Imperial College London

DrBalarkoChaudhuri

Faculty of EngineeringDepartment of Electrical and Electronic Engineering

Reader in Power Systems
 
 
 
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Contact

 

b.chaudhuri Website

 
 
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Assistant

 

Miss Guler Eroglu +44 (0)20 7594 6170

 
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Location

 

1107DElectrical EngineeringSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
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136 results found

Chaudhuri B, Ramasubramanian D, Matevosyan J, OMalley M, Miller N, Green T, Zhou Xet al., 2024, Rebalancing needs and services for future grids: system needs and service provisions with increasing shares of inverter-based resources, IEEE Power and Energy Magazine, Vol: 22, Pages: 30-41, ISSN: 1540-7977

The primary objective of electricity grids is to reliably meet the electricity demand at a minimum cost. This objective can be broken down into a set of needs that are met through services. These services are procured by mandating them either in grid codes or via market mechanisms. While grids in different countries/regions share common features in terms of needs and services, there are variations arising in physical, regulatory, and policy contexts. With the increased use of inverter-based resources (IBRs), such as wind and solar photovoltaic (PV) power and battery energy storage systems (BESSs), grids are undergoing changes that are altering the balance between needs and services. This balance is crucial in managing changes that will ensure that grids will continue to be able to meet demands. As increasingly more synchronous machines (SMs) are replaced by IBRs, the services inherently provided by the remaining SMs are dwindling, thus requiring the IBRs to contribute where they can.

Journal article

Vochoska J, Javaid MS, Akhtar Z, Chaudhuri Bet al., 2024, Small-signal stability of power systems with a mix of synchronous generators and inverter-based resources, 2023 IEEE PES Innovative Smart Grid Technologies Europe (ISGT EUROPE), Publisher: IEEE

This paper focuses on the problem of small-signalinstability due to the inverter-based resource (IBR) used to interface renewable energy sources (e.g., offshore wind farms) in a traditional power system with synchronous generators (SGs). A power system consisting of an IBR, SG, transmission line, and resistive inductive (RL) load was used to represent an aggregated system. The small-signal stability of the SG-IBR-RL system was investigated for varying levels of IBR penetration (η), followed by three case studies: i) a parameter sensitivity analysis, ii) a model adequacy analysis, and iii) a stability margin improvement study. The sensitivity analysis found that variations across the typical range of most parameters resulted in maximum stable η changes of around 5%, with parameters such as the IBR PI controller gains, the load concentration, and the transmission line impedance having very strong effects on the permissible η. The model adequacy analysis showed that neglecting the SG stator dynamics led to a larger deviation from the “full” model compared to neglecting the transmission dynamics. Finally, the stability margin improvement study found that fast IBR controls coupled with slow SG controls resulted in permissible η values above the base case.

Conference paper

Gao J, Chaudhuri B, Astolfi A, 2024, An optimization-based method for transient stability assessment, IEEE Conference on Decision and Control, Publisher: IEEE, ISSN: 2576-2370

The paper proposes an optimization-based method for the transient stability assessment of lossy multi-machine power systems. To achieve this objective, a global control Lyapunov function candidate including an auxiliary state is introduced. On this basis, a new excitation control law is proposed. This control law is well-defined provided that an ‘index’ matrix remains non-singular along the closed-loop trajectories. Such a matrix plays a key role in the formulation of an optimization problem, which allows calculating the so-called critical value associated to the introduced Lyapunov function. This permits a direct assessment of transient stability property of the considered post-fault power system. To illustrate the effectiveness of such an optimization-based method, a case study on the model of a three-machine system is presented.

