Methods for detecting sources of power quality disturbances.

摘要

Power quality has attracted a great deal of attention in recent years due to an increasing utilization of sensitive power electronic-based loads in power systems. Power disturbances can cause severe damage to equipment and costly problems for customers. One of the important steps for power quality management is to determine the locations of disturbances. Only after a disturbance-source location is known can disturbance mitigation be further carried out. With the deregulation of the power industry, utilities have become increasingly interested in quantifying the responsibility for power quality problems. Consequently, research on how to identify which customer load or supply system is responsible for a power quality disturbance has become an important topic.; Voltage sag is one of the main power quality disturbances. This thesis presents a novel method for voltage sag-source detection. Its principle is to estimate the equivalent impedance of the non-disturbance side by utilizing voltage and current changes caused by the sag. The impedance estimation is derived using system identification and least-squares methods. The sign of the estimated resistance can reveal the location of the sag disturbance. Extensive tests using the method have shown that it is effective and reliable. A comparison of sag-source results with other published sag-source detection methods is also provided.; Voltage flicker is another type of power quality disturbance. It can be considered as repetitive voltage sags. The proposed system identification-based method is extended for flicker-source detection in this thesis. This research work further analyzes interharmonic-caused voltage flickers and proposes a method to determine the interharmonic-related flicker sources.; Relationships between interharmonics and flickers are also investigated. A limit for interharmonic emission is proposed by utilizing the published limits on voltage flicker. The limit is represented as an interharmonic-magnitude versus interharmonic-frequency curve and is called an interharmonic-flicker curve. A systematic method to derive the limits for interharmonics is presented. Potential applications of the results are discussed.