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The Dynamic Economic Dispatch (DED) problem consists in satisfying a certain demand for electric power among scheduled generating units over a certain interval of time while satisfying the operating constraints of these units. The consideration of the valve-point effect (VPE) makes the problem more practical but also more challenging due to the non-linear and non-smooth constraints that are required for representing the model. We present a method, based on a sequence of piecewise linear approximations, which produces a feasible solution along with a lower bound on the global solution. In this way, this deterministic approach can trade off the speed which characterizes certain heuristics that are usually used to solve the DED-VPE for a better solution and insights about the problem. The method is applied to a widely used case study and provides a lower solution objective than the best known solution to date.

The unprecedented growth of renewable energy has led to various challenges in power system operations. Demand response can provide additional flexibility to the system in order to balance the effects of the massive integration of renewable resources. This presentation focuses on the comparison of two approaches for enabling demand response, real-time pricing and priority service pricing. This analysis is centered on the impact to consumers by assessing the effects of these schemes on their comfort and bill. We use an example based on realistic electrical consumption of a household contained in the Pecan Street dataset. The example provides an end-to-end illustration of (i) how a household selects options from a priority service menu, (ii) how devices in the household are dispatched by a home energy router, and (iii) what consumer welfare losses are relative to the golden standard of real-time pricing with or without a battery.

The Dynamic Economic Dispatch (DED) problem consists in satisfying a certain demand for electric power among scheduled generating units over a certain interval of time while satisfying the operating constraints of these units. The consideration of the valve-point effect (VPE) makes the problem more practical but also more challenging due to the non-linear and non-smooth constraints that are required for representing the model. We present a method, based on a sequence of piecewise linear approximations, which produces a feasible solution along with a lower bound on the global solution. In this way, this deterministic approach can trade off the speed which characterizes certain heuristics that are usually used to solve the DED-VPE for a better solution and insights about the problem. The method is applied to a widely used case study and provides a lower solution objective than the best known solution to date.

Continuous intraday electricity market has become increasingly important in recent years, due to the increasing integration of renewable resources in power systems. Trading in this market is challenging due to the multistage nature of the problem, its high uncertainty, and the fact that decisions need to be made rapidly in order to lock in profitable trades. We cast the problem of trading in continuous intraday markets as a reinforcement learning problem, and tackle the problem using policy function approximation. We specifically parametrize the trading policy using price thresholds, and optimize the choice of these thresholds using the REINFORCE algorithm. We demonstrate the effectiveness of our proposed policy by showing that it outperforms the method, classically used in the industry, rolling intrinsic of 4:2% (out of sample) on the 165 last days of 2015 in the German continuous intraday market.

The operation of power systems faces great challenges as the penetration of variable renewable energy keeps increasing rapidly. Meanwhile, the electrification of transportation and heating systems can increase future peak demand. As a result, grid infrastructures will need to be reinforced, including construction of combustion turbines in order to meet peak demand and offer flexibility to the system, and investment in transmission and distribution lines. However, there exists massive flexibility potential on the demand side, which can be exploited in order to reduce or postpone the upgrade of current power systems. Meanwhile, investment in smart meters is necessary to enable demand response. In this paper, we build a capacity expansion model for the European system and carry out a cost-benefit analysis considering the scenario of year 2050. We identify substantial flexibility potential in the residential sector and we find that the investment cost in smart meters can be justified from the perspective of energy suppliers.

Low-voltage distribution networks are emerging as an increasingly important component of power system operations. From a computational standpoint, the proactive utilization of these resources places daunting challenges due to their vast number and the non-linear physics that govern power flow in low-voltage networks. For this reason, a hierarchical approach to the organization of distribution markets which can better cope with computational scalability may be desirable. This paper models various alternatives to the coordination of transmission and distribution system operations, and investigates their relative performance on a small-scale network in terms of allocative efficiency, consistency with physical constraints, and pricing.

We present a stochastic unit commitment model for assessing the reverse requirements resulting from the large-scale integration of renewable energy sources and deferrable demand in power systems. We present three alternative demand response paradigms for assessing the benefits of demand flexibility in absorbing the uncertainty and variability associated with renewable supply: centralized co-optimization of generation and demand by the system operator, demand bids and coupling renewable resources with deferrable loads. We present simulation results for a model of the Western Interconnection.

