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Journal articleHui SYR, Lee CK, Wu F, 2012, , IEEE Transactions on Smart Grid, Vol: 3, Pages: 1552-1561, ISSN: 1949-3053
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Journal articleJerez JL, Ling KV, Constantinides GA, et al., 2012, , IET Control Theory and Applications, Vol: 6, Pages: 1029-1041, ISSN: 1751-8652
Model predictive control (MPC) is an optimisation-based scheme that imposes a real-time constraint on computingthe solution of a quadratic programming (QP) problem. The implementation of MPC in fast embedded systems presents newtechnological challenges. In this paper we present a parameterised field-programmable gate array implementation of acustomised QP solver for optimal control of linear processes with constraints, which can achieve substantial acceleration overa general purpose microprocessor, especially as the size of the optimisation problem grows. The focus is on exploiting thestructure and accelerating the computational bottleneck in a primal-dual interior-point method. We then introduce a new MPCformulation that can take advantage of the novel computational opportunities, in the form of parallel computational channels,offered by the proposed pipelined architecture to improve performance even further. This highlights the importance of theinteraction between the control theory and digital system design communities for the success of MPC in fast embedded systems.
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Journal articleBuchstaller D, Kerrigan EC, Constantinides GA, 2012, , IET Control Theory and Applications, Vol: 6, Pages: 1071-1079
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Journal articleCasagrande D, Sassano M, Astolfi A, 2012, , IEEE CONTROL SYSTEMS MAGAZINE, Vol: 32, Pages: 74-91, ISSN: 1066-033X
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- Citations: 19
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Journal articleAhmed S, Kerrigan EC, Jaimoukha IJ, 2012, , IEEE Transactions on Signal Processing, Vol: 60, Pages: 3942-3952, ISSN: 1053-587X
This paper presents a tractable method for solving a robust attitude estimation problem, based on a weighted least squares approach with nonlinear constraints. Attitude estimation requires information of a few vector quantities, each obtained from both a sensor and a mathematical model. By considering the modeling errors, measurementnoise, sensor biases and offsets as infinity-norm bounded uncertainties, we formulate a robust optimization problem, which is non-convex with nonlinear cost and constraints. The robust min-max problem is approximated with a non-convex minimization problem using an upper bound. A new regularization scheme is also proposed to improve the robust performance. We then use semidefinite relaxation to convert the suboptimal problem with quadratic cost and constraints into a tractable semidefinite program with a linear objective function and linear matrix inequality constraints. We also show how to extract the solution of the suboptimal robust estimation problem from the solution of the semidefinite relaxation. Further, a mathematical proof supported by numerical results is presented stating the gap between the suboptimal problem and its relaxation is zero under a given condition, which is mostly true in real life scenarios. The usefulness of the proposed algorithm in the presence of uncertainties is evaluated with the helpof examples.
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Conference paperPipelzadeh Y, Chaudhuri B, Green TC, 2012,
Inertial Response from Remote Offshore WindFarms Connected Through VSC-HVDC Links: ACommunication-less Scheme
, IEEE Power and Energy Society General Meeting 2012A communication-less scheme that allows remoteoffshore wind farms connected through HVDC links to participatein primary frequency control and contribute to systeminertia is discussed in this paper. As a HVDC link decouples theoffshore system from the onshore side, real-time communicationof onshore frequency is normally required for the primaryfrequency control loop of the wind farms. Dependance on remotecommunication which could be unreliable at times is a problem.To obviate the need for communication, appropriate droopcontrol on the offshore and onshore converters is used in thispaper to translate the variation in onshore frequency to anequivalent variation on the offshore end. Thus the need for communicatingonshore frequency to the offshore side is mitigatedwhich ensures reliable operation. Such a communication-lessscheme is compared against the conventional approach involvingremote communication of onshore grid frequency to the windfarm site. Along side physical and analytical justification, a casestudy is presented to demonstrate that the communication-lessscheme performs similar to the conventional one in terms ofreducing grid frequency variations.
