• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.2
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• pp.232-238
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• 2009

Flicker, also known as voltage fluctuation, is a newest problem of power quality issues, because it is caused by nonlinear loads such as electrical arc furnace and large-scale induction motor, which are country-widely used as the heavy industries of a country develop. An international standard, International Electrotechnical Commission (IEC) 61000-4-15, was published in 1997 and revised in 2003. With increasing concerns about flicker, its mitigation methods have been also studied. General countermeasures for flicker are divided into three categories: a) enhancing the capacity of supplying system, b) Series elements including series reactor and series capacitor and c) power electronic devices including static VAR compensator (SVC) and static synchronous compensator (STATCOM). This paper introduces how to mitigate the voltage flicker at the point of common coupling (PCC) and presents how to simulate and compare the flicker alleviating effects by each mitigation method, using IEC flickermeter based on the Matlab/Simulink program.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.1
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• pp.77-84
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• 1998

This paper describes a control system design for the transmission STATCOM by applying a no-linear state feedback, and the performance analysis of the control system by simulations and scaled-model experiments. A mathematical model for the STATCOM was derived using a 3-phase equivalent circuit and a perturbation state equation with respect to a typical operating point. A transfer function to describe the dynamics of STATCOM was derived by considering nonlinear state feedback. A controller design was completed by analyzing the feedback system stability with root locus method. The performance analysis of the conceived control system was verified by simulations with the EMTP and experiments with scaled model, assuming that the STATCOM is connected to an 154kV transmission system. The results show that the conceived control system has excellent performance to control the reactive power of the transmission system.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.7
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• pp.281-289
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• 2006

Advanced controllers among Flexible AC Transmission System(FACTS) devices employ self-commutated switching converters, VSI (Voltage Sourced Inverters), as the synchronous voltage source. Such controllers are SSSC (Static Synchronous Series Compensator), STATCOM (Static Synchronous Compensator) and UPFC (Unified Power Flow Controller). UPFC is series-shunt combined controller. Its series and shunt inverters can be modeled as SSSC and STATCOM but the dependant relation between the inverters is very complex. For that reason, the complexity makes it difficult to develop the UPFC model by simply combining the SSSC and STATOM models when we apply the model for conventional power system dynamic simulation algorithm. Therefore, we need each relevant models of VSI type FACTS devices for power system analysis. This paper proposes a modeling approach which can be applied to modeling of VSI type FACTS devices. The proposed method using Newton-type current injection method can be used to make UPFC, SSSC, and STATCOM models. The proposed models are used for 2-area test system simulation, and the results verify their effectiveness.

• Journal of Power Electronics
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• v.4 no.4
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• pp.205-216
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• 2004

In this paper, a three-phase induction machine-based wind power generation scheme is proposed. This scheme uses a low-cost diode bridge rectifier circuit connected to an induction machine via an ac load voltage regulator (AC-LVR) to regulate dc power transfer. The AC-LVR is used to regulate the DC load voltage of the diode bridge rectifier circuit which is connected to the three-phase self-excited induction generator (SEIG). The excitation of the three-phase SEIG is supplied by the static VAR compensator (SVC). This simple method for obtaining a full variable-speed wind turbine system by applying a back-to-back power converter to a wound rotor induction generator is useful for wind power generation at widely varying speeds. The dynamic performance responses and the experimental results of connecting a 5kW 220V three-phase SEIG directly to a diode bridge rectifier are presented for various loads. Moreover, the steady-state simulated and experimental results of the PI closed-loop feedback voltage regulation scheme prove the practical effectiveness of these simple methods for use with a wind turbine system.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.51-52
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• 2014

전력계통은 전력수요의 지속적인 성장에 따라서 전력설비의 추가를 지속적으로 추진하고 있지만, 심해지는 환경문제 등으로 인해 용지 확보에 어려움이 있다. 이로 인해 송전선로 장거리화, 용량부족량 등 전력계통에 여러 가지 복잡한 문제가 야기되는데, 이것은 곧 전력계통의 안정도와 직결된다. 이러한 문제를 효과적이면서 경제적인 해결방법으로 FACT(Flexible AC Transmission System)기술이 주목 받고 있다. FACTS 기기 중 SVC(Static Var Compensator)는 상용운전 중이며, 기존 동기조상기에 비해 저렴하고, 신속 정확한 전압제어를 하는 장점이 있다. SVC는 TCR(Thyristor Controlled Reactor)과 TSC(Thyristor Switched Capacitor), FC(Fixed Capacitor)등 여러 종류의 구성을 가질 수 있다. TCR과 TSC는 실제 운전에 앞서 여러 가지 방법으로 검증이 필요하다. 합성 시험회로 설비(Synthetic Test Circuit)는 TCR과 TSC 안에 존재하는 Thyristor Valve의 동작을 실제 동작 조건으로 동작시켜, 동작의 신뢰성을 검증하는 설비이다. 본 논문에서는 TCR의 Operational Test를 위한 STC를 기술하고 있다. 설계된 STC는 PSCAD를 사용하여 검증하였다.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.53 no.3
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• pp.122-128
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• 2004