Conference paper

Ducoin E, Gu Y, Chaudhuri B, Green Tet al., 2024, Analytical design of contributions of grid-forming & grid-following inverters to frequency stability, IEEE Transactions on Power Systems, ISSN: 0885-8950

Most of the new renewable generation in power systems is connected through Grid-Following inverters (GFL). The accompanying decline of fossil-fuelled synchronous generation reduces the grid inertia. As these two trends progress, instabilities become more likely. To allow more renewables onto the grid, the use of combinations of GFL and Grid-Forming inverters (GFM) has been proposed, however, it is unclear how to parametrise these inverters for system objectives. This paper tackles the issue of parametrizing each GFM and GFL to ensure frequency trajectories at all buses, expressed in terms of frequency deviation, Rate of Change of Frequency and settling time, are stable, recognising that local frequencies can deviate substantially from the Center of Inertia (COI). The procedure to achieve this comprises simple closed-form equations, and yields the required values of droop slopes, GFM filter bandwidth and GFL Phase-Locked Loop bandwidth. These equations are derived from an analytical formulation of swing equations for GFM and GFL which are combined to describe the behaviour of not only the COI but also each bus. The detailed EMT simulations of a modified IEEE 14-bus network demonstrate that the simplifying assumptions made in the analysis are justified by the close correspondence between simulation and analytical projections.

Journal article

Priyamvada IRS, Das S, Chaudhuri B, 2023, Method to quantify modal interactions between converter interfaced generators and synchronous generators, IEEE Transactions on Power Systems, Vol: 38, Pages: 5033-5044, ISSN: 0885-8950

The aim of this paper is to quantify the interactions between the oscillation modes of power systems within the realm of small-signal stability. This paper focuses on the interactions between Converter Interfaced Generator (CIG) oscillation modes and electromechanical oscillation modes of Synchronous Generators (SGs). It is difficult to determine the modal interactions using the existing analysis such as mode sensitivity, mode loci and participation factors. This paper proposes an extension to eigenvalue sensitivity analysis in order to determine the interaction between modes and impact of the interaction on system stability. Interaction coefficients are proposed to quantify the interaction between the modes. A modified IEEE 39-bus system with CIGs is considered to carry out the proposed analysis. The analysis is carried out to investigate the impact of PLL parameters on the interaction among the oscillation modes. The analysis is also carried out considering renewable energy penetration levels of 50-70%. It is observed that the interaction between CIG and electromechanical modes of SG results in increased participation of SGs' states in CIG modes. This increased participation of SG states in CIG modes results in reduced damping of oscillations in SG states.

Journal article

Chu Z, Lakshminarayana S, Chaudhuri B, Teng Fet al., 2023, Mitigating load-altering attacks against power grids using cyber-resilient economic dispatch, IEEE Transactions on Smart Grid, Vol: 14, Pages: 3164-3175, 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.

Journal article

Ducoin E, Gu Y, Chaudhuri B, Green Tet al., 2023, Swing equation modelling of GFL inverter and comparison of its damping and inertia with GFM inverter, The 19th International Conference on AC and DC Power Transmission, Publisher: IET, Pages: 108-114

The increasing integration of inverter-based renewable generation into the network as Grid-Following inverters (GFL), combined with the reduction in traditional Synchronous Generation (SG) leads to a reduction in inertia and to instabilities. To alleviate this, researchers have proposed using a mix of GFL and Grid-Forming controllers (GFM). However, there is a lack of simple system-wide analytical models. This paper proposes a swing equation to describe the transient frequency response of GFL that has droop regulation of real and reactive power. The swing equation for GFL with droop has an inertia and a damping term as do SG and GFM swing equations. Simulations show that the use of swing equations for GFM and GFL is accurate to study the transient frequency stability following a loss of infeed. GFM and GFL damping are equivalent, and their sum allows prediction of frequency deviation. However, although SG and GFM inertia terms limit the initial Rate of Change of Frequency (RoCoF), the GFL inertia term is found not to contribute towards limitation of the initial RoCoF. Instead, the GFL RoCoF isseen to follow adjacent GFM RoCoF and worsens slightly when the GFL Phase Locked Loop (PLL) bandwidth is reduced.

Conference paper

Gao J, Chaudhuri B, Astolfi A, 2023, Lyapunov-based transient stability analysis, IEEE Conference on Decision and Control, Publisher: IEEE, Pages: 5099-5104, ISSN: 2576-2370

The paper presents an analytical control solution to the problem of transient stabilization of lossy multi-machine power systems. Firstly, a new form of control Lyapunov function candidates with a flexible potential-energy-like term is proposed. This is achieved mainly by introducing an auxiliary state that contributes to the derivation of a cross-term. Based on the Lyapunov function candidates, a new control law ensuring asymptotic stability of the desired closed-loop operating equilibrium is proposed. Finally, a case study on the model of a two-machine system to illustrate the effectiveness of the proposed control solution is presented.

