Degradation of high-power IGBT modules adversely influences the safety of inverters and can cause significant economic loss in industrial applications. Due to various factors affecting the degradation of IGBTs, lots of advanced monitoring methods still struggle to comprehensively evaluate the current health status of IGBT modules during power converter operation. Therefore, this paper proposed an improved online degradation method for high-power IGBT modules based on the estimation of on-state resistance. This method has reduced component numbers and circuit complexity with higher monitoring accuracy and wider applications. The proposed condition monitoring methodology is verified experimentally on a three-phase inverter setup and the test results are presented.

Though e-motorbikes comprise a considerable proportion of electric vehicles (EVs), it's drive-train design is rarely presented in the literature. This paper focuses on reviewing the important design considerations for drive-train inverters of next-generation e-motorbikes. A compilation of state-of-the-art e-motorbikes' specifications reveals that the inverter requirements are diverse in terms of power with a thrust towards enhanced efficiency and power density. A review of the power-electronic design of this inverter is presented to elicit the topology choices, battery-pack design based on DC-link voltage choice, as well as the benefits of using new wide-bandgap devices and latest ceramic capacitors. An overview of the inverter's cooling system design shows the merits of liquid-cooling for compact inverter design.

With the switched-capacitor based topologies, voltage rating of capacitors has been a critical issue for high voltage applications. In this paper, a new five-level unity gain inverter (5L-UGI) topology has been proposed which uses low voltage rating devices. With the voltage rating of all capacitors used in the proposed 5L-UGI topology being half of the peak of output voltage, the cost of the topology is relatively less. Further, a fault-tolerant topology derived from the developed 5L-UGI has been discussed which is capable of handling single-switch open circuit faults and can restore the pre-fault conditions. A comparative study has been provided to show the improvement in the proposed topology. Finally, the proposed 5L-UGI topology has been verified with simulation results for different operating conditions.

On commercial ports, during loading/unloading on cruise, carrier, container, or tanker, its diesel engine creates pollution. Therefore, in ports, shore-to-ship power (Cold Ironing) supply is an alternative way to overcome the pollution issue at shipyards. However, different ships of different countries and different companies require different types of power with different electrical connections, such as ac power with 50 Hz and 3-phase 3-wire connection, ac power with 60 Hz and 3-phase 4-wire connection, ac power with 50 Hz and 1-phase 2-wire connection, dc power, etc. The ship's power requirements are always in the megawatt range and its required potentials are in the kilovolt range. Therefore, in this article, a smart high power charging network and its control mechanism are developed for cold ironing on the ports, which is capable of serving almost all types of power with different types of power supply network. This developed supply system is capable of providing ac power, dc power, 50 Hz frequency, 60 Hz frequency, single phase, three phases, 3 wire, 4 wire, and 5 wire networks, different ac, dc voltages, etc. The capability of the developed smart power network is validated for different types of ships and vessels, on the simulation platform as well as through experimentation on real-time hardware-in-the-loop. The test results on both the platforms satisfactorily demonstrate the proposed power network and control scheme.

To avoid air and noise pollution on seaports, the use of electric vessels and shore-to-ship power supply based charging station on seaports are in trend, which is also known as cold ironing (CI) infrastructure. In the starting stage, electric vessels charging stations are being implemented on the most busiest commercial ports, where modern electronic devices are used to serve different types of vessels. These devices only take care of the quality of output power. However, on the input side, it creates a serious harmonic issue. During CI, megawatt range of power is supplied to the ships, so generated harmonics and interharmonics in the high-power supply based charging system become more dangerous for the grid. In this article, we propose a novel power quality improved cold ironing (PQICI) system (charging mechanism) to overcome this issue. Moreover, due to inherent multipurpose useability, this novel PQICI is able to supply different types of power to various types of vessels, such as ac power, dc power, 50 Hz frequency, 60 Hz frequency, single phase, three phases, three-wire network, four-wire network, five-wire network, and different ac and dc voltages. Furthermore, this PQICI supply system is capable of serving four vessels at a time. In every type of loading condition with different kinds of power supply mode, the PQICI maintains the power quality on the input side, with fulfilling the varieties of the power demand of vessels. The capability of the developed “PQICI” system is tested for different types of ships and vessels on the simulation platform as well as through real-time hardware-in-the-loop experimentation. On IEEE standard 519, satisfactory test results on both platforms show the efficiency of the developed system and its control mechanism.

In industrial sector, certain demands that are associated with operations of pumps are accompanied by reservoirs with storage capabilities for chemicals or solvents. Consequently, such industries possess inherent demand flexibility that can be utilized. This work proposes the coordinated control of industrial pump loads for participation in Singapore’s Demand Response (DR) programme by adjusting the electrical demand for revenue and power grid benefits. A novel Transactive Energy based energy management system (EMS) is proposed for coordinated operation scheduling of such industrial pumps to become responsive to electricity market prices. The optimal scheduling problem here is formulated based on detailed mathematical model of a water distribution system and a constrained linear programming based control technique is proposed. Case studies are performed in MATLAB environment using Singapore’s electricity market data and proposed EMS controlling the water distribution system. Results show that the proposed EMS is effective in shifting electrical demand away from peak price periods according to real Singapore market price signals while maintaining operational constraints, which leads to significant reduction in electricity costs. Further, in case of DR activations, significant demand may be reduced during DR target periods and revenue from the DR market participation is found to be lucrative.

