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Although 75% of the vehicle miles traveled in the US by 2040 could be electric, few studies have quantified their impact on the distribution network even at low GEV penetration levels. This paper presents a Monte Carlo simulation of transformer life degradation using a fundamental and harmonic transformer thermal model, historical distribution transformer load profiles, hourly temperature data, and surveyed vehicle data to determine transformer loss of life. A simple control strategy, based on transformer current, is proposed to mitigate lifetime degradation. Simulation results are presented for a fleet of distribution transformers in Phoenix, AZ and Seattle, WA under controlled and uncontrolled charging scenarios

The likelihood of widespread GEV adoption will be determined by pending vehicle, business model and policy design choices. Most designs to date have not made large-scale adoption a central design goal. We review the impacts of maximum charging rate, vehicle-to-grid (V2G) and vehicle-to-building (V2B) capabilities, and the charging business model on consumer acceptance and on the electric distribution, electric power, and overall energy systems. The analysis suggests that poor design choices can lead to significant increased cost and decreased consumer adoption. Competing technologies, such as high efficiency internal combustion engines (ICEs) and biofuels, increase the importance of GEV design choices.

While direct AC/AC converters like matrix converters have been around for a while, their applications are generally limited to low voltages due to complexity and issues in scaling to high voltages, including inadequate fault tolerance, complex switching patterns where errors can lead to device failures, and complex gate drive requirements for voltage sharing among the devices. For these reasons, voltage source inverters (VSI)-based topologies remain the de facto standard in medium to high voltage power conversion applications. This paper will propose an actively-controlled AC snubber concept that addresses the scalability issues with direct AC and AC/AC converters. The paper will use the previously proposed single-phase direct AC topology known as the dynamic capacitor (D-CAP) to demonstrate the operation of the AC snubber. However, the proposed snubber concept is equally valid for any topologies employing series-connected devices to scale up to higher voltages.

Increasing use of non linear loads in residential distribution systems can cause significant growth in neutral to earth voltages and false ground relay trips. Since it is impractical to enforce the residential and other small commercial customers to limit harmonics, utilities need an effective low cost harmonic filtering solution to limit 3rd harmonic propagation. This paper presents a Directional Triplen Hybrid Active Filter (DTHAF) for 3-ph 4-wire multi grounded radial distribution systems. The directionality feature enables isolating downstream triplen harmonic current from the system and blocking upstream triplen harmonic currents even with source voltage distortion. This feature restricts filter size to that of the harmonic load downstream. Hybrid active filter approach enables using a fractionally rated active filter and thereby reducing the cost of the filter. Existing power factor correction capacitors (PFC) on the system can be utilized for retrofit applications.

The cost of photovoltaic (PV) electricity is competitive with some high cost forms of natural gas electricity in some areas. However, the variability of PV energy increases the cost to utilize it. This increased cost is partially shouldered by imbalance penalties assigned to the plant owner. Energy storage and forecasting services are two techniques that have been proposed to reduce the penalties. This paper quantifies the level of energy storage and forecasting necessary to reduce, or firm, the intra-hour variability of a PV plant. It also assesses the economics of using a battery energy storage system (BESS) to firm output, finding that more than a 90% cost reduction is required to justify deployment of a BESS. Finally, the viability of a BESS providing multiple services to the power system is assessed

Dynamic control over real and reactive power flow is one of the key areas of concern for the modern grid. Traditional FACTS based devices have proven to be too costly and complex to achieve any significant market penetration. Modifying existing transmission assets to make them controllable may be a cost-effective method of increasing the grid controllability. Controllable Network Transformers (CNTs) have been shown theoretically to be an effective real and reactive power flow controller. The various options for filter design of a CNT are presented in this paper. The paper also discusses the design and testing of a medium voltage CNT prototype with an integrated hybrid active filter, rated at 200 kVA and 2.4 kV.