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Conference paperSegundo Sevilla FR, Jaimoukha I, Chaudhuri B, et al., 2012,
Fault-tolerant Wide-area Control for PowerOscillation Damping
, IEEE PES General Meeting 2012 -
Journal articleLin D, Yan W, Zissis G, et al., 2012, , IET SCIENCE MEASUREMENT & TECHNOLOGY, Vol: 6, Pages: 229-237, ISSN: 1751-8822
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- Citations: 4
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Journal articleLuis Dominguez-Garcia J, Gomis-Bellmunt O, Trilla-Romero L, et al., 2012, , COMPUTERS & MATHEMATICS WITH APPLICATIONS, Vol: 64, Pages: 102-114, ISSN: 0898-1221
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- Citations: 37
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Conference paperKuenzel S, Kunjumuhammed LP, Pal BC, et al., 2012,
Wind Power Plants Inertial Response Capability Considering Wake Effect
, 11th International Workshop on Large-Scale Integration of Wind Power into Power Systems as well as on Transmission Networks for Offshore Wind Power Plants, Lisbon -
Journal articleSu Y, Liu X, Lee CK, et al., 2012, , IEEE TRANSACTIONS ON POWER ELECTRONICS, Vol: 27, Pages: 3050-3056, ISSN: 0885-8993
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- Citations: 31
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Conference paperPinuela M, Yates DC, Mitcheson PD, et al., 2012,
Current State of Research at 天美传媒 in RF Harvesting and Inductive Power Transfer
, 2nd International Workshop on Wireless Energy Transport and Harvesting, Pages: 1-4This paper presents simulation and experimental results for ambient RF energy harvesting and Inductive Power Transfer systems. End-to-end and dc-load efficiency measurements and calculations were performed to demonstrate the capabilities of both systems, respectively. An RF spectral survey was conducted across all the 270 underground stations in London. DTV, GSM900, GSM1800 and 3G were selected as the highest contributors and single banded rectennas were fabricated for all frequencies. Ground level measurements demonstrate that more than 50 stations have suitable channel power levels per band to allow ambient RF energy harvesting. Efficiencies of up to 40% were achieved with a single banded rectenna operating at GSM 900, and efficiencies higher than 20% were achieved for TV and 3G. Furthermore a high frequency, semi-resonant Class-E driver was used to transfer 60 W of power across a 30 cm distance with a dc-load efficiency of 66%.
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PatentGREEN TC, MERLIN MMC, OKAEME N, et al., 2012,
MODULAR MULTILEVEL CONVERTER
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Journal articleBianchi FD, Egea-Alvarez A, Junyent-Ferre A, et al., 2012, , CONTROL ENGINEERING PRACTICE, Vol: 20, Pages: 539-546, ISSN: 0967-0661
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- Citations: 11
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Journal articleAngeli D, Kountouriotis P-A, 2012, , IEEE TRANSACTIONS ON CONTROL SYSTEMS TECHNOLOGY, Vol: 20, Pages: 581-592, ISSN: 1063-6536
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- Citations: 142
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Conference paperVasilakos C, Strbac G, Pudjianto D, et al., 2012,
European Transmission Tariff Harmonization: A Modeling Analysis
, 9th International Conference on the European Energy Market EEM12 -
Journal articleFalugi P, Kountouriotis P-A, Vinter RB, 2012, , IEEE Transactions on Automatic Control, Vol: 57, Pages: 2778-2788, ISSN: 1558-2523
Surge tanks are units employed in chemical processing to regulate the flow of fluids between reactors. A notable feature of surge tank control is the need to constrain the magnitude of the Maximum Rate of Change (MROC) of the surge tank outflow, since excessive fluctuations in the rate of change of outflow can adversely affect down-stream processing (through disturbance of sediments, initiation of turbulence, etc.). Proportional + Integral controllers, traditionally employed in surge tank control, do not take direct account of the MROC. It is therefore of interest to explore alternative approaches. We show that the surge tank controller design problem naturally fits a differential games framework, proposed by Dupuis and McEneaney, for controlling a system to confine the state to a safe region of the state space. We show furthermore that the differential game arising in this way can be solved by decomposing it into a collection of (one player) optimal control problems. We discuss the implications of this decomposition technique, for the solution of other controller design problems possessing some features of the surge tank controller design problem.