Despite some recent efforts towards multi-objective design optimization of multilevel converters, design optimization of solid-state-transformers (SSTs) are not presented much in the literature mainly because of the lack of computationally feasible techniques. This paper is dedicated towards a computational feasibility study of multi-objective design optimization techniques for medium-voltage (MV) grid-connected SSTs. After defining the application and scope of SST design optimization problem, a brief description of the possible solution techniques are discussed which shows the merits of semi-numerical/hybrid design optimization techniques. Subsequently, a machine learning (ML) aided hybrid optimization technique is executed for a 15 kVA single-stage SiC-based SST design. Suitable component modelling is presented and a strong agreement is observed between theoretical optimization and experimental results. Finally, a comparative evaluation of the analytical, numerical, standalone hybrid and ML-aided hybrid optimization techniques (deployed for the same 15 kVA SiC-based SST design) reveals that the ML-aided hybrid strategy is best suited for SST design optimization as it requires feasible computational time for <5% error.

Modern buildings have multiple distributed electrical resources (DERs) such as renewable energy sources and energy storage devices, flexible loads, and utility connection. Coupled with smart meters and new energy pricing plans, these physical assets present new opportunities for building operators to save energy, reduce operational costs, avoid carbon emissions and improve occupant comfort. The concept of Energy Nodes is proposed to represent the electrical resources and loads within a building and their electrical interactions, which can be programmed/controlled through software. A scaled-down hardware emulation test-bed representing commercial buildings is developed with commercial DER interfaces, controllable loads and Transactive Energy based Energy Management System to realize a cyber-physical Energy Node. Through studies on this test-bed, it is demonstrated that the proposed energy nodes can automatically act based on building operator's economy preferences, save electricity bills, and provide Demand Response service by reacting to electricity price signals from the markets.

This paper presents a framework for designing scalable and sustainable electrification solutions for off-grid electrification in energy deficient areas. A case study is presented on the development of a community microgrid solution in an energy deficient village on the Sumba island in Indonesia, based on the available renewable energy sources, batteries and a small diesel generator. The target of this off-grid solution is empowering the existing communities and development of new businesses. The microgrid solution also supports the basic community services (such as drinking water, schools, primary health centres) and household needs. This framework can be deployed in any community by customizing the type of energy sources and income generating loads according to the available resources. Validation of the proposed microgrid through simulation and test-bed emulation is reported. A solar microgrid implemented in this island is utilized to study the economic and social impact of electrification.

Air-conditioning and mechanical ventilation (ACMV), power distribution systems, elevators, and lighting systems are critical electrical assets of a smart building. Based on electrical components of these assets such as electrical motors, transformers, solid-state lighting and power electronic converters, a detailed analysis of failure mechanisms and statistics is presented in this paper. Further, suitable electrical and mechanical signals along with prevalent condition monitoring methods are suggested for condition monitoring of these assets based on the presented statistical analysis. This paper lays down the necessary foundation to understand the operating model of critical electrical equipment in buildings and provides a holistic picture for implementation of a predictive and preventive maintenance paradigm. This will enable the building operators to identify potential failures of building equipment and their evolution in real-time, driving decisions on scheduling repair or replacement of components to minimize downtime, save maintenance costs, improve occupant satisfaction, save energy, and maximize resilience.

Cascaded H-bridge (CHB) multilevel converter is widely used for medium voltage motor drives, Static Synchronous Compensator (STATCOMs) and solid-state transformers because of its advantages such as modular design, low harmonic distortion of input current and lower grid-side filter requirements compared to two-level converters. Among the failures in active devices, detection and localization of open-circuit (OC) faults either due to bond-wire lift off (device-side failures) or malfunction of gate driver (drive-side failures) are extensively studied. In this paper, fault detection and localization methods proposed in literature for CHB multilevel converters are analyzed and compared with respect to the time taken for fault localization and additional sensor requirements. For ease of understanding, the methods are classified as model-based, feature-based and hardware-based, and suitability of each classification is recommended for different applications.

Electrical grid's modernization inevitably requires higher integration of renewable energy sources and new technologies to handle their unique features that differ from conventional energy sources. Power generation that is local to the consumption is a new emergent feature when solar energy is harnessed through photovoltaic panels. Consequent to that, radial electrical networks within the distribution grids would have the potential to transform into networks that are more meshed in their topologies. The complexity introduced by such configuration change is compounded by sudden power variability inherent in the solar-based generations. The technology for computationally determining power-flow for such scenarios, to ensure adequate, safe and economic supply, needs new capabilities. In this work, the application of a fast non-iterative power-flow technique to a meshed grid among buildings, based on holomorphic embedding, is validated for the context of Singapore.

