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In cascaded H-bridge (CHB) multilevel inverters (MLIs), phase-shifted pulse width modulation (PSPWM) and level-shifted pulse width modulation (LSPWM) are the two prominent techniques to attain multilevel and better performance. But both of them have certain drawbacks like in PSPWM the switching loss of all the semiconductors is high, and in LSPWM the power-sharing between the cascaded modules is not identical. These two drawbacks have been addressed in this article by proposing a novel modulation technique, named the phase opposed disposed phase-shifted PWM (PODPSPWM). In this technique, the level-shifted carriers have been rotated in such a way that there should not be any active power loss and simultaneously the carriers are phase-shifted as per the PSPWM technique. A detailed mathematical analysis of switching loss for all three methods has been presented. Moreover, the power-sharing and harmonic spectrum of the proposed PODPSPWM over other PWMs have been discussed. This novel modulation technique has been simulated in the MATLAB/Simulink software to validate the superiority of the operation. The 1.5-kW experimental prototype is developed to validate the performance of the proposed PODPSPWM modulation. 2022 IEEE. This work was supported by NPRP-EP through the Qatar National Research Fund (a member of Qatar Foundation) under Grant X-033- 2-007. Scopus

Reliability is of importance for operation maintenance and cost reduction in power electronics and systems. Based on the reliability models of power devices, reliability-oriented power sharing in microgrids enforces the redistribution of power among converters to prolong the lifetime of the entire system, and droop control is typically used herein. However, this could affect the system stability, which contradicts the prerequisite of secure operation. In light of the above, this article is aimed to reveal this limitation of reliability-oriented droop control and emphasize its impact on system stability. Accordingly, a framework of stability-constrained reliability-oriented droop control is proposed, together with solutions that can help to enhance the stability. With this, the reliability of the system could be further improved without violating the stability criteria. Moreover, experimental tests and long-term reliability evaluations are included, which demonstrates that the aforementioned issues can be effectively addressed alongside with the proposed framework and solutions.

With the rapidly increasing deployment of distributed energy resources (DERs), electric power systems across the world are moving towards more distributed designs and operations. While not every distributed device will be part of a microgrid, microgrids do offer solutions for scalability and interoperability, and for coordination with centralized utility control systems. The challenge is that the microgrids will be heterogenous with respect to ownership, operational objectives, resource mix, and control systems. Due to these variations within the population of microgrids, there will be significant challenges with coordinating their operations to achieve global objectives using existing centralized controls and optimizations. This paper presents a framework for the coordination of heterogeneous groups of microgrids using consensus algorithms. The framework enables the active engagement of utility and non-utility microgrids using a distributed architecture to support end-use loads during the loss of the bulk power system. Results from laboratory testing and preliminary implementations, as well as details of an ongoing operational deployment at the Electric Power Board of Chattanooga are presented in this paper.

Power system benchmarks are transmission and distribution networks used to evaluate novel control algorithms and simulate grid evolution scenarios. These benchmarks range in size, system characteristics, and use cases. Although active working groups have created and published many benchmarks, these networks are not all representative of a given region and may not consider certain aspects such as increased penetration levels of distributed energy resources. To address these issues, synthetic benchmark networks and methodologies for generating them have been developed by various research groups. This paper provides a comprehensive survey of procedures commonly used to generate synthetic networks and a detailed account of the various metrics used to define and validate benchmarks. Existing models are categorized into different approaches, including expert design, anonymized clustering, statistical sampling, and heuristic algorithms. Deep graph generation based techniques are also presented and recommended for the network generation problem. A comparative summary is provided to highlight the different existing works in this area and reveal research gaps, along with a list of published datasets and their characteristics.

