Chang Y.-C.,Cheng Shiu University
IET Generation, Transmission and Distribution | Year: 2014
Owing to the continuously increased electricity demands and power transactions, power systems are becoming more vulnerable to insecurity, generally incurred by overutilised transmission facilities or any contingency. In order for existing transmission networks to accommodate more power transfers with less network expansion cost, proper installation of thyristor controlled series compensator (TCSC) is validated to be one of the most 'promising options'. The multi-objective optimal TCSC installation strategy proposed in the study first applies the performance index sensitivity factor technique to investigate which lines are most necessary for TCSC installation and with the lines specified for TCSC installation and the multiobjective function consisting of maximum system loadability and minimum TCSC installation cost, the problem to determine the capacity for each TCSC installation is then formulated as a multi-objective optimisation problem and solved by using the fitness sharing multi-objective particle swarm optimisation method. Finally, in the Pareto front set obtained, the solution with the TCSC installations that can make the power system provide the required loadability with biggest utilisation index value is recommended. The modified IEEE-14 buses, IEEE-118 buses systems and a practical power system are used to validate the performance of the proposed method. © The Institution of Engineering and Technology 2014.
Kang T.-K.,Cheng Shiu University
Applied Physics Letters | Year: 2012
Experimental evidence for the giant piezoresistance (PZR) effect in n-type silicon nanowires (SiNWs) on silicon-on-insulator wafers, also called SiNW field-effect transistors (SiNWFETs), is demonstrated. While an external mechanical strain is applied to SiNWFETs depleted by a back-gate bias, a marked increase in the subthreshold drain current is found, thus supporting the widely reported giant piezoresistance effect. This increase can be attributed to the change in Si/SiO 2 interface states, further suggesting interface trap-induced giant piezoresistance. Furthermore, through repeated cycles of tensile and released strain, the electromechanical response of the subthreshold drain current with time offers a potential for creating strain-gated SiNWFETs. © 2012 American Institute of Physics.
Chang Y.C.,Cheng Shiu University
International Journal of Electrical Power and Energy Systems | Year: 2014
Owing to the constantly increased electricity demands and transactions, power systems are becoming more vulnerable to voltage instability generally incurred by over-utilized transmission facilities or any contingency. In order for transmission networks to accommodate more power transfers with less expansion cost, proper installation of Flexible AC Transaction Systems (FACTS) is a promising way. The power system loading margin enhancement problem to determine an optimal Static Synchronous Compensator (STATCOM) installation scheme can be formulated as a mixed discrete-continuous nonlinear optimization problem (MDCP). In the paper, to improve the efficiency of solving the MDCP, an ordinal optimization (OO) STATCOM installation strategy is proposed to seek a good enough solution rather than the optimal solution. In the strategy, under each N - 1 contingency with bigger risk index (RI) value, first the crude model of the MDCP is used to estimate the rough solution of each candidate in the representative set, and then the exact method is applied to a smaller set selected from the candidates with better rough solutions to determine the good enough solutions. Finally, obtained from the union of the respective good enough solutions for all considered contingencies, the scheme with the smallest number of STATCOM units or least capacity for installation enabling the network to provide required LM is recommended. The efficiency of the proposed method is confirmed with the results studied on IEEE-24 bus reliability test system. © 2013 Elsevier Ltd. All rights reserved.
Leou R.-C.,Cheng Shiu University
International Journal of Electrical Power and Energy Systems | Year: 2011
Due to the deregulation of power industry, the transmission expansion plan is different from the process done by the integrated monopolies. In a monopoly electric market, the transmission expansion plan is carried out by the vertically integrated utility. The power company integrates its generations' exploiting plans and its transmission expansion plans to maintain the system reliability. While in a deregulated power industry, generation, transmission, and distribution companies belong to different owners. The problem becomes more difficult. Generators experiencing transmission constraints can be expected to lobby for new transmission facilities that might relieve their constraints, while generators closer the load centers will likely toward not to build any new transmission facilities that would increase their competition. In order to provide a fair environment for all market participants, this paper proposed a reasonable expansion plan taking the operation cost, load curtailment cost, and investment cost into account. Due to the complexity of this model, the algorithm that combines the genetic algorithm with the linear programming method (GA-LP) is used to solve this problem. The 6-bus system and 24-bus IEEE reliability test system are used to verify the proposed model, and comparisons of test results between the proposed model and the traditional model are also demonstrated in this paper. © 2010 Elsevier Ltd. All rights reserved.
Kang T.-K.,Cheng Shiu University
Nanotechnology | Year: 2012
The piezoresistive effect in n-type silicon nanowires on silicon-on-insulator wafers, also called junctionless nanowire transistors (JNTs), is investigated. A marked change in the subthreshold drain current for strained JNTs is observed. This change can be attributed to strain-induced interface state modification, due to an increase in the interface state for tensile strain or a decrease in the trap activation energy for compressive strain. Through many long-time cycles of compressive and released strain, the electromechanical response of subthreshold IDS with time is found, thus supporting the widely reported giant piezoresistance effect. In addition, JNTs involving a back-gate and an additional top-gate electrode may become a new prospect for high-precision sensor applications and next-generation multigate transistors. © 2012 IOP Publishing Ltd.