This task force paper presents multi-domain tools and their interfacing issues to perform simulations that require expertise in multiple areas of physics, such as electrothermal, electromechanical, electrochemical, and electromagnetic simulations, etc. Features of single multi-domain simulation tools, which are capable of simulating more than one system such as electrical chemical, mechanical, etc., are discussed. In addition, programs that are not capable of performing multi-domain simulation independently but can be interfaced with other programs to perform multi-domain simulation are also covered. Two case studies are reported where multi-domain simulations are performed in offline and real-time environments through the interfacing of more than one simulation tool.

International audience; The transformations of conventional Internal Combustion Engine (ICE)-powered vehicles into electrified vehicles are of growing interest. The retrofit hybridization of a Peugeot 308 SW passenger car is studied. For this purpose, a complete hybridization system is added to the rear axle of the vehicle. As a result, the control of the initial ICE-powered vehicle has to be updated. The aim of this paper is to deduce the potential fuel saving thanks to this hybridization. The simulation results show an energy saving of at least 9% and potential consump-tion reduction on a Worldwide harmonized Light-duty Vehi-cles Test Cycle (WLTC).

SNCF is the largest electricity consumer in France. The rolling stock has the highest share of France railway system electricity consumption at 84%. The traction power of High-Speed Trains (HST) can reach up to 50% of the total rolling stock electricity consumption during the rush hours of weekdays. Given the new policies regarding energy regulation in peak power demand periods, load modulation by the traction power of HST is one of the flexibilities that are investigated by SNCF in the Smart Grid project. This paper presents the study related to the feasibility of a Targeted Traction Power Modulation (TTPM) of HST. Experimental tests have been achieved as proof of concept on the SNCF South-Europe-Atlantic HS line. Experimentation results showed between 20 and 30% of energy savings during the peak power demand period. Refereed/Peer-reviewed

Grid-connected converters (GCCs) are showing potential in providing virtual inertia and has attracted wide attention recently. For the virtual inertia emulated by GCCs, it is proportional with the DC-link capacitance, and thus, the DC-link capacitance can directly affect the dynamic performance for the GCC emulating inertia through modifying the inertia constant. However, the impacts of the DC-link capacitance have never been discussed in any literature before. Considering this issue, the influence of the DC-link capacitance on the dynamic performance for the GCC providing virtual inertia is analyzed in this paper. In addition to that, the selection approach of the DC-link capacitance is presented by tuning the system damping ratio within its optimal range. Simulations verify the correctness. Accepted version

International audience; With the increasingly rapid penetration of power electronics into AC grid, there is an urgent need in enhancing stability and performance of grid-connected converters. An advanced $H_{\infty}$ multi-input multi-output (MIMO) control using linear matrix inequality (LMI) techniques is introduced and applied for electromagnetic transient (EMT) three-phase voltage source converter (VSC) grid-connected system (simple STATCOM). The proposed control is compared with classical cascade vector control through a validation test of short-circuit event.The comparison results prove that the advanced control approach provides much better performance and transient behaviour compared to classic vector controls, as a result of using $H_{\infty}$ optimization technique to minimize the effect of frequency's and grid voltage's variations. The validation test is done using MATLAB Simscape in EMT simulation, and also gives a step-by-step path of implementation for applying advanced control in industrial-level application of power converter.These results will be further used to control the units of the new concept of \textit{Dynamic Virtual Power Plant} introduced in the H2020 POSYTYF project.

