Load modeling is very important to power system operation and control. Measurement-based load modeling has been widely practiced in recent years. Mathematically, measurement-based load modeling problem are closely rel...
详细信息
Although the fault component impedance relay has many perfect performances, it is still restricted by high fault resistance. In order to improve its resistive tolerance and overcome unreliable operation, a new type re...
详细信息
Although the fault component impedance relay has many perfect performances, it is still restricted by high fault resistance. In order to improve its resistive tolerance and overcome unreliable operation, a new type relay with double circular characteristic is put forward, as well as its operating boundary and general operating equation are researched in this paper. The relay is comprised of two groups operation equations, one of them is calculated by sampling integral arithmetic to achieve its ultra-high speed while the other by Fourier arithmetic to enhance the relay capability against high resistance. dynamic simulation test has been made with a typical two sources system operating at 750 kV to verify the relay performance. Theoretical analyses and test results show that the fault component impedance relay with double circular characteristic is simple, reliable and secure with ultra-high speed and great capability against fault resistance.
Recent developments in the field of supercapacitors have led to the achievement of high specific energy and high specific power devices which are suitable for energy storage in high power electronic applications, espe...
详细信息
The radiation and propagation of electromagnetic (EM) waves generated from PD caused by the obstruction of main transformer components are studied by FDTD simulation in order to get more information for PD location an...
详细信息
After a fault occurs in a power system, generally some operating information of protective relays and circuit breakers could be obtained. Because protective relays and circuit breakers might improperly operate or fail...
详细信息
After a fault occurs in a power system, generally some operating information of protective relays and circuit breakers could be obtained. Because protective relays and circuit breakers might improperly operate or fail to operate, and some errors and distortion may exist in data acquisition and communication, as a result uncertainties could be involved in the received information. A fault diagnosis model based on fuzzy set-covering theory and mode identification technique is proposed in this paper. With the fuzzy technology, the above mentioned uncertainties could be dealt with very well. Meanwhile, as the protective relays and circuit breakers may fail to operate in some cases, there are several different operating modes in protective relays and circuit breakers even for a same electrical device failure. Based on the received information, the proposed model could identify the most possible operating mode, and then the information corresponding to a fault hypothesis could be obtained. In the proposed model, the proposed fault diagnosis problem is described as a 0-1 integer programming one, and thus could be solved by the widely employed search technology, i.e., the well-known Tabu search method. The feasibility and efficiency of the proposed model is demonstrated by a sample power system.
Power system restoration decision-making is one of the most important and indispensable issues for ensuring fast power supply restoration to end users. In recent years, the power industry around the globe has been und...
详细信息
Power system restoration decision-making is one of the most important and indispensable issues for ensuring fast power supply restoration to end users. In recent years, the power industry around the globe has been undertaking an in-depth restructuring, and this has led to some new challenges to the problem of power system restoration. In this paper, several important issues related to power system restoration in the traditional power industry and in the electricity market environment are analyzed and compared, and then the impacts of the restructuring efforts on the power system restoration are identified and clarified from several aspects including black-start, restoration tests, dispatching and distribution system service restoration. Up to now, in most of the practically operating electricity markets around the globe power system restoration ancillary service is still based on cost compensation rather than market mechanism.
With start of trial operation of direct purchasing electricity for large consumers in China, the method on how to allocate wheeling costs among large consumers is of vital theoretical and practical significance. An in...
详细信息
With start of trial operation of direct purchasing electricity for large consumers in China, the method on how to allocate wheeling costs among large consumers is of vital theoretical and practical significance. An integrated method for allocating fixed wheeling cost among larger consumers is presented taking time-of-use (TOU) feature, power quality demand and electricity quantity of direct purchase into account. TOU index modeling and power quality index modeling is proposed. The weights of three indices are determined by interacting between the transmission service provider (TSP) and large consumers based on multilevel models to get comprehensive evaluation indices for all consumers. The postage stamp method is modified to allocate the cost using the integrated indices instead of electric energy. Numerical example shows that the proposed approach can allocate fixed cost more reasonable and fair.
Voltage sag, one of the modern power quality problems, may cause tremendous economic loss, which needs scientific method to evaluate. This paper proposes an approach using quality loss function and signal-to-noise rat...
详细信息
Voltage sag, one of the modern power quality problems, may cause tremendous economic loss, which needs scientific method to evaluate. This paper proposes an approach using quality loss function and signal-to-noise ratio (SNR) in quality engineering theory to make economic assessment to voltage sag. The inverted normal probability loss function is used to describe losses of single-type sags, where SNR method is applied to integrate different types together. The index of sag-caused loss is proposed, which is an important parameter for PQ evaluation. A five-node 35 kV distribution system is used to verify the proposed approach. The result shows that the proposed method could effectively assess financial losses caused by sags and be a reasonable instruction for PQ evaluation, improvement and pricing.
Load modeling is very important for power systemdynamic analysis and control. The composite load model widely applied recently in the power system operation centre consists of the static load and the equivalent motor...
详细信息
Load modeling is very important for power systemdynamic analysis and control. The composite load model widely applied recently in the power system operation centre consists of the static load and the equivalent motor. Current practices in measurement-based load modeling identify all the parameters in this composite load model. However, it is not clear whether all these parameters could be identified from the measurements. This paper investigates the identifiability of the equivalent motor parameters in the composite load model. Trajectory sensitivity approach is applied first to find the motor parameters that have great effects on the measured active as well as reactive load dynamics. The analysis results show that the motor outputs have various sensitivities with respect to the parameters. Since the voltage disturbance, the active load and the reactive load dynamics are applied to identify the motor parameters, those parameters affecting the measurements to a great extent are observable, thus identifiable from the measurements; while those that have little effects on the motor outputs are unobservable from the measurements and consequently unidentifiable. The case studies verify the identifiability of the motor parameters.
Synchronized phasor measurement technology has been gaining increasingly interests in China due to its wide area time synchronization capability and fast transmission speed. Over 10 years of implementation of wide are...
详细信息
Synchronized phasor measurement technology has been gaining increasingly interests in China due to its wide area time synchronization capability and fast transmission speed. Over 10 years of implementation of wide area measurement system (WAMS) in Chinese power grid have shown its great value in power systemdynamicmonitoring and potential applications in system modeling and validation, feedback control and system wide protection. This paper reviews the overall implementation of WAMS in China and analyzes the corresponding characteristics of WAMS. Moreover the challenges for bulk power systemprotection with synchronized phasor measurement technology are presented also.
暂无评论