A scheme for controlling parallel-connected inverters in a standalone AC supply system is presented. This scheme is suitable for control of inverters in distributed source environments such as in isolated AC systems, large and distributed uninterruptible power supply (UPS) systems, photovoltaic systems connected to AC grids, and low-voltage DC power transmission meshes. A key feature of the control scheme is that it uses feedback of only those variables that can be measured locally at the inverter and does not need communication of control signals between the inverters. This is essential for the operation of large AC systems, where distances between inverters make communication impractical. It is also important in high-reliability UPS systems where system operation can be maintained in the face of a communication breakdown. Real and reactive power sharing between inverters can be achieved by controlling two independent quantities: the power angle and the fundamental inverter voltage magnitude. Simulation results are presented. >

Smart Wires is a family of three Distributed FACTS (D-FACTS) technologies able to realize low-cost transmission line monitoring and power flow control in meshed networks. Smart Wires will allow utilities to increase power transfers in meshed networks by increasing average line utilization. The technology is projected to have significantly lower cost and lead time than alternatives, namely new line construction, reconductoring, or conventional FACTS technology. This paper overviews the work done to date to demonstrate the feasibility and impact of the technology, including prototype development and system simulations.

The higher reliability of meshed grids, whether in power or communication, when compared with radial grids is well established. However, while meshed grids provide higher reliability, protection of meshed grids is challenging. In smaller systems such as microgrids, line impedances can be small and many branches may experience approximately the same level of fault current. Locating faults quickly before damage to the equipment and system occurs becomes a non-trivial task and cannot be achieved without communication. This paper discusses a comprehensive scheme for protecting meshed microgrids with multiple levels of protection for redundancy. Power line carrier (PLC) technology is proposed as cost effective and robust means of communication, obviating the need for additional cabling.

Utilities require improved monitoring of their assets to ensure reliable power for their customers. Sensors presently available in the market cater to measuring multiple asset parameters and thus are expensive. This inhibits the utilities' ability to deploy such sensors on a large scale. This paper addresses design and implementation of a low cost self-powered “Stick-on” wireless current and temperature sensor that can be mass deployed by utilities. Novel energy harvesting circuit design techniques have been discussed and shown to operate over a wide current range. Technical challenges pertaining to energy storage, communication network, temperature and current sensing have been analyzed given the constraints of low cost. A first prototype has been developed and shown to operate successfully. The envisioned Stick-on sensor has the capability to monitor a variety of utility assets. Technology solutions like these hold prime importance as the power grid moves towards a Smart Grid.

Control areas are often interconnected to each other by tie-lines over which the operators have little or no real-time control. Congestion of any one of the lines in the transmission corridor limits its Available Transfer Capacity (ATC), even if there is available spare capacity in some parallel paths. Increasing inter-area ATC is key to increasing penetration of renewable generation, since the geographical location of renewable generation sites are often far from the load centers. Traditional methods of increasing inter-area ATC like transmission upgrade or FACTS installations are expensive and also require significant lead-time. Controllable Network Transformers (CNTs) are low-cost power flow controllers which can be realized by augmenting existing Load Tap Changing (LTC) transformers. The paper shows from a system level perspective, the application of CNTs to increase inter-area tie-line ATC, thereby allowing increased inter-area green energy transfer.

Technologies such as dynamic line rating and FACTs have emerged to increase the utilization and the reliability of the existing T&D network without requiring new line construction. The development of the Distributed Series Reactance (DSR) technology, a distributed FACTs (D-FACTs) solution also known as Smart Wires, has been funded by the utility community, given the promise of DSR for reliable and inexpensive power flow control. The DSR is capable of increasing the line reactance, pushing power onto other lines, but it is unable to decrease line reactance and draw power flow onto the line. Utilities have noted the value of a technology capable of injecting inductance or capacitance into the line. A previous approach to push or pull power used an inverter based variable injection technique, but was expensive and was unable to meet utility expectations for MTBF and maintenance requirements. Active Smart Wires (ASW) is a new concept for a low-cost, high reliability method to increase or decrease power flow in a transmission line. Simulation results are provided.

The concept of Dynamic Capacitor or D-CAP has been previously introduced by the authors. D-CAP is able to provide dynamic VAR and harmonic compensation in one single integrated unit. The topology is based on an AC chopper with the control based on the novel concept of virtual quadrature sources, where energy is exchanged between virtual sources at different frequency, instead of between DC and AC sources such as in voltage source inverters (VSIs). This paper addresses issues pertaining to scaling of the D-CAP to Medium Voltage levels that include safe commutation of the switches, equal voltage sharing, good spectral content, and fault tolerance in direct AC converters such as the D-CAP. Different topologies for scaling to higher voltages with their respective advantages and disadvantages are presented.

