252 results found
Pal B, Lekshmi D, Rather Z, et al., 2024, Online estimation of disturbance size and frequency nadir prediction in renewable energy integrated power systems, IEEE Transactions on Power Systems, Vol: 39, Pages: 1126-1137, ISSN: 0885-8950
The displacement of conventional synchronous generation by Inverter-Based Resources (IBRs) poses critical challenges to the frequency stability of Renewable Energy (RE) integrated power systems. An increased shift towards green energy by integrating RE sources that provide little or no inertia results in a high Rate of Change of Frequency (RoCoF) and deteriorated frequency nadir/zenith following a credible system disturbance. Prediction of frequency metrics, such as frequency nadir and RoCoF, immediately after disturbances will help grid operators to take preventive/corrective actions, such as the deployment of faster frequency control, to ensure secure and stable grid operation. This paper presents an easy-to-implement analytical method to estimate disturbance size in a power system immediately following a contingency which is then used for predicting frequency nadir. The proposed estimation method uses active power measurements from a limited number of monitoring nodes and an adaptive bus admittance matrix of the system for the disturbance size estimation. The estimated disturbance size is then used to predict frequency nadir using a Neural Network (NN) based method. The performance and accuracy of the presented approach are evaluated using a standard IEEE 39 bus system and a real-life Gujarat power system in India through extensive simulations in DIgSILENT PowerFactory, considering various cases of disturbance size, type, and location.
Pawar B, Batzelis EI, Chakrabarti S, et al., 2023, Interfacing Synchronous Machine Model Including Stator Transients With Network for Stability Studies, IEEE Transactions on Power Systems, Vol: 38, Pages: 5941-5944, ISSN: 0885-8950
A detailed multi-time scale model of synchronous machines (SM) with stator transients is necessary to capture the complex interactions in inverter-integrated power systems. The conventional detailed SM model, including stator transients, is incompatible with that of the step-up transformer in the dq domain as both are modeled as current sources in series. This letter proposes an efficient approach for interfacing the detailed SM model with the transformer by reformulating the SM model as a voltage source without accuracy loss. MATLAB/Simulink numerical simulations using New England 39-bus test system validate the computational efficiency of the proposed approach.
Wang Y, Pal B, 2023, Destabilizing attack and robust defense for inverter-based microgrids by adversarial deep reinforcement learning, IEEE Transactions on Power Systems, Vol: 14, Pages: 4839-4850, ISSN: 0885-8950
The controllers of inverter-based resources (IBRs) can be adjustable by grid operators to facilitate regulation services. Considering the increasing integration of IBRs at power distribution level systems like microgrids, cyber security is becoming a major concern. This paper investigates the data-driven destabilizing attack and robust defense strategy based on adversarial deep reinforcement learning for inverter-based microgrids. Firstly, the full-order high-fidelity model and reduced-order small-signal model of typical inverter-based microgrids are recapitulated. Then the destabilizing attack on the droop control gains is analyzed, which reveals its impact on system small-signal stability. Finally, the attack and defense problems are formulated as Markov decision process (MDP) and adversarial MDP (AMDP). The problems are solved by twin delayed deep deterministic policy gradient (TD3) algorithm to find the least effort attack path of the system and obtain the corresponding robust defense strategy. The simulation studies are conducted in an inverter-based microgrid system with 4 IBRs and IEEE 123-bus system with 10 IBRs to evaluate the proposed method.
Chakravarthi K, Bhui P, Sharma NK, et al., 2023, Real Time Congestion Management Using Generation Re-Dispatch: Modeling and Controller Design, IEEE TRANSACTIONS ON POWER SYSTEMS, Vol: 38, Pages: 2189-2203, ISSN: 0885-8950
Yu Y, Nduka O, Ul-Nazir F, et al., 2023, A three-stage stochastic framework for smart electric vehicle charging, IEEE Access, Vol: 11, Pages: 655-666, ISSN: 2169-3536
As one of the most significant part of carbon neutralisation, the rapid growth of electric vehicle (EV) market in past few years has greatly expedited the transport electrification, which, however, has brought in new challenges to power system including isolated distribution network for commercial and industrial set up. Stochastic and complex EV behaviours would violate network permissible operation region and increase costs for system operators. To address these problems, a chance-constrained smart EV charging strategy in a DC microgrid (DCMG) supporting large office complex is proposed to minimize system cost from distribution network and fleet battery degradation cost from EVs providing ancillary service to the DCMG. When dealing with uncertainties from EVs, a Markov Chain Monte Carlo (MCMC) model is built to couple different parameters in load profiles and characterize the time series of likelihood of charging and discharging. A state-of-charge (SOC) space random walk method is then proposed to solve the resultant massive recursive probabilistic charging requirements. Based on that, a three-stage optimization framework is established to illustrate the work flow in system level. Numerical results verifying the effectiveness of the proposed method are also presented.
