Principal Research Results

Power System Dynamic Simulation Method for Integrated Simulations ofActive Power Control and Reactive Power Control−Development of a Computer Program for Dynamic Simulations of Electric Power
Systems under Long-term Change in System Generations and Loads−
BackgroundIn the liberalization of electric power transaction, the active power will be treated separately from the reactive power. From
viewpoint of the electric power supply security, however, it is necessary to consider the active and reactive power at one time. In addition, more severe operations of power systems will be requested from the need of more effective uses of existing power apparatus. In
these situations, for technical studies on more proper operations of the active power control and the reactive power control, dynamicsimulation method for integrated simulations of those controls becomes essential. However, conventional simulation methods for theactive power control are not able to present behavior of the reactive power and voltage, and simulation methods for the reactive power
control are not able to present behavior of the active power and frequency.

Objectives
To develop a new power system dynamic simulation method for integrated simulations of the active power control and thereactive power control, and to demonstrate simulation performance of the developed method

Principal Results
1. Features of developed method
A computer program for power system dynamic simulation method has been developed, which enables integrated simulations of the active power control and the reactive power control of power systems under the long-term change in power generations
and loads. Summary of available simulation conditions and models of the developed program is shown in Table-1, and outline ofstructure of the program is shown in Figure-1. The features of the developed program are as follows:
1) A new numerical integration algorithm with variable time-step has been developed to achieve the high-accuracy and high-speed at
the same time for the long-term simulations. The algorithm shortens the simulation time-step when fast phenomena such as the synchronous power swings occur.
2) The simplified models of the voltage/reactive control and the load frequency control can be comparatively easily replaced to theprogram user’s inherent detailed models. This feature enables detailed simulations associated with needs of the user.
2. Performance of developed method
The results of application of the developed program to the IEEJ ＊ 1 EAST-30-generators test-power system shows that thepower system dynamic behaviors under changes in the system generations and loads in the time frame of one-hour is simulated witharound 1 to 2 minutes in CPU ＊ 2 time. The example of the simulations (Figure-2) shows dynamic responses of generator active powers, node voltages, system frequency and tie-line power flows, which cannot be simultaneously presented by the conventional simulation methods.
3. Expected application fields of developed method
The developed method is expected to be a new method for supporting technical studies on more delicate security control andmore effective operation of power systems, including analysis of dynamic voltage stability, examination of proper generator regulation
capacity for load frequency control and voltage control (Table-2).

Future Developments
After enhancing the available simulation conditions and models, the developed method will be proposed to the electric power companies of Japan.
Main Researcher: Toshio Inoue,
Senior Research Scientist, Electric Power Systems Sector, System Engineering Research Laboratory
ReferenceT. Inoue, T. Kumano, “Power System Long-term Dynamic Simulation for Integrating Frequency/Active Power Control andVoltage/Reactive Power Control”, CRIEPI Research Report No. T03046, April 2004 (in Japanese)＊1：Institute of Electric Engineers of Japan＊2：Intel Celeron 1.2GHz

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4. Power Delivery - Cost reduction and ensuring reliability of power delivering

Table1 Available simulation conditions and models
Simulation conditions and models
Change in system generations and loads
On-line/off-line of generator
Time series data of generations and loads
Transmission line fault (3LG-O-C)
Generator (detailed Park model)Models
Generator AVR(1) Generations
Generator OEL
Generator prime mover (Fossil-fired plant)
Induction motor(2) Loads
Constant impedance(3) System control Simplified voltage/reactive power control
Simplified load frequency control
Conditions

Fig.1 Structure of developed method(1) Regulation of generator active power(2) Load node voltage(3) Frequency and tie-line power flow

Fig.2 Simulation results of dynamic behaviors of a test power system under system load decrease (example)< IEEJ EAST-30-generators test-power system where 8 generators are operated in active power regulation >Table 2 Expected application fields of developed method
Example of application fields
Effective simulation of voltage stability
including dynamic behaviors of generatorsand loads

Technical studied on proper generator
regulation capacity for load frequency
control and voltage/reactive power control

Advantage of developed method
Dynamic simulations of the voltage stability in rapid loadincrease period and so on can be implemented much fasterthan the conventional method. In the simulations,activation of the generator over-excitation limiter, and its
ill effects upon the synchronous stability are included.
Interaction between the generator active power regulation
capacity for control of system frequency and tie-line power
flow, and the reactive power regulation capacity forcontrol of node voltages is able to be simulated. Thus
technical studies on more effective generator regulation
capacity and control scheme are available.

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