This paper proposes a Modular Solid-State-Transformer (SST) topology consisting of bidirectional Matrix-Based AC-DC Dual-Active-Bridge (DAB) submodules. Unlike the conventional SST topologies, the proposed topology offers a single stage Medium Voltage AC (MVAC) - Low Voltage DC (LVDC) conversion. The discussion is focused on the AC-DC DAB submodule of a 1 MVA SST for the Energy Control Centre (ECC) of a microgrid/nanogrid. The possible modulation modes along with the corresponding power transfer limits are presented and a suitable steady-state modulation scheme is identified for the required operating point. The modeling and small-signal analysis of the AC-DC submodule is comprehensively explained. Simulation results including the steady-state operation and the frequency response of the 17.6 kW submodule are presented.

With rapidly advancing technologies, it is more critical than ever to assess and enhance the cyber-physical grid security. This paper aims to provide a comprehensive review and insights of the electrical power generation system security issues using the National Institute of Standards and Technology (NIST) security framework. Besides, it highlights the research gaps that need to be addressed for a secured system. This paper first evaluates the risk in the cyber-physical system to suggest for a more strategic defense specifically against False Data Injection Attacks (FDIA). Next, it highlights the importance of developing state-of-the-art protection measures to secure the system. This work then proposes a detection in-depth structure for holistic detection of attacks in the system. Lastly, it reviews the response and recovery measures and discusses the emergence of digital forensics in the smart grid.

In the past decade, cyber-attack events on the power grid have proven to be sophisticated and advanced. These attacks led to severe consequences on the grid operation, such as equipment damage or power outages. Hence, it is more critical than ever to develop tools for security assessment and detection of anomalies in the cyber-physical grid. For an extensive power grid, it is complex to analyze the causes of frequency deviations. Besides, if the system is compromised, attackers can leverage on the frequency deviation to bypass existing protection measures of the grid. This paper aims to develop a novel specification-based method to detect False Data Injection Attacks (FDIAs) in the multi-area system. Firstly, we describe the implementation of a three-area system model. Next, we assess the risk and devise several intrusion scenarios. Specifically, we inject false data into the frequency measurement and Automatic Generation Control (AGC) signals. We then develop a rule-based method to detect anomalies at the system-level. Our simulation results proves that the proposed algorithm can detect FDIAs in the system.

Leakage inductance of transformer windings is widely used as a health indicator especially for detecting winding anomalies. This test is also routinely carried out before and after short-circuit withstand test which is a part of factory acceptance test. Change in leakage inductance can possibly reveal damages in the winding assembly. Some research efforts report that leakage inductance captures structural alteration in the winding, viz., winding movement. However, diagnosing the extent of damage is not, in general, possible from the deviation in leakage inductance. Asymmetry introduced by the movement of windings makes a transformer vulnerable to short-circuit forces and therefore diagnosing the severity of such movements is crucial. This paper analyzes the change in leakage inductance for various degrees of radial and axial movements of windings. The investigation was carried out using Finite Element Method on a typical power transformer design. It was found that leakage inductance is affected by large movements in the axial direction while it was found to be practically insensitive to small axial movements. Radial movements were found to yield no significant change in leakage inductance irrespective of its severity. Simulations performed using Ansys Maxwell are reported and the observations are explained using the behavior of computed magnetic fields.

This paper presents the design, analysis, and experimental validation of a fault detection and identification (FDI) scheme for dc-dc power electronic converters. The FDI scheme includes two new classes of fault filters: (1) a linear-switched fault detection (FD) filter and (2) a bank of linear-switched fault identification (FI) filters. Both the FD filter and the bank of FI filters have a structure similar to that of Luenberger observer. The FD filter detects a fault event and the bank of FI filters identify a faulted converter component, for instance, failure in switching or passive components. We present simulation and experimental results for a prototype 2 kW solar photovoltaic (PV) boost dc-dc converter system to demonstrate the efficacy of the proposed FDI scheme. The experimental results demonstrate accurate fault detection and identification for a collection of catastrophic component faults in PV dc-dc power converters.

A modular multilevel converter (MMC) with traditional cascaded PI control structure suffers from poor steady state and dynamic performance. This is due to the limited harmonic rejection capability of PI controller thus failing to alleviate even order harmonics in circulating current and due to the slower outer average voltage control loop resulting in significant deviation in submodule capacitor voltages during load transients. This paper presents a new control structure with a repetitive controller (RC) in conjunction with a Lyapunov function-based controller (LFC) in the inner circulating current loop and an additional load current feed forward loop in addition to the outer voltage loop to improve both steady-state and dynamic performance of MMC. RC has a good steady-state harmonic suppression capability therefore can effectively alleviate the circulating harmonic currents, where as LFC ensures a stable operation and superior dynamic performance of the converter against load disturbances. Analytical equations governing the design of both the controllers are presented. Model of a single phase, 5-level MMC is developed on a PLECS RT box real-time simulator for hardware-in-the-loop (HIL) testing, it operates along with the external Texas Instruments DSP controller hosting the developed control scheme. Real-time simulation results are presented to substantiate the improvement in steady state and dynamic performance of MMC with the proposed repetitive and Lyapunov function based circulating current controller.

