Search or filter publications

Filter by type:

Filter by publication type

Filter by year:

to

Results

  • Showing results for:
  • Reset all filters

Search results

  • Journal article
    Gu Y, Chaudhuri B, Green T, Xiaoyao Z, Ramachandran Jet al., 2025,

    Multi-layered defense against oscillations

    , IEEE Power and Energy Magazine, ISSN: 1540-7977

    Increasing shares of inverter-based resources (IBRs) in power grids are triggering complex dynamic interactions and new stability challenges. A particular challenge for system operators is poorly damped sub-synchronous oscillations (SSO) induced by adverse interaction among IBRs through the network. These oscillations are difficult to foresee, threaten system security and often force grid operators to limit the instantaneous share of IBRs. The Control and Power research group at Imperial College London are working with the Network Operability team in National Energy System Operator (NESO) in the UK to develop a multi-layered defense strategy to identify and mitigate the risk of poorly damped SSO. Starting from advanced IBR control design which is the genesis of the SSO problem, these layers are: 1) an enhanced IBR connection compliance process capture the risk of SSO more comprehensively, 2) new system strength metrices to identify parts of the grid vulnerable to SSO, 3) characterize operating point dependency of IBRs to detect incipient SSO near real-time and 4) post-event root-cause analysis for targeted and effective mitigation of SSO. Success of this research will enable secure grid operation with high fractions of renewables to facilitate net zero transition.
  • Conference paper
    Javaid MS, Chaudhuri B, Teng F, Akhtar Zet al., 2025,

    Impact of inner control in GFM-induced sub-synchronous oscillations

    , 2025 IEEE PES General Meeting, Publisher: IEEE

    n power systems dominated by grid-forming inverters (GFMs), strong grid conditions can lead to sub-synchronous oscillations (SSOs) due to the reduced time-scale separation between GFM control loops and network dynamics, potentially causing instability. Modal analysis reveals that states associated with inner control (comprising current and voltage control loops) and network dynamics are the primary contributors to these oscillatory modes. This paper provides an analytical explanation of adverse interactions between GFM inner control and network dynamics that lead to SSOs. Through damping ratio sensitivity analysis, we establish that increasing the current control closed-loop bandwidth and the voltage control proportional gaincan effectively mitigate these oscillations. The proposed control adjustments also prove effective in larger systems with 100% inverter-based resources penetration, comprising of a mix of both grid-following and grid-forming inverters.
  • Journal article
    Gao J, Chaudhuri B, Astolfi A, 2025,

    An explicit direct method for transient stability analysis of multimachine power systems with nonzero transfer conductances

    , IEEE Transactions on Control Systems Technology, ISSN: 1063-6536

    We propose an explicit analytical direct method for the transient stability analysis of multimachine power systems with nonzero transfer conductances (TCs). The proposed method addresses two issues. In the first issue, we study the transient stabilization of the entire power system through excitation control design. To this end, a globally well-defined Lyapunov function is constructed, and a locally well-defined dynamic passivity-based control law is proposed. The closed-loop equilibrium is therefore guaranteed to be locally asymptotically stable. In the second issue, we study the transient stability property of post-fault initial states. To this end, an optimization-based approach to calculate the critical level set of the proposed Lyapunov function is proposed. This allows to estimate an explicit region of attraction of the closed-loop equilibrium. Therefore, the transient stability property of a post-fault initial state can be directly assessed. A case study on the IEEE 10-machine 39-bus power system, to demonstrate the performance and effectiveness of the proposed direct method, is presented.
  • Conference paper
    Javaid M, Chaudhuri B, Teng F, Akhtar Zet al., 2025,

