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Adaptive Gain-based Stable Power Smoothing of a DFIG
Lee, Hyewon,Hwang, Min,Lee, Jinsik,Muljadi, Eduard,Jung, Hong-Ju,Kang, Yong Cheol The Korean Institute of Electrical Engineers 2017 Journal of Electrical Engineering & Technology Vol.12 No.6
In a power system that has a high wind penetration, the output power fluctuation of a large-scale wind turbine generator (WTG) caused by the varying wind speed increases the maximum frequency deviation, which is an important metric to assess the quality of electricity, because of the reduced system inertia. This paper proposes a stable power-smoothing scheme of a doubly-fed induction generator (DFIG) that can suppress the maximum frequency deviation, particularly for a power system with a high wind penetration. To do this, the proposed scheme employs an additional control loop relying on the system frequency deviation that operates in combination with the maximum power point tracking control loop. To improve the power-smoothing capability while guaranteeing the stable operation of a DFIG, the gain of the additional loop is modified with the rotor speed and frequency deviation. The gain is set to be high if the rotor speed and/or frequency deviation is large. The simulation results based on the IEEE 14-bus system demonstrate that the proposed scheme significantly lessens the output power fluctuation of a WTG under various scenarios by modifying the gain with the rotor speed and frequency deviation, and thereby it can regulate the frequency deviation within a narrow range.
Rotor Speed-based Droop of a Wind Generator in a Wind Power Plant for the Virtual Inertial Control
Lee, Jinsik,Kim, Jinho,Kim, Yeon-Hee,Chun, Yeong-Han,Lee, Sang Ho,Seok, Jul-Ki,Kang, Yong Cheol The Korean Institute of Electrical Engineers 2013 Journal of Electrical Engineering & Technology Vol.8 No.5
The frequency of a power system should be kept within limits to produce high-quality electricity. For a power system with a high penetration of wind generators (WGs), difficulties might arise in maintaining the frequency, because modern variable speed WGs operate based on the maximum power point tracking control scheme. On the other hand, the wind speed that arrives at a downstream WG is decreased after having passed one WG due to the wake effect. The rotor speed of each WG may be different from others. This paper proposes an algorithm for assigning the droop of each WG in a wind power plant (WPP) based on the rotor speed for the virtual inertial control considering the wake effect. It assumes that each WG in the WPP has two auxiliary loops for the virtual inertial control, i.e. the frequency deviation loop and the rate of change of frequency (ROCOF) loop. To release more kinetic energy, the proposed algorithm assigns the droop of each WG, which is the gain of the frequency deviation loop, depending on the rotor speed of each WG, while the gains for the ROCOF loop of all WGs are set to be equal. The performance of the algorithm is investigated for a model system with five synchronous generators and a WPP, which consists of 15 doubly-fed induction generators, by varying the wind direction as well as the wind speed. The results clearly indicate that the algorithm successfully reduces the frequency nadir as a WG with high wind speed releases more kinetic energy for the virtual inertial control. The algorithm might help maximize the contribution of the WPP to the frequency support.
