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This letter proposes an analytical approach to estimate local and the network wide influence of a static compensator (STATCOM), configured for voltage unbalance (VU) mitigation. In addition, it provides guidelines for determining the most appropriate location for active mitigation. The proposed generalised formulation is able to demonstrate the VU mitigation provided by a STATCOM regardless of the control strategy used or the network conditions. [ABSTRACT FROM AUTHOR]

With the increased interest in controlling and managing voltage unbalance (VU), network operators are now increasingly being motivated to obtain the state of their networks with greater details. Distribution system state estimation (DSSE) is a prominent tool that enables network operators to estimate the level, location, and related impacts of VU. DSSE techniques developed to date which use the polynomial or exponential load models are deficient in recognizing VU attenuation associated with three-phase induction motors (IMs) that are directly connected to the ac network. Adoption of adequate three-phase models of IMs, which are used in full unbalanced load flow, into the existing DSSE techniques is not feasible due to several factors including requirement of extensive data, additional computational efforts, and major constraints related to incorporating the necessary modifications. As a solution, this paper proposes a novel formulation for postprocessing the results of current DSSE techniques to reflect the aforementioned behavior of IMs. Simulations are carried out using the IEEE 13 bus distribution network for a range of scenarios to verify the developed methodology. The work presented in relation to VU attenuation in interconnected networks also complements the existing treatise in IEC documentation that only deals with radial networks. [ABSTRACT FROM AUTHOR]

Inertia emulation methods exist to compensate for the reduced inertial support provided by doubly fed induction generator (DFIG) based wind turbines. Instead of emulating inertia, this paper proposes to temporarily convert DFIGs to synchronous generators, enabling supply of real inertia to the system. In order to achieve this, the voltage supplied to the DFIG rotor needs to be made independent of the grid frequency. Feeding the rotor with a fixed dc voltage while it is rotating at synchronous speed enables the DFIG to operate in synchronism with the grid and couple the inertia of its rotating mass to the power system. The rotor side converter of a DFIG can be controlled to function as the dc voltage source, allowing convenient switching between the two operation modes according to system requirements. [ABSTRACT FROM AUTHOR]

Voltage unbalance (VU) management of power systems requires the development of well researched engineering practices to maintain acceptable VU levels while utilising the total VU absorption capacity of the power system. In this regard, IEC/TR 61000-3-13:2008 prescribes a VU emission allocation methodology based on a stochastic approach which uses a general summation law in order to aggregate numerous sources of unbalance to take into account their random variations. On the other hand, recent deterministic studies on VU emission assessment at the post-connection stage of unbalanced installations present a complex VU factor based approach to determine constituent components of the post-connection VU emission at a point of evaluation. The primary objective of the work presented in this paper is to develop statistical approaches for compliance assessment using the outcomes of the deterministic methodologies on VU emission assessment, thus refining the existing general summation law. A revised general summation law is established, introducing weighting factors to evaluate the influences made by different sources of unbalance separately, in order to assess VU emission in radial networks. [ABSTRACT FROM AUTHOR]

Voltage unbalance propagation is an important aspect in relation to the voltage unbalance management process which aims to maintain acceptable voltage unbalance levels in the power system. The IEC Technical Report IEC/TR 61000‐3‐13:2008 incorporates the effects of voltage unbalance propagation in the voltage unbalance emission allocation methodology by introducing the voltage unbalance transfer coefficient, in order to evaluate the influence made by background voltage unbalance at the point of evaluation. However, no comprehensive approaches exist in the literature to evaluate these coefficients and the IEC work follows some approximations, which are deduced based on simulations and practical measurements. Recent work completed on voltage unbalance emission assessment at the post‐connection stage of unbalanced installations allows separation of the voltage unbalance emission contribution made by upstream/surrounding unbalance sources as a constituent component of the resultant voltage unbalance emission level at the point of evaluation. These new methodologies implicitly deal with the important aspects of voltage unbalance propagation and allow the quantification of coefficients associated with voltage unbalance propagation, which is the main thrust of this study. The theoretical work completed by considering different types of loads in radial and interconnected networks is supplemented by the simulation results. [ABSTRACT FROM AUTHOR]