This paper presents the design process, detailed analysis, and a comparative study on the advantages of axial-flux induction machines (AFIM). A radial-flux induction machine (RFIM) is also studied as benchmark motor. Both motors are designed with six poles, 36 stator slots, and 32 rotor bars. Finite-element analysis is used to predict the performance of the two motors under both transient and steady state conditions. A complete comparative study along with the simulation results are reported. It is found that the studied AFIM has higher efficiency and power density. Refereed/Peer-reviewed

Replacement of traditional synchronous generators by renewable energy sources in modern power systems reduces the rotating inertia and causes stability and damping problems. Large scale battery energy storage systems (BESS) are now becoming an integral part of modern power systems to address the intermittency issues of renewables. This paper proposes a method of utilizing the BESS for damping rotor angle oscillations by modulating the machine output power through controlling the BESS current. First, an analytical expression for extra damping provided by the BESS is derived for a simple system. The effectiveness of the proposed method is then tested on a single-machine infinite bus (SMIB) system for both classical and higher order machine models using Matlab Simulink and DIgSILENT PowerFactory software. The control scheme is also tested in a multi-machine system. The additional damping provided by the BESS is compared with that obtained by using a static synchronous compensator (STATCOM). It is demonstrated that BESS is more effective than STATCOM in damping rotor angle oscillations. Refereed/Peer-reviewed

In this work, a novel distribution grid level peer-to peer (P2P) power market framework is proposed. The proposed market framework enables the satisfaction of distribution grid constraints such as the voltage limits and transfer capacity limits, for all P2P power transactions between each producer-consumer pair. An Alternating direction method of multipliers (ADMM)- based coordinating algorithm is proposed in which the P2P power trading is facilitated at the first step, and the second step involves ancillary services market clearing considering the grid constraints and the power injections of the P2P participants, in a distributed and interactive manner. The distribution locational marginal prices are iteratively computed in the process so that the costs associated with P2P energy transactions are allocated to the respective producer-consumer pairs. As such, the proposed algorithm enables optimal P2P power trading while supporting optimal voltage and congestion management of the distribution grid. The case studies illustrate the effectiveness of the proposed ADMM-based coordination algorithm. Ministry of Education (MOE) Accepted version This work was supported by the Singapore Ministry of Education Academic Research Fund Tier 1 Grant (MOE2018- T1-002-093) This work was supported by the Agency for Science, Technology and Research (A*STAR) through its Singapore-Germany Academic-Industry (2+2) International Collaboration under Grant A1990b0060.

Development of multi-energy integration for the commercial/Industrial sector introduces a high level of interdependency between different energy carriers which requires integrated modeling of these multi-energy systems (MESs). Transportation electrification such as the integration of plug-in electric vehicles (PEVs) has the potential to have a significant effect on the operation of commercial MESs which are equipped with large scale PEVs' parking lots. Although the development of energy management models to optimally integrate PEVs into MES leads to higher benefits, the associated operational uncertainties can bring additional costs for system operators. Ignoring these uncertainties can result in nonoptimal or even infeasible operational solutions for MES facilities. In this paper, a two-stage robust energy management model has been proposed for MESs equipped with PEV parking facilities to optimally schedule MES facilities and its interaction with upstream network, while, supplying the required PEV charging patterns, considering the uncertainties of MES loads and energy market prices. The proposed model is developed as a min-max-min optimization problem which is solved through a column-and-constraint methodology, recasting the tri-level problem into a first-stage min problem and a second-stage maxmin problem. The second-stage problem is solved through duality theory and Big-M linearization technique. A comprehensive case study has been conducted to evaluate the effectiveness of the proposed model. According to the obtained results, MESs are able to supply PEVs and multi-energy loads, while participating in upstream network energy market with operational solutions that are robust against uncertainties, resulting in extra benefits and lower operational costs. Refereed/Peer-reviewed

This paper optimally determines the configuration of the system, as well as each component capacity, in order to design a cost-effective and environment-friendly AC mini-grid hybrid power system for a remote area in South Australia. To this purpose, a modified Multi-Objective Particle Swarm Optimization (MOPSO) algorithm is applied. In each iteration of the modified proposed MOPSO, first, renewable power sources, including photovoltaic arrays and wind turbines along with energy storage components, are selected to form a hybrid power system along with the diesel generator. Then, the capacities of the components are optimized based on two objective functions, including Levelized Cost of Energy (LCOE) and CO2 emission, by analyzing the system using real data in hourly time-step for the load, solar insolation, ambient temperature, and wind speed over a 20-year timespan. Afterward, positions for system configuration and component capacities are updated according to the objective functions. Refereed/Peer-reviewed