In switch-mode power electronic converters, DC offset of the magnetizing flux in the isolation transformer can cause saturation. In typical single-ended dc/dc converters, this is handled using a current loop which ensures that the average current in the winding is zero. For bi-directional dc/dc converters with active bridges on both sides, there exists a danger of impressing dc offsets from both sides, creating significant issues in terms of preventing transformer saturation. This paper demonstrates the issue for the Dual Active Bridge Buck Boost converter (DAB3). The paper also presents a control strategy for avoiding such saturation, eliminating DC currents on both sides, while realizing full converter control. The paper presents simulation results to prove the proposed control technique.

Meeting RPS mandates and accommodating EVs poses a difficult problem for utilities. This paper proposes coupling EV charging with the availability of renewable energy at the point of use to realize dramatic system level benefits. A realistic set of scenarios are simulated, using real-time grid data from NYISO and wind farm data from NREL, to prove that with a small percentage of wind energy penetration and flexible EV charging, GHG emissions of the light-duty transportation sector can be dramatically reduced. This is achieved without any additional generation requirements from the existing power grid, while providing the additional benefit of reducing the spinning reserve requirements needed to cope with the intermittency problem of the new wind resource. The concept of a parallel market structure as a means to practically implement the concepts in this paper is also introduced.

To assist utilities in utilizing the overhead power lines more effectively and thus to optimize the utilization of the existing system, it is important to know how to accurately assess the real-time dynamic overload current capacity of lines down to a ‘per span’ level of granularity. Accurate prediction of the conductor temperature ahead of time subject to various conductor overload conditions is the most critical and challenging step when determining the line dynamic thermal rating. An Echo State Network (ESN) based identifier has been demonstrated to identify the overhead conductor thermal dynamics under different weather conditions in a batch learning mode with good accuracy [1]. Through the use of the ESN model, the prediction of conductor temperature can be obtained easily, which in turn helps determine the line dynamic rating in real time. This paper proposes a Sliding-Window (SW) based online learning algorithm to obtain the online adaptation of the ESN-based thermal dynamics identifier to any new/changed ambient weather conditions along the overhead conductor on a continuous base. Both simulation and experimental results are presented to validate the performance of the proposed algorithm. This method requires only temperatures and line current as inputs and its simplified calculation makes it an attractive and cost effective solution to real-time implementation.

This paper presents two alternative electric market structures that increase market efficiency and reduce the cost of implementing RPS mandates. A review of existing market operation and the structure of RPS mandates provides necessary context. One alternative market structure combines a parallel market for stochastic renewable energy with incremental power flow control based on emerging power electronic solutions. This alternative market maintains the existing market and may be politically preferential to the second alternative, which requires emissions limits and a change in consumer behavior. System operation is simulated using historical load and wind resource data to demonstrate the impact of the parallel market.1

‘Thin’ power electronics concentrates on the design of minimal and cost effective power converters. Part of the research effort targets the direct processing of an AC input to an AC output without the use of an intermediate DC stage. Particular examples include the inverterless active filter and the controllable network transformer, both of which in their simplest form employ a buck switcher as the active element. Existing analysis of these circuits has dealt with a continuous approximation to the modulating function with applications to relatively high switching frequencies. This paper addresses the problem of selecting a low frequency switching pattern that achieves the correct transformation of an AC input composed of a set of arbitrary harmonics into an AC output containing a desired set of harmonics. This is achieved by constructing a model of the converter in the frequency domain so as to allow a systematic description of the interaction between linear filters and the buck converter via a set of non-linear equations that closely approximate the behaviour of the physical circuit. These equations are set in the form of a constrained optimization problem, the solution of which represents an optimal switching pattern that satisfies a set of harmonic constraints. The method is presented in a general way, facilitating direct application to other systems composed of linear filters and a buck converter. The inverterless active filter is considered as an example problem and the method is used to construct optimal switching patterns that provide harmonic correction of the current drawn by a three phase passive rectifier.