    A novel tuning method of grid-forming inverter voltage control

    , IEEE PowerTech 2025, Publisher: IEEE

    Grid-forming inverters (GFMs) may experience instabilityin strong grids, often resulting from voltage controlinterference, particularly when multiple voltage sources are electrically close. This issue is further exacerbated when control gains are obtained under avoidable assumptions. A temporary solution is to retune control gain, yet it yields suboptimal performance. To address this, we propose a novel tuning technique for GFM control that employs a concurrent design approach for d and q axes voltage control. The proposed method also incorporates the dynamics of an equivalent grid model in the design process. The required design specifications are translated into weighting functions, formulating the H∞ minimization problem for optimal tuning. The proposed tuning method is compared against direct synthesis and symmetrical optimum methods. The comparison reveals the advantages of the proposed method in mitigating the impact of grid strength. Their performance is evaluated on 9-bus and 11-bus test systems. It is shown that the proposed approach achieves higher control bandwidth and improved stability margins compared to conventional designs.
  • Journal article
    Javaid MS, Chaudhuri B, Teng F, Akhtar Zet al., 2025,

    EMT−RMS modeling trade-off for IBR-driven sub-synchronous oscillations

    , IEEE Transactions on Power Systems, ISSN: 0885-8950

    Low-frequency electromechanical oscillations (<2Hz) are time-separated from faster network dynamics, allowing network dynamics to be safely neglected in positive-sequence RMS (RMS+) studies. However, with increasing shares of inverter-based resources (IBRs), sub-synchronous oscillations (SSOs) occur at higher frequencies (>5 Hz) within the electromagnetic timescales. The shift challenges using RMS+ tools for planning IBR-dominated grids, as the time-scale separation is no longer as distinct as in synchronous machine-based systems. This paper demonstrates that relying on RMS+ studies in high-IBRscenarios can lead to erroneous conclusions about SSO, including a false assurance of stability. We explain how the interaction between IBR control and network dynamics affect the damping of SSO. This highlights the need for EMT-dq with network dynamics in a synchronously rotating reference frame as a middle ground between EMT-abc (point-on-wave) and RMS+ for studying IBR-drivenSSO. EMT-dq is computationally simpler than EMTabcand allows frequency-domain analysis for deeper insightand effective SSO mitigation. This emphasizes the necessity of established (rather than bespoke) EMT-dq tools to quickly screen SSO-prone scenarios for detailed investigation in EMT-abc.
  • Conference paper
    Gao J, Chaudhuri B, Astolfi A, 2025,

    Enhanced transient stabilization with damping assignment

    , 13th IFAC Symposium on Nonlinear Control Systems, Publisher: Elsevier, ISSN: 2405-8963

    The paper proposes an analytical nonlinear control approach for enhancing the transient performance of lossy multi-machine power systems. The prominent feature of thisapproach lies in the inclusion of damping assignment, whereby the oscillation of the power system frequency is dampened out more effectively. In this regard, the proposed control approach is said to achieve enhanced transient stabilization, which is desirable in practical applications.A case study demonstrates the enhanced performance of the proposed control approach over existing nonlinear control approaches.
  • Journal article
    O'Malley M, Holttinen H, Cutululis N, Vrana TK, King J, Gevorgian V, Wang X, Rajaei-Najafabadi F, Hadjileonidas Aet al., 2024,

    Grand challenges of wind energy science - meeting the needs and services of the power system

    , Wind Energy Science, Vol: 9, Pages: 2087-2112, ISSN: 2366-7443

    The share of wind power in power systems is increasing dramatically, and this is happening in parallel with increased penetration of solar photovoltaics, storage, other inverter-based technologies, and electrification of other sectors. Recognising the fundamental objective of power systems, maintaining supply–demand balance reliably at the lowest cost, and integrating all these technologies are significant research challenges that are driving radical changes to planning and operations of power systems globally. In this changing environment, wind power can maximise its long-term value to the power system by balancing the needs it imposes on the power system with its contribution to addressing these needs with services. A needs and services paradigm is adopted here to highlight these research challenges, which should also be guided by a balanced approach, concentrating on its advantages over competitors. The research challenges within the wind technology itself are many and varied, with control and coordination internally being a focal point in parallel with a strong recommendation for a holistic approach targeted at where wind has an advantage over its competitors and in coordination with research into other technologies such as storage, power electronics, and power systems.
  • Conference paper
    Thakar S, Ramasubramanian D, Matevosyan J, Najafabadi FR, O’Malley Met al., 2024,

