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In order that the supply of electric power remain stable and sustainable, a certain level of power quality must be maintained while securing energy resources and resolving environmental issues. The distributed generation (DG) has become an essential and indispensable element of such distribution systems from both an environmental and an energy security perspective. However, the installation of DGs in distribution systems may cause variations of voltage on distribution feeder because the DG power outputs may change randomly and dramatically. Generally, the sending voltage at substation in distribution systems can be regulated by an under load tap changer (ULTC) designed to maintain customers' receiving voltages within a predetermined range. Voltage regulation performed by ULTC calls for two parameters: the equivalent impedance and the load center voltage. Therefore, in distribution networks with DG interconnections, these parameters should be designed with attention not only to load variations but also to DG outputs. This paper proposes a method for designing ULTC parameters with reference to variations in DG output. The proposed algorithm is tested with IEEE 13-node system and Korean model network. The results demonstrate the validity of the proposed design method for varying DG distribution. Index Terms--Distributed generation, LDC parameters (equivalent impedance, load center voltage), line drop compensation (LDC), under load tap changer (ULTC), voltage regulation.

In this paper, the authors propose a fuzzy-optimization approach to dynamic economic dispatch, considering the uncertainties in deregulated energy and reserve markets. The methodology was developed from the viewpoint of a generation company wishing to maximize its own profit and to hedge its risks as a participant in the energy market and 10-min spinning reserve market. The uncertainties in the current paper were represented with fuzzy numbers, and consist of the demand and reserves required in each market, prices cleared in each market, and the probability that reserves are called upon in actual operation. The energy and reserve markets were coordinated by the generator ramp rate limits. The optimal amounts of power and reserve were determined by solving the optimization problem. Two reserve payment methods, payment for power delivered and payment for reserve allocated, were investigated in this paper. Index Terms--Competitive environment, deregulation, dynamic economic dispatch, fuzzy approach, restructured power system.

With the opening of the power industry to competition, the power system structure is changing. According to these changes, power system operation, planning, and control need modifications. In the past, utilities had to produce power to satisfy their customers with objective to minimize costs and all demand/reserve were met. However, it is not necessary in a restructured system. Under new structure, generation companies (GENCOs) schedule their generators with objective to maximize their own profit without regard for system social benefit. Power and reserve prices become important factors in decision process. This paper proposes a new tool, profit-based unit commitment (UC) considering power and reserve generatings. The proposed method helps GENCO to make a decision, how much power and reserve should be sold in markets, and how to schedule generators in order to receive the maximum profit. A hybrid method between Lagrange Relaxation (LR) and evolutionary programming (EP) is used for solving this problem. Simulations are carried out to show the performance of the proposed methodology. Index Terms--Competitive environment, deregulation, evolutionary programming, Lagrange relaxation, power system operation planning and control, profit-base unit commitment, restructured system.

Dynamic economic dispatch (DED) is one of the main functions of power generation operation and control. It determines the optimal settings of generator units with predicted load demand over a certain period of time. The objective is to operate an electric power system most economically while the system is operating within its security limits. This paper proposes a new hybrid methodology for solving DED. The proposed method is developed in such a way that a simple evolutionary programming (EP) is applied as a based level search, which can give a good direction to the optimal global region, and a local search sequential quadratic programming (SQP) is used as a fine tuning to determine the optimal solution at the final. A ten-unit test system with nonsmooth fuel cost function is used to illustrate the effectiveness of the proposed method compared with those obtained from EP and SQP alone. Index Terms--Dynamic economic dispatch (DED), evolutionary programming (EP), global solution, power generation operation and control, sequential quadratic programming (SQP), stochastic optimization techniques.

A new dual-stage actuator for positioning a magnetic head for high-density hard disk drives was proposed and developed. This dual-stage actuator device is characterized by the sputter-deposited thin-film PZT, featuring large displacement of 1.2 [micro]m and high-resonance frequency over 15 kHz. In this paper, reliability against temperature, humidity, and mechanical shock was investigated to ensure the practical application to the drive products. Index Terms--Dual-stage actuator, magnetic disk drive, microactuator, piezoelectric actuator, PZT.