119 results found
Sevilla FRS, Liu Y, Barocio E, et al., 2022, State-of-the-art of data collection, analytics, and future needs of transmission utilities worldwide to account for the continuous growth of sensing data, INTERNATIONAL JOURNAL OF ELECTRICAL POWER & ENERGY SYSTEMS, Vol: 137, ISSN: 0142-0615
- Author Web Link
- Citations: 5
Chu Z, Lakshminarayana S, Chaudhuri B, et al., 2022, Mitigating Load-Altering Attacks Against Power Grids Using Cyber-Resilient Economic Dispatch, IEEE Transactions on Smart Grid, ISSN: 1949-3053
Large-scale Load-Altering Attacks (LAAs) against Internet-of-Things (IoT) enabled high-wattage electrical appliances pose a serious threat to power system security and stability. This paper investigates, for the first time, the optimal mitigation strategy from a system perspective against such attacks. In particular, a Cyber-Resilient Economic Dispatch (CRED) concept is proposed and seamlessly integrated with attack detection and identification to form a cyber resiliency enhancement framework. Instead of only relying on local resources, CRED coordinates the frequency droop control gains of Inverter-Based Resources (IBRs) in the system to mitigate the destabilizing effect of LAAs while minimizing the overall operational cost. To achieve this, the LAA-inclusive system frequency dynamics is formulated and the corresponding system stability constraints are explicitly derived based on parametric sensitivities, which are further incorporated into the system scheduling model with minimum error through a novel recursive linearization method. In addition, a distributionally robust approach is proposed to account for the uncertainty associated with system dynamics driven by the LAA detection/parameter estimation errors. The overall performance of the proposed CRED model is demonstrated through extensive simulations in a modified IEEE reliability test system.
Lee CK, Liu H, Tan S-C, et al., 2021, Electric spring and smart load: technology, system-level impact and opportunities, IEEE journal of emerging and selected topics in power electronics, Vol: 9, Pages: 6524-6544, ISSN: 2168-6777
Increasing use of renewable energy sources to combat climate change comes with the challenge of power imbalance and instability issues in emerging power grids. To mitigate power fluctuation arising from the intermittent nature of renewables, electric spring has been proposed as a fast demand-side management technology. Since its original conceptualization in 2011, many versions and variants of electric springs have emerged and industrial evaluations have begun. This paper provides an update of existing electric spring topologies, their associated control methodologies, and studies from the device level to the power system level. Future trends of electric springs in large-scale infrastructures are also addressed.
Chen T, Zheng Y, Chaudhuri B, et al., 2020, Distributed electric-spring-based smart thermal loads for overvoltage prevention in LV distributed network using dynamic consensus approach, IEEE Transactions on Sustainable Energy, Vol: 11, Pages: 2098-2108, ISSN: 1949-3029
Overvoltage arising from reverse power flow in low-voltage (LV) distribution network caused by surplus roof-top photovoltaic (PV) energy generation is a major challenge in the emerging smart grid. This paper reports a study on the use of distributed thermal Smart Loads (SLs) for overvoltage prevention along a LV feeder. The basic principle involves the combined use of electric springs (ESs) and storage-type electric water heaters (EWHs) as distributed smart loads. Through distributed control, these smart loads play the important roles of mitigating reverse power flow problems and maintaining local mains voltage within the specified tolerance. Detailed modeling of the combined ES and EWH including their practical electrical and thermal capacities and constraints is adopted and optional distributed energy storage system (ESS) is also considered in the evaluation. Based on the Sha Lo Bay residential LV network in Lantau Island, Hong Kong, these case studies confirm the feasibility of the proposed approach for overvoltage prevention. The proposed distributed SLs-plus-ESS method is proved to be a cost-effective and environmental friendly way for overvoltage prevention in LV distributed network with high PV penetration.