Majority of the wind power resources are typically sited at remote locations in power networks and generated power is transmitted through rural transmission corridors to load centres. With increased penetration level of the wind generation there is an increased requirement to provide ancillary services from distributed wind power resources, hence they are operated under different control strategies to provide ancillary services to the network. The control strategies and capability characteristics will significant impact on voltage fluctuations in distribution networks. This paper presents a comparative analysis between different wind generator control strategies (i.e. power factor control strategy, voltage control strategy and reactive power dispatch strategy) on network voltage fluctuations during variable wind conditions while considering extended reactive power capability (i.e. with both generator and power electronic converter reactive power capabilities) for the doubly-fed induction generator (DFIG). Voltage fluctuations are analysed using real wind data measured at a DFIG based wind farm, and the wind farm model was verified against real measurements. Study has shown that voltage fluctuations are exacerbated when wind generator is at mode transition (i.e. from power optimisation mode to power limitation mode). A sensitivity analysis has shown that voltage fluctuations are exacerbated due to the limitations of the reactive power capability of the DFIG, and the operating point of the DFIG power curve irrespective of the control strategy implemented at the wind generator. Furthermore, a mitigation strategy was developed as an integrated control scheme to the main control scheme in order to reduce voltage fluctuations due to wind power variations. However, effectiveness of the mitigation strategy is greatly affected by the reactive power capability of the DFIG, in particular during high wind turbulences. [ABSTRACT FROM AUTHOR]

Voltage rise caused by high levels of distributed generation is manifesting as voltage regulation challenges for many electricity network service providers. In this environment it would be ideal to reduce supply voltage magnitudes, however, many network operators are hesitant to do so due to concerns related to consumer appliance performance at reduced supply voltage magnitudes. Voltage regulation requirements are defined by network standards and network service providers must ensure voltages remain within specified limits. Through an evaluation of domestic appliance performance when supplied at various voltage magnitudes, this paper examines the impact of varying voltage levels on residential appliances. Equipment energy demand, operation and actuation were monitored for each applied voltage magnitude. While no equipment failures were recorded, appliance behaviour varied significantly with applied voltage magnitude. Individual appliance conservation voltage reduction (CVR) factors have also been established. The results highlight the importance of good voltage regulation and provide substantiated appliance performance figures for future studies. The outcomes of this paper allow electricity network service providers to understand the implications of supply voltage magnitude on domestic appliance performance, whether it be understating of the impact of higher voltage magnitudes caused by distributed generation or implications of reducing voltage magnitudes to provide headroom for distributed generation integration. [ABSTRACT FROM AUTHOR]

Voltage fluctuations caused by rapidly changing loads, such as arc furnaces, can propagate to different parts of a power system. Although the flicker level at its origin can be high, levels that are measured at other sites are subject to attenuation, a process that is influenced by fault levels, transformer impedances, line impedances, and composition of the connected loads. This paper presents the methodology, measurement results, and data analysis in relation to synchronized flicker measurements carried out in a high-voltage (HV)/medium-voltage (MV) power system which contains an arc furnace supplied by a dedicated feeder connected to the HV busbar. The flicker transfer coefficients derived from measurement results clearly indicate that flicker transfer from the arc furnace site to the upstream HV busbar is governed by the fault levels at the two locations. However, the transfer of flicker from the upstream HV busbar to other downstream busbars is dependent on the downstream load composition. These flicker transfer coefficients are vital in the application of methodologies described in many reports and standards in relation to establishing planning levels at various voltage levels and in the allocation of flicker emission to customers. [ABSTRACT FROM AUTHOR]

Focuses on the development of a pulse-width-modulation (PWM) switching strategy, which gives an improved performance in comparison to existing switching strategies in relation to harmonic elimination, minimal total harmonic distortion (THD) and lower switching losses at low switching frequency. Survey on commonly used PWM switching strategies; Asymmetric regular PWM sampling techniques; What is the basic of the equal sampling technique.