This paper presents a three-phase single-stage bidirectional isolated matrix based AC-DC converter for energy storage. The matrix (3 × 1) topology directly converts the three-phase line voltages into high-frequency AC voltage which is subsequently, processed using a high-frequency transformer followed by a controlled rectifier. A modified Space Vector Modulation (SVM) based switching scheme is proposed to achieve high input power quality with high power conversion efficiency. Compared to the conventional two stage converter, the proposed converter provides single-stage conversion resulting in higher power conversion efficiency and higher power density. The operating principles of the proposed converter in both AC-DC and DC-AC mode are explained followed by steady state analysis. Simulation results are presented for 230 V, 50 Hz to 48 V isolated bidirectional converter at 2 kW output power to validate the theoretical claims.

This paper presents a technique based on leakage flux to detect the winding fault in coupled inductors using a single flux sensor. An analytical model is developed and analysis on leakage flux for different load conditions and severity of fault is carried out. Using the developed model a comparative study of leakage flux at the outer limb and center of the yoke under the winding fault is carried out. The simulation study revealed that leakage flux at center of the yoke is found to be effective in identifying the fault. The analytical model is validated experimentally by using a three phase, star connected 1.2 H, 2.2 A coupled inductor. Both analytical model based and experimentally obtained results are found to follow the same trend in leakage flux during the winding short circuit conditions. The trend has been verified for different loading and severity conditions. The proposed technique is relatively simple to implement in real-time. The technique requires a single, inexpensive and low bandwidth hall-effect based flux sensor and is capable of detecting winding abnormality in a three phase coupled inductor.

This paper proposes a low-voltage DC (LVDC) architecture to replace the conventional low-voltage AC (LVAC) architecture in a diving support vessel (DSV). A genetic algorithm based optimization algorithm is also adopted to minimize the fuel consumption of the DSV. The DSV in study spends a majority of its time in dive or dynamic positioning (DP) mode, in which all four diesel generators are online to ensure redundancy and fast response to unpredictable sea conditions. Conventionally, the allocation of power generation for the diesel generators is performed via equal loading, which may not result in minimal fuel consumption. A comparison of fuel consumption in normal operation modes for the conventional LVAC and proposed LVDC architectures are performed, both with equal loading and optimization with GA. Additional constraints are then applied for fuel consumption comparisons in dive and DP operating modes.

In a modular multilevel converter (MMC), ripple component in the capacitor voltages of the submodules(SMs) results in second- and other even-order harmonics in the circulating currents. When, MMC is used for variable frequency applications like a front end converter in variable speed wind generator or as an inverter in a motor drive, the circulating current harmonic frequencies varies over a wide range because of the change in fundamental operating frequency. Traditional controllers like proportional resonant (PR) controller and time-domain based repetitive controllers have limited harmonic rejection capability at variable frequencies. This paper presents a control structure with spatial repetitive controller (SRC) to alleviate the circulating harmonic currents in MMC, when used for variable frequency applications. SRC has a good steady-state harmonic suppression capability and is independent of frequency. Submodule capacitor voltage balancing control strategy is also presented. Analytical equations governing the operation of a 3-phase MMC are derived and presented. MATLAB/Simulink model of a 3-phase, 9-level (Ln-Ln) MMC is developed to demonstrate the effectiveness of the developed submodule capacitor balancing and circulating harmonic current suppressing controller.

The vision of smart grid shares goals with that of smart modern buildings, including better automation through improved observation using intelligent submetering. Electrical submetering of modern buildings can lead to energy savings and better awareness to the end-user regarding their energy consumption pattern. It can also help in getting information regarding the quality of power and expedite the automation of energy management. This paper presents a novel configuration of electrical submeter which can facilitate the implementation of smartness not as an end product, but as a quality that can evolve without changes in the physical aspects of the submeter. The submeter is inclusive of an inexpensive and small single-board computer, which can then install or change the digital application associated with submetering. When newer or advanced data-analytics are designed, the proposed submeter can be repurposed to carry out the new computations and the upgrade can be done through remote access mechanisms. This strategy can be useful for cost reduction in the ever-changing domain of smart techniques and the need for customization.

This manuscript presents the investigations on three different types of low voltage AC (LVAC) power distribution architectures of diesel-electric propulsion system for diving support vessel (DSV). It focuses on the qualitative analysis of three LVAC power distribution architectures employing: (1) the conventional 12-pulse converter and (2) active front end (AFE) converter and (3) the proposed 6-pulse converter with shunt active filter (SAF). The reliability evaluation of all the three power architectures has been performed to confirm the viability of the proposed architecture. Further a qualitative analysis of all the three different power architectures has also been furnished.

