• JOURNAL OF ELECTRICAL WORLD
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• s.427
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• pp.30-35
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• 2012

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.192-193
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• 2006

An AC electrical railroad system has rapidly changing dynamic single-phase load, and at a feeding substation, three-phase electric power is transformed to the paired directional single-phase electric power. There is a great difference in electrical phenomenon between the load of AC electrical railroad system and that of general power system. Electric characteristics of AC electrical railroad's trainload are changed continuously according to the traction, operating characteristic, operating schedule, track slope, etc. Because of the long feeding distance of the dynamic trainload, power quality problems such as voltage drop, voltage imbalance and harmonic distortion may also occur to AC electrical railroad system. These problems affect not only power system stability. but also power quality deterioration in AC electrical railroad system. The dynamic simulation model of AC electrical railroad system presented by PSCAD/EMTDC is modeled in this paper, and then, it is analyzed voltage drop and power quality for AC electrical railroad system both with single-Phase distributed STATCOM(Static Synchronous Compensator) installed at SP(Sectioning Post) and without.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.4
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• pp.299-305
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• 2013

The complexity and severe nonlinearity of multi-machine power systems make it difficult to design a control input for voltage regulation using modern control theory. This paper presents a model-based PID control scheme for the regulation of the bus voltage to a desired value. To this end, a fourth-order linear system is constructed using input and output data obtained using the TSAT (Transient Security Assessment Tool); the input is assumed to be applied to the grid through the STATCOM (STATic synchronous COMpensator) and the output from the grid is a bus voltage. On the basis of the model, it is identified as to which open-loop poles of the system make the response to a step input oscillatory. To reduce this oscillatory response effectively, a model-based PID control is designed in such a way that the oscillatory poles are no longer problematic in the closed loop. Simulation results show that the proposed PID control dampens the response effectively.

• Journal of Power Electronics
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• v.13 no.5
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• pp.909-918
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• 2013

This paper proposes a coordinated control of the reactive power between the STATCOMs (static synchronous compensators) and the grid-side converters (GSC) of wind farms equipped with PMSGs (permanent-magnet synchronous generators), by which the voltage fluctuations at the PCC (point of common coupling) are mitigated in the steady state. In addition, the level of voltage sags is reduced during grid faults. To do this, the GSC and the STATCOM supply reactive power to the grid coordinately, where the GSCs are fully utilized to provide the reactive power for the grid prior to the STATCOM operation. For this, the GSC capability of delivering active and reactive power under variable wind speed conditions is analyzed in detail. In addition, the PCC voltage regulation of the power systems integrated with large wind farms are analyzed for short-term and long-term operations. With this coordinated control scheme, the low power capacity of STATCOMs can be used to achieve the low-voltage ride-through (LVRT) capability of the wind farms during grid faults. The effectiveness of the proposed strategy has been verified by PSCAD/EMTDC simulation results.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.163-164
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• 2015

LNG복합발전은 수요지 인근에 건설이 가능한 장점이 있어 수도권 인근 발전소 중 상당한 부분을 차지하고 있다. 이러한 LNG 복합발전은 수도권 부하비율 감소에 따라 발전량이 줄어들게 된다. 2018년 계통데이터를 기반으로 수도권의 부하수준이 70%까지 떨어졌을 때, 거의 모든 수도권 복합발전이 정지함을 확인할 수 있다. 이 때, 신가평과 강원을 잇는 765kV급 융통선로의 2회선 상정사고 발생 시 수도권 무효전력 공급원이 줄어들어 전압이 불안정해진다. 이와 같은 상정사고를 대비해 수도권 복합발전 중 일부는 제약운전을 시행해야 한다. 본 논문에서는 제약운전을 하는 수도권 LNG복합발전의 발전량을 대체할 수 있는 대안으로 적절한 위치에 FACTS설비를 투입하고자 한다. FACTS설비를 효율적으로 운전시키기 위해 LNG복합발전의 발전량 감소에 따른 전압변화에 대해 Tangent Vector Component가 가장 큰 수도권 345kV 모선을 선정해 STATCOM을 투입하고 그 결과를 확인한다. 이를 확인하기 위한 방안으로 제약운전을 하는 복합발전의 발전량을 감소시키고 관찰하고자 하는 모선과 거리가 먼 비수도권 발전량을 증가시켜 수급을 맞춘 뒤 전압의 변화를 관찰한다. 이 때, 하나의 계통을 2개의 지역으로 구역화하여 전압을 확인할 수 있는 F-V 해석을 이용한다.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.6
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• pp.494-502
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• 2014