This paper presents a novel dynamic programming (DP) technique for the determination of optimal investment decisions to improve power distribution system reliability metrics. This model is designed to select the optimal small-scale investments to protect an electrical distribution system from disruptions. The objective is to minimize distribution system reliability metrics: System Average Interruption Duration Index (SAIDI) and System Average Interruption Frequency Index (SAIFI). The primary input to this optimization model is years of recent utility historical outage data. The DP optimization technique is compared and validated against an equivalent mixed integer linear program (MILP). Through testing on synthetic and real datasets, both approaches are verified to yield equally optimal solutions. Efficiency profiles of each approach indicate that the DP algorithm is more efficient when considering wide budget ranges or a larger outage history, while the MILP model more efficiently handles larger distribution systems. The model is tested with utility data from a distribution system operator in the U.S. Results demonstrate a significant improvement in SAIDI and SAIFI metrics with the optimal small-scale investments.

Space vector (SV)-based estimation algorithms represent attractive methods for synchronized phasor, frequency, and rate of change of frequency measurements in three-phase ac power systems. Recently, a phase-locked-loop (PLL) solution for improving the demodulation of the SV signal has been proposed. In this article, the potentialities of the SV-PLL approach are investigated in order to optimize accuracy and computational load. First, the impact of the PLL update rate on achieved performance is analyzed. Then, a novel two-step SV-PLL algorithm is presented so that the accuracy of a fast PLL execution frequency can be matched with a considerably lower computational cost. The behavior in the case of fast phase angle variations has been also significantly improved. The proposed synchrophasor estimation technique has been validated through simulations; exemplary dynamic performance suggests that it is particularly suitable for grid control applications. Experimental tests carried out on a real-time implementation confirm simulation results.

Solid-state transfer switch (SSTS) becomes the most crucial technology for electric power transmission, distribution and control system. SSTS is useful in supplying the power to sensitive loads uninterruptedly and critical loads economically and efficiently. However, a few concerns could hamper the effectiveness of SSTS including voltage swell, sag, inappropriate structure, poor power factor and inefficient control methods. Hence, this paper comprehensively surveys the diverse SSTS topologies, applications, operations, issues, and future directions. The SSTS configuration, design, control system, benefits and shortcomings are discussed rigorously. A detailed comparative analysis of various SSTS are carried out concerning topologies, control operations and applications. In line with that, the different control models and schemes are narrated briefly. This paper also highlights existing challenges and issues before providing a few important future prospects to enhance the configuration and efficiency of SSTS. All the key information obtained from this review would be beneficial to the researchers and power system engineers to develop an advanced and efficient SSTS toward future performance enhancement.

This paper proposes an improved discontinuous pulse-width modulation (DPWM) method based on phase-shifted PWM (PS-PWM) for three-phase cascaded H-bridge (CHB) multilevel inverters. Due to the CHB multilevel inverters employ a large number of power semiconductor switches, they suffer from device failures because the switches are one of the major failure factors in a power electronic system. Therefore, the reliability and life-time of CHB multilevel inverters are mainly determined by the reliability of switches. The most failure of switches is occurred by its accumulated thermal stress which is generated by power losses including the conduction and switching loss. By applying the conventional DPWM, the life-time of switches can be extended because it reduces the switching loss. The conventional DPWM, however, still operates with high speed carrier frequency and it is not enough to reduce the switching loss of the CHB multilevel inverter with a large number of inverter cells. The proposed novel DPWM method provides the improved switching loss reduction through the different switching behaviors for each leg. Additionally, the rotation scheme promises even power distribution and life-time management among inverter cells in a CHB multilevel inverter. The simulation results and experimental results confirm the switching loss reduction and even power distribution abilities of the proposed modulation method.

A novel method based on phasor interpolation is proposed for solving the distribution system problem of computing bus neutral voltages as functions of bus grounding impedances. The proposed approach has the salient feature of exponentially reduced computational complexity, with respect to the number of groundable buses, when compared to the standard procedure of iterating load flow for all grounding impedance setups. This is achieved by computing load flow for a subset of grounding impedances and subsequently estimating voltage for the remaining cases via phasor interpolation. To validate the proposed method, case studies based on computer simulations are considered for assessing estimation error and processing time of the proposed method. Obtained results confirm that the proposed methods yields significant reduction of execution time with low error in the estimation of neutral voltages, compared to exact results computed via standard procedures based on iteration of load flow algorithms.