Two chiral fluoranthene-based polyaromatics were isolated from a Diels-Alder cycloaddition between two molecules of 7,9-diphenylcyclopenta[ a]acenapthylene-8-one. The two highly coloured, novel compounds were characterized by a combination of spectroscopic techniques and single crystal X-ray diffraction. Structural differences between the unexpected products included the nature of their conjugated fluoranthene portions and the position, strain and handedness of their chiral centres. [ABSTRACT FROM AUTHOR]

The emergence of distributed generation such as solar systems has introduced new challenges in distribution networks that are becoming more apparent with increasing penetration levels. The time mismatch between peak load and peak generation can make voltage levels in distribution networks swing towards extreme limits during a day. Distribution network service providers are struggling to cater for new distributed generation installations while ensuring that the quality of steady state supply voltage meets stipulated requirements. The segregation between medium and low voltage networks in control strategies may result in unnecessary or worse, opposing control actions leading to voltage issues and control on one side of the distribution network influencing the other. By developing an efficient volt/var control method, the steady state voltage level and voltage unbalance in a comprehensive distribution network can be controlled simultaneously. This paper analyses voltage issues and volt/var control in medium and low voltage networks as a whole, unabridged problem. This paper proposes a pragmatic and effective volt/var control method that addresses voltage regulation and voltage unbalance simultaneously using existing infrastructure. The proposed control method is implemented on three types of representative Australian distribution networks and results obtained demonstrate that the proposed volt/var control can simultaneously manage voltage level and voltage unbalance whilst reducing the number of tap change operations and maximizing solar penetration. [ABSTRACT FROM AUTHOR]

• High frequency (HF) emissions are a new power quality concern. • Photovoltaic (PV) inverters are major HF emission sources. • No PV inverter models suitable for HF studies are found in current literature. • A generic method is proposed to develop black box models of PV inverters for HF studies. • The models developed have less than 6.5% errors with 95% confidence. There is a growth of high frequency (HF) emissions in the range of 2–150 kHz (also known as Supraharmonics) in electricity distribution networks, primarily due to the increasing number and capacity of AC grid connected equipment having power electronic interfaces. Although PV inverters are a major HF source in electricity distribution networks, PV inverter models that are suitable for HF emission studies are yet to be developed. To this end, a generic method that can be used to develop HF models of small-scale (<5 kW), grid-tied, single-phase PV inverters using a black box approach is presented in this paper. Accordingly, HF models of three PV inverters that are commonly used in domestic and commercial installations are developed assuming standard network conditions. It is shown that these HF models are capable of successfully capturing the HF performance of the selected PV inverters under a wide range of operating conditions. The outcomes of this work are expected to broaden the knowledge pertaining to the HF emissions in the frequency range considered. [ABSTRACT FROM AUTHOR]

Abstract: Reaction of B16H20 with [RuCl2(PPh3)3] gives a [(PPh3)2RuB16H20] species of which the metallaborane cluster configuration consists of a conventional nido ten-vertex {B10} unit fused via a common {B3} face with a ten-vertex {RuB9} unit of novel ‘neonido’ ten-vertex shape. [Copyright &y& Elsevier]

Large-scale renewable energy plants, flexible AC (alternating current) and high voltage DC (direct current) transmission systems, and modern consumer devices utilize power electronics that tend to increase harmonic emissions. Furthermore, such emissions are nowadays known to exceed the traditional 2 kHz range typically considered for harmonic analysis. However, the accuracy of such harmonic measurements in medium and high voltage networks is questionable due to the lack of accuracy specifications for the respective instrument transformers that are being used in the measurement chain. Therefore, the motivation of this study is to review the existing techniques for measuring high-frequency voltage harmonics, i.e., those in the range 2–9 kHz, in medium-, high-, and extra high-voltage electricity networks, where most large-scale power electronic converters are being connected. Different transducer types are compared in terms of measurement accuracy. The reviewed literature indicates that some transducers can introduce errors due to their nonlinearities. The study also identifies the limitations of calibrating these transducers at frequencies above 2 kHz due to the unavailability of suitable sources capable of generating the required test waveforms. Furthermore, the study emphasizes the necessity for establishing accuracy limits for harmonic measurements above 2 kHz. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the author discusses several topics including power quality aspects associated with solar photovoltaic systems, modeling and analysis of grid connected power electronic interface, and flicker meter accounting for different lamp technologies.

