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Journal articleArana C, Evangelou SA, Dini D, 2015, , IEEE/ASME Transactions on Mechatronics, Vol: PP, ISSN: 1083-4435
This paper explores the application of the recently introduced Series Active Variable Geometry Suspension (SAVGS) to the control of chassis attitude motions and the directional response of cars. A co-design methodology, involving a component dimensioning framework and a multi-objective control scheme, is developed to maximize the SAVGS control capabilities while respecting vehicle and actuator design constraints. The dimensioning framework comprises: a steady-state mathematical model based on the principle of virtual work; a parameter sensitivity analysis that sheds light on the dependencies that exist between the properties of the passive suspension, the SAVGS and the chassis; and an algorithm to size the main SAVGS components for any given vehicle and steady-state performance objectives. The general multi-objective control scheme is presented for general application, and the particular case of combined chassis attitude control and overturning couple distribution control is developed in detail. The proposed scheme is subsequently applied to a high performance sports car and a fully laden SUV and tested under a wide range of operating conditions through the simulation of standard open-loop maneuvers. Results demonstrate the SAVGS potential to favorably regulate the attitude motions and directional response in both vehicle classes.
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Conference paperUstinova T, Woolf M, Ortega Calderon JE, et al., 2015,
Analysis of Customers' Performance in Industrial & Commercial Demand Side Response Trials
, 23rd International Conference on Electricity Distribution (CIRED 2015) -
Conference paperSchofield J, Carmichael R, Tindemans S, et al., 2015,
Experimental validation of residential consumer responsiveness to dynamic time-of-use pricing
, 23rd International Conference on Electricity Distribution (CIRED)This paper describes the first analysis from the LowCarbon London (LCL), residential dynamic time-of-use(dToU) pricing trial that took place in the London areaduring 2013. High price induced peak reductions fornetwork constraint management are investigatedalongside the temporal availability of demand responsefor supply balancing. By examining both these use caseswe identify potential conflicts between network andsystem objectives. Demand response results are stratifiedby a ranking metric for engagement with the dToU tariffas well as household occupancy and socio-economicclassification.
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Journal articlePapadaskalopoulos D, Strbac G, 2015, , IEEE Transactions on Smart Grid, Vol: 7, Pages: 1137-1146, ISSN: 1949-3061
Price-based management of distributed energy resources within microgrids is continuously gaining ground due to scalability and privacy limitations of centralized architectures. However, the concentration of flexible loads' response to the lowest-priced periods yields inefficient solutions. A previously proposed measure imposing a flexibility restriction on flexible loads might raise acceptability and feasibility concerns by the users. This paper develops a novel fully price-based approach where this hard restriction is replaced by a soft nonlinear price signal. This signal is customized to the operating properties of the different flexible load types by penalizing the square of the demand and the duration of cycle delay of loads with continuously adjustable power levels and deferrable cycles, respectively. This approach is shown to produce more efficient solutions than the flexibility restriction measure for both types of loads. For the latter type, randomization of the nonlinear prices brings additional benefits, especially in low operating diversity cases. These contributions are supported by case studies on a microgrid test system with electric vehicles and wet appliances used as representative examples of the above flexible load types.
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Journal articleTrutnevyte E, Strachan N, Dodds PE, et al., 2015, , Energy Policy, Vol: 85, Pages: 170-181, ISSN: 1873-6777
Affordability and costs of an energy transition are often viewed as the most influential drivers. Conversely, multi-level transitions theory argues that governance and the choices of key actors, such as energy companies, government and civil society, drive the transition, not only on the basis of costs. This paper combines the two approaches and presents a cost appraisal of the UK transition to a low-carbon electricity system under alternate governance logics. A novel approach is used that links qualitative governance narratives with quantitative transition pathways (electricity system scenarios) and their appraisal. The results contrast the dominant market-led transition pathway (Market Rules) with alternate pathways that have either stronger governmental control elements (Central Co-ordination), or bottom-up proactive engagement of civil society (Thousand Flowers). Market Rules has the lowest investment costs by 2050. Central Co-ordination is more likely to deliver the energy policy goals and possibly even a synergistic reduction in the total system costs, if policies can be enacted and maintained. Thousand Flowers, which envisions wider participation of the society, comes at the expense of higher investment and total system costs. The paper closes with a discussion of the policy implications from cost drivers and the roles of market, government and society.