Nazir FU, Pal B, Jabr R, 2023, Affinely adjustable robust Volt/VAr control without centralized computations, IEEE Transactions on Power Systems, Vol: 38, Pages: 656-667, ISSN: 0885-8950
This paper proposes a completely non-centralized Volt/VAr control (VVC) algorithm for active distribution networks which are faced with voltage magnitude violations due to the high penetration of solar photovoltaics (PVs). The proposed VVC algorithm employs a two-stage architecture where the settings of the classical voltage control devices (VCDs) are decided in the first stage through a distributed optimization engine powered by the alternating direction method of multipliers (ADMM). In contrast, the PV smart inverters are instructed in the second stage through linear Q(P) decision rules - which are computed in a decentralized manner by leveraging robust optimization theory. The key to this non-centralized VVC routine is a proposed network partition methodology (NPM) which uses an electrical distance metric based on node Q-V 2 sensitivities for computing an intermediate reduced graph of the network, which is subsequently divided into the final partitions using the spectral clustering technique. As a result, the final network partitions are connected, stable, close in cardinality, contain at least one PV inverter for zonal reactive power support, and are sufficiently decoupled from each other. Numerical results on the UKGDS-95 bus system show that the non-centralized solutions match closely with the centralized robust VVC schemes, thereby significantly reducing the voltage violations compared to the traditional deterministic VVC routines.
Cheng Y, Fan L, Rose J, et al., 2023, Real-World Subsynchronous Oscillation Events in Power Grids With High Penetrations of Inverter-Based Resources, IEEE TRANSACTIONS ON POWER SYSTEMS, Vol: 38, Pages: 316-330, ISSN: 0885-8950
Ghosh S, Bakhshizadeh MK, Yang G, et al., 2023, Nonlinear Stability Investigation of Type-4 Wind Turbines With Non-Autonomous Behavior Based on Transient Damping Characteristics, IEEE ACCESS, Vol: 11, Pages: 76059-76070, ISSN: 2169-3536
Lin H, UI Nazir F, C Pal B, et al., 2023, A linearized branch flow model considering line shunts for radial distribution systems and its application in Volt/VAr control, Journal of Modern Power Systems and Clean Energy, Vol: 11, Pages: 1191-1200, ISSN: 2196-5625
When urban distribution systems are gradually modernized, the overhead lines are replaced by underground cables, whose shunt admittances can not be ignored. Traditional power flow (PF) model with π equivalent circuit shows non-convexity and long computing time, and most recently proposed linear PF models assume zero shunt elements. All of them are not suitable for fast calculation and optimization problems of modern distribution systems with non-negligible line shunts. Therefore, this paper proposes a linearized branch flow model considering line shunt (LBFS). The strength of LBFS lies in maintaining the linear structure and the convex nature after appropriately modeling the π equivalent circuit for network equipment like transformers. Simulation results show that the calculation accuracy in nodal voltage and branch current magnitudes is improved by considering shunt admittances. We show the application scope of LBFS by controlling the network voltages through a two-stage stochastic Volt/VAr control (VVC) problem with the uncertain active power output from renewable energy sources (RESs). Since LBFS results in a linear VVC program, the global solution is guaranteed. Case study exhibits that VVC framework can optimally dispatch the discrete control devices, viz. substation transformers and shunt capacitors, and also optimize the decision rules for real-time reactive power control of RES. Moreover, the computing efficiency is significantly improved compared with that of traditional VVC methods.
