STUDY OF DIGITAL SIMULATION FOR THE CIRCUIT ELEMENTS AND ELECTROMAGNETIC RELAYS COMMONLY USED IN RELAY PROTECTIVE DEVICES

This paper applies the Gear-4 algorithm to constitute the companion models lor the circuit elements and electromagnetic relays commonly used in relay protective devices. The interface computation, which describes the node equation of companion model and differential equation of mechanical moving part for the electromagnetic Jelay, is also presented. For the reason mentioned above, it makes possible* to solve more accurately the transient process of relay protective devices including electromagnetic relay using the companion model method. The simplicity and effectiveness of interface computation have been proved by the example calcultaion.     

EQUIVALENT CIRCUIT METHOD FOR DYNAMIC DIGITAL SIMULATION OF HVDC CONVERTERS

This paper presents a transient mathematical model of the HVDC converters-Equivalent Circuit Method(ECM), which can describe all possible states of converter valves in a simple and explicit way. With the converter model, programs have been implemented for single and double bridge HVDC systems. The results of simulation to the normal and fault operation of HVDC system show that the method is flexible and reliable, and has the advantages of small calculation amount and less computer storage requirments. The programs based on this paper provide convenient, inexpensive and feasible tools for computer dynamic or transient analysis of the HVDC systems.     

SIMULATION STUDY OF ACTIVE POWER DISTORTION COMPENSATOR

In this paper, the effectes of modulation index, modulation frequency, modulation method and LPF parameters on current-fed active compensator arc studied by using digital simulation and the performances of voltage-fed active compensator are compared with those of the current-fed active compensator.     

MATHEMATICAL MODEL AND DIGITAL SIMULATION FOR A REGENERATIVE HEATING SYSTEMS OF 200MW REHEATING STEAM TURBINE

Based on the physical processes of regenerative heating systems, the mathematical models of regenerative system,reheat system and steam turbine for a 200MW reheating steam turbine are presented, and the digital simulation of them on IBM-PC is also provided in this paper. The present work is a part of the study of the dynamic characteristics of all power systems. The mathematical model is expressed into state space form ,and its matrix is standardized to avoid the repeatation of establishing the models of heat exchangers.     

A FAST ALGORITHM FOR DIGITAL SIMULATTON OF HVDC SYSTEMS

After considering the features of the differential equations which have described the dynamic behaviours of HVDC systems, a fast algori -thm is presented for these equations. Compared with the fourth Runge-Kutta Method,this method has less amount of calculation with the same precision, numerical stability and other properties. Therefore, the use of the method has greatly increased the speed of the digital simulation of HVDC systems.In this paper an example of calculation is given, and the results obtained hv using this example are compared with the results obtained by calculating with the fourth Runge-Kutta Method. The speed of simulation by using this method is about 1.8 timss as fast as that by using the fourth Runge-Kutta Method.     

AN ON-LINE ALGORITHM FOR PREDICTING THE TEMPERATURE OF POWER TRANSFORMER WINDINGS

The paper presents an on-line algorithm for predicting the average temperature of power transformer winding according to its load current. The algorithm has accounted for the whole history of load current and variations of ambient temperature. The overload capabilities of transformer can be increased by monitoring and controlling the winding temperature and the necessary durability of the transformer can be ensured. The algorithm can also forecast the future winding temperature and the time of reaching the max, permitted the assumed future load current and oil temperature.     

DIGITAL SIMULATION OF HIGH VOLTAGE AC/DC PARALLEL SYSTEMS

The method of companion model is applied to the digital simulation of high voltage hybrid AC/DC systems for the first trme in this thesis.The mathematical model of the digital simulation of hybrid AC/DC systems is represented. This method can model the normal states, faults and games of faults of any hybrid AC/DC systems. The method has a series of advantages : saving the computation and the amounts of memory, high precision and fast calculation and it can be used with convenience. The simulation results of a hybrid AC/DC system arc in consistent with that of theoretical analysis. It shows that the mathematical model, the simulation method and the program in this thesis are correct.     

THE ERRECT OF HIGH HARMONICS ON THE SELECTION OF THE SIZE OF TRANSFORMER CONDUCTOR

This paper analyses the additional stray losses of transformer winding caused by harmonics,and suggests that the influence of harmonics should be taken into consideration in the selection of the conductor' s size in rectifier transformer and converter transformer design.     