This paper studies the sizing problem of PV-battery-diesel hybrid systems using convex optimization approach. The case study takes place in an Indonesian island where the load demand fully depends on a single diesel generator (DG). The goal is to optimize the number of solar panels and batteries to be installed to reduce the total cost of the system over the lifetime of 25 years. Real solar irradiance and temperature profiles, together with forecasted diesel prices, are used. A heuristic method, particle swarm optimization, is also employed as a benchmark for performance evaluation. Our results show that the total cost obtained from our proposed method is the lowest since it reaches the global optimal solution. The advantage of a PV-battery-diesel hybrid system over systems operated by a single DG and systems formed by a single DG and solar panels is exposed as, in comparison to them, it achieves a reduction of the total cost (between 7% to 11% and 0% to 4%, respectively) and of the CO2emissions (between 19% to 29% and 10% to 21%, respectively).

This paper describes a non-isolated matrix based buck-boost converter applicable for the aircraft systems. A matrix based topology is used which converters the three phase low frequency input ac voltages into an intermediate high frequency ac voltage. The high frequency ac voltage is rectified using Current Doubler Rectifier (CDR). The output voltage of the CDR circuit is further stepped-up by using a dc-dc boost converter to obtain the desired output voltage. Both, the conventional three phase buck and the three phase boost converter have limitations over the maximum and minimum voltage gain, respectively. The proposed buck-boost converter overcomes such limitations and provides output dc voltage with reduced current distortion and improved power conversion efficiency. Moreover, the novelty of the paper lies in integrating the output filter inductor of the matrix topology with the input inductor of the boost stage resulting in complete elimination of the intermediate filter capacitor and the input boost inductor. The topology and the principles of the operation of the proposed converter are explained in details. Further, the analysis of the converter is carried out. Moreover, the performance of the proposed converter is compared with the boost-buck and conventional buck-boost power converters. The proposed converter is simulated in MATLAB 2015b and results are presented to validate the performance of the converter.

Fault tolerance in high power multilevel converters is a desirable feature particularly in applications such as marine propulsion where continuity of service is critical. However, the medium voltage drive system's reliability becomes vulnerable due the number of power semiconductor devices in the system. Therefore it is utmost important to identify the faulty device as fast as possible to isolate it from the system. In this paper the medium voltage drive chosen is a cascaded H-bridge on which the proposed fault detection technique is applied. The proposed technique uses only current signature to detect the faulty module and hence no extra sensors are required. The feasibility of the proposed method is verified in simulation.

Electricity markets in countries around the world are being restructured in pursuit of economic efficiency through competition. However, unpredictability in electricity prices and previous occurrences of market failure have indicated a need to better understand the complex interactions between the various market participants as well as to design market rules that maximizes efficiency and security. In this paper, the techniques of Agent-based Computational Economics (ACE) are employed to simulate the behavior of the GenCo participants in the National Electricity Market of Singapore (NEMS). The use of Reinforcement Learning (RL) in the agent-based modeling will be a more realistic representation of the GenCo and will bring about more accurate electricity market simulation outcomes. Actor-Critics constitute an important aspect of RL and in this paper we propose an adaptive actor-critic mapping using Particle Swarm Optimization (PSO). A simulation platform is built with the proposed model for Genco's learning and is tested in the conditions of varying vesting contract levels. Simulation results indicate that the proposed learning algorithm is able to procure higher GenCo revenue when benchmarked with existing learning algorithms.

This paper presents a bio-inspired robotic fish undulatory swimming behaviour modeling and control using modulated pattern generators (MPG). Carangiform fish locomotion pattern is closely mimicked using a LH body wave (with its parameters: Tail-beat frequency (TBF) and Caudal amplitude (CA)) modulated by rhythmic central pattern generator (CPG) signal. A Matsuoka based non-linear oscillator CPG structure is used to generate desired rhythmic pattern preserving control properties like system stability (limit cycle behaviour) and synchronization. A two level locomotion control architecture based on vertebrate fish biology is proposed. Higher level controller generates desired trajectory as encoded patterns MPGs. Synchronization of the desired trajectories at each joint with the robotic fish dynamics generates desired fishlike locomotion behavior. Lower level control scheme uses an inverse dynamics model based policy for tracking this locomotion pattern (joint positions). It is shown that MPGs can represent the shape (amplitude) and phase (frequency) patterns of high-dimensional periodic inputs using simple kinematic parameters. Proposed inverse dynamics model based tracking control strategy is found to perform in a stable operating margin..

Transformer loading is quite crucial for industry as it has significant influence on transformer insulation deterioration as well as its remained life. Transformer load monitoring even becomes more substantial once transformer is operated in high ambient temperatures. Having real-time information about transformer thermal stress and insulation medium is indeed necessity. An intelligent system should be developed to monitor the transformer condition and giving online information on transformer insulation deterioration. Hence, this study is concentrated on an online prognosis system predicting transformer aging rate as well as remained life. Cast-resin transformer thermal modeling is discussed and influences of load and ambient temperature are investigated. Prognosis software is developed based on introduced model and transformer aging rate is examined through different simulation studies. At the end, developed prognosis system is utilized to keep the transformer aging rate on a specific value in course of transformer operating period. Different simulations on this plan are carried out and results are discussed.