Guo J, Tong C, Chaudhuri B, et al., 2020, Stability of isolated microgrids with renewable generation and smart loads, IEEE Transactions on Sustainable Energy, Vol: 11, Pages: 2845-2854, ISSN: 1949-3029
This paper investigates the low frequency (< 30 Hz) oscillations in isolated microgrids (IMGs) with smart loads (SLs) alongside converter-interfaced distributed generators (CDGs) fuelled by renewable energy resources (e.g. wind, solar) with battery energy storage. In an IMG with normal loads (active or passive), such oscillations are typically associated with the droop control of the CDGs operating in grid forming mode. This paper shows that SLs have marginal influence on these low frequency oscillations but introduce a new oscillatory mode at a slightly higher frequency (>20 Hz). First, the stability analysis model (linearized state-space model) of an IMG is extended to include the dynamics of a smart load with a series-shunt converter arrangement in its voltage compensator. It is shown that the dynamics of the phase-locked loop (PLL), DC link along with the control loops of the series and shunt converters of the smart load dictates the lower limit of its droop gain for stable operation. This is not apparent from the simplified SL models (i.e. neglecting the dynamics of the shunt converter and DC link) reported previously. Impact of smart loads on low frequency oscillations in IMGs is demonstrated in this paper through stability analysis and time domain simulation.
Chen T, Guo J, Chaudhuri B, et al., 2020, Virtual inertia from smart loads, IEEE Transactions on Smart Grid, Vol: 11, Pages: 4311-4320, ISSN: 1949-3053
The inertia of future power systems is expected todecrease with increasing penetration of renewable energyresources. Sufficient inertia is required to avoid large fluctuationsin grid frequency and also limit the excessive rate of change offrequency (RoCoF). Unlike many previous works focusing onvirtual inertia on the power supply side, this paper studies andquantifies potential virtual inertia from the load side. The analysisshows that, voltage-dependent loads coupled with electric spring(ES) technology can be operated as smart loads (SL) within the +/-5% tolerance of the ac mains voltage and offer virtual inertia.Following the U.K. National Grid frequency requirements, it isshown that the ES based SL can provide virtual inertia up to aninertia coefficient of HSL=2.5 s (when np=2) with respect to its loadpower rating. The effectiveness of such virtual inertia extractionfrom SL has been verified by the simulation study on a CIGREbenchmark microgrid with high-resolution domestic demandmodel. The value of HSL is shown to be around 1.3 s during themost part of the day and can increase the overall system inertiacoefficient by 0.53 s if all the domestic loads are transformed intothe proposed smart loads.
Guo J, Badesa Bernardo L, Teng F, et al., 2020, Value of point-of-load voltage control for enhanced frequency response in future GB power system, IEEE Transactions on Smart Grid, Vol: 11, Pages: 4938-4948, ISSN: 1949-3053
The need for Enhanced Frequency Response (EFR)is expected to increase significantly in future low-carbon GreatBritain (GB) power system. One way to provide EFR is touse power electronic compensators (PECs) for point-of-loadvoltage control (PVC) to exploit the voltage dependence of loads.This paper investigates the techno-economic feasibility of suchtechnology in future GB power system by quantifying the totalEFR obtainable through deploying PVC in the urban domesticsector, the investment cost of the installment and the economicand environmental benefits of using PVC. The quantificationis based on a stochastic domestic demand model and genericmedium and low-voltage distribution networks for the urbanareas of GB and a stochastic unit commitment (SUC) modelwith constraints for secure post-fault frequency evolution is usedfor the value assessment. Two future energy scenarios in thebackdrop of 2030 with ‘smart’ and ‘non-smart’ control of electricvehicles and heat pumps, under different levels of penetration ofbattery energy storage system (BESS) are considered to assessthe value of PEC, as well as the associated payback period. Itis demonstrated that PVC could effectively complement BESStowards EFR provision in future GB power system.
