The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
C C Huang - One of the best experts on this subject based on the ideXlab platform.
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Recovery of a reversed Phase Sequence in one ternary liquid-crystal-mixture system.
Physical review. E Statistical nonlinear and soft matter physics, 2009Co-Authors: Shun Wang, B K Mccoy, S T Wang, R Pindak, H T Nguyen, C C HuangAbstract:The nOHFBBB1M7 (n=10) compound, 10OHF, shows a reversed SmC{FI2}-SmC Phase Sequence, unique among all known antiferroelectric liquid crystals. This reversed Phase Sequence is stabilized when 10OHF is doped with 9OTBBB1M7(C9) or 11OTBBB1M7(C11). In contrast, doping of the homologous members ( n=9 , 11, or 12) eliminates the SmC{FI2} Phase. One 10OHF/11OHF mixture without the SmC{FI2} Phase was selected for further studies. By adding C9 into this particular mixture, the reversed Phase Sequence is revived. To our surprise, even though 11OHF destabilizes the SmC_{FI2} Phase in binary mixtures with 10OHF, it significantly increases the SmC_{FI2} temperature range in the 10OHF/11OHF/C9 ternary mixtures.
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Recovery of a reversed Phase Sequence in one ternary liquid-crystal-mixture system.
Physical Review E, 2009Co-Authors: Shun Wang, B K Mccoy, S T Wang, R Pindak, H T Nguyen, C C HuangAbstract:The $n\text{OHFBBB}1\text{M}7$ $(n=10)$ compound, 10OHF, shows a reversed $\text{Sm}{C}_{FI2}^{\ensuremath{\ast}}\text{-Sm}{C}^{\ensuremath{\ast}}$ Phase Sequence, unique among all known antiferroelectric liquid crystals. This reversed Phase Sequence is stabilized when 10OHF is doped with 9OTBBB1M7(C9) or 11OTBBB1M7(C11). In contrast, doping of the homologous members ($n=9$, 11, or 12) eliminates the $\text{Sm}{C}_{FI2}^{\ensuremath{\ast}}$ Phase. One 10OHF/11OHF mixture without the $\text{Sm}{C}_{FI2}^{\ensuremath{\ast}}$ Phase was selected for further studies. By adding C9 into this particular mixture, the reversed Phase Sequence is revived. To our surprise, even though 11OHF destabilizes the $\text{Sm}{C}_{FI2}^{\ensuremath{\ast}}$ Phase in binary mixtures with 10OHF, it significantly increases the $\text{Sm}{C}_{FI2}^{\ensuremath{\ast}}$ temperature range in the 10OHF/11OHF/C9 ternary mixtures.
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Effects of doping on an unusual smectic- C*alpha-smectic-C*FI2-smectic-C* Phase Sequence.
Physical Review E, 2008Co-Authors: B K Mccoy, Shun Wang, R Pindak, H T Nguyen, Sheng Wang, C C HuangAbstract:: The compound 10OHF has a partially inverted Phase Sequence, unique among the series of nOHF homologous compounds and all other known liquid crystals, with the smectic-C*FI2 (SmC*FI2) Phase occurring at higher temperature than the smectic-C* (SmC*) Phase. We present ellipsometric data to identify the Phase Sequences of 9OHF, 10OHF, 11OHF, and 12OHF. Binary mixtures of 10OHF with C11, a compound with the typical Phase Sequence among the smectic Phases, show that the unusual Phase Sequence of 10OHF stabilizes upon mixing and that SmC*FI2 predominates over SmC* throughout the entire mixing Phase diagram. In thin films of some mixtures, surface interactions induce a reentrant SmC*FI2-SmC*-SmC*FI2 transition in the rest of the film.
Habong Chung - One of the best experts on this subject based on the ideXlab platform.