Phase swapping, which rebalances the unbalanced three-phase low voltage (LV, 415 V) networks, improves network efficiency by reducing capacity waste and energy losses. A key challenge against phase swapping is that the majority of LV networks are data scarce, i.e., there is a general lack of data in LV networks. In light of this, this paper proposes a new statistical approach to develop phase swapping guidance for data-scarce LV networks with neither time-series network measurements nor customer metering data. First, given a set of data-rich LV networks (with time-series phase currents data collected at LV substations throughout a year), typical load profiles and their weights in each of the three phases are extracted by applying a nonnegative matrix factorization method. Then, phase swapping guidance are developed for data-rich LV networks along with their rebalancing potentials (rebalancing potentials refer to the reduction of phase imbalance degree). Second, a rapid screening model is developed to efficiently identify the data-scarce LV networks with high rebalancing potentials. Phase swapping guidance are then developed for these data-scarce networks with high rebalancing potentials. Case studies reveal that the statistical approach produces effective phase swapping guidance, which reduce the phase imbalance degrees for 99% of the LV networks and the maximum reduction is 35%. Validation results show that the average reduction of the phase imbalance degree for data-scarce networks is only 14.3% less than that for data-rich networks.

Solid-state transformer (SST) is an emerging technology integrating with a transformer power electronics converters and control circuitry. This paper comprehensively reviews the SST topologies suitable for different voltage levels and with varied stages, their control operation, and different trends in applications. The paper discusses various SST configurations with their design and characteristics to convert the input to output under unipolar and bipolar operation. A comparison between the topologies, control operation and applications are included. Different control models and schemes are explained. Potential benefits of SST in many applications in terms of controllability and the synergy of AC and DC systems are highlighted to appreciate the importance of SST technologies. This review highlights many factors including existing issues and challenges and provides recommendations for the improvement of future SST configuration and development.

Electric distribution systems around the world are seeing an increasing number of utility-owned and non-utility-owned (customer-owned) intelligent devices and systems being deployed. New deployments of utility-owned assets include self-healing systems, microgrids, and distribution automation. Non-utility-owned assets include solar photovoltaic generation, behind-the-meter energy storage systems, and electric vehicles. While these deployments provide potential data and control points, the existing centralized control architectures do not have the flexibility or the scalability to integrate the increasing number or variety of devices. The communication bandwidth, latency, and the scalability of a centralized control architecture limit the ability of these new devices and systems from being engaged as active resources. This paper presents a standards-based architecture for the distributed power system controls, which increases operational flexibility by coordinating centralized and distributed control systems. The system actively engages utility and non-utility assets using a distributed architecture to increase reliability during normal operations and resiliency during extreme events. Results from laboratory testing and preliminary field implementations, as well as the details of an ongoing full-scale implementation at Duke Energy, are presented.

Energy management in distribution systems has gained attention in recent years. Coordination of electricity generation and consumption is crucial to save energy, reduce energy prices and achieve global emission targets. Due to the importance of the subject, this paper provides a literature review on recent research on energy management systems and classifies the works based on several factors including energy management goals, the approaches taken for performing energy management and solution algorithms. Furthermore, the paper reviews some of the most proficient techniques and methodologies adopted or developed to address energy management problem and provides a table to compare such techniques. The current challenges and limitations of energy management systems are explained and some future research directions have been provided at the end of the paper.

This paper proposes a support vector regression (SVR)-based model predictive control (MPC) for the volt-var optimization (VVO) of electrical distribution systems. First, measurement data from a few days of operation of a distribution system, gathered using advanced metering infrastructure (AMI), are used to train an SVR model of the system. The trained model is then employed by the MPC in a closed-loop control scheme to control capacitor banks and tap changers of the distribution system so that the power loss is minimized, and voltage profiles are maintained within a specific range. In contrast to the many existing VVO methods, the proposed scheme does not require any circuit-based simulations for its operation, nor does it assume that the distribution system is radial. The simulation results of applying the proposed SVR-based MPC to IEEE123 bus test feeder proves that despite its measurement-based feature, the proposed approach is capable of providing close to optimal solutions to the VVO problem. The simulation results also suggest a satisfactory outcome of the proposed approach in controlling meshed grids or in the presence of distributed energy resources (DERs).