The voltage rise of the low voltage (LV) power distribution grid to which multiple solar photovoltaic (PV) systems are integrated is a critical technical problem that should be addressed. With PV systems that are integrated to the LV power distribution grid (with an R to X ratio greater than unity) via voltage source converters, the opportunity exists to regulate the respective point of common coupling (PCC) voltages by dynamically controlling the active and reactive power response of PV systems. In this paper, two closed-loop controllers that are able to regulate the PCC voltage by dynamically controlling the active and reactive power response of the PV system are presented. The design methodology is presented with considerable detail. The plant model of each controller is derived and the design procedure of each controller is explained in detail. By combining the dynamic active and reactive power controllers proposed in this paper, two novel operating strategies for PV systems, fixed minimum power factor operation and fixed maximum apparent power operation, are introduced. The latter operating strategy has been identified as the most efficient way of regulating the PCC voltage of a PV system. The simulation results and experimental validation confirm the accuracy of the derived plant models, the robustness of the designed controllers and the feasibility of implementing the proposed novel operating strategies in PV systems. [ABSTRACT FROM AUTHOR]

Voltage sag mitigation utilizing dynamic voltage restorers (DVRs) can be classified as a common-pool resource (CPR) good. However, the ability of DVRs in improving voltage sag performance of only downstream customers provides the ability to exclude the non-contributors selectively. Therefore, unlike traditional CPR goods, the DVR allocation problem can give rise to partial excludability. Here, the non-collocated customers have been divided into feasible clusters through suitable positioning of DVRs using the proposed graph-partitioning principle. In the absence of trustworthiness, especially with the participation of electricity supply companies, the participants may ask an external agent and share their willingness-to-pay information to design the optimal set of clusters. Alternatively, the customers, including electricity supply companies, can also share internal information as an open system. Strategies for sharing internal information to avoid free-riding are also discussed. The utility distribution would ensure the viability of contribution group formation. Here, the results from three different utility-distributing solution concepts, such as an alternative definition of the core, the nucleous, and Shapley value, are compared. The simulation results are numerically verified for a small scale system and validated utilizing a large scale system. The proposed methodology can be used for any real-world system that follows similar properties. [ABSTRACT FROM AUTHOR]

Highlights: [•] Capability curve based coordinated reactive power controller for the DFIG. [•] Impact of extended reactive power capability of the DFIG on network stability enhancement. [•] Utilisation of partially loaded DFIG wind farms as dynamic reactive power resources. [•] Network adaptive droop control methods and their feasibility for network voltage control. [Copyright &y& Elsevier]

Lamp flicker levels that arise as a result of voltage fluctuations can exceed limits set by appropriate standards. New lamp types such as compact fluorescent lights are less sensitive to voltage fluctuations as their flicker characteristics are considerably different compared to those of the traditional incandescent lamp. These differences could support the moderation of the present voltage fluctuation and flicker standards and hence the associated limits. The potential detrimental effects on electrical equipment which may be caused by relaxation of these limits should be investigated before any changes to the present standards take place. The impact of voltage fluctuations on a full-bridge rectifier with a capacitor filter is considered as a case study in this paper. Such a circuit is found at the front end of many different types of equipment that are connected to the public ac supply network. The capacitor ripple current characteristic is of particular interest. The research reported in this paper indicates that the filter capacitor will accumulate and dissipate increased amount of charge when the rectifier is subjected to ac source voltage fluctuations. The consequence is that the RMS value of the capacitor current will increase, where the magnitude of this increase is related to the modulation frequency and magnitude of the fluctuating voltage. Therefore, an ac supply with a voltage fluctuation component will cause a full-bridge rectifier with capacitor filter to sustain increased stress. This stress may accelerate the capacitor ageing process, eventually resulting in premature equipment failure. The research indicates that there is a need for indices other that the short-term and long-term flicker indices required for equipment compatibility levels. [ABSTRACT FROM PUBLISHER]