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Journal articleTao X, Hui SYR, 2012, , IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, Vol: 59, Pages: 1751-1759, ISSN: 0278-0046
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- Citations: 49
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Journal articleChen HT, Tao XH, Hui SYR, 2012, , IEEE TRANSACTIONS ON POWER ELECTRONICS, Vol: 27, Pages: 2176-2183, ISSN: 0885-8993
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- Citations: 49
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Journal articleTao X, Chen H, Li SN, et al., 2012, , IEEE TRANSACTIONS ON POWER ELECTRONICS, Vol: 27, Pages: 2184-2192, ISSN: 0885-8993
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- Citations: 23
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Journal articleNg WM, Lin DY, Hui SY, 2012, , IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, Vol: 59, Pages: 1849-1858, ISSN: 0278-0046
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- Citations: 11
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Journal articleLee CK, Zhong WX, Hui SYR, 2012, , IEEE TRANSACTIONS ON POWER ELECTRONICS, Vol: 27, Pages: 1905-1916, ISSN: 0885-8993
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- Citations: 245
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Journal articleAzcondo FJ, Marcos Alonso J, Hui SYR, 2012, , IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, Vol: 59, Pages: 1686-1688, ISSN: 0278-0046
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- Citations: 1
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Journal articleLi SN, Zhong WX, Chen W, et al., 2012, , IEEE TRANSACTIONS ON POWER ELECTRONICS, Vol: 27, Pages: 2153-2162, ISSN: 0885-8993
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- Citations: 70
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Journal articleDatta S, Chakraborty D, Chaudhuri B, 2012, , IEEE TRANSACTIONS ON AUTOMATIC CONTROL, Vol: 57, Pages: 1051-1056, ISSN: 0018-9286
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- Citations: 35
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Journal articlePiplezadeh Y, Chaudhuri B, Green TC, 2012, , IEEE Transactions on Control Systems Technology
Power oscillations can be damped effectivelythrough modulation of both active and reactive power of a voltage source converter based high voltage direct current link. The challenge, however, is how to coordinate the control action properly at the two ends of the link without using a centralised control scheme, which requires fast communication of control signals to remote actuator (converters) sites. A full centralised controller may result in a closed-loop performance worse than that of an open loop in case of a communication loss of feedback signal(s). Alternatively, with a block-diagonal control structure, the individual control loops are decoupled from each other, which is not only easier to implement in a decentralized way, but also shown to guarantee a certain level of performance. Here, the concept of homotopy is applied to obtain a single block-diagonal controller from a set of full controllers, individually designed to ensure specified closed-loop performance for a set of operating conditions. Simulation studies in DIgSILENT PowerFactory are carried out on two test systems to demonstrate both the robustness and control coordination in a decentralised framework.
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Journal articleJerez JL, Kerrigan EC, Constantinides GA, 2012, , Automatica, Vol: 48, Pages: 999-1002, ISSN: 1873-2836
The computational burden that model predictive control (MPC) imposes depends to a large extent on the way the optimal control problem is formulated as an optimization problem. We present a formulation where the input is expressed as an affine function of the state such that the closed-loop dynamics matrix becomes nilpotent. Using this approach and removing the equality constraints leads to a compact and sparse optimization problem to be solved at each sampling instant. The problem can be solved with a cost per interior-point iteration that is linear with respect to the horizon length, when this is bigger than the controllability index of the plant. The computational complexity of existing condensed approaches grow cubically with the horizon length, whereas existing non-condensed and sparse approaches also grow linearly, but with a greater proportionality constant than with the method presented here.
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Journal articleClark JMC, Vinter RB, 2012, , Stochastics-An International Journal of Probability and Stochastic Processes, Vol: 84, Pages: 667-681, ISSN: 1744-2516
This paper concerns the problem of controlling a stochastic system, with small noise parameter, to prevent it leaving a safe region of the state space. Such problems arise in flow control and other areas. We consider a formulation of the problem, in which a control is sought, to maximize a cost which is related to the expected exit time, but modified to reduce the probability of an early exit, according to a specified level of risk aversion (‘risk sensitive’ stochastic control). Formally letting the noise parameter tend to zero, we find that the optimal control strategy for this problem coincides with the optimal feedback control strategy for a differential game. We identify a class of differential games arising in this way, the so called decomposable differential games, for which the optimal control strategy can be easily obtained and illustrate the proposed solution technique by applying it to a flow control problem arising in process systems engineering.
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Conference paperShabbir W, Evangelou SA, Arana C, 2012,
Series hybrid electric vehicle supervisory control based on off-line efficiency optimization
, 2012 IEEE International Electric Vehicle Conference -
PatentBrandon NPB, Mitcheson PD, Yufit V, et al., 2012,
Battery Monitoring in Electric Vehicles, Hybrid Electric Vehicles, and other Applications
, WO/2012/025706
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