Low Frequency Oscillation Analysis in Parallel AC/DC System by a Novel Dynamic Model

A novel approach is presented for efficientlymodeling a power system which indudes pardel-connectedHVAC, and HVDC transmission systems. The proposed modelhas been dehved for a system in which an AC generator isconnected to an infinite bus system through a parallel AC lieline and a ITVDC link In addition to state-spacerepresentation, a block diagram representation has beenformed to analyze system stability. In this new block diagramrepresentation, the dynamic chsractenstks of the system areexpressed in terms of a newly developed H constant. Thedevelopment of the block diagram and associated H constantsare explained. The new model is evaluated usingPSCAD/RTDS real time digital simulation. Based on this newmodel, the low frequency oscillation phenomenon in pardelAC/DC system is studied and the results are show

Novel dynamic modelling of parallel HVAC/HVDC

Belgium Herbarium image of Meise Botanic Garden

Novel dynamic modelling of parallel HVAC/HVDC

A novel approach is presented for eficiently modeling a power system which incIudes parallel-connected HVAC, andHVDC transmission systems. The proposed model has been derived for a system in which an AC generator is connected toan infinite bus system through a parallel AC tie line and a HVDC link. In addition to state-space representation, a blockdiagram representation has been formed to analyze system stability. In this new block diagram representation, the dynamiccharacteristics of the system are expressed in terms of a newly developed H constant. The development of the blockdiagram and associated H constants are explained. The new model is evaluated using PSCADiRTDS real time digitalsimulation

Laboratory investigation into the use of MV current transformers for transient based protection

The practical implementation of transient basedprotection and its application to power system protectionschemes depends on the availability of transducers suitable forproviding access to the higher frequency transients producedby faults and other system disturbances.This paper presents the results of a laboratory investigationinto the suitability of using MV distribution system currenttransformers as transducers for accessing the high frequencytransients used in transient based protection schemes.The investigation has concentrated on the frequency range of1 to 100 kHz and examined a variety of current transformersof different types and ages. These included standarddistribution system CTs, class X CTs and split core CTs. Theages of these CTs varied from new devices that had recentlybeen manufactured to units that had been withdrawn fromservice after thirty or more years in the field.In addition to examining the high frequency response of thecurrent transformers while they were operating with standardpower system frequency signals, the investigation alsoexamined their high frequency response when their coreswere saturated

Mānuka (Leptospermum scoparium) roots forage biosolids in low fertility soil

Potentially, biosolids could be applied to low fertility or degraded soils to establish mānuka (Leptospermum scoparium), an economically important plant species used for honey and essential oil production. Given that this pioneering species is adapted to low-fertility soils, it is unclear whether it would respond positively to biosolids. We aimed to determine the growth, root morphology and elemental uptake of L. scoparium in contrasting soils amended with biosolids, distributed either homogeneously or heterogeneously. Pot and rhizobox experiments revealed that the roots of L. scoparium morphologically foraged patches of biosolids in soil. This finding is in contrast to previous reports that foraging is uncommon in plants adapted to low fertility soils. In a low-fertility sand, biosolids increased the growth 40-fold, irrespective of the distribution of biosolids. This increase was lower (60%) in an orthic brown soil. In the biosolids-amended soils, the foliar concentrations of N, P, K, S, Mg and Ca were above 2%, 1.5 g kg⁻¹, 0.8%, 2.0 g kg⁻¹, 1.7 mg kg⁻¹ and 0.8% respectively, which is within the range of concentrations found in native species in their natural habitat. In the control soils, foliar concentrations of N, P & S were significantly lower, indicating that these elements may be limiting. The maximum concentration of Mn (660 mg kg⁻¹), Zn (211 mg kg⁻¹), and Cd (1.5 mg kg⁻¹) in leaves of plants growing in biosolids-amended soil should not cause concern to plant health, but it should be taken into account for their potential effect on trophic networks. Further experiments should focus on the design of field-scale applications of biosolids for improving L. scoparium growth and determine the effect of biosolids distribution on nutrient losses