Conference paper

Sevilla FRS, Liu Y, Barocio E, Korba P, Andrade M, Bellizio F, Bos J, Chaudhuri B, Chavez H, Cremer J, Eriksson R, Hamon C, Herrera M, Huijsman M, Ingram M, Klaar D, Krishnan V, Mola J, Netto M, Paolone M, Papadopoulos P, Ramirez M, Rueda J, Sattinger W, Terzija V, Tindemans S, Trigueros A, Wang Y, Zhao Jet 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

Journal article

Lee CK, Liu H, Tan S-C, Chaudhuri B, Hui Set 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.

Journal article

Gao J, Chaudhuri B, Astolfi A, 2021, A direct bounded control method for transient stability assessment, 7th IFAC Workshop on Lagrangian and Hamiltonian Methods for Nonlinear Control (LHMNC), Publisher: Elsevier, Pages: 294-301, ISSN: 2405-8963

The paper proposes a direct method for transient stability assessment, which is more efficient than traditional time-domain simulation methods. To achieve this objective, a new bounded control law for the model of a power system is designed. This yields superior closed-loop transient performances when compared to those achievable with traditional automatic voltage regulators and power system stabilizers. The designed control law allows defining an energy-based Lyapunov function which is instrumental in assessing transient stability properties of the post-fault system. A case study on a single machine infinite bus power system model is presented to illustrate the merits of the proposed method.

Conference paper

Chen T, Zheng Y, Chaudhuri B, Hui SYRet 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.

Journal article

Guo J, Tong C, Chaudhuri B, Hui Set 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.

Journal article

Chen T, Guo J, Chaudhuri B, Hui Set 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.

Journal article

Guo J, Badesa Bernardo L, Teng F, Chaudhuri B, Hui S, Strbac Get 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.

Journal article

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.

Journal article

Akhtar Z, Opatovsky M, Chaudhuri B, Hui SYRet 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.

Journal article

Trovato V, Sanz IM, Chaudhuri B, Strbac Get al., 2019, Preventing cascading tripping of distributed generators during non-islanding conditions using thermostatic loads, INTERNATIONAL JOURNAL OF ELECTRICAL POWER & ENERGY SYSTEMS, Vol: 106, Pages: 183-191, ISSN: 0142-0615

Journal article

Chakravorty D, Guo J, Chaudhuri B, Hui SYRet 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.

Journal article

Pipelzadeh Y, Chaudhuri NR, Chaudhuri B, Green Tet al., 2018, Coordinated Control of Offshore Wind Farm and Onshore HVDC Converter for Effective Power Oscillation Damping, IEEE-Power-and-Energy-Society General Meeting (PESGM), Publisher: IEEE, ISSN: 1944-9925

Conference paper

Rousis AO, Chairiman, Pipelzadeh Y, Chaudhuri B, Green T, Strbac Get 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

Conference paper

Pipelzadeh Y, Moreno R, Chaudhuri B, Strbac G, Green Tet al., 2018, Corrective Control With Transient Assistive Measures: Value Assessment for Great Britain Transmission System, IEEE-Power-and-Energy-Society General Meeting (PESGM), Publisher: IEEE, ISSN: 1944-9925

Conference paper

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.

Journal article

Yan S, Wang MH, Yang TB, Tan SC, Chaudhuri B, Hui SYRet 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.

Journal article

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.

Conference paper

Sanz IM, Judge PD, Spallarossa CE, Chaudhuri B, Green TC, Strbac Get 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.

Conference paper

Martinez Sanz I, Judge P, Spallarossa C, Chaudhuri B, Green Tet 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.

Journal article

Trovato V, Sanz IM, Chaudhuri B, Strbac Get 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.

Journal article

PIpelzadeh Y, Moreno R, Chaudhuri B, Strbac G, Green Tet 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.

Journal article

Chaudhuri B, Sanz IM, Majumder R, 2017, HVDC Connection to Large Nuclear Power Plants: A Case Study on Moorside in Great Britain, IEEE Power and Energy Society General Meeting

Conference paper

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