Energy and economy are increasing the relationship over the years, where the energy becomes a significant resource to keep a country developing, and it supports its economy. Then, more reliable the energy should become, especially the distribution network, to keep the entire process running. In this level of energy distribution, where residential consumers and medium and small industries are supplied, the number of interconnections of the network is enormous. However, for economic and environmental aspects, these complex systems, which are operating close to their capacity, needs to increase the automation, appearing the concept of smart grids and the Advanced Distribution Management System (ADMS) and its methods to control. Inside of the ADMS, there are a lot of essential techniques. Among them, there are two techniques which are the most relevant for this paper: the self-healing and load management. In an ADMS system, these two techniques are treated separately, but the best solution occurs when they are computed together. In this paper, it is proposed an approach that can address both problems at the same time or individually, i.e., in place to have a sequential method to solve step-by-step the issues in the networks. The proposed algorithm, through reinforcement learning technique, can handle both problems together. The proposed approach is tested in a real urban distribution network with some created scenarios to compare the results with outages and overloads. Some comparisons with other methods are carried out.

Electric transportation systems are a challenging load for three-phase transmission lines due to load variations, reactive power, imbalance, and harmonic pollution. Many power quality conditioners and compensation technologies have been developed to ensure compatibility with power systems. The most important ones are investigated, identifying parameters and performances for comparison, including evaluation of cost and size. A reference case is used for simulation, focusing on three-phase current intensity, current rate of rise, dc-link voltage, and dynamic response under various combinations of traction line load. The objective is to identify key characteristics supporting the selection of the appropriate compensation strategy for a new electrified railway system.

This work describes a technique to define a single parametric equation that estimates remote conditions within a distribution network, in an online setting, without dedicated telemetry. In this novel approach, a departure from conventional state estimation is explored to facilitate a fully decentralized operation. Derived based on fundamental treatment of ac power flow, the electrical behavior of a section of network is defined to a tractable constraint space using regression analysis. In this non-iterative technique, a measurement set consisting of the local voltage magnitude, active and reactive power injections at a single node are the input to pre-computed polynomials. Remote current flow, active power and reactive power flow as well as remote and local voltages and sensitivities are estimated in a direct calculation from period to period. Accurate estimations are also found in the presence of transducer errors. To assess the applicability of this technique at differing voltage levels a range of reactance to resistance ratios are considered. Science Foundation Ireland

Voltage limit violation is one of the main factors that impact large-scale integration of electric vehicles in distribution networks. In order to improve voltage profiles, active charging management techniques can be deployed in real-time, considering voltage sensitivities of customer buses. The study in this paper investigates a real-time charging management approach for electric vehicles, clustered according to voltage sensitivities among the customer buses, in a local network. Constant power (CP) and constant current (CC) models, representing a range of electric vehicle battery chargers (EVBCs), are used in simulations with high-resolution stochastic EV charging and residential demand profiles. The paper quantifies the performance of the proposed management approach in a local network model based on real data and IEEE European Low Voltage (LV) Test Feeder.

Agent-based modeling of active distribution network helps to understand the dynamics and to design the control strategies for overall system efficiency. There is, however, a lack of generic and multipurpose agent definitions in existing studies. In this paper, a multi-agent system-based modeling of an active distribution network is presented using cooperative agents. A method to solve a network-wise objective of state estimation is explained with the proposed model. The network component agents are defined to be cooperative to meet the overall objectives and greedy to fulfil individual objectives such as energy cost minimization. A token-ring protocol is deployed for the agent communication among themselves, as well as with market and network operator agents. Furthermore, a MATLAB/Simulink model of active distribution network is used to simulate the emerging stochastic loading scenario, while the autonomous prosumer agents optimize their total energy cost responding to market price variations.