THE PRECISE SOLUTION OF MATHEMATICAL MODEL FOR TWO-STEP CARBURIZATION TREATMENT

The precise solution of mathematical model for two-step carburigation has been induced which is under the condition of the third boundary. This solution has been compared with the finite difference technique and its correctness and practicality have been proved.     

谷物通风干燥的数学模拟及试验

根据已发表的谷物干燥数学模型编写了谷物通风干燥模拟计算程序。利用该程序玉米,稻谷在不同干燥条件下的干燥时间,计算干燥过程中沿气流运动方向谷堆各点的水分及粮温变化,并可对谷物机械通风干燥的性能进行综合分析研究。     

STATE VARIABLE METHOD FOR DYNAMIC SIMULATION OF HVDC SYSTEMS

A flexible mathematical model used for dynamic simulation studies of HVDC systems which is based on the stale variable method is presented, and the correspongding computer program has been implemented. Generality, easy to use, and suitable to run on microcomputers are the main features of the model and the computer program. Therefore the model is easy to be extended for application. An example is given in the paper to verily the coneclness of the model and the program.     

THE COMPARISON OF TWO METHODS FOR LOAD EXPRESSION IN PRODUCTION SIMULATION

Two methods for load expression in production simulation are studied,and the errors are analyzed and compared when the two methods are used in the direct method of probabilistic production simulation.     

MATHEMATICAL MODEL OF CAPACITANCE SENSOR FOR MOISTURE MEASUREMENT

This paper presents a theoretical mathematical model of capacitance sensor for moisture measurement. The practical mathematical model is provided using least squares theory, an applied example shows higher accuracy of the model.     

INFORMATION THEORY COMBINATION FOR ERROR ANALYSIS OF. SAMPLING-QUANTIZATION FOR DIGITAL MEASUREMENT SYSTEMS

This paper presents a new error analysis method based on the information theory. The analyse results of error of a digital measurement system will be illustrated more reasonably. This method is defined information theory combination, it will overcome the unintention between the uncertainty and the standard error of measuring results by traditional error analysis. On the basis of error spectrum analysis of sampling and quantization, an optimum digital filtering method is also presented in this paper. Simulation and testing show that the method is more resultful.     

STUDY ON HEAT TRANSFER MATHEMATICAL MODEL BETWEEN BILLETS AND ROLLERS FOR THE SECONDARY COOLING ZONE IN BILLET CONTINUOUS CASTING

A mathematcal model of heat transfer between the billet and the roller for the seeondary cooling zone in billet continuous casting is established. By means of the simulated test,a regres sion relation between the heat flow from the billet into the roller and the surface temperature and cast ing speed and spray water density obtained. The calculated theoretical values for change of surface temperature are in agreement with the measured data, these studies may contribut to the quantitative analysis and the calculation of the heat transfer of the secondary cooling zone.     

THE ANISOTROPY DISCONTINUITY MODEL DUO TO THE STRIKE OF THE TAGGED DISCONTINUITIES

In this paper, on the base of the original shapes of discontinuities in engineering gedogy, we mainly discuss the ralations among the shape of discontinuity, the restraining effects of discontinuity deformations (including the normal deformation and the shear deformation ) and the crustal stress. Then we put forword the concept of the pseudo-dilatancy ungle which can indicate the motion direction, set up the anisotropic discontinuity model, and give some important results and formula for illustrating truly the discontinuities in rock engineering.     

APPLICATION OF ARMA MODEL AND PARAMETER IDENTIFICATION TO SIMULATION OF PULSATING WIND

With the wide use of tall buildings,highrise structures,suspended structures and some other flexible structures,the analysis ofstructure responses under pulsating wind has been more and more valuedin the field of engineering.It is necessary to effectively give pulsatingwind records with certain stochastic characteristics for the analysis ofstructure responses under winds and the design of anti-vibration struc-tures.Using autoregressive moving average(ARMA)model and techoniqueof parameter identification,this paper studies the method to simulatingpulsating winds which are compatible with given factors(such as powerspectrum or other stochastic characteristics).The conclution shows thatit is an effective method.     

The Staged Simulation Method for Power Electronics Circuits

This paper in troduces a staged simulation method fur power electronics circuits,presents an exampleued the method for the CSI/IM drive system.