the efficiency and performance of electric equipment, but also leads to a considerable shortening of the life of electric equipment. Thus, the detection and improvement of power quality is a pressing and important project in the operation of the current power distribution network.By far, there has been a relatively perfect theoretical system in terms of the research in the field of power quality. First of all, this paper sheds light on the basic conceptions and theories in power quality in details. What's more, it also provides different definitions for power quality put forward by some researchers of different periods in electric power system, analyzes the classification of power quality, introduces the current national standards of the detection and improvement in power quality, and in the end confirms the concrete objectives of power quality control. In terms of the index for stead and transient states of power quality as well as the detection standard for harmonic wave, this paper elaborates the means of calculation for the power quality index. FFT and detection method based on instantaneous reactive powerare mainly are applied in the detection of the level of harmonic wave. The means of digital signal detection of dynamic power quality indicators, such as voltage flicker, mainly include wavelet detection algorithm and Hilbert transform algorithm.Based on the intelligent electronic devices in smart substation, such as protection and mesurement-controll devices, this paper designs an integrated monitoring device for power quality and expounds the overall design for both the software and hardware. With regard to the hardware design, the paper focuses on the introduction of the implementation schemes for main processor module, Ethernet communication interface module, human computer interface module; with regard to the software design, it mainly dwells on the overall design of the monitoring module of power quality, interrupts and tasks assignment, calculation method of power quality indexs and information modeling accoding with IEC61850.This paper researches some special problems of power quality in the power distribution network, summarizes the major means of controlling and improving power quality, which cover voltage and reactive power compensation, active power filter, static var compensator and static synchronous compensator. In addition, the paper analyzes the principles and effects of various improvement measures for power quality. Considering the current situation and the existing prominent problem in the power distribution network of a certain county, the paper selects some appropriate control and improvement measures. In the end, it analyzes and summarizes the effect of improvement.