Device-to-device (D2D) communications have recently emerged as a novel transmission paradigm in wireless cellular networks. D2D transmissions take place concurrently with the usual cellular connections, and thus, controlling the interference brought to the macro-cellular user equipment (UE) is of vital importance. In this letter, we consider the uplink transmission of a tier of D2D users that operates as an underlay for the traditional cellular network. Using a network model based on stochastic geometry, we derive the equilibrium cumulative distribution function (CDF) of the D2D transmit power. Considering interference-limited and relatively lossy environment cases, closed-form equations are derived for the power CDF. Finally, a tight closed-form upper-bound for the derived power distribution is proposed, and the analytical results are validated via simulation.

Three-phase imbalance causes uneven voltage drops along low voltage (LV) feeders. Under long-term load growth, the phase with the lowest terminal voltage will trigger network reinforcements, which are earlier than if the three phases were balanced. This leads to a higher voltage-driven reinforcement cost (VRC) than the balanced case. Three-phase power flow analyses are not suitable for VRC estimations under serious data deficiency (without customers’ phase connectivity and smart metering data), and are not scalable due to the iterative nature which brings a prohibitively high computation burden on a utility level with millions of feeders. To overcome the challenges, this paper proposes a novel scalable methodology for VRC estimations that is applicable from an individual feeder to millions of feeders where the level of information is insufficient to support accurate three-phase power flow studies. The key is to use five types of load current distributions to represent customers’ phase allocations and individual demands, and to incorporate these distributions into an equivalent impedance matrix which allows a straightforward VRC estimation without iterations. This paper applies this methodology to an individual feeder, showing that: 1) the VRC decreases (increases) with the increase of the K (beta) factor of the trapezoid (triangular-rectangular) distribution, given that other conditions remain the same; 2) the VRC is more sensitive to voltage imbalance than to current imbalance; and 3) if the three phases are balanced, the change of any single variable results in an increase of the VRC, given that all other input variables remain constant.

The concept of dynamic rating (DR) implies that the capacity of a component varies dynamically as a function of external parameters, while the rating traditionally is based on the worst-case. The value of DR thus lies in utilizing existing equipment to a greater extent. By implementing DR and correlating the new ratings with wind power generation, more generation can be implemented. The aim is hence to facilitate connection of renewable electricity production. This paper provides two main contributions: 1) a general dynamic line rating (DLR) calculation model on overhead lines; and 2) an economic optimization simulation model regarding wind power integration comparing DLR with more traditional approaches. These models can both be implemented together, but also separately. The DLR calculation model is easy to use by companies in daily operation where the dynamic line capacity is calculated as a function of static line capacity, wind speed, and ambient temperature. The DLR calculation model is furthermore compared with more comprehensive calculations that validate that the model is accurate enough. This paper also provides an application study where both proposed models are exemplified together and evaluated. Results from this study conclude that it is a significant economic potential of implementing DR within wind power integration. QC 20140902

In recent years, extreme weather events have severely affected the performance of the electric grid. Very large-scale events (VLSE) with potentially catastrophic impacts on the grid pose more than an inconvenience in today's electricity-driven lifestyle, and the frequency and severity of such events may continue to increase as a consequence of global climate change. This article summarizes the state of the art in leveraging distributed resources to improve resilience of the electric grid. It also highlights the technical questions that need to be addressed through additional research and development if the value of distributed resources is to be maximized. Published in "Power and Energy Magazine", Volume: 12, Issue: 5

Dispersed storage systems (DSSs) can represent an important near-term solution for supporting the operation and control of active distribution networks (ADNs). Indeed, they have the capability to support ADNs by providing ancillary services in addition to energy balance capabilities. Within this context, this paper focuses on the optimal allocation of DSSs in ADNs by defining a multi-objective optimization problem aiming at finding the optimal trade-off between technical and economical goals. In particular, the proposed procedure accounts for: 1) network voltage deviations; 2) feeders/lines congestions; 3) network losses; 4) cost of supplying loads (from external grid or local producers) together with the cost of DSS investment/maintenance; 5) load curtailment; and 6) stochasticity of loads and renewables produc- tions. The DSSs are suitably modeled to consider their ability to support the network by both active and reactive powers. A convex formulation of ac optimal power flow problem is used to define a mixed integer second-order cone programming problem to opti- mally site and size the DSSs in the network. A test case referring to IEEE 34 bus distribution test feeder is used to demonstrate and discuss the effectiveness of the proposed methodology.

