IEEE9 Buses System Simulation and Modeling in
PSCAD
Hongyan Teng,  Chongru Liu, Minxiao Han North China Electric Power University
Beijing, P.R. China
ayida1986@126
Shiying Ma,  Xiaojiang Guo China Electric Power Research Institute
Beijing, P.R. China
guoxiaojiang@epri.ac
Abstract—Based on the IEEE9 buses system provided by the simulation software BPA, the electromagnetic transient model of the 9-bus system in PSCAD/EMTDC is modeled in this paper. The steady-state characteristics and dynamic characteristics of IEEE9 buses system in BPA and PSCAD/EMTDC are compared in this paper. Then, the differences of simulation results between the elec
tromechanical transient model and the electromagnetic transient model are analyzed and the reasons of the difference are figured out in this paper.
Keywords- Power system simulation; BPA; PSCAD/EMTDC; Steady-state characteristics; Dynamic characteristics
I.I NTRODUCTION
Simulation system is an analog power system model and it can not describe the practical power system absolutely [1]. The simulation of power system is divided into two categories, one is analog simulation and another is digital simulation. Most of them are off-line simulations, and very few are on-line simulations. In order to get a reliable simulation result that approaches to the practical system or represents the characteristics of the practical system, the common method is to use various simulation tools to model and simulate the same system, and compare the simulation results for authenticity judgment [2-6]. It is very difficult to determinate which model is more accuracy when simulation results are different. In such situation, the theoretical calculation result or experience is usually needed to receive a reasonable judgment. If the model is accuracy, the steady-state and dynamic characteristics of the same system in different simulation software should be consistent to some extent. Therefore, thi
s method is generally used to judge the accuracy and the validity of the simulation model, especially for the two kinds of popular simulation software.
Every simulation tool has its own data format and sometimes they are not universal. But all the models base on the same physical model of the real power system, and for that they have many similar properties. Thus, the conversion of the data formats and the mathematical model of different simulation software are achievable and necessary. First of all, the differences and relationship between different models which described the same physical instrument in different simulation software must be analyzed.
In this paper, based on IEEE9 buses system provided by BPA, an electromagnetic transient model for the IEEE9 buses system is built in PSCAD/EMTDC. To illustrate the effectiveness of the model built in this paper, comparisons have been made for each individual kind of element model between BPA and PSCAD/EMTDC. The simulation results show that the electromagnetic transient model built in this paper has the same steady-state characteristics and similar dynamic characteristics compared with the model of the same system in BPA.
II.I NTRODUCTION OF BPA AND PSCAD
A.Introduction of BPA
BPA program is an off-line analysis tool for large power system which is developed by the computation method development team of Energy's Bonneville Power Authority (BPA) of U.S. federal Department in the 1960s. At present, the BPA which has been widely used in China is the Chinese version developed from the 1983’s version of US BPA by China Electric Power Research Institute. It has been used in power system for planning, designing, dispatching, operating, etc. It has become one of the important tools in power system analysis in China. The basic solution algorithm of Chinese BPA2.0 version is that linearizing differential equation, solving by trapezoidal quadrature rule, decomposing the admittance matrix with triangular method, and solving the network equation by iteration. This program is divided into two parts: power flow program and stability program [7-8].
B.Introduction of PSCAD
The main function of PSCAD is simulation of power system in time domain and frequency domain. It also can be used in harmonic research of AC system, analysis of transient torque, the starting of HVDC system and HVDC commutation. For AC/DC system, it can simulate for the electromagnetic transient process of a series or parallel multi-terminal transmission system, and    the interaction betwe
en the parallel AC and DC lines on the same tower, and so on. EMTDC program has the “snapshot” function. That is, it can record the sections at some time instants of the system. Based on this function further study on system transient process can be carried on.
Element library of PSCAD/EMTDC almost includes all kinds of elements in power system and this program also provides interface to MATLAB, through which we can easily use the visual numerical calculation function in MATLAB [7, 9-11].
This work is supported by Special Fund of the National Key Technology
R&D Program of China (2008BAA14B05) and National Natural Science
Foundation of China (50807013) and partially supported by “111”Project
(B08013) of China.)
978-1-4244-4813-5/10/$25.00 ©2010 IEEE
III. T HE ESTABLISHMENT OF SIMULATION MODEL  A. IEEE9 buses system in BPA
The wiring diagram of IEEE9 buses system is shown in
Figure.1:
Figure 1. Geographical system connection diagram of IEEE9 buses system
Models of the various elements of IEEE9 buses system in BPA are as follows:
1) Load model
Constant power models are used in the given BPA model. 2) Generator model
The dual-axis model with damper winding (sub-transient model) is chosen in the given BPA model. Generator 1 is a hydraulic turbine without excitation system, and generator 2 is a steam turbine with exciter, stabilizer, turbine governor and the prime mover. Generator 3 is a hydraulic turbine without excitation system. Generator 1 is the balancing machine.  3) Line model
Lumped parameter model is used, and all the values are per-unit one.
