Publications
136 results found
Yan S, Tan SC, Lee CK, et al., 2016, Use of Smart Loads for Power Quality Improvement, IEEE Journal of Emerging and Selected Topics in Power Electronics, Vol: 5, Pages: 504-512, ISSN: 2168-6777
Electric spring (ES) was originally proposed as a distributed demand-side management technology for making noncritical loads adaptive to the availability of intermittent renewable power generation. The second generation of ES, fed with batteries (ES-2) and associated with a noncritical load, can form a new kind of combined smart load and distributed energy storage technology for smart grids. With its four-quadrant operation, ES-2 is able to offer ancillary grid services in addition to its major functions of voltage and frequency regulation. This paper presents the operating principles and the input current control of ES-2 for power quality improvement such as power factor correction and harmonics reduction. The operating principles and the proposed input current control have been verified with the experimental results obtained from a small-scale power grid. Another weak single-phase power system fed by intermittent wind power is set up to prove the combined operation of ES-2 for power quality improvement and ES-1 (ES with capacitor storage) for voltage stabilization. The experimental results show that ES-2 with input current control can carry out power quality improvement as its ancillary function.
Martınez-Sanz IM, Chaudhuri B, Junyent-Ferre A, et al., 2016, Distributed vs. Concentrated Rapid Frequency Response Provision in Future Great Britain System, IEEE Power and Energy Society General Meeting, Publisher: IEEE, ISSN: 1944-9933
Two major sources of rapid frequency response(RFR) to counter the reducing system inertia problem of theGreat Britain (GB) system are “synthetic inertia” from windturbines and fast demand response (FDR). In this paper, weconsider a future low inertia scenario to show the effectivenessof RFR provision from the large offshore wind farms (OWFs)planned in the North Sea (concentrated response) against FDRfrom loads spread across the GB system (distributed response).The spatial variation in transient frequencies, which can bepronounced in the aftermath of a disturbance and is criticalfor the response activation of these actuators, is accounted. Casestudies using a reduced GB system model show the effectivenessof distributed FDR and concentrated support from OWFs inproviding RFR when disturbances occur in different areas of thesystem where different inertia levels are present.
Chakravorty D, Akhtar Z, Chaudhuri B, et al., 2016, Comparison of Primary Frequency Control Using Two Smart Load Types, IEEE Power and Energy Society General Meeting, Publisher: IEEE, ISSN: 1944-9933
Primary frequency control using smart loads withreactive only compensation (SLQ) has been shown in the past.In this paper, further improvement in frequency regulation isshown using smart loads with a back-to-back converter (SLBC)arrangement. This introduces additional flexibility and thereby,allows independent and wider control over active and reactivepower consumption of the smart load. The improvement infrequency regulation with SLBCs is compared against SLQsthrough two separate case studies on 4-generator, 2-area testsystem and also the 39-bus New-England test system. A futurescenario with reduced system inertia is considered for both casestudies. Unlike previous exercises involving smart loads, in thisstudy a detailed representation is used for both the multi-machinetransmission system and the distribution networks down to themedium voltage (MV) level where the smart loads (SLBC/SLQ)are connected. This avoids the inaccuracies associated with loadaggregation or use of system equivalents wherein the networkconstraints, spatial voltage variations etc. are not capturedproperly.
Pipelzadeh Y, Ray Chaudhuri N, Chaudhuri B, et al., 2016, Coordinated control of offshore wind farm and onshore HVDC converter for effective power oscillation damping, IEEE Transactions on Power Systems, Vol: 32, Pages: 1860-1872, ISSN: 1558-0679
Damping contribution from wind farms (WFs) islikely to become a mandatory requirement as part of the gridcodes. For remote offshore WFs, connected through a voltagesource converter (VSC)-based direct current (DC) link, the mostconvenient option for the onshore transmission system operator(TSO) is to modulate the reactive power at the onshore VSCwithin their own jurisdiction. In this paper, we show thatsupplementary control through the onshore VSC alone, althoughattractive for TSOs, could result in unacceptable voltage variationsin the onshore power grid. On the other hand, modulation ofactive power output of the wind turbine generators (WTG) aloneturns out to be inadequate due to the limited overload capabilityof the WTGs and the on- and offshore VSCs. Coordinated controlover both onshore VSC and aggregated WF output overcomes theabove limitations and is shown to be effective for power oscillationdamping. A homotopy approach is used to design the coordinatedcontroller, which can be implemented locally (at offshore WF andonshore converter site) using a decentralized architecture. Casestudies on two test systems show that the proposed controlleryields similar system dynamic response as supplementary controlthrough the WF alone.