Guo J, Chaudhuri B, Hui S, 2019, Flexible demand through point-of-load voltage control in domestic sector, IEEE Transactions on Smart Grid, Vol: 10, Pages: 4662-4672, ISSN: 1949-3061
Demand reduction through voltage control at substations is commonly used. However, during high loading conditions the allowable depth of voltage reduction could be limited by the large voltage drop across the feeders. Distributed voltage control at the points of connection of individual loads (e.g. supply point of a cluster of domestic customers) allows larger flexibility in demand especially, during high loading as demonstrated in this paper. A high-resolution stochastic demand model and the aggregate power-voltage sensitivity of individual domestic customers are used to compare the demand reduction capability of point-of-load voltage control (PVC) against voltage control at substation (VCS). The rating of the voltage compensators required for PVC is evaluated to weigh the benefits against the required investment. First, the results are shown on a generic low voltage network with random distribution of clusters of domestic customers at various buses and random length of feeder segments to draw general conclusions. Then, the Cigre benchmark medium-and low-voltage (MV/LV) networks are used to substantiate the findings. A case study on an islanded microgrid is presented to show that PVC reduces frequency variations caused by fluctuating wind power generation.
Akhtar Z, Opatovsky M, Chaudhuri B, et al., 2019, Comparison of point-of-load vs. mid feeder compensation in lv distribution networks with high penetration of solar photovoltaic generation and electric vehicle charging stations, IET Smart Grid, Vol: 2, Pages: 283-292, ISSN: 2515-2947
Increasing use of distributed generation (DG), mainly roof-top photovoltaic (PV) panels and electric vehicle (EV) charg-ing would cause over- and under-voltage problems generallyat the remote sections of the low voltage (LV) distribution feeders. Asthese voltage problems are sustained for a few hours, power electronic compensators (PECs) with input voltage control,i.e. electricsprings can not be used due to the unavailability of non-critical loads that can be subjected to non-rated voltages for long durationof time. However, PECs in output voltage control mode could be used to inject a controllable series voltage either somewhereon the feeder (mid-feeder compensation, MFC) or between thefeeder and each customer (point-of-load compensation, PoLC)both of which are effective in tackling the voltage problem without disrupting PV power output and EV charging. In this paper, acomparison between the MFC and PoLC option is presented in terms of their voltage control capability, required compensatorcapacity, network losses, PV throughput, and demand response capability. The criteria for selection of optimal location of thesecompensators is also discussed. Stochastic demand profile for different types of residential customers in the UK and a typicalEuropean LV network is used for the case study.
Chakravorty D, Guo J, Chaudhuri B, et al., 2019, Small Signal Stability Analysis of Distribution Networks with Electric Springs, IEEE Transactions on Power Systems, Vol: 10, Pages: 1543-1552, ISSN: 0885-8950
This paper presents small signal stability analysis of distribution networks with electric springs (ESs) installed at the customer supply points. The focus is on ESs with reactive compensation only. Vector control of ES with reactive compensation is reported for the first time to ensure compatibility with the standard stability models of other components such as the interface inverter of distributed generators (DGs). A linearized state-space model of the distribution network with multiple ESs is developed which is extendible to include inverter-interfaced DGs, energy storage, active loads etc. The impact of distance of an ES from the substation, proximity between adjacent ESs and the R/X ratio of the network on the small signal stability of the system is analyzed and compared against the case with equivalent DG inverters. The collective operation of ESs is validated through simulation study on a standard distribution network.
