• 대한전기학회논문지:전력기술부문A
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• 제49권1호
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• pp.6-12
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• 2000

This paper presents various processes of dynamic voltage collapse which is initiated by various power system disturbances, and the impacts of dynamic voltage controllers. According to the analysis results, the composition of induction motors with short time constants affects the voltage collapse strongly. Also, it is proved that the addition of fast acting reactive compensation devices, such as SVC, at high reactive loss sensitivity($$\delta$$Q$$_luss/\delta$$P$$_L$$) buses could be one of the best countermeasure to escape the voltage collapse.

• 대한전기학회논문지:전력기술부문A
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• 제48권9호
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• pp.1103-1111
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• 1999

STACOM will be utilized to control substation voltage in the near future. Although STACOM shows good voltage regulation performance owing to its rapid and continuous response, it needs additional reactive power compensation device to keep control margin for emergency such as fault. ULTC transformer is one of good candidates. This paper presents a Kohonen Neural Network (KNN) based coordination control scheme of ULTC transformer and STACOM. In this paper, the objective function of the coordination control is minimization of both STACOM output and the number of switchings of ULTC transformer while maintaining substation voltage magnitude to the predefined constant value. This coordination, control is performed based on reactive load trend of the substation and KNN which offers optimal tap position in view of STACOM output minimization. The input variables of KNN are active and reactive power of the substation, current tap position, and current STACOM output. The KNN is trained by effective Iterative Condensed Nearest Neighbor (ICNN) rule. This coordination control applied to IEEE 14 bus system and shows satisfactory results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 F
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• pp.2470-2474
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• 1999

The main drawback of parallel type active power filters (APFs) is the large capacity required for harmonic compensation. This paper evaluates the APF capacity requirement for harmonic/reactive power compensation for thyristor converter load. Theoretically achievable maximum power factor under partial load is evaluated. it is shown that the APF capacity can be considerably reduced by deliberately limiting the peak current, while maintaining the filtering performance with an acceptable total harmonic current level. the minimum capacity requirement of APF with current limiting is evaluated as a function of the firing angle of thyristor converter and short circuit ratio(SCR).

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 A
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• pp.289-291
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• 2001

This paper represents the application of the Static Var Compensator (SVC) on the electric railway power supply system to compensate for the voltage drop. The high reactance of line and a heavy train load consume a significant amount of the reactive power which results the voltage drop. This paper shows that the SVC is necessary for voltage compensation in the railway power supply system and verify effectiveness of the SVC through the simulation by using PSCAD/EMTDC. In this paper, the case studies were performed with the various line length and train loads.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.149-151
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• 2005

This paper deals with the novel control algorithm of single-phase hybrid active power filter for the compensation of harmonic current components in nonlinear R-L load with passive active power filters. To construct two-axes coordinate, an imaginary second phase was made by giving time delay to line current. In this proposed method, the new signal, which was the delayed through the filtering by the phase-delay property of low-pass filter, is used as the secondary phase. Because two phases have different phase, instantaneous calculation of harmonic current is possible. In this paper, a reference voltage is created by multiplying gain of filter by compensation current using the rotating reference frames that synchronizes with source-frequency, not applying to instantaneous reactive power theory which has been used with the existing fixed reference frames. This paper shows the experimental results, which provide a high accuracy and extremely fast response of single-phase hybrid active Bower filter under the operation with the proposed control method.

• Journal of Electrical Engineering and Technology
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• 제12권2호
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• pp.751-760
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• 2017

This paper proposes a point of common coupling (PCC) voltage compensation algorithm using a current limitation strategy for use in distributed generation (DG). The proposed strategy maintains the PCC voltage by prioritizing currents when an output current reference is larger than the current capacity of the power condition system (PCS) of the DG. With this strategy, the DG outputs the active current, reactive current, and the negative sequence current. The DG uses the reactive current for maintaining the PCC voltage within a normal range; the negative sequence current is used for reducing the PCC voltage unbalance. The proposed method was verified using PSIM simulation and experimental results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 D
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• pp.886-890
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• 1997

This paper presents shows various process of dynamic voltage collapses which were initiated by power system disturbances, and the impacts of dynamic voltage controllers. According to the analysis results, the composition of induction motors with short time constant strongly affect the voltage collapse. To escape the voltage collapse, adding fast acting reactive compensation device, such as SVC, at high reactive loss sensitivity(${\partia}Qloss/{\partia}PL$) point could be one of a good countermeasure.

• Journal of Power Electronics
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• 제9권4호
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• pp.612-622
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• 2009

The short circuit ratio (SCR) of a given grid is able to show the stability of the system in the case of unwanted elements, such as wind turbulence. This paper presents the simulation of a model of the doubly fed induction generator in the simulation software PSCAD/EMTDC. This model has been used to study flicker during continuous operation and the effect of SCR and grid impedance angle on flicker emission. Simulation results show that compensation of the stator reactive power is an effective method to considerably reduce the flicker levels, irrespective of the grid conditions.

• Journal of Power Electronics
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• 제13권5호
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• pp.877-883
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• 2013

This paper discussed a transformer-less shunt static synchronous compensator (STATCOM) with consideration of the following aspects: fast compensation of the reactive power, harmonic cancelation and reducing the unbalancing of the 3-phase source side currents. The STATCOM control algorithm is based on the theory of instantaneous reactive power (P-Q theory). A self charging technique is proposed to regulate the dc capacitor voltage at a desired level with the use of a PI controller. In order to regulate the DC link voltage, an off-line Genetic Algorithm (GA) is used to tune the coefficients of the PI controller. This algorithm arranged these coefficients while considering the importance of three factors in the DC link voltage response: overshoot, settling time and rising time. For this investigation, the entire system including the STATCOM, network, harmonics and unbalancing load are simulated in MATLAB/SIMULINK. After that, a 35KVA STATCOM laboratory setup test including two parallel converter modules is designed and the control algorithm is executed on a TMS320F2812 controller platform.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 정기총회 및 학술대회 전문대학교육위원
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• pp.98-99
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• 2008

The first swing instability is the very important problem in power system operation. In this paper, the effective countermeasures to the instability. We studied the reinforcement of the transmission lines, generation tripping and reactive compensation are considered as alternative to improve transient stability.