    System services from inverter based resources for reliable operation

    , 2024 IEEE Power & Energy Society General Meeting (PESGM), Publisher: IEEE, Pages: 1-5

    With the increasing penetration of inverter based resources (IBRs) in present and future power systems, it is important to consider the different grid services needed from/provided by IBRs. To ensure network stability after a contingency such as trip of a synchronous generator or a fault, a grid may require services (for example, fast voltage control) from various IBRs. New IBRs to be installed with future capabilities (inherent blackstart capability) are often seen as a potential source for such services. However, the capability of many existing IBRs today are underutilized and if the capability from existing IBRs is utilized efficiently, it could greatly improve the network performance and reduce services needed from the future IBRs. This paper provides few illustrative examples detailing some of the services that may be needed by an IBR-dominated grid and the impact of asking these services from future IBRs and/or supplementing with services from existing IBRs.
  • Journal article
    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, Vol: 39, Pages: 6345-6358, 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
    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
    Xu L, Feng K, Lin N, Perera ATD, Poor HV, Xie L, Ji C, Sun XA, Guo Q, OMalley Met al., 2024,

    Resilience of renewable power systems under climate risks

    , Nature Reviews Electrical Engineering, Vol: 1, Pages: 53-66, ISSN: 2948-1201

    Climate change is expected to intensify the effects of extreme weather events on power systems and increase the frequency of severe power outages. The large-scale integration of environment-dependent renewables during energy decarbonization could induce increased uncertainty in the supply–demand balance and climate vulnerability of power grids. This Perspective discusses the superimposed risks of climate change, extreme weather events and renewable energy integration, which collectively affect power system resilience. Insights drawn from large-scale spatiotemporal data on historical US power outages induced by tropical cyclones illustrate the vital role of grid inertia and system flexibility in maintaining the balance between supply and demand, thereby preventing catastrophic cascading failures. Alarmingly, the future projections under diverse emission pathways signal that climate hazards — especially tropical cyclones and heatwaves — are intensifying and can cause even greater impacts on the power grids. High-penetration renewable power systems under climate change may face escalating challenges, including more severe infrastructure damage, lower grid inertia and flexibility, and longer post-event recovery. Towards a net-zero future, this Perspective then explores approaches for harnessing the inherent potential of distributed renewables for climate resilience through forming microgrids, aligned with holistic technical solutions such as grid-forming inverters, distributed energy storage, cross-sector interoperability, distributed optimization and climate–energy integrated modelling.
  • Journal article
    Veers P, Dykes K, Basu S, Bianchini A, Clifton A, Green P, Holttinen H, Kitzing L, Kosovic B, Lundquist JK, Meyers J, O'Malley M, Shaw WJ, Straw Bet al., 2022,

    Grand Challenges: wind energy research needs for a global energy transition

    , Wind Energy Science, Vol: 7, Pages: 2491-2496, ISSN: 2366-7443

    Wind energy is anticipated to play a central role in enabling a rapid transition from fossil fuels to a system based largely on renewable power. For wind power to fulfill its expected role as the backbone – providing nearly half of the electrical energy – of a renewable-based, carbon-neutral energy system, critical challenges around design, manufacture, and deployment of land and offshore technologies must be addressed. During the past 3 years, the wind research community has invested significant effort toward understanding the nature and implications of these challenges and identifying associated gaps. The outcomes of these efforts are summarized in a series of 10 articles, some under review by Wind Energy Science (WES) and others planned for submission during the coming months. This letter explains the genesis, significance, and impacts of these efforts.
  • Journal article
    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
    Chen B, Pin G, Ng WM, Hui SYR, Parisini Tet al., 2018,