Robustness, low cost and high torque density are the main characteristics of switched reluctance machines (SRM) that have made them promising for a variety of applications. In this paper a small diameter, long stack length (small aspect ratio) 6kW SRM is designed. In the first step, the dimensions of the studied SRM are derived based on conventional sizing equations. The significance of the rotor and stator pole arcs and also the effective torque zone as a constraint of the design are discussed. A finite-element study is carried out to validate the analytical model of the proposed SRM. The performance of the machine is comprehensively studied in different operating speeds. Simulation results demonstrate the capability of the machine for operation over a wide speed range.pa Refereed/Peer-reviewed

Load flow problems in electricity distribution systems (EDS) are generally solved through iterative methods such as Newton-Raphson, Gauss-Seidel, Forward-backward Sweep-based methods, etc. These methods are subject to problems such as poor convergence for EDSs with high R/X ratio branches and huge mathematical/programing burden in some cases. Moreover, in EDS studies such as power loss minimization, energy management, EDS planning/expansion, etc., load flow calculations need to be conducted alongside the required objective function and the related constraints of the study. To solve such models, optimization techniques such as metaheuristic methods, are used in which load flow calculation is conducted in each iteration, bringing extra mathematical burden. To address these limitations, this paper presents a new directly solvable and non-iterative load flow model which is developed using a new bus indexing procedure. A connectivity matrix is introduced to characterize the configuration of EDS and provide a feasible general representation of load flow equations. This enables the proposed modified load flow equations to be mergeable in any type of EDS study as model constraints. Moreover, unlike previous iterative models, it can be solved directly through standard optimization packages in a single shot with no need to further iterative optimization procedures, such as metaheuristic methods. This results in a moderate mathematical and programing burden. The 33-bus system is employed to evaluate the effectiveness of the proposed load flow model. The obtained results are reported and compared with forward-backward sweep-based load flow as a benchmark. Accordingly, it is shown that the proposed model maintains the same outcome without using iterative optimization techniques. Refereed/Peer-reviewed

With the predicted proliferation of Electric Vehicles (EV) worldwide over the next decades, effective EV charging strategies and the associated costs are of utmost interest. In addition to EV charging at home, various countries are introducing public charging facilities for fast charging of EVs. While there are implications of the various charging strategies on the load demand profile of the grid, the cost of charging EVs as well as the overall energy cost for households remain important drivers for the uptake of EVs in countries around the world. This paper investigates these critical aspects in the South Australian context, by examining various EV charging strategies and tariffs. The paper also investigates the impact of the charging strategies on the South Australian load demand profile. Refereed/Peer-reviewed

This paper presents the design and analysis of a novel axial-flux synchronous reluctance motor (AFSynRM). A magnetic equivalent circuit (MEC) model for the proposed axial-flux machine is derived. The feasibility of fabrication is discussed. Finite-element analysis is applied to predict the performance of the proposed motor design. This paper provides a baseline study by comparing the performance of the proposed AFSynRM design with a similar rating radial-flux motor. The motors are designed to have similar volume and both have three rotor barriers. The operating parameters are obtained through static and dynamic FEA. The power, torque, power factor and efficiency of the motors are studied. The saturation and flux distribution in the motor structures are investigated. Refereed/Peer-reviewed

This paper investigates a comparative study on optimal sizing of fuel cell (FC) and battery energy storage (BES) systems coupled with solar photovoltaic (PV) and wind turbine (WT) for a remote area power system. Two system configurations: (1) PV-WT-BES and (2) PV-WT-FC are optimally sized based on actual annual data of wind, solar radiation, ambient temperature and load profile of a remote area community in South Australia. The costs of generation and storage units are considered based on real Australian market prices. The levelized cost of electricity (LCOE) is used as the objective function and appropriate optimization constraints are considered for each system. It is found that the BES technology is more economic than FC system for power system design in Australian remote areas. However, the PV-WT-FC system results in lower dumped energy. Sensitivity analysis is conducted to investigate the effects of the FC system price and its efficiency on LCOE and dumped energy of the system. The option of adding reactor/reformer to the FC system to produce hydrogen from the human waste is also studied in terms of optimal capacities, economic and dumped energy. Refereed/Peer-reviewed

