Phase Coordinate Method Research Articles

ИССЛЕДОВАНИЕ ОДНОФАЗНОГО ЗАМЫКАНИЯ НА ЗЕМЛЮ В ЭЛЕКТРИЧЕСКИХ СЕТЯХ 6-35 КВ С ИЗОЛИРОВАННОЙ НЕЙТРАЛЬЮ

Ground faults in networks with an isolated neutral are not switched off by relay line protections due to low capacitive currents. It is recommended to disconnect the line with a earth fault as quickly as possible, but sometimes it is difficult to find and localize the damage. To analyze the emergency mode of single-phase ground fault in networks with an isolated neutral, the phase coordinate method for calculating phase voltages is used. At the point of damage, the values of the phase-to-phase voltages remain unchanged, and the phase voltages change. Real research and analysis of electrical network modes of 6-35 kV with an isolated neutral is rather time-consuming task. Therefore, the calculation of phase voltages at the substation during an earth fault is carried out through the transition resistance on the line based on the phase coordinate method. The authors developed a virtual model of studied power transmission line for analyzing asymmetric modes of three-phase networks and checking the operability of the method in the MATLAB Simulink simulation package. The simulation results showed that there was no discrepancy between the voltage and current values of the original model in phase coordinates and the Simulink model. As a result of the research, the authors have found that the phase coordinate method helps calculate emergency modes with the overlay of several component accidents taking into account load currents. The model in phase coordinates will allow analyzing relay protection operation at high speed under different operating modes of the electric power system.

Short-Circuit Fault Analysis of the Sen Transformer Using Phase Coordinate Model

The Sen Transformer (ST) provides an economical solution for power flow control and voltage regulation. However, fault analysis and evaluation of the performance of the transmission protection system in the presence of a ST have not been investigated. Hence, a short-circuit model of the ST using the phase coordinate method is proposed in this paper. Firstly, according to the coupled-circuit ST model, the nodal admittance matrix between the sending end and receiving end of the ST was deduced. Subsequently, a fully decoupled mathematical model was established that can reflect three characteristics, including its winding connection structure, electrical parameters, and ground impedance. Thus, with the help of the phase-coordinate-based solving methodology, a short-circuit ST model may be built for various short-circuit faults. The MATLAB and PSCAD/EMTDC software were employed to carry out simulated analyses for an equivalent two-bus system. The short-circuit currents obtained from the time-domain simulation and the analytic calculation utilizing the proposed model reached an acceptable agreement, confirming the simulation’s effectiveness. Moreover, the variation of the fault currents with the variation of the compensating voltage after single-phase-to-ground and three-phase short-circuit faults was demonstrated and used to analyze the effect of the ST on the fault currents.

Comments and further results on "A New Critical Formula and Mathematical Model of Double-Tap Interphase Reactor in a Six-Phase Tap-Changer Diode Rectifier

This paper presents some comments and further results concerning the mathematical model of double-tap interphase reactor (IPR) in a six-phase tap-changer diode rectifier. On the basis of coupling circuit principle and phase-coordinate method, the proposed model, which reduces the mutual inductance coupling completely, describes the double-tap IPR by an admittance matrix containing the information about the connection way and electrical quantities. Some computer simulation and experiments are included to support the theoretical analysis of the model.

Modeling for a Multitap Interphase Reactor in a Multipulse Diode Bridge Rectifier

This paper presents a new mathematical model for tapped interphase reactor (IPR) in a six-phase diode bridge rectifier. On the basis of coupling circuit principle and phase coordinate method, the proposed model, which reduces the mutual inductance coupling completely, describes the IPR by an admittance matrix containing the information about the connection way and electrical quantities. To double-tap IPR as an example, and using the proposed method, the full-decoupling model is set up. Compared with the model built by Kirchhoff's law, the proposed model is easier to realize in simulation software. The proposed method can well be extended to the multitap IPR. Some theoretical analysis, computer simulation, and experiments are included to verify the correctness of the model.

