• KIEE International Transactions on Power Engineering
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• v.4A no.2
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• pp.51-57
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• 2004

This paper describes the dynamic performance of a variable speed wind turbine system responding to a wide variety of wind variations. Modeling of the wind generation using power electronics interface is proposed for dynamic simulation analysis. Component models and equations are addressed and their incorporations into a transient analysis program, PSCAD/EMTDC are provided. A wind model of four components is described, which enables observing dynamic behaviors of the wind turbine resulting from wind variations. Controllable power inverter strategies are intended for capturing the maximum power under variable speed operation and maintaining reactive power generation at a pre-determined level for constant power factor control or voltage regulation control. The components and control schemes are modeled by user-defined functions. Simulation case studies provide variable speed wind generator dynamic performance for changes in wind speed

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.5
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• pp.376-383
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• 2022

The improved performance of computer parts, such as graphic card, CPU, and main board, has led to the need for power supplies with a high power output. The dynamic load profile rapidly changes the usage of power consumption depending on load operations, such as PC power and air conditioner. Under dynamic load profile conditions, power consumption can be classified into maximum, normal, and standby power. Several problems arise in the case of maximum power. Peak power is generated at the system power source in the maximum-power situation. Frequent generation of peak power can cause high-frequency problems and reduce the life of high-pressure parts (especially high-pressure capacitors). For example, when a plurality of PCs are used, system overload occurs due to peak power generation and causes problems, such as power failure and increase in electricity bills due to exceeded contract power. To solve this problem, a system peak power limit/compensation power circuit is proposed for a power supply under dynamic load profile conditions. The proposed circuit detects the system current to determine the power situation of the load. When the system current is higher than the set level, the circuit recognizes that the system current generates peak power and compensates for the load power through a converter using a super capacitor as the power source. Thus, the peak power of loads with a dynamic load profile is limited and compensated for, and problems, such as high-frequency issues, are solved. In addition, the life of high-pressure parts is increased.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.4
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• pp.444-450
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• 2013

This paper presents the criteria for setting the dynamic operating mode of BESS(Battery Energy Storage System) in the bulk power systems. ESS has been expected to improve the degraded dynamic performance of the power system with high penetration of the renewable resources. While ESS is controlled in steady state or dynamic operating mode for its better effectiveness depending on the operating conditions of power systems, the criteria for setting the dynamic operating mode for the transient period needs to be robust enough to cover all the different conditions. The proposed criteria consider the varying conditions and the operating practices of the bulk power systems.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.10
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• pp.3810-3830
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• 2015

In this paper, we investigate the differential game theoretic approach for distributed dynamic cooperative power control in cognitive radio ad hoc networks (CRANETs). First, a payoff function is defined by taking into consideration the tradeoff between the stock of accumulated power interference to the primary networks and the dynamic regulation of the transmit power of secondary users (SUs). Specifically, the payoff function not only reflects the tradeoff between the requirement for quickly finding the stable available spectrum opportunities and the need for better channel conditions, but also reveals the impact of the differentiated types of data traffic on the demand of transmission quality. Then the dynamic power control problem is modeled as a differential game model. Moreover, we convert the differential game model into a dynamic programming problem to obtain a set of optimal strategies of SUs under the condition of the grand coalition. A distributed dynamic cooperative power control algorithm is developed to dynamically adjust the transmit power of SUs under grand coalition. Finally, numerical results are presented to demonstrate the effectiveness of the proposed algorithm for efficient power control in CRANETs.

• Journal of Power Electronics
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• v.12 no.1
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• pp.145-156
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• 2012

These days, the application of electronic power transformers (EPTs) is expanding in place of ordinary power transformers. These transformers can transmit power via three or four wire converters. Their dynamic performance is extremely important, due to their complex structure. In this paper, a new method is proposed for improving the dynamic performance of distribution electronic power transformers (DEPT) by using sliding mode control (SMC). Hence, to express the dynamic characteristics of a system, different factors such as the voltage unbalance, voltage sag, voltage harmonics and voltage flicker in the system primary side are considered. The four controlling aims of the improvement in dynamic performance include: 1) maintaining the input currents so that they are in sinusoidal form and in phase with the input voltages so they have a unity power factor, 2) keeping the dc-link voltage within the reference amount, 3) keeping the output voltages at a fixed amount and 4) keeping the output voltages in sinusoidal and symmetrical forms. Simulation results indicate the potential and capability of the proposed method in improving DEPT behavior.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.6
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• pp.325-336
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• 2006