Developing sensing technologies to measure and characterize local Electromagnetic field (EM) signatures around overhead line conductors has become an appealing solution to successfully implement a low-cost, distributed and massively deployed power line sensor network (PLSN) for power grid monitoring. Such sensing technologies potentially assess the local healthiness of power lines and to predict incipient faults of lines, such as proximity of tree limbs, or violation of conductor-to-ground clearance. This kind of information is normally not available to conventional fault detection devices. This paper proposes a novel Multiple-Displacement-Current-Sensor (mDCS) to capture the spatial mapping of the electric field (E-field) distribution around overhead line conductors. In stead of considering total induced equivalent electric charge, the distribution of the electric charge density induced on the mDCS surface is analyzed. A DQ-axis decomposition technique is applied to separate the capacitive coupling effects to the mDCS from adjacent conductors in different directions. The decomposed DQ-axis components have potential to enable independent measurement of conductor-to-ground clearance and overhead conductor voltage. Simulation results are presented to validate the proposed idea.

Fossil fuel generators like diesel and natural gas gen-sets are the mainstays of microgrids for reliable power generation. This paper investigates different methods or modes to maximize fuel efficiency of the online generators in a microgrid where a substantial portion of the total generation capacity comes from fossil fuel generators. Energy storage is used to facilitate high efficiency operation of the generators and ensure conformation with the power quality standards and reliability metrics. The methods to maximize fuel efficiency, involving generator scheduling, peak shaving, and power cycling, are discussed. Various case studies are simulated to determine the impact of these three methods or modes on fuel consumption for two particular types of load profiles.

Increasing load growth, decreasing investments and increasing penetration of dynamic sources and loads have severely increased the stress on the electric grid. This growing stress has forced operators and regulators to think of delivering energy in a smart, controllable and reliable way to the customers. Tie-lines connecting two systems are one of the traditional methods used by utilities to improve the system reliability. However, often specially during contingencies, tie-lines get overloaded due to the lack of power flow controllability through them. Controllable Network Transformers (CNTs) are smart assets which can be realized by augmenting existing Load Tap Changing (LTC) transformers in order to achieve power flow control. This paper proposes the use of CNTs in tie-lines to make them smart and controllable, without compromising the system reliability.

Increasing societal concern for global warming and energy security have led many of the US states to adopt policies like Renewable Portfolio Standards (RPS). Introduction of these environmental policies in the energy market are expected to have significant impact on grid operation as well transmission investment. The energy delivery system has to be upgraded significantly in order to make it capable of handling these changes. It has been claimed that upgrading the present transmission system to a Smart Grid would facilitate the integration of renewable resources. Controllable Energy Flows (CEF) is one method to realize power flow control on the Smart Grid. The CEF method controls transactions of incremental power using distributed assets like Distributed Series Impedances of Controllable Network Transformers. The paper studies the benefit of Smart Grid technologies like Controlled Energy Flows in reducing transmission investment that is required to implement policies like the RPS.

Increasing societal concern for global warming and energy security have led many of the US states to adopt policies like Renewable Portfolio Standards (RPS). Introduction of these environmental policies in the energy market are expected to have significant impact on grid operation as well transmission investment. The energy delivery system has to be upgraded significantly in order to make it capable of handling these changes. It has been claimed that upgrading the present transmission system to a Smart Grid would facilitate the integration of renewable resources. Smart Wires are distributed, low cost, autonomous smart assets that are capable of controlling power flow in a meshed transmission network. This paper studies the benefit of Smart Grid technologies like Smart Wires in reducing transmission investment that is required to implement policies like the RPS.

A widely and massively distributed power line sensor network (PLSN) has been proposed to monitor the status of utility assets to enhance line reliability and maximize the existing power grid utilization. One of its important applications is monitoring and evaluating the short-term overload capacity of an overhead power line (OHPL) down to a 'per span' level of granularity in real-time, and to determine the Real-time Dynamic Thermal Rating (RDTR) of the line under variant ambient weather conditions. Formulation of the RDTR requires repeated calculation to predict the conductor temperature ahead of time under various ambient conditions, often complex and difficult for real-time implementation. This paper, on the other hand, proposes a MLPN based parameter estimation scheme, by which the dynamic thermal rating is evaluated directly under different weather conditions with no conductor temperature prediction required. This method requires only temperatures and line current as inputs and its simplified calculation makes it an attractive and cost effective solution to real-time implementation. Furthermore, by continuously providing accurate real-time line thermal condition information, this method can assist in utilizing the power lines more effectively.