Discrete or event type power quality (PQ) disturbances mainly include voltage sags, swells, and the transients. An extensive literature survey suggests that there is no generally accepted method for characterization of these disturbances and suitable limits are not yet found in any international standard. One of the reasons for the lack of characterization methods is the difficulty of defining suitable site indices for each discrete disturbance type. In this paper existing characterization methods are reviewed and discussed. A new generalized approach is then given to show a better way of characterizing voltage sags, swells and transients. This is followed by a proposed new method of defining MV/LV distribution discrete disturbance limits for general utility networks and their suitability is shown by an examination of some Australian sites. [ABSTRACT FROM PUBLISHER]

Fused double-cluster [(η5-C5Me5)IrB18H18(PH2Ph)] (8), from syn-[(η5-C5Me5)IrB18H20] (1) and PH2Ph, retains the three-atoms-in-common cluster fusion intimacy of 1, in contrast to [(η5-C5Me5)HIrB18H19(PHPh2)] (6), from PHPh2 with 1, which exhibits an opening to a two atoms-in-common cluster fusion intimacy. Compound 8 forms via spontaneous dihydrogen loss from its precursor [(η5-C5Me5)HIrB18H19(PH2Ph)] (7), which has two-atoms-in-common cluster-fusion intimacy and is structurally analogous to 6. [Copyright &y& Elsevier]

Power generation through solar photovoltaics has shown significant growth in recent years. However, high penetration of solar PV creates power system operational issues as a result of solar PV variability and uncertainty. Short-term PV variability mainly occurs due to the intermittency of cloud cover. Therefore, to mitigate the effects of PV variability, a sky-image-based, localized, global horizontal irradiance forecasting model was introduced considering the individual cloud motion, cloud thicknesses, and the elevations of clouds above the ground level. The proposed forecasting model works independently of any historical irradiance measurements. Two inexpensive sky camera systems were developed and placed in two different locations to obtain sky images for cloud tracking and cloud-based heights. Then, irradiance values for onsite and for a PV site located with a distance of 2 km from the main camera were forecasted for 1 minute, 5 minutes, and 15 minutes ahead of real-time. Results show that the three-level cloud categorization and the individual cloud movement tracking method introduced in this paper increase the forecasting accuracy. For partially cloudy and sunny days, the forecasting model for 15 min forecasting time interval achieved a positive skill factor concerning the persistent model. The accuracy of determining the correct irradiance state for a 1 min forecasting time interval using the proposed model is 81%. The average measures of RMSE, MAE, and SF obtained using the proposed method for 15 min forecasting time horizon are 101 Wm-2, 64 Wm-2, and 0.26, respectively. These forecasting accuracy levels are much higher than the other benchmarks considered in this paper. [ABSTRACT FROM AUTHOR]

Integration of renewable distributed generation (DG) units into distribution networks is gaining widespread popularity. However, uncertainties in generation availability associated with renewable DG units pose a major challenge. These uncertainties should be properly addressed to ensure acceptable system performance and improve customer-side reliability. In this article, the reliability assessment of distribution systems embedded with renewable DG sources has been carried out giving emphasis to system uncertainties and optimal restoration strategies. The uncertainties associated with the power output from renewable resources, time-varying load demand, stochastic prediction errors, and random fault events have been accounted for in the restoration optimization formulation for reliability evaluation. In this article, a parameter-free particle swarm optimization (PSO) technique is applied to address the complexity involved in the formulation. Moreover, a problem-specific encoding scheme is also proposed in conjunction with PSO to ensure optimality. [ABSTRACT FROM AUTHOR]

With a view to combining the desirable electronic and photochemical properties of hexabenzocoronene (HBC) and the C–C bond forming capabilities of thiophenes, 1-(3-thienyl)-2,3,4,5,6-penta(4-tert-butyl-phenyl)benzene (1) was oxidised using FeCl3. The resulting products, superaromatic thiophene (2) and its 5,5′-dimer (3), are S-HBC systems and provide a new pair of spectral comparators. [ABSTRACT FROM AUTHOR]