Pal B, Guo Y, Jabr R, 2022, Model-free optimal control of inverter for dynamic voltage support, IEEE Transactions on Power Systems, ISSN: 0885-8950
Inverter-based resources (IBRs) are required to provide dynamic voltage support (DVS) during voltage dips to enhance the low-voltage ride-through capability. In this paper, a model-free control method is developed to achieve the optimal DVS (ODVS) without relying on the knowledge of grid parameters. Delving into the optimum trajectory of the ODVS problem, it is found that the current constraint and the maximum active power constraint of IBRs are both binding, or one of them is binding. This inspires us to search for the optimum in a closed-loop way by a perturb-and-observe (P&O)-based optimum seeking (OS) controller with either the power factor angle or the reactive current being the manipulated (perturbed) variable. The system is guaranteed to converge asymptotically to the optimum provided the stepsize sequence is diminishing and non-summable. The proposed model-free optimal control is finally implemented within a single-stage photovoltaic (PV) system, where dynamic simulations demonstrate the optimal and fast DVS performance. Moreover, the implementation strategy for other types of IBRs that are not self-protected by nature is also discussed.
Fan L, Miao Z, Shah S, et al., 2022, Real-World 20-Hz IBR Subsynchronous Oscillations: Signatures and Mechanism Analysis, IEEE TRANSACTIONS ON ENERGY CONVERSION, Vol: 37, Pages: 2863-2873, ISSN: 0885-8969
Ortiz-Villalba D, Llanos J, Munoz-Jadan Y, et al., 2022, Optimizing system operation with nadir considerations via simulations of detailed system dynamic responses, ELECTRIC POWER SYSTEMS RESEARCH, Vol: 212, ISSN: 0378-7796
Kampitsis G, Batzelis E, Antonis K, et al., 2022, A generalized phase-shift PWM extension for improved natural and active balancing of flying capacitor multilevel inverters, IEEE Open Journal of Power Electronics, Vol: 3, Pages: 621-634, ISSN: 2644-1314
The emergence of wide bandgap power devices has brought the attention back to the flying capacitor (FC) multilevel inverters witha large number of stages, in an effort to increase the power density by minimizing the passive components. The main challenge that such systemsface, particularly the ones based on high-frequency Gallium-Nitride devices and small-value ceramic capacitors, relate to the stringentrequirements for precise and fast capacitor balancing. Conventional natural balancing techniques exhibit poor settling times, while most improvednatural balancing methods are not easily scalable to more than five levels. The alternative of active balancing normally requires one isolatedsensor per FC which increases the overall system cost and footprint, or a single ac-side sensor that is more compact but calls for sophisticatedPWMs that again are not available for multiple levels. In this paper we introduce a generalized pulse width modulation (PWM) strategy based onthe phase-shift and carrier swapping principles for an arbitrary number of levels. We provide an easy and intuitive method for the extraction ofthe PWM pattern, the switching states, and their sequence. Simulations were carried out in Matlab/Simulink and experimental tests were conductedon a single-phase 7-level GaN inverter prototype. Not only is the extended PWM advantageous in natural balancing, but it also provides the rightzero switching states for ac-side FC sensing in active balancing
Guo Y, Pal BC, Jabr RA, et al., 2022, Global optimality of inverter dynamic voltage support, IEEE Transactions on Power Systems, Vol: 37, Pages: 3947-3957, ISSN: 0885-8950
This paper investigates the dynamic voltage support (DVS) of inverter-based resources (IBRs) under voltage sags to enhance the low-voltage ride-through performance. The DVS problem is formulated as a nonconvex optimization program that maximizes the positive-sequence voltage magnitude at the point of common coupling (PCC) subject to the current, active power, and synchronization stability constraints. Then, we perform the optimality analysis to explore the global optimum analytically. It is found that the unique global optimum has three scenarios/stages (S1S3), which depends on the specific relationship among grid voltage, grid strength, and physical limits of IBRs. The explicit closed-form solutions in S1 and S3 are derived, and the optimality conditions (an implicit solution) of S2 are provided, which guarantees the global optimality and enables the compatibility with fast real-time control. Finally, we implement the optimum with a grid-connected single-stage photovoltaic (PV) power plant by integrating a DVS controller. Dynamic simulations are carried out under different scenarios to test our proposal. The robustness against model errors is also discussed. Dynamic simulations are carried out under different scenarios to test our proposal and compare it with other existing methods.