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Journal articleAgalgaonkar Y, Pal BC, Jabr RA, 2015, , IEEE Transactions on Sustainable Energy, Vol: PP, Pages: 1-10, ISSN: 1949-3037
Variable over voltage, excessive tap counts andvoltage regulator (VR) runaway condition are major operationalchallenges in distribution network while accommodating generationfrom Photovoltaics (PVs). The conventional approach toachieve voltage control based on off-line simulation for voltage setpoint calculation does not consider forecast errors. In this work,a stochastic optimal voltage control strategy is proposed whileconsidering load and irradiance forecast errors. Stochastic operationalrisks such as overvoltage and VR runaway are definedthrough a chance constrained optimization (CCO) problem. Thisclassical formulation to mitigate runaway is further improvedby introducing a stochastic index called the Tap Tail Expectation.Operational objectives such as power losses and excessive tapcount minimization are considered in the formulation. A samplingapproach is proposed to solve the CCO. Along with other voltagecontrol devices, the PV inverter voltage support features arecoordinated. The simulation study is performed using a realisticdistribution system model and practically measured irradianceto demonstrate the effectiveness of the proposed technique.The proposed approach is a useful operational procedure fordistribution system operators. The approach can minimize feederpower losses, avoid voltage violations and alleviate VR runaway.
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Journal articleScarciotti G, Praly L, Astolfi A, 2015, , IEEE Transactions on Automatic Control, Vol: 61, Pages: 648-661, ISSN: 1558-2523
Several theorems, inspired by the Krasovskii-LaSalle invariance principle, to establish “lim inf” convergence results are presented in a unified framework. These properties are useful to “describe” the oscillatory behavior of the solutions of dynamical systems. The theorems resemble “lim inf” Matrosov and Small-gain theorems and are based on a “lim inf” Barbalat's Lemma. Additional technical assumptions to have “lim” convergence are given: the “lim inf”/“lim” relation is discussed in-depth and the role of some of the assumptions is illustrated by means of examples.
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Conference paperTrovato V, Tindemans SH, Strbac G, 2015, , 2015 IEEE 15th International Conference on Environment and Electrical Engineering (EEEIC), Publisher: IEEE, Pages: 1003-1008
Future power systems will have to integrate large amounts of wind and solar generation to drastically reduce CO2 emissions. Achieving this goal comes at the cost of a reduced level of the system inertia and an increased need for fast response services. Previous research has shown the effectiveness of thermostatically controlled loads (TCLs) providing frequency response, and the ability to accurately control the aggregate power consumption of TCLs. In this paper, we explore the design space of frequency response patterns of flexible TCLs. Two distinct frequency response implementations are presented. The first makes the TCLs' power consumption a linear function of system frequency and/or its rate of change; in the second, TCLs respond to a frequency event tracking a pre-programmed reference power profile. Computer simulations illustrate strengths and weaknesses of the proposed implementations in the context of the GB 2020 Gone Green scenario.
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Journal articleMueller MA, Angeli D, Allgoewer F, 2015, , IEEE Transactions on Automatic Control, Vol: 60, Pages: 1671-1676, ISSN: 1558-2523
In this paper, we study a dissipativity property which was recently used in several results on economic model predictive control to ensure optimal operation of a system at steady-state as well as stability. In particular, we first investigate whether this dissipativity property is not only sufficient, but also necessary for optimal steady-state operation. In the most general case, this is not true; nevertheless, under an additional controllability assumption, we show that dissipativity is in fact necessary. Second, we provide a robustness analysis of the dissipativity property with respect to changes in the constraint set, which can result in a change in the considered supply rate.