4) Transformer model
Double-winding transformer model is used, with the leakage reactance (p.u.) given.
B. Establish IEEE9-bue system in PSCAD
According to the parameters of IEEE9 buses system given in BPA, an IEEE9 buses system in PSCAD is built in this paper. The transformation rules of the parameters of the different models are in the following:
1) Load model
In correspondence with BPA, constant power models are used. Pay attention that the parameters of active and reactive power of the load are the value of single-phase.
2) Generator model
Synchronous machine models are used. Generator 1 and 3 are with excitation system and generator 2 is the one with exciter, stabilizer and turbine governor. Generator 1 is the balancing machine. It must be noticed that the parameters of generators in PSCAD are with the valid value.reactivepower
3) Line model
Overhead line models are used in correspondence with BPA.
4) Transformer model
Two-winding transformer models are used and the leakage reactance, the primary side and secondary side voltage in PSCAD is easy to get from the model card given by BPA. 5) Frequency
In PSCAD, default base frequency is 60Hz. Reset the frequency as 50Hz in this paper.
The model of IEEE9 buses system in PSCAD is as follows:
Figure 2. The model of IEEE9 buses system in PSCAD
IV. C OMPARISON OF SIMULATION RESULTS
A. Steady-state Characteristics
First, the power flow of IEEE9 buses system between BPA and PSCAD is compared to verify whether these two simulation models are represented the same power system. The results are shown in TABL
E.1:
TABLE I.  L OAD FLOW COMPARING FOR IEEE9 BUSES SYSTEM  name Voltage level /kV BPA PSCAD Difference Voltage /pu Angle /(°) Voltage /pu Angle /(°) Voltage /pu Voltage /%
Angle /(°)
Gen2 18.0 1.01 5.1 1.0065 5.1387 0.0035 0.3426-0.0387 Gen3 13.8 1.01 1.5 1.0059 1.5478 0.0041 0.4109-0.0478 Bus1 230 1.039 -3.4 1.0297 -3.4318 0.0093 0.89220.0318 Bus2 230 1.043 -0.7 1.0347 -0.6956 0.0083 0.7967-0.0044 Bus3 230 1.053 -1.3 1.0451 -1.2629 0.0079 0.7502-0.0371 BusA 230 1.006 -6.2 0.9983 -6.1707 0.0077 0.7643-0.0293 BusB 230 1.022 -5.5 1.0150 -5.4328 0.0070 0.6877-0.0672 BusC 230 1.032 -3.1 1.0241 -3.0721 0.0079 0.7645-0.0279 Balancing machine power/MVA
105.4+j43.7 104.6+j44.27  The results of comparison about the magnitude and angle of bus voltage in IEEE9 buses system between BPA and PSCAD show that the error of magnitude is less than 10-2  and the error of angle is less than 10-1. The simulation results of IEEE9 buses system prove the conversion from BPA to PSCAD in this paper is successful. BPA is an electromechanical transient simulation tool while PSCAD is an electromagnetic transient simulation tool They have different simulation accuracy and simulation speed. Thus it will bring some differences in simulation. The Tab.1
shows that the difference occurs at the second position after the decimal point.
B. Dynamic Characteristics
The duration of a three-phase grounding fault at line 1-B is 0.1s. The comparison of the generator power and the power flow of lines nearby the fault point are illustrated in following
figures:
Figure 3.
Active power of line1-A
Figure 4.
Reactive power of line1-A
Figure 5.
Active power of line1-B
Figure 6.
Reactive power of line1-B
Figure 7.
Active power of generator 1
Figure 8.
Reactive power of generator 1
Figure 9. Active power of generator 2
Figure 10.
Reactive power of generator 2
Figure 11.
Active power of generator 3
Figure 12. Reactive power of generator 3
It can been seen from the figures that the variation values of power of generators and power flow of lines are roughly equivalent in the duration of fault beginning, clearing and recurring to a steady-state situation. The amplitudes of generators active power and lines active power are roughly equivalent, but the reactive power of generators and lines are not very identical. The reasons for difference of reactive curves are due to the difference of exciting systems in the two simulation software.
V.
C ONCLUSION
The simulation results of IEEE9 buses system between BPA and PACAD are compared in this paper. It is shown that the steady-state characteristics are of good identity between these two simulation tools. But for the dynamic characteristics, there is a little difference in the duration and restoration process of fault. This phenomenon occurs because of the different exciting systems in the two simulation tools.
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