With ever increasing penetration of inverter-interfaced generators and consequent reduction in available inertial reserve, traditional allowable delay in the provision of the primary frequency reserve will threaten the security of the future grids. However, droop control with fast-enough inertia-less generators can limit the post-contingency frequency excursion. To conform with the fast-enough reserve provision requirement in a reduced and varying-inertia system, an economical clearing of the reserve requires an allowable delay heuristic corresponding to the desired system frequency excursion characteristic; while alleviating the causality dilemma introduced by the unavailability of maximum delay heuristic itself before clearing. The proposed heuristic establishes a relationship among the system parameters, such as the aggregated system inertia, regulation factor, system frequency, desired frequency response, and allowable delay margin. The Padé approximation technique is utilized for deriving the transfer function of such a system, allowing calculation of the allowable delay with various damping ratios corresponding to the dominant poles. The impact of different Padé order on the determined heuristic is analyzed. The regulation factor of the generators is calculated based on the reserve bid volume to ensure proportional injection during contingencies. The impacts of regulation factor and associated delay on the frequency response are also studied. [ABSTRACT FROM AUTHOR]

In an open system, system resources are managed by the contributors themselves. Because the participation needs to be voluntary and contributors true utility will remain unmonitored, proper communication among the participants is essential. In the discussed common-pool resource (CPR) problem, all the members need not be contributors, but the non-excludable component of the resource is required to be multiplied with each of the member's rivalrous component, and all these products are needed to be summed up to calculate the overall resource requirement. This characteristic applies to a typical power system optimization problem, where, if a customer group installs a common dynamic voltage restorer, voltage improvement can be treated as non-excludable quantity, while the peak load of individual customers can be treated as rivalrous quantity. In this work, we consider, the participants sharing the CPR contribute to form an open system to capitalize on ‘economy of scale’, while discouraging the unilateral free-riding benefit. Considering the benefit and average production cost curve represented by piecewise linear functions we have shown that the utility function is convex. Furthermore, for the given problem, we have numerically calculated the utility distribution scheme by solving an optimization problem. [ABSTRACT FROM AUTHOR]

Highlights • Theoretical formulation for volt/var control in distribution networks is proposed. • Formulation is universally applicable across MV and LV distribution networks. • Development of a holistic volt/var control across MV and LV distribution networks. • Validation of the proposed method against a general, conventional method. • Suitability of the proposed method is demonstrated through results. Abstract Voltage regulation in medium voltage (MV) and low voltage (LV) distribution networks has always been considered and approached as separate issues. However, changes in voltage magnitudes in an MV network can affect voltage magnitudes in an associated LV network and vice versa. In addition, voltage changes in an MV network can be contrary to changes in the associated LV network. This paper presents a voltage regulation methodology for MV and LV networks as a combined, network-wide problem. A theoretical formulation is developed to present MV and LV networks in a holistic manner, applicable for the development of an efficient voltage regulation approach. The proposed formulation is tested on a modified IEEE 13 node test feeder and verified using OpenDSS. The results confirm that the proposed formulation can successfully solve both MV and LV networks simultaneously. Based on the developed theoretical formulation, this paper proposes an integrated volt/var control philosophy to perform voltage regulation in both MV and LV networks jointly. The proposed volt/var control method is tested on the same test feeder over a 24-h period with varying load and generation. The results confirm that the proposed volt/var control method can successfully improve voltage profiles across both MV and LV networks in comparison to using a conventional volt/var control method. [ABSTRACT FROM AUTHOR]