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Journal articleChen HT, Tan S-C, Hui SYR, 2015, , IEEE TRANSACTIONS ON POWER ELECTRONICS, Vol: 30, Pages: 3334-3344, ISSN: 0885-8993
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- Citations: 32
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Conference paperKwan CH, Kkelis G, Aldhaher S, et al., 2015, , Pages: 1-7
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Journal articleChen B, Pin G, Ng WM, et al., 2015, , International Journal of Adaptive Control and Signal Processing, Vol: 29, Pages: 1591-1608, ISSN: 1099-1115
The problem of estimating the amplitude, frequency, and phase of an unknown sinusoidal signal from a noisy-biased measurement is addressed in this paper by a family of parallel prefiltering schemes. The proposed methodology consists in using a pair of linear filters of specified order to generate a suitable number of auxiliary signals that are used to estimate—in an adaptive way—the frequency, the amplitude, and the phase of the sinusoid. Increasing the order of the prefilters improves the noise immunity of the estimator, at the cost of an increase of the computational complexity. Among the whole family of estimators realizable by varying the order of the filters, the simple parallel prefilters of orders 2 + 2 and 3 + 3 are discussed in detail, being the most attractive from the implementability point of view. The behavior of the two algorithms with respect to bounded external disturbances is characterized by input-to-state stability arguments. Finally, the effectiveness of the proposed technique is shown both by comparative numerical simulations and by a real experiment addressing the estimation of the frequency of the electrical mains from a noisy voltage measurement.
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Conference paperPipelzadeh Y, Moreno Vieyra R, Chaudhuri B, et al., 2015,
Role of Smart Grid Technology and Corrective Control in Enhancing Network Capacity Utilisation in Great Britain with HVDC links
, CIGRE SYMPOSIUM, Publisher: CIGREA range of advanced, technically effective and economically efficient corrective (or postfault) actions has been proposed to release latent transmission network capacity of the existing system and thus reduce network congestion and accommodate increased connection of low-carbon generation. Although the increased use of corrective control that can manage post-fault transmission overloads has proven to be clearly beneficial from an economic perspective, there are concerns related to the consequent stability (angular and voltage) of transmission systems. In this context, this paper demonstrates various corrective control measures (that can be undertaken by Special Protection Schemes –SPS–) including rapid response of generation and demand against double line outages (N-2) under extremely high power transfer conditions. To demonstrate these benefits, case studies are carried out on a detailed (full) dynamic system model of the Great Britain (GB) transmission network in DIgSILENT, which includes the Western Line-Commutated Converter based High Voltage Direct Current (LCC-HVDC). The value of corrective control measures, based on generationand demand response accompanied by Transient Assistive Measures (TAM) such as rapid changes in DC power order to improve system stability is demonstrated. It is shown that such measures can significantly increase the power transfers through the England-Scotland inter-connector while maintaining N-2 security. Moreover, it is demonstrated that although a generation ramp up/down response is naturally slower than a step-change tripping action over generation and demand (tripping actions are preferred in SPS) and therefore more prone to transient instability problems, generation-only operational measures can be deployed to deal with double circuit (N-2) outages under extremely high power transfers, given that the right portfolio of TAM is deployed. Thus TAM can effectively enhance the set of correctivecontrol measures considered b
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Journal articleNanchian S, Majumdar A, Pal BC, 2015, , IEEE Transactions on Smart Grid, Vol: PP, Pages: 1-11, ISSN: 1949-3061
This paper proposes a method for three-phase stateestimation (SE) in power distribution network including on-loadtap changers (OLTC) for voltage control. The OLTC tap positionsare essentially discrete variables from the SE point ofview. Estimation of these variables in SE presents a formidablechallenge. The proposed methodology combines discrete andcontinuous state variables (voltage magnitudes, angles, and tappositions). A hybrid particle swarm optimization (HPSO) isapplied to obtain the solution. The method is tested on standardIEEE 13- and 123-bus unbalanced test system models. Theproposed algorithm accurately estimates the network bus voltagemagnitudes and angles, and discrete tap values. The HPSO-basedtap estimation provides a more accurate estimation of losses inthe network, which helps in fair allocation of cost of losses inarriving at overall cost of electricity