Rousis AO, Chairiman, Pipelzadeh Y, et al., 2018, Voltage Support from Distribution Level Resources in South-East England, IEEE-Power-and-Energy-Society General Meeting (PESGM), Publisher: IEEE, ISSN: 1944-9925
Chakravorty D, Chaudhuri B, Hui S, 2018, Estimation of aggregate reserve with point-of-load voltage control, IEEE Transactions on Smart Grid, Vol: 9, Pages: 4649-4658, ISSN: 1949-3053
Voltage dependent loads can collectively provide a certain amount of power reserve (by virtue of the ability to change their power consumption within the stipulated voltage tolerance) which could be exploited for grid frequency regulation through voltage control at the substation/feeder or at the point ofload. The amount of such power reserve would vary with time of the day depending on the incidence of different types of voltage dependent loads and also the voltage profile across the feeders. It is important for the grid operators to know the aggregate power reserve from the voltage dependent loads during different times of the day in order to schedule other forms of reserves accordingly. This paper presents a methodology to estimate such power reserve from the measured power and voltage at the bulk supply points without knowing the actual distribution network topology and/or load profile of individual customers. The proposed method is applied to estimate the time variation of the aggregate reserve offered by the voltage dependent loads within the domestic sector in Great Britain (GB). Studies on astandard IEEE distribution network are presented to validate the estimated reserve margins under typical voltage profiles across the distribution feeders.
Yan S, Wang MH, Yang TB, et al., 2018, Achieving multiple functions of 3-phase electric springs in unbalanced 3-phase power systems using the instantaneous power theory, IEEE Transactions on Power Electronics, Vol: 33, Pages: 5784-5795, ISSN: 0885-8993
IEEE Three-phase electric spring (3-ph ES) has recently been proposed as a fast demand response technology for applications in unbalanced power systems fed with a mixture of conventional and renewable power generation. Using the Instantaneous Power Theory as the theoretical framework, this paper presents the criteria and conditions for minimizing the average and oscillating power of the 3-ph ES for the first time. A detailed analysis of the use of 3-ph ES is included for providing multiple control objectives of voltage regulation and power balancing of the 3-ph power system, and minimization of the average and oscillating ac power of the ES. A corresponding control scheme implementable in a single controller is included and explained. The control scheme has been practically verified with experiments.
Martinez Sanz IM, Chaudhuri B, Majumder R, 2018, HVDC connection to large nuclear power plants: a case study on Moorside in Great Britain, 2017 IEEE Power and Energy Society General Meeting, Publisher: IEEE
Use of HVDC links for direct connection of a largenuclear power station to the existing power grid is unprecedented.Control of such HVDC connection for stable and secure operationof the nuclear power station is challenging and untested. Forthe Moorside nuclear power station planned close to the LakeDistrict in Great Britain, there is tremendous pressure to useHVDC cables for the southern connection route (which wouldpass through the picturesque landscape) to avoid the visualimpact of overhead lines. This paper shows that it is feasibleto connect a large nuclear power station, such as Moorside,through a VSC-HVDC cable route alongside a northern ACroute where there are no objections to overhead transmission.Use of a proposed control of the VSC-HVDC is shown to achieveautomatic and rapid redirection of power on to the VSC-HVDClink following sudden outage of the AC route. Moreover, if thegenerators at Moorside were to shut down accidentally, the samecontrol strategy for VSC-HVDC can back feed the power stationauxiliaries which is essential for nuclear safety. Thus, a mix ofAC and HVDC connection routes achieves similar (if not better)transient responses as compared to using both AC routes whichin this case faces serious opposition.
Sanz IM, Judge PD, Spallarossa CE, et al., 2018, Effective Damping Support through VSC-HVDC Links with Short-Term Overload Capability, IEEE PES Innovative Smart Grid Technologies Conference Europe (ISGT-Europe), Publisher: IEEE, ISSN: 2165-4816
Damping service provision through VSC-based HVDC links has been extensively covered in the literature. However, little or no attention has been paid to the available range of active and reactive power modulation when the HVDC link is already operating at rated capacity. In these conditions some overload capability is usually assumed, ignoring the physical constraints imposed by the safe operating area of the IGBT modules in the converter. This paper presents, in a unified framework, the provision of damping support from VSC-HVDC links equipped with additional control for short-term overload capability. The performance of a Model Predictive Control (MPC) damping controller that accounts for the extended P/Q operating area of the converter is analysed. Case studies are presented to show that the extracted short-term overload capability can significantly improve the damping support from VSC-HVDC links. Simulation results also include the impact of damping control action on the junction temperatures of the IGBT modules of the converters, quantifying the effect of this service on the semiconductor temperature dynamics.