Yan S, Lee CK, Yang TB, et al., 2016, Extending the Operating Range of Electric Spring using Back-To-Back Converters: Hardware Implementation and Control, IEEE Transactions on Power Electronics, Vol: 32, Pages: 5171-5179, ISSN: 0885-8993
This paper presents the first hardware implementation and control of an electric spring based on a back-to-back converter configuration. Because of its ability to provide both active and reactive power compensation, this back-to-back electric spring (ES-B2B) can substantially extend the operating range of the original version of the electric spring (ES-1) and provide enhanced voltage support and suppression functions. The hardware system and control of the ES-B2B have been successfully developed and tested. The experimental results have confirmed the effectiveness of the ES-B2B in supporting and suppressing the mains voltage. Particularly, the voltage suppression ability of the ES-B2B is superior over that of ES-1. The use of ES-B2B in a simulation study of a weak power grid has also been conducted. The ES-B2B has been found to be highly effective in mitigating voltage fluctuation caused by intermittent renewable power generation.
Martinez Sanz I, Chaudhuri B, Strbac G, 2016, Coordinated corrective control for transient stability enhancement in future Great Britain transmission system, 19th Power Systems Computation Conference (PSCC 2016), Publisher: IEEE
This paper demonstrates a corrective control strategy through fast actuators (TCSC FACTS and HVDC links, both LCC and VSC) in order to enhance the transient stability in the future Great Britain (GB) transmission network. A model predictive control (MPC) scheme that relies on system wide-area measurements is employed for coordinated control action through these power electronic devices with the aim of preserving the system stability without having to constrain pre-fault transfer levels. Case studies employing detailed dynamic models are presented to demonstrate the effectiveness of the proposed approach for different formulations on a representative equivalent model of the future GB transmission grid.
Akhtar Z, Chaudhuri B, Hui SYR, 2016, Smart loads for voltage control in distribution networks, Power and Energy Society General Meeting (PESGM), 2016, ISSN: 1944-9933
Luo X, Akhtar Z, Lee CK, et al., 2016, Distributed voltage control with electric springs: Comparison with STATCOM, Power and Energy Society General Meeting (PESGM), 2016, ISSN: 1944-9933
Chakravorty D, Chaudhuri B, Hui SYR, 2016, Rapid Frequency Response from Smart Loads in Great Britain Power System, IEEE Transactions on Smart Grid, Vol: 8, Pages: 2160-2169, ISSN: 1949-3053
Flexibility in certain types of loads could be exploited to provide fast and controllable power reserve if the supply voltage/frequency is controlled using existing power electronic interfaces (e.g. motor drives) or additional ones like recently proposed Electric Springs. Such a load together with its power electronic interface forms a so called ‘smart load’. Effectiveness of static smart loads for primary frequency response provision has been shown in previous papers through case studies ona segment of the LV/MV distribution network. In this paper, collective contribution of both static and motor type smart loads to rapid frequency response provision is demonstrated through a case study on the Great Britain (GB) transmission system. The active power reserve available from such smart loads are quantified and aggregated at each node at the transmission level (275/400 kV). The study shows that the smart loads collectively offer a short-term power reserve which is comparable to the spinning reserve in the GB system and thus can ensure acceptable frequency deviation and its rate of change (RoCoF) following a large infeed loss.