In a perfectly competitive electricity market, it is important to ascertain the contribution of each of the generators towards a given load and towards individual line loadings. This will help in charging the customers for the services and the products they use. The technique can also provide information, such as the path of green electrons which can be vital for proper implementation of imminent carbon taxes. Many researchers have proposed various techniques for solving this problem — the most notable being the topological approach [1]. However, none of the researches address the problem when the network has a loop flow. The paper extends the concept of topological approach in order to solve this problem even in networks with loop flows.

The growth in the demand for electric power is increasing stress on the existing grid infrastructure. Power utilities today require methods to provide dynamic grid control due to the increased penetration of renewable energy resources and increase in consumption of electricity. FACTs devices provide one possible solution. High cost and low reliability of these devices has impeded widespread use. A novel solution has been proposed in [2] where existing grid assets are augmented with thin ac converters to provide increased control capabilities. The low cost solution is realized by using a direct ac converter in tandem with existing grid assets. The converter uses a simple ac chopper as a building block with no bulk energy storage. Scaling has been shown possible in [2] by cascading the basic building block. Realistic and robust scaling of these converters lies in the ability to effectively control the voltages in every block to the desired level. This paper discusses the multilevel direct ac converter and provides methods to control the converter to ensure safe and reliable operation while maintaining low cost and high reliability.

A new method of power flow control in a meshed network has been presented earlier, to enable power dispatch along a defined path without impacting flows on branches adjacent to the path. This paper explores the type of power converter topology that could optimally provide the desired control function. This includes well known FACTS devices such as Back-to-Back Converters (BTB) and Unified Power Flow Controllers (UPFC), as well as newer devices such as Controllable Network Transformers (CNT), and Distributed Series Impedance (DSI) devices. Equipment ratings are calculated for the BTB, UPFC, CNT and CNT-DSI hybrid solutions. Scalability to grid voltages and power levels is also discussed. Power flow capability, implementing the proposed solution with ideal voltage sources, is shown via simulation for the IEEE 39 bus system. Finally, functionality is simulated in a meshed, four-bus system using switching devices. Proposed functionality would allow more efficient market operation, incentivize transmission investment and ensure physical delivery of contracted energy, thus enabling real-time markets for lowcarbon (green) sources.

A widely distributed power line sensor network (PLSN) has been proposed to monitor such a utility asset's status. One of its important applications is to evaluate the real time dynamic current capacity of overhead power lines down to ‘per span’ level of granularity, and thus to maximize the existing power grid utilization. How to predict the conductor temperature ahead of time subject to various conductor overload conditions is the most critical and challenging task to evaluate the line dynamic thermal rating. This paper proposes an Echo State Network (ESN) to adaptively identify the nonlinear overhead conductor thermal dynamics under different weather conditions, and to predict the conductor temperature. This method requires only temperatures and line current as inputs and its simplified calculation makes it an attractive and cost effective solution to real-time implementation. Furthermore, by continuously providing accurate real-time line thermal conditions, this method can assist in utilizing the power lines more effectively.

The concept of Distributed Flexible AC Transmission Systems (D-FACTS) was introduced in order to provide a cost-effective solution for power flow control. Determining the location and amount of distributed compensation to be employed is an important problem. Proper deployment of DFACTS is necessary for optimal control of the power flow in a large meshed network. Being a distributed solution, DFACTS provides flexibility in terms of deployment. This often makes the problem even more computationally intensive. Recent studies show that Particle Swarm Optimization (PSO) technique gives better results than classical optimization techniques, when applied to power engineering optimization problems. This paper shows the application of PSO for the optimal deployment of DFACTS. The technique is applied on the IEEE 39 bus system. Details of the method and the results obtained are presented in the paper.

The drive for higher reliability has motivated many utilities to move towards a more meshed system. Two control areas are often connected together with tie-lines. Power flow through the tie-lines connecting two control areas is difficult to control. This lack of controllability of power flow is one of the major issues in the modern grid. It causes asymmetric stress on the grid assets. This makes some grid assets more vulnerable to failure than others and therefore decreases the overall system reliability. Presently utilities can achieve very limited power flow control using devices like Load Tap Changing (LTC) transformers and Phase Shifting Transformers (PST). Controllable Network Transformers (CNT) were introduced as a simple, low cost solution to the power flow problem. This paper develops a theoretical analysis for the operation of CNT in a meshed network. It also shows the various possible applications of the CNT. Experimental validation of the working principle of a small scale prototype CNT is also provided.