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On the Phase Sequence set of SLM OFDM scheme for a crest factor reduction
IEEE Transactions on Signal Processing, 2006Co-Authors: Jong-seon No, Habong ChungAbstract:The crest factor distribution of orthogonal-frequency-division-multiplexing (OFDM) symbol Sequences is evaluated, and it is shown that OFDM symbol Sequences with a short period are expected to have a high crest factor. The crest factor relationship between two input symbol Sequences, Hamming distance D apart, is also derived. Using these two results, two criteria are proposed for a Phase Sequence set of the selected mapping (SLM) OFDM scheme and suggest the rows of the cyclic Hadamard matrix constructed from an m-Sequence as a near-optimal Phase Sequence set of the SLM OFDM scheme.
P.j. Moore - One of the best experts on this subject based on the ideXlab platform.
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Determination of Phase Sequence and voltage level of high-voltage double-circuit overhead conductors using non-contact technique
2006 IEEE Power Engineering Society General Meeting, 2006Co-Authors: F. Li, P.j. MooreAbstract:Determination of Phase Sequence and voltage level of double-circuit overhead conductors is investigated using non-contact sensors situated on a moving platform at ground level. Based on the investigation of the electric field beneath double-circuit transmission lines through finite element analysis (FEA) simulations and laboratory experiments with a scale model, a determination methodology is proposed. Experiments taken beneath 400 kV double-circuit transmission lines are presented in detail. Analysis of the experimental results shows that the proposed determination methodology can successfully evaluate the Phase Sequence arrangement and voltage level of high-voltage double circuit conductors
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Determination of the Phase Sequence and Voltage Level of Overhead Conductors Using Non-contact Sensors
2005 IEEE PES Transmission & Distribution Conference & Exposition: Asia and Pacific, 2005Co-Authors: F. Li, P.j. MooreAbstract:This paper describes how the Phase Sequence and voltage level (132 kV, 275 kV or 400 kV) of single-circuit overhead conductors can be determined from the measurements which are made by passive, non-contact sensors situated on a moving platform at ground level. The investigation relies on sensing of the electric field along the lateral profile beneath overhead conductors. Firstly, the passive sensor fabricated is described together with an analysis of its performance. Then experimental results obtained in the laboratory have led to the determination technique of voltage level and Phase Sequence from the spatial variation of the amplitudes and Phase angles of electric field. 1 kHz AC supply has been used to energize overhead conductors rather than 50 Hz supply. This greatly improves the signal noise ratio (SNR) of induced voltage measured and makes the investigation of electric field in vicinity of conductors with low-level voltage possible in the laboratory. Finally, investigations made in a 400 kV substation in the UK shows that the proposed technique can successfully evaluate the Phase Sequence and voltage level of high-voltage overhead conductors
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Non-contact determination of the Phase Sequence and voltage level of overhead conductors in air insulated substations
2005 International Power Engineering Conference, 2005Co-Authors: F. Li, P.j. MooreAbstract:This paper describes how the Phase Sequence and voltage level (132 kV, 275 kV or 400 kV) of single-circuit overhead conductors can be calculated from measurements made by passive, non-contact sensors situated on a moving platform at ground level. The investigation relies on sensing the electric field along the profile of the conductors through the use of passive sensors. The fabrication of the passive sensor is described together with an analysis of its performance. The variation of the vertical component of electric field strength along the lateral profile beneath single-circuit conductors has been studied using finite element modeling software, ANSYS. The results of this simulation have led to a proposed method of determining the magnitude and Phase Sequence information from overhead conductors via analysis of the induced voltages on the sensors. The paper concludes with an investigation made in a 400 kV substation in the UK. Analysis of the experimental results shows that the proposed technique can successfully evaluate the Phase Sequence, voltage level, the spacing between Phases and the orientation of high-voltage overhead conductors
T.a. George - One of the best experts on this subject based on the ideXlab platform.
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Negative-Phase-Sequence reduction with adjacent static reactive-power compensators
IEE Proceedings - Electric Power Applications, 1994Co-Authors: G. Ledwich, T.a. GeorgeAbstract:Static reactive power (VAr) compensators (SVCs) can be used to reduce negative Phase Sequence (NPS) voltages by balancing, for example, Phase-to-Phase-connected loads. In such cases, they are effective until their controlled elements, usually thyristor-controlled reactors, reach their operating limits. Once this happens, NPS currents flow in the system and produce NPS voltages. If several load balancing SVCs are located in close electrical proximity, adjacent load balancing SVCs are able to absorb some of this uncompensated NPS current, reducing the overall NPS voltage profile. The mutual support thus provided should be considered when designing the ranges of such load balancing SVCs. The paper describes how to quantify the mutual support in a system with multiple load balancing SVCs.
