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.
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.
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 system dynamicmonitoring 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 system protection with synchronized phasor measurement technology are presented also.
Load modeling is very important for power system dynamic 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 system dynamic 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.
This paper presents a model and control strategy for one multi-module-converter based VSC-HVDC system. Each converter operates with a fairly low switching frequency, and thus it is applicable to select high-power low-...
详细信息
This paper presents a model and control strategy for one multi-module-converter based VSC-HVDC system. Each converter operates with a fairly low switching frequency, and thus it is applicable to select high-power low-switching-frequency and low-conduction-loss electronic devices such as IGCT or GTO in high-power applications. A mathematical model is developed for the overall multi-module-converter based VSC-HVDC system. A controller is also designed systematically for the HVDC system based on the developed system model. Performance of the overall HVDC system and effectiveness of the designed controller are evaluated based on digital time-domain simulations in the MATLAB software environment.
Recent years, some DG (distributed generation) have been introduced in distribution systems, and the voltage violation problem has been at stake for the distribution system. The impact of DG integration on distributio...
详细信息
Recent years, some DG (distributed generation) have been introduced in distribution systems, and the voltage violation problem has been at stake for the distribution system. The impact of DG integration on distribution system is studied in this paper, and the transient stability mechanism of DG is analyzed theoretically. This paper investigates the dynamic analysis of a DVR when applied to correct the voltage distortion in distribution system. Then the model of DG is built by Matlab/Simulink. And it is used to study the impact of DG integration on the distribution system. Then the voltage regulation-dynamic voltage restorer (DVR) is introduced to distribution network with distributed generation. A calculation method for DVR in distribution system with distributed generation is proposed, which is based on a semi-period algorithm to extract fundamental component from fault signal then extract the fundamental positive sequence voltage by the decomposition instantaneous link, and then the quantity of voltage compensation can be solved by direct detection algorithm. Simulation results show that the introduction of DVR (dynamic voltage restorer) to the distribution system with distributed generation is good for voltage regulation and making a good guarantee of the voltage quality of sensitive loads; and the algorithm for DVR is simple and effective.
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
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 related to the parameter identification area. Consequently, an efficient optimization method is needed to derive the load model parameters based on the feedback of estimation errors between the measurements and model outputs. This paper reports our work on applying genetic algorithms on measurement-based load modeling research. Due to its robustness to the initial guesses on the load model parameters, genetic algorithms are very suitable for load model parameter identification. Two cases including both the real measurement in a power station and the digital simulation are studied in the paper. For comparison purpose, the classical nonlinear least square estimation method is also applied to find the load model parameters. The simulated outputs from the load model confirm the efficiency of genetic algorithms in measurement-based load modeling analysis. Future work will focus on fastening the converging speed of the genetic algorithms, and/or utilizing more efficient evolutionary computation methods.
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
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 and diagnosis. Current filament, perfect conductive cylinder and perfect conductive spiral coil models are used to simulate the radiation and the influences of iron-core and transformer coil to the propagation of EM waves. The results demonstrate dynamic propagation process of EM waves in time order, and prove the correctness of the shortest optical path principle. But the attenuation and distortion of EM waves-especially the first peak amplitude-caused by the obstruction of large solid conductive obstacle like iron-core are quite intensive that it may cause great difficulties to identify exact arriving time position of incident waves coming along the shortest optical path. While the influences of the coil to the propagation of EM waves are so little that HF EM waves can penetrate it in almost linear path.
Electromagnetic interference (EMI) on secondary de cable in cable tunnel due to a direct lightning strike in substation threatens the safe operation of electronic equipment and system connected to the cable. In order ...
详细信息
Electromagnetic interference (EMI) on secondary de cable in cable tunnel due to a direct lightning strike in substation threatens the safe operation of electronic equipment and system connected to the cable. In order to reduce EMI, the cable shield is generally connected to the grounding grid at both ends. Ground potential difference between two grounding points of the cable shield can be high due to high impedance of the grounding grid at high frequencies. In this paper, we present a hybrid method to analyze this complex system. As a result, both the current flowing in the cable shield and the transverse voltage between the cable core and shield are calculated. Compared with the measured results, the proposed method is demonstrated to be correct and effective.
A practical ride through scheme bases on super capacitor energy storage system for ASD (Adjustable Speed Drive) equipment is presented in this paper. The topology of ASD discussed adopts AC-DC-AC structure and 12 puls...
详细信息
ISBN:
(纸本)9780780391932
A practical ride through scheme bases on super capacitor energy storage system for ASD (Adjustable Speed Drive) equipment is presented in this paper. The topology of ASD discussed adopts AC-DC-AC structure and 12 pulses diode rectifier as input interface. Super capacitor (SC) module connects to inverter DC bus to support DC voltage while power quality problems such as voltage sag or short-term outage take place in power source. A SC energy storage system based 15kVA ASD prototype was developed. Digital simulation and physical experiments were carried out to verify the correctness and validity of proposed ASD ride through topology and control strategies.
暂无评论