This paper explores the existing energy harvesting technologies, their stage of maturity and their feasibility for powering sensor nodes. It contains a study of the energy requirements of the sensor nodes that are a part of the commercial domain. Further, it investigates methods and concepts for harvesting the energy from electric and magnetic fields present near utility assets through laboratory experimentation. The flux concentrator based approach that scavenges the magnetic field was considered to be the most promising solution providing nearly 250mW of power sufficient to power a sensor node.

Industrial plants are faced with stringent requirements by the utility to maintain a near unity power factor. These plants have traditionally utilized switched capacitor banks as a cost-effective means for power factor correction (PFC). However, if there is a significant level of harmonics present in the current that is disturbing the neighboring loads, then a separate unit for harmonic filtering is required as well. By the time a realistic system is configured, significant cost and complexity are encountered. The concept of a dynamic capacitor (D-CAP) was previously introduced as a means by which to achieve dynamic VAR injection as well as active harmonic filtering in one single integrated unit. The topology consists of taking an existing asset like a PFC capacitor, adding a pair of ac switches and small LC components per phase, and thereby realizing an asset with augmented functionalities. Although the power stage is simple, the underlying control is very challenging. This paper discusses the intricacies of controlling such an architecture and provides keen insights into how one would go about designing a controller.

A widely and massively distributed power line sensor network (PLSN) has been proposed to monitor such a utility asset's status for enhancing line reliability and maximizing the existing power grid utilization. One of its important applications is to monitor and evaluate the real time dynamic overload current capacity of overhead power lines down to ‘per span’ level of granularity. How to predict the conductor temperature ahead of time subject to various conductor overload conditions is the most critical and challenging task to evaluate the line dynamic thermal rating. This paper proposes an Echo State Network (ESN) to adaptively identify the nonlinear overhead conductor thermal dynamics under different weather conditions, and to predict the conductor temperature. This method requires only temperatures and line current as inputs and its simplified calculation makes it an attractive and cost effective solution to real-time implementation. Furthermore, by continuously providing accurate real-time line thermal condition information, this method can assist in utilizing the power lines more effectively.

The drive for higher reliability has motivated many utilities to move to a more meshed system. Increasing interconnection increases the reliability but on the down side also increases the fault current levels. High fault current levels increase the stresses on the existing circuit breakers, which are expensive to replace. Fault current limiters are used to reduce the fault currents below the ratings of the circuit breakers in order to prevent any permanent damage or malfunction of the circuit breakers. The paper proposes a dual device which not only can limit the fault current, but also can control the power flow through the transmission line in steady state.

The task of monitoring asset status and optimizing asset utilization for the power grid, given millions of assets and hundreds of thousands of miles of power lines distributed over millions of square miles, seems costly, if not impossible. Given the traditionally high cost of sensing and communications, the current grid has minimal ‘smarts’ with much of the intelligence located at major substations. Dramatic reductions in sensor, computing and communications costs, coupled with significant performance enhancements has increased the possibility of realizing widely and massively power line sensor networks (PLSNs) to monitor utility asset status. A NSF funded a project, “Power Line Sensornet for Enhancing Line Reliability and Utilization”, has led to the development of an integrated multi-task power line sensor (PLS) module. This paper mainly addresses the design and implementation issues for such a sensor module.

Distributed static series compensators (DSSC) are used to modulate series impedance of critical transmission lines in order to improve voltage stability margin. Voltage margin sensitivity is derived with respect to the applied control using DSSC. An example where applying load shedding results in reduction in margin is presented. In this case a DSSC is able to increase the margin substantially.

Three DC/DC converter topologies suitable for high-power-density high-power applications are presented. All three circuits operate in a soft-switched manner, making possible a reduction in device switching losses and an increase in switching frequency. The three-phase dual-bridge converter proposed is shown to have the most favorable characteristics. This converter consists of two three-phase inverter stages operating in a high-frequency six-step mode. In contrast to existing single-phase AC-link DC/DC converters, lower turn-off peak currents in the power devices and lower RMS current ratings for both the input and output filter capacitors are obtained. This is in addition to smaller filter element values due to the higher-frequency content of the input and output waveforms. Furthermore, the use of a three-phase symmetrical transformer instead of single-phase transformers and a better utilization of the available apparent power of the transformer (as a consequence of the controlled output inverter) significantly increase the power density attainable. >