This paper presents a control method of the modular multilevel converter - high-voltage direct current (MMC-HVDC) system to regulate grid voltage on the basis of the Jeju Island power system. In this case, the MMC-HVDC system is controlled as a static synchronous compensator (Statcom) to exchange the reactive power with the power grid. The operation of the MMC-HVDC system is verified by using the PSCAD/EMTDC simulation program. The Jeju Island power system is first established on the basis of the parameters and measured data from the real Jeju Island power system. This power system consists of two line-commutated converter - high-voltage direct current (LCC-HVDC) systems, two Statcom systems, wind farms, thermal power plants, transformers, and transmission and distribution lines. The proposed control method is then applied by replacing one LCC-HVDC system with a MMC-HVDC system. Simulation results with and without using the MMC-HVDC system are compared to evaluate the effectiveness of the control method.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.11
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• pp.625-631
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• 2003

The purpose of this paper is to assess experimentally system stability of the 154 ㎸ transmission system due to the current of the forthcoming AC High-Speed Railway (HSR) era. It introduces a simple method to evaluate the system stability The proposed method also shows the relationship between stability and power losses, and the stability indices made by the numerical process proposed in this paper will be used to assess whether a system can be stabilized or not. This paper also presents the improvement of the stability via loss reduction using STATCOM. Reactive power compensation is often the most effective way to improve both power transfer capability and system stability. The suitable modeling of the electric railway system should be applicable to the PSS/E. In the case study the proposed method is tested on a practical system of the Korea Electric Power Corporation (KEPCO) which will be expected to accommodate the heavy HSR load. Furthermore, it prove that the compensation of voltage drop and its by-product, loss reduction is closely related to improvement of system stability.

• Journal of Electrical Engineering and Technology
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• v.9 no.4
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• pp.1258-1268
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• 2014

Improving grid connection of wind farms is a relevant issue to be addressed, especially for fixed-speed wind turbines. Certain elements, such as FACTS (Flexible AC Transmission Systems), are able to perform voltage and reactive power regulation in order to support voltage stability of wind farms, and compensate reactive power consumption from the grid. Several devices are grouped under the name of FACTS, which embrace different technologies and operating principles. Here, three of them are evaluated and compared, namely STATCOM (Static Synchronous Compensator), SVC (Static Var Compensator) and SSSC (Static Synchronous Series Compensator). They have been modeled in MATLAB/Simulink, and simulated under various scenarios, regarding both normal operation and grid fault conditions. Their response is studied together with the case when no FACTS are implemented. Results show that SSSC improves the voltage stability of the wind farm, whereas STATCOM and SVC provide additional reactive power.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.240-249
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• 2018

Individual DC voltage balance problem is an inherent issue for cascaded H-bridge (CHB) based converter. When the CHB-based static synchronous compensator (STATCOM) is operating at zero current mode, the software-based individual DC voltage balancing control techniques may not work because of the infinitesimal output current. However, the different power losses of each cell would lead to the individual DC voltages unbalance. The uneven power losses on the local supplied cell-controllers (including the control circuit and drive circuit) would especially cause the divergence of individual DC voltages, due to their characteristic as constant power loads. To solve this problem, this paper proposes an adaptive voltage balancing module which is designed in the cell-controller board with small size and low cost circuits. It is controlled to make the power loss of the cell a constant resistance load, thus the DC voltages are balanced in zero current mode. Field test in a 10kV STATCOM confirms the performance of the proposed method.

• Proceedings of the KIEE Conference
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• summer
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• pp.156-158
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• 2004

Recently electrical industry has been rapidly restructured by deregulation in the developed countries. The voltage stability problem of a power system is associated with a rapid voltage drop due to heavy load and it occurs because of inadequate reactive power supply at some critical buses. More effective power system control means for line flow and bus voltage are required for applying FACTS. In this paper Jacobian method used to study on the voltage stability, The Jacobian method is to check the eigenvalue of the load flow Jacobian matrix. If the power system is unstable, one of the eigenvalues, at leasL has crossed the imaginary axis. This paper demonstrate enhancement of ATC by application of STATCOM at WSCC 9-bus system.