• Journal of Power Electronics
• /
• v.7 no.3
• /
• pp.233-237
• /
• 2007

This paper deals with the new HVDC interaction which was observed in the Jeju-Haenam HVDC system. The interaction is not from a system malfunction or controller loop problem but from the change of AC network scheme and the network operating condition. We have found that the interaction is caused by the voltage oscillation between synchronous compensator and HVDC shunt reactor. We analyzed the cause of the interaction and suggested a solution.

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.55 no.4
• /
• pp.163-171
• /
• 2006

This paper presents a definition of sync phenomenon occurring in power systems, and describes the characteristics of sync in basic electric circuits. In addition, sync observed in basic circuits was extended to the analysis of dynamic characteristics in power systems. This paper, moreover, describes the sync occurring among system outputs from time domain simulation for two-area systems. In power systems, sync is a common phenomenon that is always observed among generator powers or bus voltages. Thus, we can use sync to obtain the characteristics of power systems without being bound to a specific operating point. Sync can be useful information in power system operation and planning.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.56 no.10
• /
• pp.1807-1813
• /
• 2007

This paper deals with extending the variable natural oscillation frequency range of an active integrated FET oscillator. In this paper, we conform experimentally that the variable range of the natural oscillation frequency is expanded about three times in the oscillator controlled by the varactor diode. When the frequency difference is given to the oscillators in the two element antenna system, phase difference appeared between the oscillators. The 2-, 3-, 4-, 5-element patch antenna arrays are composed for the beam scanning experiments. All the above patch antennas show good phased array characteristics. The range of the scanning angle is about $30^{\circ}$, and the radiation power is gradually increased from $50{\mu}W\;to\;200{\mu}W$. The radiation patterns we sharpened as the number of elements is increased.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.38 no.5
• /
• pp.337-342
• /
• 1989

Since the late 1960s, the selection of the parameters of power system stabilizer (PSS) to damp out sustained low frequency oscillation of power generators in the steady state has been an active research area. This paper presents a new approach to select the optimal PSS parameters using the sensitivity of the quadratic performance with respect to the PSS parameters. The proposed algorithm has been applied to Seo-Cheon fossil power plant.

• Proceedings of the KIEE Conference
• /
• 2011.07a
• /
• pp.1292-1293
• /
• 2011

Electric double layer capacitor (EDLC) is used to overcome power quality problem caused by output power oscillation of wind turbines. A novel EDLC application for permanent magnet synchronous generator type wind power generation system is proposed in this paper. The structure of the proposed system is cost-effective and efficient. The proposed system including an EDLC is modeled and analyzed by PSCAD/EMTDC. The simulation results show the effectiveness and major features of the proposed system.

• Proceedings of the KIEE Conference
• /
• 1998.11a
• /
• pp.326-328
• /
• 1998

This paper presents an optimal fuzzy power system stabilizer to damp out low frequency oscillation. The fuzzy logic controllers has been applied to a power system stabilizing controllers. But the design of a fuzzy logic power system stabilizer relies on empirical and heuristic knowledge of human experts as well as many trial-and-errors in general. This paper presents the optimal design method of the fuzzy logic stabilizer using the genetic algorithm, which is the optimization method based on the mechanics of natural selection and natural genetics. The proposed method tunes the parameters of the fuzzy logic stabilizer in order to minimize the consuming time during the design process. In this paper, the proposed method tunes the shape of membership function of the fuzzy variables. The proposed system is applied to the one-machine infinite-bus model of a power system. Through the case study, the efficiency of the fuzzy stabilizing controller tuned by genetic algorithm is verified.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.35 no.8
• /
• pp.353-362
• /
• 1986

This paper shows that 6 pulse converter instead of 12 pulse converter can be used for the control of Superconducting Magnet Energy Storage(SMES) to improve the stability and to suppress the voltage fluctuation of power system. In order to prevent the commutation failure, when 6 pulse converter used for simultaneous control of real power and reactive power is asymmetrically controlled, stable control region has been presented by analyzing the commutation phenomena at critical points which distinguish the stable control region from the unstrol control region. Harmonic components of line current and output voltage have been calculated. Finally, computer simulation of power system stabilization has been presented to show the effectiveness of the proposed method. According to the computation results, SMES controlled by the 6 pulse converter is an effective measure in reducing the oscillation and the transient instability of the power system.

• Proceedings of the KIPE Conference
• /
• 2012.07a
• /
• pp.273-274
• /
• 2012

This paper investigates control algorithms for a doubly fed induction generator(DFIG) with a back-to-back three-level neutral-point clamped voltage source converter in medium voltage wind power system under unbalanced grid conditions. Two different control algorithms to compensate for unbalanced conditions are proposed. Evaluation factors of control algorithm are fault ride-through(FRT) capability, efficiency, harmonic distortions and torque pulsation. Zero regulated negative sequence stator current control algorithm has the most effective performance concerning FRT capability and efficiency. Ripple-free control algorithm nullifies oscillation component of active power and reactive power. Ripple-free control algorithm shows the least harmonic distortions and torque pulsation. Combination of zero regulated negative sequence stator current and ripple-free control algorithm control algorithm depending on the operating requirements and depth of grid unbalance presents the most optimized performance factors under the generalized unbalanced operating conditions leading to high performance DFIG wind turbine system.

• Proceedings of the KIEE Conference
• /
• 2006.07a
• /
• pp.230-231
• /
• 2006

In this paper, the RCF(Resistive Companion Form) analysis method is used to analyze small signal stability of power systems including GTO controlled FACTS equipment such as SSSC. To apply the RCF analysis method in power system small signal stability problems, state transition equations of power system equipments and power systems with SSSC are presented. In eigenvalue analysis of power systems by the RCF analysis method, SSSC is modelled into the equivalents voltage source model and PWM switching circuit model. As a result of simulation, the RCF method is very powerful to calculate the oscillation modes exactly after the switching operations, and useful to analyze the small signal stability of power systems with periodic switching device such as SSSC.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
• /
• 2001.11a
• /
• pp.65-72
• /
• 2001

Power system stabilizer act efficiently to damp the electromechanical oscillations in interconnected power systems. This paper presents an algorithm for the optimal parameter selection of a power system stabilizer in two-area power systems with a series HVDC link. This method is one of the classical techniques by allocating properly pole-zero positions to fit as closely as desired the ideal phase lead between the voltage reference and the generator electrical power and by changing the gain to produce a necessary damping torque over the matched frequency range. Control of HVDC converter and inverter are used a constant current loop. Proper parameters of PI controllers are obtain based on the Root-locus technique in other to have sufficient speed and stability margin to cope with charging reference values and disturbance. The small signal stability arid transient stability studies using the PSS parameters obtained from this method show that a natural oscillation frequency of the studycase system is adequately damped. Also the simulation results using the HVDC converter and inverter parameters obtained from this proposed method show proper current control characteristics. The simulation used in the paper was performed by the Power System Toolbox software program based on MATLAB.