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Using phasors to analyze power system negative Phase Sequence voltages caused by unbalanced loads
IEEE Transactions on Power Systems, 1994Co-Authors: G. Ledwich, T.a. GeorgeAbstract:An analytical method is demonstrated which allows the level of negative Phase Sequence (NPS) voltage at a busbar to be expressed as a sum of phasors representing independent sources. The method is extended to enable the balancing capability of Static VAr Compensators (SVCs) with individual Phase voltage control to be assessed. The capability of such SVCs and the allowable levels of NPS voltage on the system, including any short term limits, can be combined in a capability chart showing the unbalanced loads which can be supplied from a substation. The approach facilitates the treatment of fixed unbalances due to filters or intentional offsets designed to maximise the SVC balancing range for specific loads. Field test results are presented which validate the analytical methods used.
Shaofeng Huang - One of the best experts on this subject based on the ideXlab platform.
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A New Phase Sequence Exchanging Control Method for Reducing Impulse Current and Voltage
IEEE Access, 2019Co-Authors: Yifan Li, Shaofeng Huang, Hui Li, Jian Zhang, Gang HuangAbstract:Phase Sequence exchanging technology (PSET) is a recently developed emergency control technology for out-of-step power systems. The PSET system does not satisfy the condition of synchronization however, and will produce impulse current and impact torque. In this paper, the impulse current and impact torque produced by PSET are calculated. Taking the three-Phase short circuit at the generator outlet as a reference, the impulse current generated by PSET is determined to be less than half of the three-Phase short circuit at the generator outlet, which is within the system's endurable range. When the system connection reactance is 0.543 times larger than generator direct axis sub-transient reactance, it can endure the impact torque produced by PSET. To reduce the impact and improve the practicability of PSET, a split-Phase switching control method is proposed in this paper. The characteristics of fast breaking are utilized to turn off the solid-state circuit breaker separately when the three-Phase current is at zero-crossing, and after exchanging the Phase Sequence, it is turned-on separately when two sides of the three-Phase voltage are equal. An example is provided to verify that the impact of PSET can be dramatically reduced by using the proposed control method instead of the traditional simultaneous switching control method.
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A New Technology Applied to Power System Stability Control: Phase Sequence Exchange Technology
IEEE Access, 2019Co-Authors: Shaofeng Huang, Yifan Li, Hui Li, Yiling HuangAbstract:AC transmission systems are often affected by stability issues. During the design Phase of such systems, their ability to cope with the various kinds of disturbance is taken into consideration, however, sudden large disturbances may still result in power angle instability, which can greatly increase the risk of an overarching power system break down. Therefore, the development of a safety protection system is a priority in the field of power system construction. In response to this problem, we propose a new exploratory solution strategy - Phase Sequence Exchange Technology (PSET). The PSET can be summarized as follows: when the power angle of an equivalent dual power supply system swings to a suitable angle between 90° and 180°, disconnect the primary side Phase of the communication line by power electronic equipment and causing the swift misalignment of the connection. The A, B, C three-Phase Sequence then, connects to the three-Phase C, A, B Sequence. The PSET instantaneously realizes this change and reduces the power angle by 120°, pulling the formerly increasing power angle back to a smaller angle and preventing the system from becoming imbalanced. In this paper, the mechanism which improves the stability of the PSET is explained by using the equal area rule. The threshold of the PSET work angle is determined by the energy function and the unbalanced potential energy in the system that can be effectively reduced by the PSET. Based on these findings, the Phase trajectory method is used to determine the evaluation criteria for the PSET. This allows us to establish whether the PSET is effective by examining the state of the system after the fault is removed. Finally, an example is given in order to verify the effectiveness of the PSET and to prove that PSET is able to prevent the system from becoming imbalanced while still maintaining its structural integrity.