This paper presents a control approach for designing a fuzzy-PI controller for a synchronous generator excitation and SVC system. A combination of thyristor-controlled reactors and fixed capacitors(TCR-FC) type SVC is recognized as having the most flexible control and high speed response, which has been widely utilized in power systems, is considered and designed to improve the response of a synchronous generator, as well as controlling the system voltage. A Fuzzy-PI controller for SVC system was proposed in this paper. The PI gain parameters of the proposed Fuzzy-PI controller which is a special type of PI ones are self-tuned by fuzzy inference technique. It is natural that the fuzzy inference technique should be based on humans intuitions and empirical knowledge. Nonetheless, the conventional ones were not so. Therefore, In this paper, the fuzzy inference technique of PI gains using MMGM(Min Max Gravity Method) which is very similar to humans inference procedures, was presented and applied to the SVC system. The system dynamic responses are examined after applying all small disturbance condition.

• Journal of Electrical Engineering and Technology
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• v.5 no.1
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• pp.116-128
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• 2010

Modeling of the three phase electric arc furnace and its voltage flicker mitigation are the purposes of this paper. For modeling of the electric arc furnace, at first, the arc is modeled by using current-voltage characteristic of a real arc. Then, the arc random characteristic has been taken into account by modulating the ac voltage via a band limited white noise. The electric arc furnace compensation with static VAr compensator, Thyristor Controlled Reactor combined with a Fixed Capacitor bank (TCR/FC), is discussed for closed loop control of the compensator. Instantaneous flicker sensation curves, before and after accomplishing compensation, are measured based on IEC standard. A new method for controlling TCR/FC compensator is proposed. This method is based on applying a predictive approach with closed loop control of the TCR/FC. In this method, by using the previous samples of the load reactive power, the future values of the load reactive power are predicted in order to consider the time delay in the compensator control. Also, in closed loop control, two different approaches are considered. The former is based on voltage regulation at the point of common coupling (PCC) and the later is based on enhancement of power factor at PCC. Finally, in order to show the effectiveness of the proposed methodology, the simulation results are provided.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.09a
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• pp.19-22
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• 2001

For stabilization and improving power factor in the power lines, various Static Var Compensators(SVC) have been considered to be installed and partly applicated already. With all these merits of the SVC, it stil has demerits, principally evoking harmonic problems. So far, many harmonic reduction type inverters have been used in various parts. In this paper, the reactive power is controlled by amplitude of the output voltage. This paper propose that the multiple voltage source inverter have controllable power factor made by load vary at receive-stage as lagging and leakage control. The theoretical analysis on this system was confirmed through the computer simulation and the experiments.

• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1039-1041
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• 1999

Recently Advanced Static Var Compensators(ASVC) or STATic Synchronous COMpesator(STATCOM) has been considered as a next generation reactive power controller. [2] STATCOM is a voltage source inverter(VSI) based static VAr compensator with only small capacitors on the do side. The main function of the STATCOM is to keep the bus voltage magnitude at the desired value. [1] This paper compares the PAM STATCOM with PWM STATCOM. The characteristics and the control method of each model is analyzed. And the simulation of STATCOMs based on the above two methods was presented.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.7
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• pp.323-331
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• 2000

Recently Advanced Static Var Compensators(ASVC) or STATic Synchronous COMpesator(STATCOM) has been considered as a next generation reactive power controller. The STATCOM is a voltage source inverter(VSI) based on the static VAr compensator with only small capacitors on the dc side. The main function of the STATCOM is to keep the bus voltage magnitude at the desired value. This paper compared the PAM STATCOM with the PWM STATCOM. The characteristics and the control method of each model is analyzed. And the simulation of STATCOMs based on the above two methods is presented.