Industrial plants are faced with stringent requirements enforced by the utility to meet power factor and power quality requirements. These plants, in order to avoid very costly penalties, have traditionally utilized switchable shunt capacitor banks with detuning reactors for power factor correction, along with a separate active harmonic filter in cases where harmonic currents are an issue as well. Alternate solutions such as SVCs and STATCOMs have been considered to be too expensive for use in industrial power conditioning applications. This paper proposes a dynamic capacitor (D-CAP) based on the family of inverter-less active filters (ILAF) that is able to provide a dynamically controllable capacitance with active harmonic compensation integrated onto the same unit. This new device is seen to be compact, and is likely to be cost competitive against simple switched shunt capacitors. It can maintain power factor close to unity, offering dynamic capabilities better than switched capacitors or SVCs, possibly lending itself for arc-furnace type of loads.

Dynamic VAR support is essential for grid support, particularly to help ride-through significant faults on the system. Conventional sources of VARs, such as capacitor banks and generators, respond too slowly to have the desired impact. Static VAR compensators (SVC) are faster, responding in 1/2 to 1 cycle, but offer reduced VAR support under fault conditions. STATCOMs are even faster, allowing for dynamic control, but are seen to be expensive as they require large dc/ac inverters and significant levels of energy storage. This paper proposes a new approach to realizing STATCOM functionality without inverters, effectively using standard shunt VAR compensating capacitors to realize the needed dynamic VAR support. The technique is seen to be scalable to high voltage and high VA levels, and promises to realize lower cost through the use of existing shunt VAR resources with thin AC converter concepts (see companion paper).

The electric power grid is under stress, caused by increasing loads, decreasing investments, and increasing penetration of dynamic sources and loads. Grid control techniques have not changed much over the last 50 years, with generator excitation providing the only 'analog' control handle. The basic control problem on the grid is to maintain node voltages while ensuring that branch currents do not exceed defined limits. This paper proposes the possibility of converting existing load tap changing (LTC) transformers into Controllable Network Transformers (CNT) using fractionally rated direct ac converters - providing vernier control of amplitude and phase angle. This would allow dynamic control to be distributed on the grid, enhancing response and reliability. The concept can be scaled to realistic power levels.

Existing techniques for realizing dynamic grid control have involved the use of FACTS devices such as STATCOMs, where the desired functionality is obtained in a single dasiablack-boxpsila device. These devices are deployed in addition to resources that already exist on the grid. This paper proposes a new approach for using dasiathin AC converterspsila to convert existing dasiadumbpsila grid assets into dasiasmart and controllablepsila assets, resulting in significant cost reduction and enhanced asset availability. The technique is seen to be scalable to high power levels, and can convert shunt VAR capacitors into STATCOMs, and can convert load tap changing transformers into dynamic network control devices. New dasiathin AC converterpsila topologies for realizing high-voltage and high-power are detailed along with analysis, control and operating results.

Power electronic DC to DC converters in plug-in hybrid and electric automotive applications demand high power bidirectional power flow capability, with wide input voltage range. Output voltage of energy storage devices like ultra capacitor or battery varies with the change in load. The converter needs to provide a successful voltage regulation on the load side for a wide range of input voltage. An isolated half bridge based converter is proposed in this project, with bidirectional power flow and minimum peak current for wide input voltage range through duty cycle, and phase shift control. The proposed converter has competitive total device rating with the conventional isolated bidirectional power converters. The converter uses the transformer leakage inductance as the primary energy transfer element. Proof of concept is realized through a small prototype.

One of the most critical application parameters of an aluminum electrolytic capacitor is its voltage capability, typically expressed in terms of rated or working voltage, surge voltage, transient voltage, etc. Exceeding the voltage capability (even for a few milliseconds) can result in the immediate failure of the capacitor, or its performance can be degraded over the longer term due to high in-rush current. Electrolytic capacitor failure modeling due to in-rush current is presented followed by experimental results.

Developed countries have become accustomed to having access to an electric grid and it is taken for granted that electrical power is available at any time. However, this is not the case in many remote villages in developing countries where insufficient infrastructure has left many people short of a basic energy supply. To address this need, a portable hand crank generating system is proposed in this paper to supplement alternative energy sources such as photovoltaic cells and wind power systems. An axial flux permanent magnet generator has been designed to provide a 50 W output and occupy a small space with a limited mass. A mechanical transmission scheme is also developed to drive the generator with two belt drive stages and a hand crank. Finally, a conceptual prototype system is presented to illustrate its applicability.