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Journal articleStrbac G, Hatziargyriou N, Lopes JP, et al., 2015, , IEEE Power & Energy Magazine, Vol: 13, Pages: 35-43, ISSN: 1540-7977
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- Citations: 120
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Journal articleTahir F, Jaimoukha IM, 2015, , IEEE Transactions on Automatic Control, Vol: 60, Pages: 1416-1421, ISSN: 0018-9286
We propose a novel algorithm to compute low-complexity polytopic robust control invariant (RCI) sets, along with the corresponding state-feedback gain, for linear discrete-time systems subject to norm-bounded uncertainty, additive disturbances and state/input constraints. Using a slack variable approach, we propose new results to transform the original nonlinear problem into a convex/LMI problem whilst introducing only minor conservatism in the formulation. Through numerical examples, we illustrate that the proposed algorithm can yield improved maximal/minimal volume RCI set approximations in comparison with the schemes given in the literature.
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Conference paperAldhaher S, Kkelis G, Yates DC, et al., 2015, , Pages: 1-4
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Journal articlePalladino M, Vinter RB, 2015, , Discrete and Continuous Dynamical Systems, Vol: 35, Pages: 4573-4592, ISSN: 1553-5231
Relaxation refers to the procedure of enlarging the domain of a variational problem or the search space for the solution of a set of equations, to guarantee the existence of solutions. In optimal control theory relaxation involves replacing the set of permissible velocities in the dynamic constraint by its convex hull. Usually the infimum cost is the same for the original optimal control problem and its relaxation. But it is possible that the relaxed infimum cost is strictly less than the infimum cost. It is important to identify such situations, because then we can no longer study the infimum cost by solving the relaxed problem and evaluating the cost of the relaxed minimizer. Following on from earlier work by Warga, we explore the relation between the existence of an infimum gap and abnormality of necessary conditions (i.e. they are valid with the cost multiplier set to zero). Two kinds of theorems are proved. One asserts that a local minimizer, which is not also a relaxed minimizer, satisfies an abnormal form of the Pontryagin Maximum Principle. The other asserts that a local relaxed minimizer that is not also a minimizer satisfies an abnormal form of the relaxed Pontryagin Maximum Principle.
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Journal articleJones BL, Heins PH, Kerrigan EC, et al., 2015, , Journal of Fluid Mechanics, Vol: 769, Pages: 687-722, ISSN: 0022-1120
This paper addresses the problem of designing low-order and linear robust feedback controllers that provide a priori guarantees with respect to stability and performance when applied to a fluid flow. This is challenging, since whilst many flows are governed by a set of nonlinear, partial differential–algebraic equations (the Navier–Stokes equations), the majority of established control system design assumes models of much greater simplicity, in that they are: firstly, linear; secondly, described by ordinary differential equations (ODEs); and thirdly, finite-dimensional. With this in mind, we present a set of techniques that enables the disparity between such models and the underlying flow system to be quantified in a fashion that informs the subsequent design of feedback flow controllers, specifically those based on the H∞ loop-shaping approach. Highlights include the application of a model refinement technique as a means of obtaining low-order models with an associated bound that quantifies the closed-loop degradation incurred by using such finite-dimensional approximations of the underlying flow. In addition, we demonstrate how the influence of the nonlinearity of the flow can be attenuated by a linear feedback controller that employs high loop gain over a select frequency range, and offer an explanation for this in terms of Landahl’s theory of sheared turbulence. To illustrate the application of these techniques, an H∞ loop-shaping controller is designed and applied to the problem of reducing perturbation wall shear stress in plane channel flow. Direct numerical simulation (DNS) results demonstrate robust attenuation of the perturbation shear stresses across a wide range of Reynolds numbers with a single linear controller.