Luo X, Lee CK, Ng WM, et al., 2016, Use of adaptive thermal storage system as smart load for voltage control and demand response, IEEE Transactions on Smart Grid, Vol: 8, Pages: 1231-1241, ISSN: 1949-3053
This paper describes how a large-scale ice-thermal storage can be turned into a smart load for fast voltage control and demand-side management in power systems with intermittent renewable power, while maintaining its existing function of load shaving. The possibility of modifying a conventional thermal load has been practically demonstrated in a refrigerator using power electronics technology. With the help of an electric spring, the modified thermal load can reduce power imbalance in buildings while providing active and reactive power compensation for the power grid. Based on practical data, a building energy model incorporating a large-scale ice-thermal storage system has been successfully used to demonstrate the advantageous demand-response features using computer simulation of both grid connected and isolated power systems. The results indicate the potential of using ice-thermal storage in tall buildings in reducing voltage and frequency fluctuations in weak power grids.
Adapa R, Chaudhuri B, Woodford D, 2016, Integrating HVDC into AC Grid, HVDC Reference Book
Sanz IM, Chaudhuri B, Strbac G, 2016, Inertial Response From Offshore Wind Farms Connected Through DC Grids, IEEE-Power-and-Energy-Society General Meeting (PESGM), Publisher: IEEE, ISSN: 1944-9925
Segundo Sevilla FR, Jaimoukha I, Chaudhuri B, et al., 2015, A semidefinite relaxation procedure for fault-tolerant observer design, IEEE Transactions on Automatic Control, Vol: 60, Pages: 3332-3337, ISSN: 0018-9286
A fault-tolerant observer design methodology is proposed. The aim is to guarantee a minimum level of closed-loop performance under all possible sensor fault combinations while optimizing performance under the nominal, fault-free condition. A novel approach is proposed to tackle the combinatorial nature of the problem, which is computationally intractable even for a moderate number of sensors, by recasting the problem as a robust performance problem, where the uncertainty set is composed of all combinations of a set of binary variables. A procedure based on an elimination lemma and an extension of a semidefinite relaxation procedure for binary variables is then used to derive sufficient conditions (necessary and sufficient in the case of one binary variable) for the solution of the problem which significantly reduces the number of matrix inequalities needed to solve the problem. The procedure is illustrated by considering a fault-tolerant observer switching scheme in which the observer outputs track the actual sensor fault condition. A numerical example from an electric power application is presented to illustrate the effectiveness of the design.
Akhtar Z, Chaudhuri B, Hui S, 2015, Smart Loads for Voltage Control in Distribution Networks, IEEE Transactions on Smart Grid, Vol: 8, Pages: 937-946, ISSN: 1949-3061
This paper shows that the smart loads (SLs) couldbe effective in mitigating voltage problems caused by photovoltaic(PV) generation and electric vehicle (EV) chargingin low-voltage (LV) distribution networks. Limitations of thepreviously reported SL configuration with only series reactivecompensator (SLQ) (one converter) is highlighted in this paper.To overcome these limitations, an additional shunt converter isused in back-to-back (B2B) configuration to support the activepower exchanged by the series converter, which increases the flexibilityof the SL without requiring any energy storage. Simulationresults on a typical U.K. LV distribution network are presented tocompare the effectiveness of an SL with B2B converters (SLBCs)against an SLQ in tackling under- and over-voltage problemscaused by EV or PV. It is shown that SLBCs can regulate themain voltage more effectively than SLQs especially under overvoltagecondition. Although two converters are required for eachSLBC, it is shown that the apparent power capacity of eachconverter is required to be significantly less than that of anequivalent SLQ.
Pipelzadeh Y, Chaudhuri B, Green T, 2015, Modelling and Dynamic Operation of the Zhoushan DC Grid: Worlds First Five-Terminal VSC-HVDC Project, International High Voltage Direct Current 2015 Conference, Publisher: IET, Pages: 87-95
This paper highlights the world’s first operational MTDC grid, namely the 5-terminal Zhoushan DC grid. The scheme went under operation in 2014. The topology and operation of the Zhoushan DC grid are demonstrated with recorded measurements obtained from the converter station, after being subjected to system disturbances. A generic modeling framework for the Zhoushan DC grid is developed inPSCAD/EMTDC. One particular concern is how the Zhoushan DC grid would react to DC side faults and the resulting power imbalance. Despite the completion of the Zhoushan MTDC grid, technological barriers such as the unavailability of fast protection systems, DC circuit breakers and highly efficient VSCs with DC side fault-clearing capabilities have all been bottlenecks at the time of commissioning, but are now under extensive research and development. The challenges and importance of DC grid protection are highlighted through case studies performed on the DC grid model in PSCAD/EMTDC.
