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The transitions of partial discharge (PD) behavior with aging in a void under ac voltages with sine wave and square wave were observed. The transition of the PD magnitude with aging under square wave showed the same tendency as that under sine wave. Moreover, the experimental results also showed some distinctive characteristics of PDs under square voltage (e.g. more than two pulses after the voltage rise time and their transition with aging). These phenomena were explained in terms of the effect of discharge area and the change in surface condition due to PD degradation.

SUMMARYA PV system's power output is not stable and fluctuates depending on weather conditions. Using a battery is one feasible measure to stabilize a PV system's power output, but it requires additional costs and results in additional waste of used batteries. In this paper, we propose a new measure for smoothing the short-term change in a PV system's power output, which is performed by tuning the characteristics of Maximum Power Point Tracking (MPPT) control without additional equipment. In our proposed measure, when the insolation increases rapidly, the operation point of MPPT control changes to a new point where the maximum power is not generated with the current insolation, so that the rate of increase in the PV system's power output is limited to a certain value. In order to evaluate the effect of the proposed measure on the operation of electric power systems, we evaluated the required capacity of generators for load-frequency control (LFC). It was revealed that the additional LFC capacity is not required even in the case where penetration of PV systems reaches 5% of the utility system's total capacity if the proposed measure is applied to all PV systems. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 152(2): 10-17, 2005; Published online in Wiley InterScience (www.interscience. wiley.com).

Articles you may be interested inStudy on thermal properties and crystallization behavior of electron beam irradiated ethylene vinyl acetate (EVA)/waste tyre dust (WTD) blends in the presence of polyethylene graft maleic anhydride (PEgMAH) AIP Conf.Thermally stimulated depolarization current studies of poly(ethylene oxide) and poly(ethylene oxide) complexed with potassium thiocyanate Thermally stimulated currents (TSC) from polyethylene and ethylene-vinyl-acetate copolymers with a variety of vinyl-acetate contents have been investigated using a TSC technique with x-ray irradiation. Five main TSC peaks, which we believe are due to trapped carriers, were observed in these polymers. The detrapping of carriers is closely related to molecular-chain motions, and trapping sites are assigned to physical defects such as cavities formed by local arrangements of molecular chains rather than carbonyl groups. One of the TSC peaks is associated with traps in the amorphous region, one with traps in the boundary region between the amorphous and the crystalline regions, i.e., in the folded region, and another with traps in the crystalline region. The TSC spectrum from the dipole of the vinyl-acetate unit under a bias field shows a TSC peak accompanied by a current inversion. The average effective dipole moment for the vinyl-acetate unit was determined to be about 1.8 D from a TSC analysis.PACS numbers: 72.20.Jv, 71.5S.Ht, 61.80.Cb a The DSC was measured at the heating rate of 10 K/min.