This paper proposes a dual rotor halbach array permanent magnet vernier machine (DRHAVM). Proposed vernier machine demonstrate high power factor with high torque density at low speed which is promising for low speed transportation applications. Proposed permanent magnet vernier machine structure omits necessity of gearbox and directly convert energy to low speed rotation. A comprehensive FEA of proposed DRHAVM including sensitivity analysis, back-EMF, torque density, torque per magnet volume, power factor, core loss, copper loss and efficiency are performed. Additionally, a detailed comparison is conducted between proposed DRHAVM and other types of Vernier machines in the literature. Results display that proposed halbach array vernier machine structure can achieve an appropriate power factor (0.84) and generate higher torque (2850 Nm) at speed rotation of 30 rpm. Refereed/Peer-reviewed

To eliminate the negative-sequence and harmonic currents in the traction system of electric trains, a novel compensatory algorithm is proposed for half-bridge-converter-based railway static power conditioner (HBRPC) by applying impedance-matching (IM) transformers. HBRPC is composed of two half-bridge converters along with two capacitors which makes use of a smaller number of power switches in comparison with conventional compensators. It consequently becomes cheaper than the conventional compensators. This article proposes an algorithm to generate reference current composing of active, reactive, and harmonic current which compensates negative-sequence and harmonic currents on the three-phase side. The simulation results show that the proposed algorithm compensates negative-sequence and harmonic currents in the same range as other compensators, respecting lower expenses.

This paper presents a novel dual-stator linear-vernier permanent-magnet (DSLVPM) machine. The proposed machine utilizes consequent-pole permanent magnets (PMs) rather than the adjacent topology of conventional linear-vernier permanent-magnet (LVPM) machines. The proposed structure of DSLPMV is analyzed and compared against the conventional topology of the LVPM machine. 2D finite-element analysis is utilized to evaluate the electromagnetic aspects and performance parameters of the machines at no-load and full-load conditions. To assess the machines with different PM volume usage, indices such as thrust force per magnet volume (FPMV) and back-EMF per magnet volume are introduced. Simulation results display a better performance of the proposed linear vernier machine in comparison with the typical machine due to the optimized usage of magnets in the consequent-pole configuration.

The proliferation of rooftop solar PV has caused reverse power flow in low voltage distribution networks leading to elevated voltage levels. As the voltage is raised, PV inverters reduce output power to combat voltage rise and may result in inverter shutdowns causing PV curtailment (loss of PV output power). Residential battery storage can store excess PV energy and hence reduce reverse power flow, over voltage and PV curtailment. This study aims to determine the reduction in PV curtailment achieved by the installation of optimally sized residential battery storage. A method to calculate the reduction in PV curtailment and the reduction in corresponding financial losses incurred by PV owners and the energy market is presented. The method is applied to an 11-kV feeder in South Australia along with prevailing feeder and inverter voltage limits. Results show that with the installation of optimally sized battery storage, PV curtailment and the corresponding financial losses can be reduced by more than 50%. Refereed/Peer-reviewed

Flexible ac transmission systems (FACTS) devices are commonly used in power systems to improve the dynamic and static performances of the system. Battery energy storage systems (BESS) are now increasingly being installed in modern power systems for energy arbitrage and ancillary services. This paper describes a technique to improve the transient stability limit of a simple power system using a BESS. A previously developed control strategy to improve stability using STATCOM is applied to control the BESS. The strategy is based on a combination of the maximum and continuous current control. The stability limit, and hence the critical clearing time, obtained using BESS is compared with that obtained using STATCOM. A classical model of the system has been implemented in Matlab Simulink and DIgSILENT PowerFactory software for the analysis. Further analysis has been conducted for a higher order machine model implemented in PowerFactory. The investigations revealed that the BESS is more effective in enhancing the stability limit of the system compared to a STATCOM of the same current rating for both classical and higher order machine models. Refereed/Peer-reviewed