    An Adaptive-Observer-Based Robust Estimator of Multi-sinusoidal Signals

    , IEEE TRANSACTIONS ON AUTOMATIC CONTROL, Vol: 63, Pages: 1618-1631, ISSN: 0018-9286

    This paper presents an adaptive observer-based robust estimation methodology of the amplitudes, frequencies and phases of biased multi-sinusoidal signals in presence of bounded perturbations on the measurement. The parameters of the sinusoidal components are estimated on-line and the update laws are individually controlled by an excitation-based switching logic enabling the update of a parameter only when the measured signal is sufficiently informative. This way doing, the algorithm is able to tackle the problem of over-parametrization (i.e., when the internal model accounts for a number of sinusoids that is larger than the true spectral content) or temporarily fading sinusoidal components. The stability analysis proves the existence of a tuning parameter set for which the estimator's dynamics are input-to-state stable with respect to bounded measurement disturbances. The performance of the proposed estimation approach is evaluated and compared with other existing tools by extensive simulation trials and real-time experiments.
  • Journal article
    Majumdar A, Pal BC, 2018,

    Bad data detection in the context of leverage point attacks in modern power networks

    , IEEE Transactions on Smart Grid, Vol: 9, Pages: 2042-2054, ISSN: 1949-3061

    This paper demonstrates a concept to detect bad data in state estimation when the leverage measurements are tampered with gross error. The concept is based on separating leverage measurements from non-leverage measurements by a technique called diagnostic robust generalized potential (DRGP), which also takes care of the masking or swamping effect, if any. The methodology then detects the erroneous measurements from the generalized studentized residuals (GSR). The effectiveness of the method is validated with a small illustrative example, standard IEEE 14-bus and 123-bus unbalanced network models and compared with the existing methods. The method is demonstrated to be potentially very useful to detect attacks in smart power grid targeting leverage points in the system.
  • Journal article
    Gu Y, Bottrell N, Green TC, 2018,

    Reduced-order models for representing converters in power system studies

    , IEEE Transactions on Power Electronics, Vol: 33, Pages: 3644-3654, ISSN: 0885-8993

    A reduced-order model that preserves physical meaning is important for generating insight in large-scale power system studies. The conventional model-order reduction for a multiple-timescale system is based on discarding states with fast (short timescale) dynamics. It has been successfully applied to synchronous machines, but is inaccurate when applied to power converters because the timescales of fast and slow states are not sufficiently separated. In the method proposed here, several fast states are at first discarded but a representation of their interaction with the slow states is added back. Recognizing that the fast states of many converters are linear allows well-developed linear system theories to be used to implement this concept. All the information of the original system relevant to system-wide dynamics, including nonlinearity, is preserved, which facilitates judgments on system stability and insight into control design. The method is tested on a converter-supplied mini power system and the comparison of analytical and experiment results confirms high preciseness in a broad range of conditions.
  • Journal article
    De Paola A, Angeli D, Strbac G, 2018,

    Integration of price-responsive appliances in the energy market through flexible demand saturation

    , IEEE Transactions on Control of Network Systems, Vol: 5, Pages: 154-166, ISSN: 2325-5870

    This paper proposes a novel decentralized technique for efficient integration of flexible demand in the electricity market. The analysis focuses on price-responsive appliances that schedule their power consumption on the basis of a demand/price signal received by a central entity. Previous work has shown that, when the devices population is sufficiently large to be described as a continuum, it is possible to provide necessary and sufficient conditions for the existence of a Nash equilibrium (no device has unilateral interest in changing its scheduling when considering the resulting profile of aggregate demand). These results are now extended in order to achieve an equilibrium also when the mentioned conditions are violated. To this purpose, a time-varying proportional constraint (equal for all devices) is introduced on the power rate of the price-responsive appliances so as to limit the variation of flexible demand that they can introduce at critical time instants. The proposed design technique not only guarantees existence of a Nash equilibrium but it also minimizes the global operation time of the appliances population. Simulation results are provided and it is shown that, under the considered assumptions, each individual appliance completes its task in minimum time.
  • Journal article
    Junyent Ferre A, Li Y, Rodríguez-Bernuz JM, 2018,

    A three-phase active rectifier topology for bipolar DC distribution

    , IEEE Transactions on Power Electronics, Vol: 33, Pages: 1063-1074, ISSN: 0885-8993