Steady-state phase-coordinate model for induction machines

Abstract A phase-coordinate model for induction machines is developed, to facilitate load-flow studies of small hydro- or wind generators connected to distribution systems. The phase-coordinate method allows ready analysis of system unbalance, and the model is applicable to both induction motors and generators under these conditions.

Unbalanced power flow calculation of a power system containing a variable-speed generator

There are some factors that render a power system network unbalanced: UHV transmission lines in which three-phase transmission lines are not transposed, an unbalanced transformer, unbalanced load as well as sustained unbalanced faults. On the other hand, the number of variable-speed generators used in pumping-up power stations has recently been increasing in Japan. This paper presents a new means of calculating unbalanced power flow of a power system which contains variable-speed pumping-up generators. This new technique is based on the phase coordinate method, because a power system which has elements of unsymmetrical impedance can easily be analyzed by using it. In this paper, phase coordinate models of the variable-speed generator and its secondary exciting circuit, composed of a GTO converter/inverter, are analyzed first. Procedures of power flow calculation of unbalanced power systems follow. © 2000 Scripta Technica, Electr Eng Jpn, 134(3): 34–43, 2001

相座標法による電力系統シミュレーション法

相座標法による電力系統シミュレーション法

A synchronous machine model for unbalanced analyses

This paper presents a new asymmetrical model of synchronous generators for power system transient stability simulations. The symmetrical component method has been used traditionally in the analysis of unbalanced faults in power systems. This is mainly because the synchronous generators, which play an important role in the power system, can be easily treated by the method. However, when analyzing a system that has elements with asymmetrical impedance, it may not be easy to use the symmetrical component method. In such cases, the simulations can be easily executed by using the phase coordinate method. However, there are few papers that derive a phase coordinate model of synchronous machines. This paper analyzes synchronous generators under asymmetrical conditions in detail by using the symmetrical component method, then derives a model of synchronous generators for the phase coordinate method. © 1997 Scripta Technica, Inc. Electr Eng Jpn 119(2): 46–59, 1997

Dual three phase transformation for comprehensive fault analysis of a six phase system

Recently there has been a growing interest in the concept of six phase transmission as an alternative to the upgradation of a line, to increase the power transfer capability within the existing right of way. In this work the six phase system is treated as two mutually coupled three phase systems and a transformation called dual three phase transformation (DTPT) is proposed for the analysis of a six phase system compared to earlier works on this subject. This method has reduced the number of significant combinations to 13, by choosing appropriate reference phases and renaming of the conductors, compared to 23 groups. The DTPT sequence networks are obtained in terms of the familiar three phase sequence components avoiding the use of complex ratio or phase shifting transformers, mutual inductances and the results completely agree with the results of fault analysis using the phase coordinate method. In a companion paper titled “Transposition of a six phase transmission line” it has been established that in the case of conversion of an existing double circuit three phase transmission line into a six phase line, a three barrel transposition somethat similar to the transposition of a double circuit line is sufficient, in which case there is mutual coupling only between the two zero sequence components of the two mutually coupled three phase systems which constitute the six phase system.

A Synchronous Machine Model for Unbalanced Analyses.

This paper presents a new unsymmetrical model of synchronous generators for power system transient stability simulations. The symmetrical component method has been used traditionally in the analysis of unbalanced faults in power system. This is mainly because the synchronous generators, which play an important role in the power system, can be easily treated by the method. However, when analyzing a system that has elements with unsymmetrical impedance, it may not be easy to use symmetrical component method. In such cases, the simulations can be easily executed by using the phase coordinate method. However, there are few papers that derive a phase coordinate model of synchronous machines. This paper analyzes synchronous generators under unsymmetrical condition in detail by using the symmetrical component method, and then it derives a model of synchronous generators for the phase coordinate method.

Aspects of induction and synchronous motor analysis using dynamic phase co-ordinate theory

The phase co-ordinate method is applied to the study of some dynamic characteristics of single-cage deep-bar and double-cage induction motors. Particular attention is given to the dynamic run-up characteristics and how they are modified by the effects of saturation, inertia or load, and, for synchronous motors, by field connection. Induction motors are studied further in the complex transient situations arising owing to nonsimultaneous breaker operation, system fault condition, reswitching and plugging operation.