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Journal articleYin J, Lin D, Lee CK, et al., 2015, , IEEE Transactions on Power Electronics, Vol: 31, Pages: 2510-2517, ISSN: 0885-8993
This paper describes a method for monitoring multiple loads from the front end of a wireless power transfer system without using any wireless communication systems. A mathematical approach based on scanning the frequency around the resonant frequency has been developed for deriving the load conditions. The proposal requires only information of the input voltage and current, thereby eliminating the requirements of using wireless communication systems for feedback control. The proposal has been practically confirmed in hardware prototype with good results.
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Journal articleMok KT, Tan SC, Hui SYR, 2015, , IEEE Transactions on Power Electronics, Vol: 31, Pages: 1216-1229, ISSN: 1941-0107
In this paper, a radial-chordal decomposition (RCD) technique is proposed to decouple the power angle and voltage control of a smart load based on the use of electric springs (ES). This RCD method is mathematically presented. A detailed comparison between the existing ES control schemes and the proposed RCD approach highlights its decoupling feature and merit on achieving multiple functionalities with a single ES. This RCD control method has been tested on a 2-kW small-scale power system. Simulation and experimental results confirmed that the power factor of the ES-integrated smart load can be improved by the chordal control while the mains voltage can be regulated by the radial control. It has also been demonstrated that the radial and chordal control can work simultaneously and independently.
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Conference paperDas HB, Evangelou SA, Jabez Dhinagar S, 2015, , SAE 2015 World Congress & Exhibition, Publisher: SAE International
The objective of this paper is to estimate characteristics parameters of two wheeler powertrain with simulated vehicle model. The evaluation is applied to define required characteristics for future motor integrated powertrain. The main parameters for the characteristics matrix are Fuel consumption and NOx gas emission. In the 1st phase of work, a mathematical model for the complete powertrain is developed using suitable modelling approach for different sub-modules of the complete system. The objectives of the model are, to simulate dynamic power-flow from the engine to wheel and to simulate NOx gas emission. The powertrain model consists of a carburetted spark ignition (S.I) engine and gear transmission system. The S.I engine model is capable of simulating dynamic torque output of engine as well as the NOx gas emission. The model is experimentally compared with available test data of production ready engine from TVS Motor Company, India. The dynamic effects of change of ignition timing and fueling on torque output and NOx gas emissions are simulated based on this model and discussed on the paper. The paper adapted two types of transmission model, one with Continuous Variable Transmission (CVT) and other one with Fixed Geared Transmission. The mathematical model for the CVT system is developed to capture automatic gear shift actuation and power transfer to the wheel. The model simulates the toque control system of the driven pulley as well as speed control system of the drive pulley. The mathematical model for the fixed gear ratio system with wet clutch system is proposed to simulate the manual gear based powertrain. The above mentioned model demands computationally intensive resources due to presence of higher order dynamics, mathematical discontinuity and non-linear functions. So this model is not suitable for control design application. In 2nd phase of work, the model is converted to lower complexity control oriented model by using feed-forward approach. The contr
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Conference paperMeisel J, Shabbir W, Evangelou SA, 2015,
Using measurable physical input variables, an implementable control algorithm for parallel architecture plug-in and non-plug-in hybrid electric vehicle (PHEV and HEV) powertrains is presented. The control of the electric drive is based on an algebraic mapping of the accelerator pedal position, the battery state-of-charge (SOC), and the vehicle velocity into a motor controller input torque command. This mapping is developed using a sequential linearization control (SLC) methodology. The internal combustion engine (ICE) control uses a modified accelerator pedal to throttle plate angle using an adjustable gain parameter that, in turn, determines the sustained battery SOC. Searches over an admissible control space or the use of pre-defined look-up tables are thus avoided. Actual on-road results for a Ford Explorer with a through-the-road (TTR) hybrid powertrain using this control methodology are presented. In addition, Matlab-based simulation results for PHEVs and HEVs using this single control algorithm are presented employing a model of the Explorer. These results show the gasoline consumption and SOC over 48 repeated cycles of three common driving schedules. Further studies of acceleration performance illustrate the trade-off of minimizing gasoline consumption vs. higher performance using more gasoline. All-electric range (AER) vs. battery capacity is also presented as well as the fuel consumption and final SOC for two PHEV control strategies.