In Smart Grid there are abundant number of grid connected Voltage Source Converters (VSC) in the form of Electric Vehicle (EV) battery chargers, Renewable Energy Source (RES) fed grid connected inverters etc., that can be used for active and reactive power support to the grid. The VSCs remain idle when the load in case of EV charger or the energy source in case of RES fed grid connected inverters is not available. This work presents a single-phase PQ theory based control strategy to improve the utilization factor of such converters by using them to support the reactive power to the local loads when they are idle. The proposed control scheme is implementable with less computational effort. The system is further analyzed by calculating appropriate minimum DC bus voltage for a given amount of reactive power to be supported. The analysis for the designed system is validated using MATLAB-Simulink based simulation and a scaled down laboratory based experimental setup. The results are in good agreement with the analysis.

This paper analyzes the feasibility of using the existing auxiliary winding in wound field brushless synchronous generator for condition monitoring. The auxiliary winding is the 4th winding placed in the stator of a three phase synchronous generator to feed exciter field through the automatic voltage regulator. This paper presents the model of a wound field synchronous generator with stator winding fault and auxiliary winding to perform simulation study for identifying the fault signatures in auxiliary winding voltage. The identified fault signatures are validated with the experimental setup. The analysis shows that the auxiliary winding voltage harmonics can be used to detect and diagnose stator winding turn-to-turn short circuit fault. Hence, it is feasible to use auxiliary winding voltage for condition monitoring of wound field brushless synchronous generators.

This paper presents optimal generation scheduling for minimization of fuel consumption (FC) in an offshore support vessel with a dynamic positioning system and diesel generator (DG) sets of 8000 kW total capacity. FC is analyzed for equal load sharing among equal capacity DGs, optimal load sharing among equal capacity DGs, and optimal load sharing among unequal capacity DGs. Due to nonlinear specific FC (SFC) curves of the diesel engines, a Genetic Algorithm is used for optimal load sharing. The SFC-vs-load relationship obtained from Brake SFC (BSFC) map of the diesel engines is characterized using a cubic spline interpolation. A solution to the problem is attained by comparing yearly fuel consumption in the three cases for the load profile of target vessel. This method can be applied to any vessel equipped with multiple generating units. A vessel with proper selection of DG capacities and closed bus-tie can achieve maximum fuel savings; however, when deciding the DG capacity and load scheduling, it is necessary to consider fuel consumption alongside concerns such as optimizing exhaust emissions after-treatment, ensuring adequate power availability for essential services, and scheduling engine maintenance.

High altitude wind power (HAWP) generating system poses several benefits over conventional wind power (CWP) generating system. An air-borne electric generator is held at high altitude above the ground surface with buoyancy provided by light gas filled blimp/aerostat. In order to minimize the size of the blimp and to reduce the number of electric components in the air-borne system, generation of electrical power is carried out at three phase medium voltage AC (MV-AC) and transmitted to the ground station (without any power conversion) using electromechanical tethers. Thus, transmitted power is interfaced into the distribution level grid at 415 V and 50 Hz. This paper evaluates possible power electronic converter (PEC) topologies that can be used to convert variable voltage and variable frequency three phase medium voltage AC power into constant frequency distribution level grid voltage. Three different PEC topologies are proposed that allow generation and grid side current control and generation side maximum power point tracking (MPPT) control. In addition, the proposed PECs provide step down of voltage and electrical isolation with the distribution grid. Suitable active and passive components are selected for 100 kW HAWP system and overall semiconductor losses are evaluated. The converters are simulated using computer software programs PSIM-9 and MATLAB. The converter that exhibits good efficiency, easy control of generation and grid side current as well as facilitates MPPT control of HAWP generation side is selected for grid interface of isolated HAWP system.

Modern smart buildings are envisioned to have both passive and active design components, which are managed by building operating systems. A building operating system consists of different functional modules which help handle the resources of the building and contribute towards the goal of efficient energy management. This paper investigates the functional part of building operating system which aims to achieve optimal demand side management, through designed scheduling of electrical appliances in a residential setting or in office buildings. The problem is formulated and solved based on the techniques of convex optimization and stochastic optimization.

This paper proposes a high frequency soft switched high voltage gain dc/dc converter for DC microgrid application. The proposed converter employs a half-bridge resonant boost converter at input and a voltage quadruple circuit at output. Resonant boost converter is operated at frequency of 150 kHz to gain advantage of low output voltage ripple and reduced magnetics. Zero voltage turn-on is achieved for all switches. Zero current turn-on and turn-off is achieved for all diodes. High frequency film capacitors increase life time of the converter. Voltage stress across switches is less and is clamped naturally without external snubber circuit. Experimental converter rated at 300 W has been designed, and tested to verify the analysis, design and demonstrate the performance of the proposed converter.