In this paper, we propose an architecture for voltage regulation in distribution networks that relies on controlling reactive power injections provided by distributed energy resources (DERs). A local controller on each bus of the network monitors the bus voltage and, whenever there is a voltage violation, it uses locally available information to estimate the amount of reactive power that needs to be injected into the bus in order to correct the violation. If the DERs connected to the bus can collectively provide the reactive power estimated by the local controller, they are instructed to do so. Otherwise, the local controller initiates a request for additional reactive power support from other controllers at neighboring buses through a distributed algorithm that relies on a local exchange of information among neighboring controllers. We show that the proposed architecture helps prevent voltage violations and shapes the voltage profile in radial distribution networks, even in the presence of considerable penetration of variable generation and loads.We present several case studies involving 8-, 13-, and 123-bus distribution systems to illustrate the operation of the architecture. © 2012 IEEE. 28 2 1470 1482

Controlled charging of electric vehicles offers a potential solution to accommodating large numbers of such vehicles on existing distribution networks without the need for widespread upgrading of network infrastructure. Here, a local control technique is proposed whereby individual electric vehicle charging units attempt to maximise their own charging rate for their vehicle while maintaining local network conditions within acceptable limits. Simulations are performed to demonstrate the benefits of the technique on a test distribution network. The results of the method are also compared to those from a centralized control method whereby EV charging is controlled by a central controller. The paper outlines the advantages and disadvantages of both strategies in terms of capacity utilization and total energy delivered to charging EVs. Science Foundation Ireland Deposited by bulk import

The paper describes the design of optimized printed circuit board (PCB) air-core toroids for high-frequency dc-dc converters with strict requirements in terms of volume and noise. The effect of several design parameters on the overall inductor volume, on dc and ac winding resistance, and on the radiated noise will be investigated. PCB toroids are compared to standard air-core solenoids and other state-of-the-art air-core toroids both theoretically and experimentally: at first, using ANSOFT Maxwell and ANSOFT Q3D simulation tools, and subsequently, with laboratory measurements (irradiated noise, efficiency, and frequency response) on several prototypes. These very flexible and rather easy to manufacture inductors appear very attractive for compact high-frequency dc-dc converters where high efficiency, low volume, and low noise are of primary concern.

The future electricity network has to be able to manage energy coming from different grids as well as from renewable energy sources (RES) and other distributed generation (DG) systems. Advanced power electronic converters can provide the means to control power flow and ensure proper and secure operation of future networks. This paper presents analysis, design, and experimental validation of a back-to-back three-phase ac-dc-ac multilevel converter employed for universal and flexible power management (UNIFLEX-PM) of future electrical grids and its advanced control technique. The proposed system has been successfully tested for bidirectional power flow operation with different grid operating conditions such as voltage unbalance, frequency variation, harmonic distortion, and faults due to short circuits.

International audience; In this paper, we propose a method for finding the optimal distribution of pilot power, which will optimize the performance of multi-carrier transmissions over power lines, using comb-type pilots. To find this optimal distribution, we took noise characteristics and channel estimation techniques based on pilot tones associated with interpolation techniques into account. We used two criteria: the classic Mean Square Error of channel estimation and an indicator of performance for multi-tones systems. With these criteria, we used the traditional Lagrange method to obtain different power distributions over pilot tones. In this paper, we show that minimizing the performance indicator is a good criterion, since it evolves as Bit Error Rate. We then present the optimal distribution of pilot power. Our results show that good performances can be achieved with a uniform distribution of pilot power, although the additive noise over pilots is highly colored

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This paper deals with the problem of reactive power and harmonics in a standard medium-voltage (MV) distribution network. It proposes a simple and inexpensive solution to enhance power quality when a particular connection to the high-voltage transmission network is required. It presents the design of a hybrid active filter topology connected to the MV level of a power distribution system. Its main task is to regulate a 132-kV voltage level. Reconfiguration of the power delivery network imposes new constraints in a distribution substation so that the reactive compensation should be increased. The topology of a shunt hybrid active filter is analyzed. It is built with the series connection of a passive filter and a low-rated active filter. The proposed filter is directly connected to a 13.8-kV level with no need of a step-down transformer. The possibility of different levels of reactive power compensation is implemented. The proposal shows very good performance for different load demands., Instituto de Investigaciones Tecnológicas para Redes y Equipos Eléctricos (IITREE)