Martinez Sanz I, Judge P, Spallarossa C, et al., 2017, Dynamic overload capability of VSC HVDC interconnections for frequency support, IEEE Transactions on Energy Conversion, Vol: 32, Pages: 1544-1553, ISSN: 0885-8969
In future power systems, reduced overall inertia caused by an increased dominance of asynchronous generation and interconnections would make frequency control particularly challenging. As the number and power rating of voltage source converter (VSC) HVDC systems increases, network service provision would be expected from such systems and to do so would require overload capacity to be included in the converter specifications. This paper studies the provision of frequency services from modular multilevel converter (MMC)-based VSC HVDC interconnections using temperature-constrained overload capability. Overload of the MMC-based HVDC system is achieved through controlled circulating currents, at the expense of higher losses, and subject to a control scheme that dynamically limits the overload available in order to keep the semiconductor junction temperatures within operational limits. Two frequency control schemes that use the obtained overload capacity to provide frequency response during emergency conditions are investigated. The controllers' performance is demonstrated in the context of the future Great Britain transmission grid through a reduced equivalent test system. Simulation results show that even modest temperature margins which allow overload of MMC-based HVDC systems for a few seconds are effective as a primary frequency reserve and also reduce the loss of infeed requirements of such interconnections.
Trovato V, Sanz IM, Chaudhuri B, et al., 2017, Advanced Control of Thermostatic Loads for Rapid Frequency Response in Great Britain, IEEE Transactions on Power Systems, Vol: 32, Pages: 2106-2117, ISSN: 0885-8950
In the Great Britain power system, reduced system inertia (particularly during low demand conditions) and larger possible infeed loss would make grid frequency regulation extremely challenging in future. Traditional primary frequency response could be insufficient to limit the frequency variation within acceptable range. This paper shows that thermostatically controlled loads (TCLs) (domestic refrigerators) can be controlled without real-time communication and in a nondisruptive way to collectively enhance the network frequency response. The aggregated power consumption of TCLs, distributed across the system, could be controlled as a 'linear' function of the locally measured frequency and its rate of change. Alternatively, their aggregated consumption could be made to follow a 'pre-set' power profile depending on the estimated infeed loss. A novel technique for accurate estimation of infeed loss and consequent postfault TCL power reduction is also proposed. The effectiveness of the two TCL control strategies is compared for primary and secondary frequency response through a case study on a 36 busbar reduced equivalent of the Great Britain power system. The effect of spatial variation of transient frequencies and the time delays in frequency measurement and filtering are considered to show how the TCLs can realistically provide rapid frequency response.
- Open Access Link
- Citations: 81
PIpelzadeh Y, Moreno R, Chaudhuri B, et al., 2017, Corrective control with transient assistive measures: value assessment for Great Britain transmission system, IEEE Transactions on Power Systems, Vol: 32, Pages: 1638-1650, ISSN: 0885-8950
In this paper, the efficacy and value of using corrective control supported by transient assistive measures (TAM) is quantified in terms of the cost savings due to less constrained operation of the system. The example TAM is a rapid modulation of the power order of the high-voltage direct current (HVDC) links in the system so as to improve transient stability during corrective control. A sequential approach is used for the offline value assessment: a security constrained economic dispatch (SCED) module (master problem) determines the optimal generation dispatch, HVDC settings, and the corrective control actions to be used post-fault (generation and demand curtailed) so as to minimize the operational costs while ensuring static security. The transient stability module (slave problem) assesses the dynamic stability for the operating condition set by the SCED and, if needed, applies appropriate TAM to maintain the system transiently stable. If this is not possible, the master module uses a tighter set of security constraints to update the dispatch and other settings until the system can be stabilized. A case-study on the Great Britain system is used to demonstrate that corrective control actions supported by TAM facilitate significantly higher pre-fault power transfers whilst maintaining N-2 security.
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.
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
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
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.
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.
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