Pipelzadeh 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: CIGRE
A 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
Akhtar Z, Chaudhuri B, Hui SYR, 2015, Primary Frequency Control Contribution From Smart Loads Using Reactive Compensation, IEEE Transactions on Smart Grid, ISSN: 1949-3061
Frequency-dependent loads inherently contribute to primary frequency response. This paper describes additional contribution to primary frequency control based on voltage-dependent noncritical (NC) loads that can tolerate a wide variation of supply voltage. By using a series of reactive compensators to decouple the NC load from the mains to form a smart load (SL), the voltage, and hence the active power of the NC load, can be controlled to regulate the mains frequency. The scope of this paper focuses primarily on reactive compensators for which only the magnitude of the injected voltage could be controlled while maintaining the quadrature relationship between the current and voltage. New control guidelines are suggested. The effectiveness of the SLs in improving mains frequency regulation without considering frequency-dependent loads and with little relaxation in mains voltage tolerance is demonstrated in a case study on the IEEE 37 bus test distribution network. Sensitivity analysis is included to show the effectiveness and limitations of SLs for varying load power factors, proportion of SLs, and system strengths.
Luo X, Akhtar Z, Lee CK, et al., 2015, Distributed voltage control with electric springs: comparison with STATCOM, IEEE Transactions on Smart Grid, Vol: 6, Pages: 209-219, ISSN: 1949-3053
The concept of electric spring (ES) has been proposed recently as an effective means of distributed voltage control. The idea is to regulate the voltage across the critical (C) loads while allowing the noncritical (NC) impedance-type loads (e.g., water heaters) to vary their power consumption and thus contribute to demand-side response. In this paper, a comparison is made between distributed voltage control using ES against the traditional single point control with STATic COMpensator (STATCOM). For a given range of supply voltage variation, the total reactive capacity required for each option to produce the desired voltage regulation at the point of connection is compared. A simple case study with a single ES and STATCOM is presented first to show that the ES and STATCOM require comparable reactive power to achieve similar voltage regulation. Comparison between a STATCOM and ES is further substantiated through similar case studies on the IEEE 13-bus test feeder system and also on a part of the distribution network in Sha Lo Wan Bay, Hong Kong. In both cases, it turns out that a group of ESs achieves better total voltage regulation than STATCOM with less overall reactive power capacity. Dependence of the ES capability on proportion of critical and NC load is also shown.
Lee CK, Chaudhuri NR, Chaudhuri B, et al., 2015, Droop Control of Distributed Electric Springs for Stabilizing Future Power Grid, General Meeting of the IEEE-Power-and-Energy-Society, Publisher: IEEE, ISSN: 1944-9925
Pipelzadch Y, Chaudhuri B, Green TC, et al., 2015, Role of Western HVDC Link in Stability of Future Great Britain (GB) Transmission System, General Meeting of the IEEE-Power-and-Energy-Society, Publisher: IEEE, ISSN: 1944-9925
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Sanz IM, Chaudhuri B, Strbac G, et al., 2015, Corrective Control through Western HVDC link in Future Great Britain Transmission System, General Meeting of the IEEE-Power-and-Energy-Society, Publisher: IEEE, ISSN: 1944-9925
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- Citations: 3
Chaudhuri N, Chaudhuri B, Majumder R, et al., 2014, Multi-terminal Direct-Current Grids, Publisher: Wiley IEEE, ISBN: 9781118729106
Commercial unavailability of efficient DC side fault current interruption technology for conventional voltage sourced converter systems This book addresses the first issue in details by presenting a comprehensive modeling, analysis and ...