The problem of reactive power and harmonics in the medium voltage level of a power distribution system is considered in this paper. Reconfiguration of the power delivery network imposes new constraints in a distribution substation so that the reactive compensation should be increased. The alternative of a shunt hybrid active filter connected to the 13.8-kV level to enhance the power quality is analyzed in this paper. This proposal uses the existing capacitor bank to build a hybrid filter in which the complementary compensation is performed by the active filter. The performance of the hybrid filter is evaluated with extensive simulations considering reactive power, harmonics, and unbalance compensation. It shows very good behavior in steady-state and transient conditions., Instituto de Investigaciones Tecnológicas para Redes y Equipos Eléctricos (IITREE)

[Abstract] The letter shows that, by the proper use of time modulation in equispaced linear arrays with uniform excitation distribution, it is possible to maintain the sidelobe zone of the radiated power below a certain - previously stipulated - level, whereas the undesired harmonics are minimized. In addition to that, the further extension of the technique to non-equispaced arrays permits a broadband response to be obtained, by simply searching the positions of the elements that reach the desired power pattern behavior within the required bandwidth.

Superconducting power links (SUPERPOLI) will offer a low-loss power transmission and fault current limitation in a single device. In the European SUPERPOLI project, a long term goal is to build a 200 m long, 20 kVrms, 28 kArms, 3-phase superconducting power link which will be refrigerated by sub-cooled liquid nitrogen. The SUPERPOLI will have a compact co-axial multitube structure which significantly reduces the ac losses. As a step towards this GVA-class application, a 2 m long, 20 kV, 2 kA/5 kA, one-phase functional model is under construction. The conductor variants considered are Bi-2212 bulk conductor and Y-123 coated film conductor. They present very different behaviors in normal operation and during the limiting phase: Bi-2212 bulk conductor has higher ac losses and allows short transients or moderate over-currents without quenching, while Y-123 film has low ac losses and immediate response for overcritical currents.

The presence of uncertain parameters in electrical power systems presents an ongoing problem for system operators and other stakeholders when it comes to making decisions.Determining the most appropriate dispatch schedule or system configuration relies heavily on forecasts for a number of parameters such as demand, generator availability and more recently weather. These uncertain parameters present an even more compelling problem at the distribution level, as these networks are inherently unbalanced, and need to be represented as such for certain tasks. The work in this paper presents an information gap decision theory based three-phase optimal power flow. Assuming that the demand is uncertain, the aim is to provide optimal and robust tap setting and switch decisions over a 24-hour period,while ensuring that the network is operated safely, and that losses are kept within an acceptable range. The formulation is tested on a section of realistic low voltage distribution network with switches and tap changers present. European Commission - European Regional Development Fund Science Foundation Ireland Programme for Research in Third-Level Institutions (PRTLI) Cycle 5

[EN] This paper describes constitution, design and operation of a passive unbalance compensator for variable loads in three-phase industrial installations. Compensator is integrated by three-phase connections of variable coils and capacitors. Values of those elements, and thus unbalance power delivered by the compensator, can be changed by switches commanded by an electronic control circuit. An important compensator design parameter introduced in this paper is the power of the unbalance step since it defines composition and values of the elements of the unbalance step, which is the basic three-phase connection of inductances and capacitances in the compensator. Because unbalances in power systems are caused by active and reactive loads, two unbalance steps have been defined: active and reactive, however, power of the unbalance compensator does not depend on the total active and reactive powers, but the differences between their values in each phase of the load., Este trabajo ha sido apoyado por el Centro de Transferencia de Tecnología de la UPV y por Eléctrica de Vinalesa, S. Coop. V., a través del proyecto INNOVA 2008, nº 1830.