Stable Short-Term Frequency Support Using Adaptive Gains for a DFIG-Based Wind Power Plant
Lee, Jinsik,Jang, Gilsoo,Muljadi, Eduard,Blaabjerg, Frede,Chen, Zhe,Cheol Kang, Yong IEEE 2016 IEEE transactions on energy conversion Vol.31 No.3
<P>For the fixed-gain inertial control of wind power plants (WPPs), a large gain setting provides a large contribution to supporting system frequency control, but it may cause over-deceleration for a wind turbine generator that has a small amount of kinetic energy (KE). Further, if the wind speed decreases during inertial control, even a small gain may cause over-deceleration. This paper proposes a stable inertial control scheme using adaptive gains for a doubly fed induction generator (DFIG)-based WPP. The scheme aims to improve the frequency nadir (FN) while ensuring stable operation of all DFIGs, particularly when the wind speed decreases during inertial control. In this scheme, adaptive gains are set to be proportional to the KE stored in DFIGs, which is spatially and temporally dependent. To improve the FN, upon detecting an event, large gains are set to be proportional to the KE of DFIGs; to ensure stable operation, the gains decrease with the declining KE. The simulation results demonstrate that the scheme improves the FN while ensuring stable operation of all DFIGs in various wind and system conditions. Further, it prevents over-deceleration even when the wind speed decreases during inertial control.</P>
PARTICIPATION AND PARTNERSHIPS IN URBAN REGENERATION AND CULTURAL TOURISM DEVLOPMENT
Jinsik Lee,Timothy Jung 세계문화관광학회 2009 Conference Proceedings Vol.10 No.0
This paper aims to explore to the extent the related stakeholders perceive culture's contribution to urban regeneration and to examine difficulties perceived on participation and partnerships among the stakeholders involved in Gwangju Project, Hub City of Asian Culture, as a case study of cultural regeneration project for urban regeneration and cultural tourism development in Korea. The qualitative interview is employed to collect data from multiple stakeholders associated with Gwangju Project and a total of 19 stakeholders who have involved both directly and indirectly in the project are participated. The results of this study suggest that public-private co-operation and collaboration in regeneration projects will give huge economic benefits to the associated stakeholders and socio-cultural impacts to Gwangju city. The study also reveals that there are gaps in terms of participation and partnerships between government and other associated stakeholders due to lack of opportunities and reliable evidence for active participation and close partnerships. To achieve these positive impacts in Gwangju Project, there needs to be closer working relationship between central-municipal government and public-private/voluntary sectors.
Rotor Speed-based Droop of a Wind Generator in a Wind Power Plant for the Virtual Inertial Control
Jinsik Lee,Jinho Kim,Yeon-Hee Kim,Yeong-Han Chun,Sang Ho Lee,Jul-Ki Seok,Yong Cheol Kang 대한전기학회 2013 Journal of Electrical Engineering & Technology Vol.8 No.5
The frequency of a power system should be kept within limits to produce high-quality electricity. For a power system with a high penetration of wind generators (WGs), difficulties might arise in maintaining the frequency, because modern variable speed WGs operate based on the maximum power point tracking control scheme. On the other hand, the wind speed that arrives at a downstream WG is decreased after having passed one WG due to the wake effect. The rotor speed of each WG may be different from others. This paper proposes an algorithm for assigning the droop of each WG in a wind power plant (WPP) based on the rotor speed for the virtual inertial control considering the wake effect. It assumes that each WG in the WPP has two auxiliary loops for the virtual inertial control, i.e. the frequency deviation loop and the rate of change of frequency (ROCOF) loop. To release more kinetic energy, the proposed algorithm assigns the droop of each WG, which is the gain of the frequency deviation loop, depending on the rotor speed of each WG, while the gains for the ROCOF loop of all WGs are set to be equal. The performance of the algorithm is investigated for a model system with five synchronous generators and a WPP, which consists of 15 doubly-fed induction generators, by varying the wind direction as well as the wind speed. The results clearly indicate that the algorithm successfully reduces the frequency nadir as a WG with high wind speed releases more kinetic energy for the virtual inertial control. The algorithm might help maximize the contribution of the WPP to the frequency support.
Lee, Heejin,Joo, Ho-yong,Yoon, Chulmin,Lee, Joonbong,Lee, Hojin,Choi, Jinsik,Park, Baeho,Choi, Taekjib Elsevier 2017 Current Applied Physics Vol.17 No.5
<P>Ferroelectric based heterostructures have shown great promises in solar water splitting due to unique photoelectrochemical (PEC) properties including polarization-induced charge separation and tunable electrochemical surface reaction. A highly ordered ferroelectric BiFeO3/TiO2 nanotube (TNT) heterostructures were fabricated by anodic oxidation and pulsed laser deposition. The microscopic morphology, optical, and PEC properties of nanostructures were characterized. The BiFeO3/TNT photoelectrode is photoactive under visible light illumination, which exhibits higher photocurrent from greater water oxidation, compared with the pure TNT photoelectrode. The coating thickness of BiFeO3 strongly affected the photoelectrochemical properties. The enhanced PEC performance could be attributed to the effective charge separation and the favorable band bending for water oxidation, originating from ferroelectric polarization-related internal field. (C) 2017 Elsevier B.V. All rights reserved.</P>