    A new three-phase active rectifier topology is proposed for bipolar dc distribution, which can achieve the independent dc-pole control, with only one two-level voltage source converter and an ac-side grounding inductor. The averaged large-signal model and linearized small-signal model of the rectifier are derived in the stationary reference frame. Moreover, a control system is proposed with proper controller parameters. Besides, the rectifier is tested on an experiment platform. Comprehensive experiment results are given and analyzed to validate the function of the proposed rectifier under different operation conditions, including the rectifier start-up performance, rectifier dynamics with unbalanced dc loads for two poles, and rectifier dynamics with asymmetrical dc voltages for two poles. Finally, the proposed rectifier is compared with other two existing ac-dc conversion approaches, in terms of required number and rating of components as well as power losses with different load imbalance levels, which further highlight some potential benefits of the proposed topology.
  • Conference paper
    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.
  • Journal article
    Judge PD, Merlin MMC, Green TC, Trainer DR, Vershinin Ket al., 2018,

    Thyristor-Bypassed Submodule Power-Groups for Achieving High-Efficiency, DC Fault Tolerant Multilevel VSCs

    , IEEE TRANSACTIONS ON POWER DELIVERY, Vol: 33, Pages: 349-359, ISSN: 0885-8977
    • Cite
    • Citations: 20
  • Conference paper
    Rodrigues T, Moreira R, Strbac G, 2018,

    Coordinated operation of distributed energy storage in low carbon networks

    , 2017 IEEE PES General Meeting, Publisher: IEEE, ISSN: 1944-9925

    Recent developments on climate change regulations are leading to significant changes in the electricity industry with volatility levels and uncertainty increasing significantly. As aresult, systemoperators are extending the procurement of flexibility to end-users and encourage more pro-active behaviors, including provision of system balancing services. In this context, this paper will investigate the potential flexibility and benefits that a coordinated operation of multiple households’ rooftop solar and energy storage can offer to the various sectors of the electricity market. The model will analyze the coordinated operation of multiple households and minimize the supply costs for the whole community while offering flexibility services to the system operator and provide peak demand reduction at the distribution network level. Fundamentally, the proposed model will consider the possibility of households to share energy resources in a peer-to-peer arrangement and thus minimize energy supply costs. In addition, the model also considers the provision of frequency response and reserve services and their associated revenues.Our results have shown significant cost savings can be achieved through a coordinated energy trading and consequently reduce energy transactions with suppliers. Provision offlexibility throughbalancing services becomes the major benefit to support the business case for coordinated operation of storagein low carbon communities.
  • Conference paper
    Padoan A, Astolfi, 2018,

    Model reduction by moment matching at isolated singularitiesfor linear systems: a geometric approach

    , 56th IEEE Conference on Decision and Control, Publisher: IEEE

    The model reduction problem for continuous-time, linear, time-invariant systems is studied at isolated singularities of the transfer function. The moments at a pole of the transfer function are shown to be uniquely specified by the solutions of certain Sylvester equations exploiting two distinct approaches based on complex analysis and on geometric control theory. This allows to determine reduced order models which preserve given poles and match the corresponding moments. An in-depth analysis of the assumptions underlying this approach is provided in a companion paper. The applicability of the approaches developed is demonstrated with simple academic examples.
  • Conference paper
    Di Franco P, Scarciotti G, Astolfi A, 2018,

    On the stability of constrained mechanical systems

    , 56th IEEE Conference on Decision and Control, Publisher: IEEE

    The problem of the stability analysis for constrained mechanical systems is addressed using tools from classical geometric control theory, such as the notion of zero dynamics. For the special case of linear constrained mechanical systems we show that stability is equivalent to a detectability property. The proposed techniques are illustrated by means of simple examples.
  • Journal article
    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
    Padoan A, Scarciotti G, Astolfi A, 2017,

    A geometric characterization of the persistence of excitation condition for the solutions of autonomous systems