This paper presents a novel switching scheme named as Switched Rectifier Inverter (SRI) modulation scheme for three phase to single phase (3×1) Matrix converter based isolated AC-DC converter. The proposed SRI modulation scheme incorporates symmetrical Space Vector Modulation (SVM) with inverter logic for switching the twelve switches of Matrix based AC-DC converter. The operation of proposed SRI modulation scheme is discussed and analyzed in details. The significant contribution of proposed modulation scheme in terms of power density, efficiency and power quality is discussed. Finally, the converter is simulated with proposed modulation scheme on MATLAB R2011b and PLECS 3.5 based software platform for an isolated three phase AC-DC converter of input 120 V(rms), 400 Hz AC (aircraft input supply) to output 400 V DC at 8 kW power.

With increasing use of renewable energy and the advancements in smart grids, demand side management has been a keen topic of interest. Buildings, both commercial and residential, have great potential in implementing load-side demand management in renewable energy source powered microgrids. Electric Spring, a smart grid technology, is able to provide instantaneous voltage support and load power shedding. Thus, providing an astute solution to the voltage instability problem associated with such microgrids. In this paper, an implementation of electric spring is presented, in conjunction with building loads like central air conditioning system, to demonstrate its properties of voltage support, load power shedding, and reactive power compensation.

In real-life applications of wireless sensor networks (WSNs), optimization of the network operation is required to extend its lifetime. A framework is proposed that enables practical development of centralized cluster-based protocols supported by optimization methods for the WSNs. Based on this framework, a protocol using harmony search algorithm (HSA), a music-based meta-heuristic optimization method, is designed and implemented in real time for the WSNs. It is expected to minimize the intra-cluster distances between the cluster members and their cluster heads (CHs) and optimize the energy distribution of the WSNs. The study of HSA cluster-based protocol is carried out in a real case where the WSNs equipped with the proposed protocol are deployed in an indoor environment to monitor the ambient temperature for fire detection. A comparison is made with the well-known cluster-based protocols developed for WSNs such as low-energy adaptive clustering hierarchy-centralized (LEACH-C) and a cluster-based protocol using Fuzzy C-Means (FCM) clustering algorithm. Experimental results demonstrate that the proposed protocol using HSA can be realized in centralized cluster-based WSNs for safety and surveillance applications in building environments. From the obtained experimental test results, it can be seen that the WSNs lifetime has been extended using the proposed HSA protocol in comparison with that of LEACH-C and FCM protocols.

This paper presents a simple concept of harvesting high altitude wind power using air-borne wind turbine-cum-electric generators supported by light gas filled blimp/aerostat. Air-borne wind turbine at high altitude extracts kinetic energy from high speed streamlined wind using buoyancy provided by the blimp. Using a suitable power electronic converter (PEC), extracted electrical power is sent to the ground using a tether. Blimp is tethered to the ground and the same tether is used for electricity transmission as well. This paper outlines major components used for harvesting high altitude wind power. Transmission of power at medium voltage DC reduces the transmission loss and volume of the conducting cable. The optimal transmission voltage level is determined that gives minimum weight of the tether for a given power level and proposes a simple and high power density power electronic converter, which converts low voltage AC to medium voltage DC in an air-borne unit. Simulation results obtained prove efficient power conversion using the proposed power electronic converter. In addition, comparative study between conventional wind energy harvesting system and high altitude wind energy harvesting system shows high altitude wind power is better in terms of capacity factor, cost of electricity (COE), ease of construction and power density than conventional wind power generating system.

Three phase low voltage power is generated using an air-borne wind turbine and electric generator in a high altitude wind power (HAWP) generation system supported by light gas filled blimp/aerostat. Generated power is transmitted at an optimal medium voltage DC to reduce the weight of an electro-mechanical tether and to increase the transmission efficiency. A 100 kW isolated DC to DC converter is proposed which converts DC link voltage to an optimal transmission voltage. Modified interleaved current fed converter is designed which gives zero voltage switching in the primary side for a wide range of load. Converter is interleaved to reduce the device rating, conduction loss and the size of passive components used in the converter. Two modules of insulated gate bipolar transistor (IGBT) H-bridge are connected in parallel in primary side and four modules of full bridge diode rectifier are connected in series in secondary side. Two extra IGBT switches for zero voltage switching (ZVS) are used to design clamp circuits for the proposed converter. This modular concept simplifies the design procedures of converter at high power level and improves the stray losses associated with in the converter. The steady state analysis of the converter is carried out and verified with the simulation results and presented in this paper. Device ratings and passive components size are determined using the steady state analysis for 100kW HAWP generation system.

