Transient electromagnetic simulation and thermal analysis of the DC-biased AC quadrupole magnet for CSNS/RCS

Due to the large eddy currents at the ends of the quadrupole magnets for CSNS/RCS, the magnetic field properties and the heat generation are of great concern. In this paper, we take transient electromagnetic simulation and make use of the eddy current loss from the transient electromagnetic results to perform thermal analysis. Through analysis of the simulated results, the magnetic field dynamic properties of these magnets and a temperature rise are achieved. Finally, the accuracy of the thermal analysis is confirmed by a test of the prototype quadrupole magnet of the RCS.

PSCAD Based Multi-infeed HVDC System Simulation Validated by a Recorded Fault

More and more high voltage direct current(HVDC) converters are being located in a load area in the Yangtze River Delta Region in China. It's large transmission capacity and intensive placement are hardly seen in other countries. Accurate and reliable study tools and methods are extremely needed for power system engineers and researchers to deal with such problems which were never met before and otherwhere. A novel approach on electromagnetic modeling of alternating current / direct current(AC/DC) system is proposed and simulation is carried out to replay a real AC 3-phase to ground fault on a multi-infeed high voltage direct current(MIHVDC) system. AC system is specially simplified. Dynamic models and real parameters are adopted in main AC/DC equipments concerned and retained. Modeling and simulation are based on the power system computer aided design/electro-magnetic transient in direct current(PSCAD/EMTDC) system software package.Comparisons between simulation results and the records from the fault recorders are studied including both AC and DC quantities.

EMTP-type Program Realization of Krylov Subspace Based Model Reduction Methods for Large-Scale Active Distribution Network

Effective model reduction methods are required to deal with new challenges in active distribution network simulations that are on a large scale and have complicated structures.In the development of advanced electromagnetic transient simulation programs,automated model reduction plays an important role.This paper proposes an automated realization algorithm for the Krylov subspace based model reduction methods of an active distribution network with which the reduced model can be automatically established according to a given threshold of reduction error.The combined state-space nodal analysis framework is employed to apply the automated model reduction algorithm in popular EMTP-type simulation programs.Simulations are performed using PSCAD and a self-developed program to show the feasibility and validity of the proposed methods.

A new method of frequency-dependent network equivalence for power system

Electromagnetic transient simulation for large-scale power system is a time-consuming problem.A new frequency-dependent equivalence method is presented in the paper,which might significantly accelerate power system electromagnetic transient simulation.In the method,an effective algorithm is designed to directly transfer the port admittance determinant of external system's mixing matrix into admittance rational function;and the step-by-step strategy for the equivalence of actual large system is put forward,which further reduces the calculation quantities needed.Moreover,the study of multiple real root pole characteristics of admittance transfer function of two-port network is performed and a proposition is achieved.Based on the proposition and residue theorem,the equivalence system for external system corresponding to the admittance rational function is obtained.The computation complexity of the step-by-step equivalence method is about o(┌n/np×T┐)(┌┐ is upper integral operation,n is the total buses number of external system,N P is the total buses number of single step equivalence network,T is single step equivalence time),which indicates that the computation complexity of the method proposed has nearly linear relationship with the buses number of external system,and the method proposed has satisfactory computation speed.Since the mixing matrix of external system includes all the information of external system,therefore,port admittance rational function derived from it can reflect its full frequency characteristic and the equivalence network achieved has high equivalence precision.Moreover,since the port rational function is gained at the condition of the external system without source,which equals stable passive network,it could not show any unstable pole and need not extra measure to make the equivalence system stable.The test results of the samples and comparison with other methods demonstrate that the new method proposed is valid and effective.

Integrated protection based on multifrequency domain information for UHV half-wavelength AC transmission line

Half-wavelength AC Transmission(HWACT)can improve capability of AC transmission significantly.According to the basic principle of HWACT,the electromagnetic transient model of HWACT is built to analyze the fault transient process of transmission line.Based on fault characteristics of HWACT,the adaptability of traditional protections for transmission lines is analyzed briefly,such as current differential protection,distance protection and over current protection.In order to solve the problems of conventional protection caused by HWACT,a novel integrated protection based on multi-frequency domain information is proposed in this paper,which uses both the power frequency information and transient information.The integrated protection based on multi-frequency domain information takes advantages of power frequency and transient protections,which can not only improve the performance of traditional protection of AC transmission line but also realize fast fault judgment by transient travelling wave protection.