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Journal articleTeng F, Pudjianto D, Strbac G, et al., 2015, , Proceedings of the ICE - Energy, Vol: 168, Pages: 107-117, ISSN: 1751-4223
This paper assesses the value of distributed energy storage and informs the business case for its multiple applications in the UK electricity system. In contrast to earlier studies that focus on the benefits of energy storage for system operation and development, this work analyses the value that it may deliver to the owner. For this purpose, three models are proposed and applied to analyse the benefit of energy storage with applications in energy and ancillary service markets, revenue maximisation in the context of feed-in tariffs and reduction of carbon dioxide emissions. A large set of studies is carried out to quantify the commercial and emissions benefits of energy storage for those applications. Sensitivity analysis across various scenarios is performed to understand the key drivers for the value of energy storage and how it is affected by energy storage parameters and other factors such as network constraints, prices of energy and ancillary services, and inherent energy system characteristics. A review of current and near-term storage technology costs and functionality is also presented.
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Journal articleMylvaganam T, Sassano M, Astolfi A, 2015, , IEEE Transactions on Automatic Control, Vol: 60, Pages: 950-965, ISSN: 0018-9286
In this paper, a class of infinite-horizon, nonzero-sum differential games and their Nash equilibria are studied and the notion of ε α -Nash equilibrium strategies is introduced. Dynamic strategies satisfying partial differential inequalities in place of the Hamilton-Jacobi-Isaacs partial differential equations associated with the differential games are constructed. These strategies constitute (local) ε α -Nash equilibrium strategies for the differential game. The proposed methods are illustrated on a differential game for which the Nash equilibrium strategies are known and on a Lotka-Volterra model, with two competing species. Simulations indicate that both dynamic strategies yield better performance than the strategies resulting from the solution of the linear-quadratic approximation of the problem.
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Conference paperBachtiar V, Kerrigan EC, Moase WH, et al., 2015, , 10th Asian Control Conference (ASCC)
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Journal articleFeldman J, Hanrahan BM, Misra S, et al., 2015, , JOURNAL OF MICROELECTROMECHANICAL SYSTEMS, Vol: 24, Pages: 289-299, ISSN: 1057-7157
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- Citations: 7
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Journal articleBowden JA, Burrow SG, Cammarano A, et al., 2015, , IEEE-ASME TRANSACTIONS ON MECHATRONICS, Vol: 20, Pages: 603-610, ISSN: 1083-4435
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- Citations: 34
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Journal articleLiu Y, Van Schijndel J, Longo S, et al., 2015, , IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS, Vol: 51, Pages: 1203-1215, ISSN: 0018-9251
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- Citations: 15
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Conference paperZhang X, Green TC, 2015, , 2015 IEEE Applied Power Electronics Conference and Exposition (APEC), Publisher: IEEE, Pages: 1743-1750
This paper presents a family of modular multilevel converters (MMCs) for high step ratio dc-dc conversion. The modular multilevel unidirectional step-down dc-dc converter topologies are presented. The high step-up ratio bidirectional modular multilevel dc-dc converter is also provided. Operation principle and analysis of the bidirectional dc-dc converter are shown, and verified by experimental results with a conversion ratio of 1 : 10. The proposed converters achieve high voltage step ratio depending on the number of sub-modules and the charging ratio.
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