The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Voltage sag has became the most concerned about power quality problems. Voltage sag source detection for power quality fault detection, diagnosis and to ease the formulation of strategy is necessary. This paper proposes a new method about voltage sag disturbance source location based on real current component. The product of the RMS current and the power factor angle at the monitoring point is employed...
This paper addresses the problem of identifying the optimal location for power quality monitors.The proposed approach is based on using the integer programming-based model and PSO to solve the optimization problem. Establish a 0-1 sensitivity equation to form the constrains of integer programming by PSCAD/EMTDC.The proposed approach gives the minimum number of power quality monitors and their locations...
The sensitivity of sensitive equipment to voltage sags depends on the characteristics of voltage sag on the power supply site and the voltage tolerance of equipment. It is multi-uncertain including stochastic and fuzzy. Cloud model is used to present the sensitivity of equipment in this paper. The direct normal cloud generator was used to translate the qualitative distribution of VTC into quantitative...
The distribution power sources and loads are integrated by microgrid technology, which could electively relieve the impacts of distribution power sources on large power grid. So, microgrid is an effective way for distribution power sources' large-scale application. There is unavailability of official release on the microgrid standard as yet at home and abroad, and grid-connected standard should be...
A wavelet-based energy content method for short duration voltage variation characterization identification during power quality disturbance is provided in this paper. The main advantage of the proposed scheme is that it uses wavelet analysis to zoom into a high frequency band for the time information, and the fundamental frequency band for the magnitude change. Also, it is shown to be effective even...
Under the concept of smart grid, a novel programming method is proposed in the paper for customer friendly distribution system considering the uncertainty properties of power quality. Due to the uncertainty of power quality during the change of power system structure, the assessment of potential cost caused by customers' equipment failures under possible disturbances for different planning schemes...
To meet the power customer's satisfaction is the essential responsibility of the utilities. Considering the property of customer's satisfaction degree, an analytical interval assessment method of voltage sag frequency is proposed. The customer satisfaction degree is presented by an interval data corresponding to the voltage tolerance of tested equipment installed at the customer side. Based on the...
Grid connected power electronic converters must be synchronized to the mains voltage by using suitable converter control circuit and gate signals, in order to function correctly. Without proper synchronization, the operation of the converter is adversely affected. This paper proposes a method to synchronize power converters to the mains voltage without using a phase-lock-loop (PLL). This is achieved...
A new on-line fault location method is proposed based on the voltage sag characteristics resulted by different faults in the power systems. Only the voltage sag measured at single end is used to locate the fault. For a given distribution system, construct a simulation model to obtain faulted section locating function and fault distance calculating function of the network. When a real short circuit...
Wind farm integrated in power system in continuous operation will cause the PCC(Point of Common Coupling) of voltage fluctuation and flicker. The wind changes can contribute to the wind turbine output power fluctuations, which can lead to a connection point of voltage fluctuation and flicker reasons. IEC61400-21 gives the wind turbine on the grid power quality requirements and analyses the flicker...
The low-voltage ride-through (LVRT) capability of a MW-Level variable speed wind turbine with a direct-driven permanent magnet synchronous generator (PMSG) is a hot topic these days. To prevent over-rated dc-link dynamic voltage, a novel dc-link voltage control scheme is proposed. In this paper comparing with traditional control method, the generator-side converter uses a doubly closed loop namely...
The fast development of wind power generation brings new necessary requirement for wind turbine to provide Low Voltage Ride-Through (LVRT) capability. The paper introduces the models of Doubly Fed Induction Generator (DFIG), converter and rotor active crowbar, and analyses characteristics of DFIG system with rotor active crowbar during grid voltage dip. A novel turn-on and turn-off control method...
This paper presents a voltage sag compensator based on a switched autotransformer by random hysteresis voltage control. The advantage of this compensator is that it uses only one controlled switch per phase with no energy storages. Also the control scheme purposed here distributes the harmonic spectrum of the load voltage and reduces its total harmonic distortion (THD). Different voltage sag events...
For doubly-fed induction generator-based wind energy conversion systems (DFIG-based WECSs), the output voltage of rotor-side converter (RSC) has to be lower than the de-link voltage due to its buck circuit topology. For this reason, under severe grid faults that cause large electromotive forces in the generator, the short circuit current can not be suppressed effectively. To evaluate the control limit...
Voltage sag has become the main culprit to high quality power supply. Solid Static Transfer Switch (SSTS) for duplex feeding is a kind of power device which can effectively alleviate the voltage sags. SSTS will switch sensitive loads to the alternate source with better power quality when the preferred source is suffering voltage sags or interruption. In this paper, the operational principle of SSTS...
Firstly this paper presents the technical aspects of designing a Dynamic Voltage Restorer (DVR) to meet some stringent requirements of voltage sags mitigation for Micro Integrated Power System (MIPS). Secondly through an analysis of configuration of DVR the optimum energy injection scheme is introduced. Thirdly the principles of a control scheme and a protection circuit for mitigating surge current...
Serious problem for failure probability evaluation of equipment due to voltage sag is the uncertainties and mathematical expression of influencing factors. The uncertainties contained in voltage sag, equipment voltage tolerance and possible operation state are researched. The intension and extension uncertainties of influencing factors are used to distinguish their property. Stochastic and fuzzy variables...
This paper analyzes the transition characteristic of the doubly-fed induction generator (DFIG) during the grid fault, and the approximate short current calculation which is based on the fifth-order DFIG model is also introduced to support the analysis. A novel method which is easier and more accurate than the past ones is proposed to verify the low voltage ride through (LVRT) characteristic of the...
There is complex uncertainty involved in evaluation of equipment sensitivity to voltage sags, and that makes it difficult for the point-valued assessment method to evaluate the impact of voltage sags on the sensitive equipment, especially in the case of small sample size. Considering the multi-valued nature of equipment status during the voltage sags, the voltage tolerance level of sensitive equipment...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.