Voltage stability in general is of paramount importance with increasing penetration levels of variable-speed wind power generators (VSWGs) in power systems. Limited knowledge exists considering the impact of VSWGs on long-term voltage stability (LTVS) of power systems, focusing on doubly fed induction generators and full-converter wind generators. This paper presents the results of a comprehensive study on the impact of VSWGs on LTVS. Integration of wind generators while operating the existing synchronous generators improves the LTVS. However, it is unlikely that power systems will retain all existing synchronous generators operating, with high wind penetration levels. Therefore, this study compares the capability of the synchronous generators and VSWGs on LTVS by considering the dynamic reactive power capabilities. The significance of overload capability of synchronous generators on LTVS is highlighted. It is also illustrated that integrating wind farms at remote and local locations from load centres has distinct impacts on LTVS. Replacement of synchronous generators located in close proximity to load centres has a detrimental effect on LTVS. Furthermore, this study demonstrates the impact of different wind generator loading levels on LTVS. The study outcomes highlight several distinct factors which influence the LTVS of power systems with high wind penetration levels. [ABSTRACT FROM AUTHOR]

Voltage stability in general is of paramount importance with increasing penetration levels of variable‐speed wind power generators (VSWGs) in power systems. Limited knowledge exists considering the impact of VSWGs on long‐term voltage stability (LTVS) of power systems, focusing on doubly fed induction generators and full‐converter wind generators. This paper presents the results of a comprehensive study on the impact of VSWGs on LTVS. Integration of wind generators while operating the existing synchronous generators improves the LTVS. However, it is unlikely that power systems will retain all existing synchronous generators operating, with high wind penetration levels. Therefore, this study compares the capability of the synchronous generators and VSWGs on LTVS by considering the dynamic reactive power capabilities. The significance of overload capability of synchronous generators on LTVS is highlighted. It is also illustrated that integrating wind farms at remote and local locations from load centres has distinct impacts on LTVS. Replacement of synchronous generators located in close proximity to load centres has a detrimental effect on LTVS. Furthermore, this study demonstrates the impact of different wind generator loading levels on LTVS. The study outcomes highlight several distinct factors which influence the LTVS of power systems with high wind penetration levels. [ABSTRACT FROM AUTHOR]

In Australia and many other countries, distribution network service providers (DNSPs) have an obligation to their customers to provide electrical power that is reliable and of high quality. Failure to do so may have significant implications ranging from financial penalties theoretically through to the loss of a license to distribute electricity. In order to ensure the reliability and quality of supply are met, DNSPs engage in monitoring and reporting practice. This paper provides an overview of a large long-running power-quality monitoring project that has involved most of Australia's DNSPs at one time or another. This paper describes the challenges associated with conducting the project as well as some of the important outcomes and lessons learned. A number of novel reporting techniques that have been developed as part of the monitoring project are also presented. A discussion about large-volume data management, and issues related to reporting requirements in future distribution networks is included. [ABSTRACT FROM PUBLISHER]

Voltage dips are considered to be one of the costliest of all power quality disturbances due to their disruption of industrial and commercial operations. The ability to characterise the voltage dip performance of distribution networks has many benefits for industry. There is considerable potential for industry to make large economic gains if voltage dip behaviour can be better understood and planned for. To put strategies in place to deal with voltage dips, there is a need for extensive data collection and analysis so that correct planning decisions can be made. This study details the characteristics of voltage dip data which has been collected at low-voltage sites in Australia over a 9 year period. The data is displayed in a number of different formats to aid analysis. [ABSTRACT FROM AUTHOR]

Recently published International Electrotechnical Committee (IEC) technical reports IEC 61000-3-13 provides detailed methodologies for managing voltage unbalance (VU) in electric power systems. A key aspect in the VU emission allocation process is the estimation of VU propagation in different parts of the network. Although the VU propagation from upstream networks to downstream networks is adequately addressed, the attenuation of VU when propagating from downstream to upstream networks at the same voltage level has not been properly taken into account in the aforementioned methodologies. Furthermore, mains connected three-phase induction motors are known to attenuate VU, and there is no methodology currently available to quantify the attenuation provided by such motors. The main motivation behind the current research is to investigate the VU propagation and attenuation in radial distribution networks and to quantify the attenuation provided by induction motor loads. This paper reports that the VU propagation from downstream to upstream in a radial distribution network with symmetrical distribution lines can be conservatively approximated by the ratio of fault levels of upstream and downstream network. Moreover, an influence coefficient has been introduced as a means of appraising the impact of induction motor loads. The theoretical work presented is verified using unbalanced load flow analysis. The outcomes presented in the paper are useful for the further development of IEC technical report on VU emission allocation. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Voltage dips are considered to be one of the costliest of all power quality disturbances due to their disruption of industrial and commercial operations. The ability to characterise the voltage dip performance of distribution networks has many benefits for industry. There is considerable potential for industry to make large economic gains if voltage dip behaviour can be better understood and planned for. To put strategies in place to deal with voltage dips, there is a need for extensive data collection and analysis so that correct planning decisions can be made. This study details the characteristics of voltage dip data which has been collected at low‐voltage sites in Australia over a 9 year period. The data is displayed in a number of different formats to aid analysis. [ABSTRACT FROM AUTHOR]