The task of monitoring asset status and optimizing asset utilization for the T&D industry, given millions of assets and hundreds of thousands of miles of power lines distributed geographically over millions of square miles, seems particularly challenging if not impossible. Given the traditionally high cost of sensing and communications, the grid has minimal 'smarts' with much of the intelligence located at major substations. Dramatic reductions in sensor, computing and communications costs, coupled with significant performance enhancements has raised the possibility of realizing widely and massively distributed sensor networks (SNs) to monitor utility asset status. Under NEETRAC funding, a survey was conducted to review existing sensor technologies and products, and to estimate the possibility of extending these to realize distributed SNs. Possible applications for such SNs were also explored, as was the issue of cost point at which such networks would become commercially viable. This paper provides an overview of the highlights from the detailed survey that was conducted, and identifies 'gaps' in currently available sensor technologies, both from a performance and cost point.

The objective of this paper is to propose a new low cost method to detect the changes in equivalent series resistor (ESR) and the capacitance value of an electrolytic capacitor in order to realize the real-time condition monitoring of an electrolytic capacitor. Experimental and simulation results are discussed to illustrate the proposed condition monitoring technique. In addition, it is shown that the proposed method can be used for a non-stationary system where waveforms are continuously varying in amplitude, frequency, and phase. The proposed on-line failure prediction method has the merits of low cost and circuit simplicity.

Voltage sags represent perhaps the major cause of productivity loss for a wide range of industrial automation equipment and continuous processes. Various solutions are available to provide ride-through and to mitigate the impact of such power disturbances, including products such as UPS, DVR and DySC. Because it is prohibitively expensive to protect against all possible power disturbances, all sag correctors rely on a statistical approach to specifying which events will be protected against, and are based at least in part, on the principle of using stored energy to allow converter operation when a voltage-sag occurs. Based on an exhaustive analysis of significant voltage sags recorded mainly at larger industrial plants, it is seen that a new approach to sag correction can be identified that is more compact, has fewer catastrophic failure modes and potentially lower cost. The concept of a 'zero energy sag corrector' or ZESC is introduced, with analysis to compare the level of protection provided against other more established sag correctors. It is seen that the ZESC system protects susceptible equipment against over 96% of all power disturbances.

Shunt active filters compensate for variable levels of harmonic currents generated by loads, essentially by producing currents in anti-phase with the offending harmonics. DC/AC inverters, with dc energy storage in electrolytic capacitors and high frequency PWM with IGBT switches, represent the most widely used technique for implementing active filters. A companion paper has introduced the concept of using simple AC choppers invoking dual virtual quadrature sources to realize amplitude, phase angle and/or harmonic control on the available ac voltage. This paper discusses a novel implementation of Inverter-Less Active Filters (ILAF), using gate controlled semiconductor switches with inductors, capacitors or existing resistive loads in a plant to realize dynamic VAR and/or harmonic compensation. Eliminating energy storage elements result in lower cost, increased robustness and longer life. The approach is seen to be applicable for single and three phase systems. ILAF are seen to provide lower cost and increased robustness and reliability when compared with conventional active filters.

Dynamic control of amplitude and phase of AC line voltage will allow node voltage and branch current in meshed systems. This has traditionally required the use of inverters with energy storage, and/or AC/AC converters with multiple phases. This paper presents a novel concept wherein dual virtual quadrature sources are used to synthesize both a direct and quadrature component of the line voltage so as to realize arbitrary amplitude and phase angle control. This approach results in simple low-cost AC converters that are robust, have minimal component count, and can realize phase shift and/or harmonic control without requiring multiple sources or energy storage elements. The approach is seen to have simple implementation and can realize potentially useful devices such as phase and amplitude controllable transformers and inverter-less active filters.

Electrolytic capacitors are responsible for frequent breakdowns of static converters. To set a predictive maintenance, adaptive filter modeling based method is presented using LMS algorithm. Signature of changes in capacitance and ESR will reflect in capacitor ripple voltage because of aging; and these changes are monitored using this adaptive filter modeling to predict the future status of the capacitor using only the input current of the system