This paper proposes geometrical parameter design optimization for a novel robotic fish prototype. The developed model of the robot fish has a streamlined rigid anterior body, multi-link rear body with pectoral and dorsal fins and an oscillating lunate caudal fin. Earlier researches on fish design have focused on the relative link lengths optimization, particular fin geometries and the conventional motion parameters for its velocity maximization. In this work, a holistic design through optimization framework is presented. It is based on estimating airfoil geometries' primary dimensions with corresponding constraints of buoyancy, physical constraints of components, their assembling as per the design rules, are imposed on the objective. NACA 4-digit series has been chosen as reference in our study which allows for symmetrical airfoil and associated relative ease in fabrication. The quasi-steady flow and fundamental airfoil theories are used to observe the hydrodynamic forces acting on the undulating links. A multi-objective optimization problem is formulated using two heuristic and two hybrid approaches. A hybrid approach of Genetic algorithm (GA) and Mini-Max algorithm is found to produce the best results. Further, a computational fluid dynamic (CFD) study for fluid-structure interaction (FSI) between fish model and surrounding fluid medium is also carried out to validate the results obtained.

This paper presents a smart-metering framework based on computations of instantaneous phasors of voltage and current signals measured at a given node. The idea and requirement of electrical transparency inside a building is presented initially. Then the implementation of phasor estimation algorithm is discussed for the purpose of smart-metering. The capability of the smart-meter to do detailed power quality analysis is also presented. The ongoing work of hardware implementation and real-time testing of such smart-metering is also mentioned in the paper.

In this paper a novel control strategy is proposed for a three-phase-four-leg UPS-inverter for data center application. The control strategy takes care of the unbalanced three-phase loading of the data center server without the manifestation of the neutral current. Thus, the power distribution unit (PDU) transformer can be eliminated from the power architecture while feeding the total data center load from a standard three-phase-three-wire utility supply. The proposed control strategy adjusts the inverter output voltages in such a way that even in the presence of unbalanced loading of the servers, the neutral current is maintained at zero in the steady-state. The proposed methodology is thus capable of reducing the thermal losses due to PDU as well as neutral wire improving the power usage efficiency (PUE) of the date center.

Previous studies focused only on the optimization of either microgrid load dispatch or reconfiguration power loss. Micorgrid economic load dispatch approach normally assumed that it could draw unlimited power from the utility grid. Network reconfiguration usually did not take microgrid into consideration. Thus, it is necessary to integrate these two sub-problems together in order to benefit the whole network. In this paper, an integrated solution that takes care of both microgrid load dispatch and network reconfiguration is proposed. The stochastic nature of wind, PV and load is taken into consideration. The forecasting of the wind, PV and load data are considered. The bio-inspired optimization scheme Vaccine-AIS is adopted to solve the problem. The results obtained have shown that the optimization technique is capable for this problem. By using the integration approach, microgrid can be incorporated into the network more effectively. The network can adjust itself more efficiently to allow the utilization of the renewable energy resources.

In this paper, a plug and play type autonomous-micro-grid system formation is proposed. Multiple distributed generating sources and loads interaction is considered pertaining to the stability of the micro-grid. The proposed method enables communication-less operation of each of the elements of the micro-grid system. It is also considered that the sources are of different power capacity as can be seen in a typical autonomous micro-grid system. Spatial Repetitive Controller (SRC) is proposed to control each of the distributed generating sources in a decentralized manner to stabilize the overall micro-grid system. The proposed system considers sudden change in load as well as other distributed generators conditions like a true plug and play operation. A novel signature frequency voltage injection method is proposed to identify the presence of special distributed generator and operation of backup distributed generators. The implemented control architecture also ensures stability of the micro-grid fundamental frequency even in the case of dynamic conditions unlike the traditional droop-control method. A detailed experimental study is carried out and the experimental results presented show the efficacy of the proposed system.

In this paper, the thrust allocation problem for semi-submersible oil rig platform is formulated as an optimization problem, with an objective to minimize the power consumption. The electrical power consumed by the oil rig platform depends on the thrust generated by the thrusters and the efficiency of the electrical propulsion system. A detailed mathematical model to compute the efficiency of the electrical propulsion system is developed and the numerical results obtained are compared with experimental test results. The formulated energy-efficient thrust allocation problem is solved using Improved Harmony Search (IHS) algorithm. The percentage savings in total power consumption for the oil rig platform as compared to the Mincon method for Genetic Algorithm (GA), Harmony Search (HS), and IHS methods are 48.76%, 51.13%, and 53.90%, respectively. In addition, the total power consumption for energy-efficient thrust allocation approach is lesser as compared to conventional thrust allocation approach for all the considered algorithms.

10.1109/IJCNN.2008.4633821

In this paper a genetic algorithm (GA) is employed to determine the desired current waveforms for switched reluctance motors (SRM) through generating appropriate reference phase torques for a given desired torque using the torque sharing function (TSF). The objective is to yield smoother phase current waveforms in general, and achieve minimum phase current variations in particular. This problem is formulated into a multiobjective optimization task with certain constraints. Due to the highly nonlinear relationship between the SRM torque and current, this optimization task is an NP-hard problem. To deal with the difficulty, the problem is further coded so that a GA can be applied to facilitate the search of global minimum. Simulation results verify the effectiveness of the proposed method.