    , IEEE Transactions on Automatic Control, Vol: 62, Pages: 5666-5677, ISSN: 0018-9286

    The persistence of excitation of signals generated by time-invariant, autonomous, linear, and nonlinear systems is studied using a geometric approach. A rank condition is shown to be equivalent, under certain assumptions, to the persistence of excitation of the solutions of the class of systems considered, both in the discrete-time and in the continuous-time settings. The rank condition is geometric in nature and can be checked a priori, i.e. without knowing explicitly the solutions of the system, for almost periodic systems. The significance of the ideas and tools presented is illustrated by means of simple examples. Applications to model reduction from input-output data and stability analysis of skew-symmetric systems are also discussed.
  • Journal article
    Kkelis G, Yates DC, Mitcheson PD, 2017,

    Class-E half-wave zero dv/dt rectifiers for inductive power transfer

    , IEEE Transactions on Power Electronics, Vol: 32, Pages: 8322-8337, ISSN: 0885-8993

    This paper analyses and compares candidate zero dv/dt half-wave Class-E rectifier topologies for integration into multi-MHz inductive power transfer (IPT) systems. Furthermore, a hybrid Class-E topology comprising advantageous properties from all existing Class-E half-wave zero dv/dt rectifiers is analysed for the first time. From the analysis, it is shown that the hybrid Class-E rectifier provides an extra degree of design freedom which enables optimal IPT operation over a wider range of operating conditions. Furthermore, it is shown that by designing both the hybrid and the current driven rectifiers to operate below resonance provides a low deviation input reactance and inherent output voltage regulation with duty cycle allowing efficient IPT operation over wider dc load range than would otherwise be achieved. A set of case studies demonstrated the following performances: 1) For a constant dc load resistance, a receiving end efficiency of 95% was achieved when utilising the hybrid rectifier, with a tolerance in required input resistance of 2.4% over the tested output power range (50W to 200W). 2) For a variable dc load in the range of 100% to 10%, the hybrid and current driven rectifiers presented an input reactance deviation less than 2% of the impedance of the magnetising inductance of the inductive link respectively and receiving end efficiencies greater than 90%. 3) For a constant current in the receiving coil, both the hybrid and the current driven rectifier achieve inherent output voltage regulation in the order of 3% and 8% of the nominal value respectively, for a variable dc load range from 100% to 10%.
  • Journal article
    De Paola A, Angeli D, Strbac G, 2017,

    Price-Based Schemes for Distributed Coordination of Flexible Demand in the Electricity Market

    , IEEE TRANSACTIONS ON SMART GRID, Vol: 8, Pages: 3104-3116, ISSN: 1949-3053
  • Journal article
    Tzelepis D, Rousis AO, Dysko A, Booth C, Strbac Get al., 2017,

    A new fault-ride-through strategy for MTDC networks incorporating wind farms and modular multi-level converters

    , INTERNATIONAL JOURNAL OF ELECTRICAL POWER & ENERGY SYSTEMS, Vol: 92, Pages: 104-113, ISSN: 0142-0615
  • Conference paper
    Di Franco P, Scarciotti G, Astolfi A, 2017,

    A note on the stability of nonlinear differential-algebraic systems

    , 20th IFAC World Congress, Publisher: Elsevier, Pages: 7421-7426, ISSN: 1474-6670

    The problem of the stability analysis for nonlinear differential-algebraic systems is addressed using tools from classical control theory Exploiting Lyapunov Direct Method we provide linear matrix inequalities to establish stability properties of this class of systems. In addition, interpreting the differential-algebraic system as the feedback interconnection of a dynamical system and an algebraic system, a sufficient stability condition has been derived using the small-gain theorem. The proposed techniques are illustrated by means of simple examples.

This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.

Request URL: http://www.imperial.ac.uk:80/respub/WEB-INF/jsp/search-t4-html.jsp Request URI: /respub/WEB-INF/jsp/search-t4-html.jsp Query String: id=955&limit=30&respub-action=search.html Current Millis: 1765059183550 Current Time: Sat Dec 06 22:13:03 GMT 2025