This paper proposes a piecewise-affine decision rule based stochastic optimal power flow approach for reserve dispatch of generators under uncertain demand and renewable energy source generation. The ambiguity set comprises a predefined set of scenarios to capture the plausible uncertain realizations. The objective is to minimize the expected generation cost under those scenarios. A piecewise-affine decision rule is established with auxiliary control parameters to compute the optimal participation of generators depending on the amounts of reserve requirements. Such a reserve dispatch rule would be less conservative compared to the traditional affine decision rule. The results illustrate that the proposed piecewise-affine generation redispatch rule improves the optimality of operation via efficient resource utilization for reserve support. Ministry of Education (MOE) Accepted version Mohasha Isuru and Eddy Y. S. Foo acknowledge the support of the Singapore Ministry of Education Academic Research Fund Tier 1 Grant (MOE2018-T1-002-093).

This paper proposes a simple method of determining the size of excitation capacitance required to buildup a predetermined no load voltage for off-grid operation of a three-phase self-excited induction generator. The method is based on the combination of the principle of L-C resonance and non-linear magnetization characteristic of the generator. For given values of voltage and speed, the magnetizing reactance of the generator is first determined from the solution of a polynomial. The size of the excitation capacitance is then obtained from the principle of L-C resonance. The effectiveness of the proposed method is checked through a more sophisticated generator model where the electrical characteristics are represented by four first-order differential equations. The voltage build-up process in time domain is also investigated through the above model. The results obtained by the proposed method are also verified through an experimental setup consisting of a 1.5-kW induction machine and are found to be in very good agreement. Refereed/Peer-reviewed

This paper proposes a two-stage data-driven methodology in condition monitoring (CM) of wind turbines (WTs). In the first stage, a fast and powerful network, namely a parallel generative adversarial network (PGAN) is proposed to resolve the problem of limited available information by generating artificial data. In the second stage, a robust deep network is designed based on a one-module Gabor filter oriented convolutional neural network and reformulation of a new loss function, namely robust deep Gabor network (RDGN). The experimental dataset of 3MW wind turbines in Ireland is used to verify the effectiveness of the proposed method and demonstrate the superiority of the proposed two-stage method in comparison with several state-of-the-art methods in terms of accuracy and reliability Refereed/Peer-reviewed

In DC electrified railways pantograph electric arcs represent not only a disturbance, but the step change of the pantograph voltage affects power losses directly and indirectly. The available line voltage is reduced if the train is in traction condition, the arc itself is characterized by ohmic power losses, and the triggered oscillating transient responses are characterized by a net power loss. In addition, if arc occurs during braking the arc voltage suddenly increases the pantograph voltage and may interfere with the dissipative braking chopper, reducing the recovered energy. This work presents the model and analysis these phenomena with the support of experimental results related to results for arcs measured on a 3 kV dc line in traction and braking conditions. Keywords—Electric arc, Energy consumption, Power Quality, Power supply transient, Power system transients, Rail transportation, Rolling Stock

This paper presents the comparative study of two permanent-magnet synchronous machines (PMSMs). It investigates the design of two different motors with different pole numbers and explores the pole effect on the performance of parameters. Considered machines in this study are 4-pole and 40-pole SPMMs with same magnet volume on the rotor. Using sizing equations, physical dimensions of the motor are identified, and performance parameter of the motor are extracted via 2D finite-element-analysis. The performance comparison of the machines includes the flux distribution across the geometry, airgap flux density, flux linkage, cogging torque, torque, and motor losses. This comparative study aims to serve useful understanding on the effect of the number of poles on performance of PMSMs for electrical vehicle applications. Refereed/Peer-reviewed

This paper presents design optimization of axialflux induction motors (AFIMs) for electric vehicles. The approach is based on an analytical resolution of the Maxwell's equations inside a set of subdomains. The analytical method is verified against 2D finite-element analysis. It allows detailed modelling and accurate steady-state performance prediction of AFIMs in a very short time (under 1sec), making possible evaluation of numerous design for the optimization. The optimization effortlessly simulates and predict the performance of various AFIM designs based on driving cycles and vehicle limitations. An optimization based on driving cycle of electric vehicles is studied through considering a driving cycle and designing minimum-mass AFIMs capable of fulfilling it. It is observed that driving-cycle based motor designs benefit from mass reduction and ensures the feasibility of all operating conditions Refereed/Peer-reviewed