We describe a series of functionalized N-containing heterosuperbenzenes, created with a view to investigating the strategic role of methoxy substituents in (i) promoting cyclodehydrogenation and (ii) tuning the electronic properties and (iii) the supramolecular order in the resultant fused products. [ABSTRACT FROM AUTHOR]

The constant current controllers at high voltage direct current (HVDC) rectifier stations and the outer loops which set the reference to the current controller have potential to introduce negative damping on the nearby generating units. It is therefore vital to investigate the torsional interaction behavior between turbine-generator (TG) units and the HVDC systems over a frequency range of interest. In this paper, subsynchronous torsional interaction (SSTI) phenomenon for hydroelectric TG units with small generator-to-turbine inertia (GTI) ratios interconnected to an HVDC system has been investigated. The sensitivity of different system parameters, such as generating capacity and loading, DC power flow, AC network strength and current controller gains, towards electrical damping contribution is also examined. Hydro units with different shaft systems are examined for SSTI proneness by conducting perturbation analysis. The impact of hydroelectric TG units with different GTI ratios has also been examined by applying a three-phase to ground fault at the rectifier station. Simulation studies have been carried out in PSCAD ® /EMTDC © environment. Due to lack of modal damping with relatively low decrement factor and logarithmic decrement, sustained and growing TG torque oscillations are noted for certain operating conditions of hydro units with small GTI ratios interconnected with an HVDC system. [ABSTRACT FROM PUBLISHER]

The ITI curve developed by the Information Technology Industry Council (USA) describes an AC input voltage envelope, which typically can be tolerated by most information technology (IT) equipment supplied by nominal 120 V 60 Hz electricity networks. Although the curve ostensibly applies only to IT equipment supplied at 120 V 60 Hz it is often used throughout the electricity supply industry, including at other nominal voltages and frequencies, without modification or consideration of applicability to provide an indication of the input voltage tolerance of a wide range of equipment. This paper details a preliminary study aimed at developing an ITI style curve to suit 230 V 50 Hz electricity networks. A range of domestic and industrial equipment has been tested to determine voltage sag susceptibility. Overall, results for domestic appliances show that equipment connected to the Australian 230 V 50 Hz electricity network has voltage sag immunity considerably better than that defined by the ITI curve. The same may be said for the majority of industrial equipment tested. As such, the suitability of the ITI curve in describing a sag immunity envelope for individual pieces of equipment connected to 230 V 50 Hz electricity networks is highly questionable. [ABSTRACT FROM AUTHOR]

The application of variable speed wind generators in hybrid remote area power supply (RAPS) systems provides opportunities for improved voltage and frequency control together with maximum power point tracking (MPPT), where limited research outcomes exist. The study presented in this paper covers two such hybrid systems: 1) permanent magnet synchronous generator (PMSG) and 2) doubly fed induction generator (DFIG) as wind turbine technologies together with a battery storage and a dump load. The battery storage system and dump load are able to assist in maintaining the active power balance during over and under generation conditions as well as sudden load changes. Through simulation studies, it has been demonstrated that both RAPS systems are able to regulate the load side voltage and frequency within the acceptable limits while extracting the maximum power from wind, which is an inherent capability of variable speed generators. The two RAPS systems and their associated control strategies have been developed and their performance is investigated using SimPowerSystems blocksets in MATLAB. [ABSTRACT FROM AUTHOR]