This paper deals with the dynamic analysis of variable speed wind power systems with doubly-fed induction generators (DFIG). First, the mathematical modeling of wind farm which consists of turbine rotor, DFIG, rotor side and grid side converter and control systems is presented. In particular, the equation for dynamic modeling of the DFIG and the AC/DC/AC converter is expressed as dq reference frame. And then, on the basis of mathematical modeling for each component of wind farm, dynamic simulation algorithms for speed and pitch angle control of wind turbine and generated active and reactive power control of the DFIG and the AC/DC/AC converter are established. Finally, Using the MATLAB/SIMULINK, this paper presents dynamic simulation model for 6MW wind power generation systems with the DFIG considering distribution systems and performs the dynamic analysis of wind power systems in steady state. Moreover, this paper also presents the dynamic performance for the case when the voltage sag in grid source and phase fault in bus are occurred.

• Journal of Digital Contents Society
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• v.10 no.2
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• pp.217-223
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• 2009

In order to decrease the power consumption in Embedded Linux environment based on XScale PXA255, We produce the device driver of DFS(Dynamic Frequency Scaling) technique, design and implement the middleware DFM(Dynamic Frequency Management) to scale the power of embedded target board with porting this device drive, suggest the method to reduce the Embedded system's power consumption.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.9
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• pp.913-919
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• 2008

Dynamic characteristics of a wrist power transmission of an industrial robot are studied. The wrist power transmission has complex structure characteristics, because it is composed with several shafts and gear system. We used an analytical method to investigate the dynamic characteristics. An analytical model is a rigid model which is composed with masses and springs. Both bearing and gear contact model represent equivalent stiffness springs which are determined by the experiment. In order to investigate the dynamic tendency of the robot wrist power transmission, we simulate the analytical model. There is a dynamic analysis tool which is called the RecurDyn. To verify the analytic results, we experiment a signal analysis which is an overall noise level of the robot. By the parametric study of the element of the robot, we study an improvement method of dynamic characteristics.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.1
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• pp.33-41
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• 2016

To verify that the friction damper used to high buildings as a kind of control technology of wind vibration can reduce dynamic behaviors of PTTs effectively, slip dampers in this paper are proposed to absorb the energy through relatively frictional movement of slip dampers applied to main post of a PTT (Power Transmission Tower) when dynamic displacement of a PTT occurs. The result of dynamic analysis is presented to determine the capacity of the damper system by controlling damping ratio on the resonance condition. It is observed that by installing slip dampers at a PTT the strain amplitudes of the main post caused by wind load are effectively reduced. Therefore it is shown that the proposed damper satisfies the strengthened wind-load design standards, and its efficacy was also validated experimentally by field testing.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.12
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• pp.2183-2189
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• 2011

Since main portion of the required electric power in Jeju Island is provided from the mainland through two HVDC lines, Jeju HVDC has a most significant impact on Jeju power system. Average wind speed of Jeju Island is the highest among several candidates in South Korea. So, Jeju Island has been a suitable site for the construction of wind farms where several wind farms are now operating and several others to be sited. Since the large-scale wind generation could have adverse impacts on the stable operation of Jeju power system, wind power is also important for the stability of Jeju power system. Therefore, accurate modeling of Jeju HVDC and wind farms is required for stability analysis of Jeju power system. In this paper, PSS/E-based dynamic modeling of Jeju HVDC and DFIG wind farms is proposed. Model-writing technique of PSS/E is used to develop USRAUX model and USRMDL model for controlling the frequency of HVDC and imposing an operation limit of wind power, respectively. Dynamic characteristics of Jeju HVDC and DFIG wind farms are analyzed through the dynamic simulations. The simulation results show the effectiveness of the developed models for Jeju power system.