Measuring the efficiency map of an electric machine is a complex and time-consuming process. This paper examines means for estimating the efficiency map of PM machines using a reduced number of tests. It uses a modified saturation model which gives good results even in the presence of high cross-saturation. It also models the iron loss variation with load and speed using curve fitting in the constant torque and power regions based on a limited number of load points. Both the flux-linkage and iron loss methods are applicable to finite element (FE) simulation and have the capability of being generalized to other electrical machine types. The results are verified both with FE simulation and experimental tests. Refereed/Peer-reviewed

Step-up DC-DC converters play a determinative role in traction vehicles by providing the required DC- link voltage for traction drives supplied by battery packages or fuel cells. Bi-directional converters are preferred to be used in the construction of battery-based traction drives to charge batteries when drivetrains system work in the generation mode. However, due to the fact that fuel-cells cannot be charged electrically, the bi-directional structure is not required for fuel cell-based traction drives. The proposed step up converter benefits from the resonance between its elements to provide the soft- switching condition for the converter switches. The resonance assists to transmit high power from input and to output while there is no high-frequency transformer or coupled inductor in the converter topology. In brief, the generated resonance not only leads to a high power density converter but also result in a soft-switching which means higher efficiency in comparison to previously introduced high-step up converters working in hard switching condition. So, the proposed high-efficiency high power density high step-up (HHH) converter could be employed as a reliable DC-DC converter for traction vehicles supplied by fuel cells. Refereed/Peer-reviewed

Self-sustainable autonomous microgrids with 100% converter-connected generation are most suitable for powering remote areas without impacting the environment. This work focuses on the regulation aspect of such islanded microgrids by sizing and controlling energy storage systems to support the renewable energy-based microgrids. Each generation unit in the microgrid acts as a voltage-source that contributes to frequency and voltage regulation, wherein the regulation is achieved by a modified droop control that emulates the inertia property of synchronous machines. The size of energy storage systems that support this task is estimated based on the allowable regulation standard and control scheme. The designed storage and control are validated with the help of real-time simulation. Accepted version

In this paper, two-dimensional (2D) analytical model is proposed for axial-flux induction motor (AFIMs) based on the solution of magnetic vector potential equations, which also considers the saturation's effect on the performance of the machine. The model is developed from the quasi- magneto-static Maxwell's equations, which are analytically solved. It considers a uniform distribution of current density in the rectangular shaped rotor/stator slots. By computing the magnetic energy of the machine, this method obtains the inductances and uses them to assess the design performance parameters. The accuracy of the 2-D analytical solutions is verified against those obtained from the finite element method (FEM). The suggested model is generic and applicable to AFIMs with any number of poles and phases. A case study on optimization axial-flux induction motor is presented to evaluate the performance of the proposed model. The proposed method can replace the FEM in designing and optimization of the AFIMs. Refereed/Peer-reviewed

This paper presents a Zero-Voltage-Detector (ZVD) circuit for buck converters working in discontinuous conduction mode (DCM). A novel comparator with pre-amplification property is proposed to provide fast sensing and comparison to optimize the switching timing of power transistors, hence minimizing the power losses caused by the reverse inductor current. The proposed DCM buck converter is fabricated using 0.18um CMOS technology with a chip area of 0.9mm 2 . The simulated sensing delay of the proposed ZVD is only about 6ns. It achieves > 85% power efficiency for load currents of > 10mA when the input and output voltages are 3.3V and 2.4V respectively. Agency for Science, Technology and Research (A*STAR) Economic Development Board (EDB) Nanyang Technological University The author would like to acknowledge MediaTek and EDB for JIP scholarship, and funding support from NTU-A*STAR Silicon Technologies Centre of Excellence under the program grant No. 11235100003.