Chaudhuri NR, Lee CK, Chaudhuri B, et al., 2014, Dynamic Modeling of Electric Springs, IEEE TRANSACTIONS ON SMART GRID, Vol: 5, Pages: 2450-2458, ISSN: 1949-3053
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- Citations: 91
Sanz IM, Chaudhuri B, Strbac G, 2014, Inertial Response From Offshore Wind Farms Connected Through DC Grids, IEEE Transactions on Power Systems, Vol: 30, Pages: 1518-1527, ISSN: 0885-8950
Yan S, Tan S-C, Lee C-K, et al., 2014, Electric Springs for Reducing Power Imbalance in Three-Phase Power Systems, IEEE Transactions on Power Electronics, Vol: 30, Pages: 3601-3609, ISSN: 0885-8993
Chaudhuri B, Hui SYR, Chaudhuri NR, et al., 2014, A power compensator, WO2013153075 A3
A power compensator for compensating voltage at a location along a power transmission line, the compensator having a controller for controlling a voltage generated across the compensator, wherein the voltage is controlled to maintain a power transmission line voltage at a value dependent on the power transmission line location.
Sanz IM, Chaudhuri B, Strbac G, 2014, Frequency Changes in AC Systems Connected to DC Grids: Impact of AC vs. DC Side Events, IEEE PES General Meeting, Publisher: IEEE, ISSN: 1944-9925
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- Citations: 6
Segundo Sevilla FR, Jaimoukha I, Chaudhuri B, et al., 2014, Fault-tolerant Control Design to Enhance Damping of Inter-areaOscillations in Power Grids, International Journal in Robust and Nonlinear Control, Accepted
In this paper, passive and active approaches for the design of fault-tolerant controllers (FTCs) are presented. The FTCs are used to improve the damping of inter-area oscillations in a power grid. The effectiveness of using a combination of local and remote (wide area) feedback signals is first demonstrated. The challenge is then to guarantee a minimum level of dynamic performance following a loss of remote signals. The designs are based on regional pole placement using linear matrix inequalities. First, a passive FTC is proposed. It is shown that the computation of the controller reduces to the solution of bilinear matrix inequalities. An iterative procedure is then used to design the controller. Next, as an alternative to active, time-varying controllers,one for each fault scenario, we propose an approach for the design of a ’minimal switching’ FTC in which only one controller is designed, but where a simple switch is incorporated into the controller structure. A case study in a linear and nonlinear Nordic equivalent system is presented to show that the closed-loop response using a conventional control design could deteriorate the performance or even destabilize the system if the remote signals are lost and to demonstrate the effectiveness of the proposed FTC designs.
Lee CK, Tan SC, Wu FF, et al., 2013, Use of Hooke's law for stabilizing future smart grid the electric spring concept, 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013, Pages: 5253-5257
Hooke's law for mechanical springs was developed in the 17th century. Recently, new power electronics devices named electric springs have been developed for providing voltage regulation for distribution networks and allowing the load demand to follow power generation. This paper summarizes recent R&D on electric springs and their potential functions for future smart grid. Electric springs can be associated with electric appliances, forming a new generation of smart loads which can adapt according to the availability of power from renewable energy sources. When massively distributed over the power grid, they could provide highly distributed and robust support for the smart grid, similar to the arrays of mechanical springs supporting a mattress. Thus, the 3-century old Hooke's law in fact provides a powerful solution to solving some key Smart Grid problems in the 21st Century. © 2013 IEEE.
Arif J, Ray S, Chaudhuri B, 2013, Multivariable Self-Tuning Feedback Linearization Controller for Power Oscillation Damping, IEEE Transactions on Control Systems Technology, Vol: 22, Pages: 1519-1526, ISSN: 1558-0865
The objective of this brief is to design ameasurement-based self-tuning controller, which does not rely onaccurate models and deals with nonlinearities in system response.A special form of neural network (NN) model called feedbacklinearizable NN (FLNN) compatible with feedback linearizationtechnique is proposed for representation of nonlinear powersystems behavior. Levenberg–Marquardt (LM) is applied in batchmode to improve the model estimation. A time-varying feedbacklinearization controller (FBLC) is employed in conjunction withthe FLNN–LM estimator to generate the control signal. Validationof the performance of proposed algorithm is done throughthe modeling and simulating both normal and heavy loadingof transmission lines, when the nonlinearities are pronounced.Case studies on a large-scale 16-machine five-area power systemare reported for different power flow scenarios, to prove thesuperiority of proposed scheme against a conventional modelbasedcontroller. A coefficient vector for FBLC is derivedand used online at each time instant, to enhance the dampingperformance of controller.
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