In this paper, an active shaping method of the capacitor voltage for a cascaded H-bridge (CHB) Iow-capacitance static synchronous compensator (LC-StatCom) is introduced. The traditional LC-StatCom is able to operate with large capacitor voltage ripples when it is operating with rated current. However, as the current is reduced below rated current, voltage ripple on the capacitors decreases. Decreasing the current therefore removes the advantages of the LC-StatCom such as better current quality and reduced switching losses. The active shaping method aims to keep consistent large voltage ripple on the capacitor using a simple boost converter cell to inject an appropriate auxiliary capacitor current. Simulation results are provided to confirm the performance of the proposed CHB-StatCom system. Accepted version

With the still increasing penetration of renewable energy, the power system is being more power electronics based and digital. The diversity of grid-connected power converters with various control strategies complicates the analysis of system dynamics, when various and detailed converter models are adopted. This paper thus proposes a universal model of grid-connected converters that can reflect the essential power-internal voltage characteristics. With that, the diversity of converter outer controllers may be discarded, as their dynamics can be represented by the deviation of active and reactive power. In the proposed model, the transfer functions from the converter output power to the internal voltage and to the Phase-Locked Loop (PLL) output frequency are obtained, enabling the exploration of the stability of the internal voltage and the PLL performance. An example system is adopted to demonstrate the proposed model and simulated in PSCAD/EMTDC. The results show that the model is accurate to reflect the impact of controller parameters on the power-internal voltage stability of the entire system. Accepted version

The use of film capacitors to substitute traditionally utilized electrolytic capacitors is a well-known trend in the power electronics industry as it significantly increases the overall reliability of the system. Control challenges arise due to the reduced capacitance of film capacitors with similar volume and weight as electrolytic capacitors. To address these control challenges, previous works have shown the good accuracy and fast dynamic performance of analytical filters to remove low-frequency capacitor voltage ripples. However, as these filters are based on an idealized mathematical model of the system, some harmonic content remains in the filtered signal due to discrepancies between the real system and utilized model, which deteriorates the overall performance of the system. In this paper, an improved adaptive filtering scheme for a low-capacitance static compensator (LC-StatCom) is proposed. The scheme mitigates both time delays and harmonic-contamination in the outer capacitor voltage control loop. Hence, the proposed solution allows the use of a high bandwidth controller and the generation of a current reference free of low-frequency harmonics. The effectiveness of the proposed approach is validated via simulation results on a seven-level 0.35-kVA single-phase LC-StatCom. The results demonstrate that the proposed solution overcomes drawbacks of previous schemes in terms of time response and filtering performance in steady-state operation. Accepted version

This paper proposes two suitable converter topologies for more electric aircraft (MEA) starter generator application. The commercially available silicon (Si) and silicon carbide (SiC) semiconductor devices are also sourced to fit the given design requirements. Different possible configurations of the evaluated converter topologies are discussed. The rectifier design methodology is presented, considering device loss distribution, converter efficiency, required heatsink thermal resistance, dc-link capacitance sizing, delivered power quality and estimated gravimetric power density. The quantitative evaluations have demonstrated the beneficial needs of driving multilevel converter at higher switching frequency operation using SiC semiconductor technology. National Research Foundation (NRF) Accepted version This work was conducted within the Rolls-Royce@NTU Corporate Lab with support from the National Research Foundation (NRF) Singapore under the Corp Lab@University Scheme.

In this paper, a new modulation technique is presented which aims to enhance the natural voltage balancing capability of neutral-point-clamped converters. The traditional carrier-based pulsewidth modulation technique with zerosequence injection faces some drawbacks, namely, its inability to balance initial capacitor voltage imbalances quickly and the divergence of the capacitor voltages in the presence of nonlinear loads with even harmonics. This paper aims to find a trade-off between voltage balance performance and switching losses by reducing the difference between the average capacitor voltages without incorporating any external circuitry. A reference neutralpoint (NP) current is generated using the average difference between the capacitor voltages. Depending on the reference NP current and predicted NP current, appropriate duty cycles are applied to switch the three phases. These duty cycles are directly linked to the voltage unbalance between the capacitor voltages and thus provides the necessary ‘push’ to mitigate deviations in natural balancing characteristics. To validate the proposed modulation technique, simulation results are presented for linear loads as well as for nonlinear loads with even harmonics. Accepted version