Dozein M, Pal BC, Mancarella P, 2022, Dynamics of inverter-based resources in weak distribution grids, IEEE Transactions on Power Systems, Vol: 37, Pages: 3682-3692, ISSN: 0885-8950
This work presents the modelling fundamentals to study the dynamics of inverter-based resources (IBRs) in weak distribution grids and derive disturbance performance characteristics describing how they should behave under different conditions. More specifically, with respect to small-signal disturbances we study the possible voltage violations following frequency response from IBRs due to low system strength and also propose specific design requirements for IBR d-q current control to guarantee a stable response. In the context of large-signal disturbances, we highlight how active power-voltage control may not be effective due to a delay imposed by the physical features of the distribution network. Further, we mathematically discuss how IBR reactive power control could enhance its phase-locked loop stability. The proposed disturbance performance characteristics are then integrated into the IBR converter control via a novel voltage-priority reference generation strategy. Simulation results on a real Australian network show the efficacy of the proposed operational and control design requirements, and highlight possible unexpected active/reactive power interactions in weak distribution grids.
Cifuentes N, Sun M, Gupta R, et al., 2022, Black-Box Impedance-Based Stability Assessment of Dynamic Interactions Between Converters and Grid, IEEE TRANSACTIONS ON POWER SYSTEMS, Vol: 37, Pages: 2976-2987, ISSN: 0885-8950
Mir AS, Singh AK, Pal BC, et al., 2022, Adequacy of lyapunov control of power systems considering modelling details and control indices, IEEE Transactions on Power Systems, Pages: 1-12, ISSN: 0885-8950
Kampitsis G, Batzelis E, Mitcheson PD, et al., 2022, A clamping circuit based voltage measurement system for high frequency flying capacitor multilevel inverters, IEEE Transactions on Power Electronics, Vol: 37, Pages: 1-1, ISSN: 0885-8993
In an era where high-frequency flying capacitor (FC) multilevel inverters (MLI) are increasingly gaining attention in energy conversion systems that push the boundaries of power density, the need for a compact, fast, and accurate FC voltage monitoring is also increasing. In this paper we designed and developed a new FC measurement system, based on precise sampling of the inverter switching node voltage, through a bidirectional clamping circuit. The deviation of FC voltages from their nominal values are extracted by solving a set of linear equations. With a single sensor per phase and no isolation requirements, as opposed to dozens of sensors in traditional FC monitoring, our approach results in significantly lower cost, complexity, and circuit-size. Detailed device-level simulations in LTspice and system-scale simulations in Matlab, validate the accuracy and speed of the proposed measurement system and the balancing strategy in steady state, abrupt load change and imbalance conditions. Experiments carried out in a 3-phase Gallium-Nitride 5-level inverter prototype, reveal a gain in precision and bandwidth that is more than 30 times that of conventional methods, at a fraction of their cost and footprint. The recorded performance renders the developed sensor an ideal solution for fast MLIs based on wide-bandgap technology
Kazmi SHH, Viafora N, Sorensen TS, et al., 2022, Offshore Windfarm Design Optimization Using Dynamic Rating for Transmission Components, IEEE TRANSACTIONS ON POWER SYSTEMS, Vol: 37, Pages: 1820-1830, ISSN: 0885-8950
Guo Y, Pal BC, Jabr RA, 2022, On the optimality of voltage unbalance attenuation by inverters, IEEE Transactions on Sustainable Energy, Vol: 13, Pages: 1492-1506, ISSN: 1949-3029
In this paper, we investigate the control of inverterbased resources (IBRs) for optimal voltage unbalance attenuation(OVUA). This problem is formulated as an optimization program under a tailored dq-frame, which minimizes the negativesequence voltage at the point of common coupling (PCC) subjectto the current, active power, synchronization stability, and feasibility constraints. The program is inherently nonconvex andintractable. So, to guarantee the optimality, a rigorous optimality analysis is performed by leveraging analytical optimization.The analysis is divided into two cases: full mitigation of VU andpartial attenuation of VU. For the former case, we directly solvethe original program since the resultant VU is immediately deducible. For the latter one, directly solving the problem becomesvery hard. Thus, we reformulate the program into an equivalentbut more tractable form under certain conditions, by which theanalytical optimum can be derived. It is found that the optimumtrajectory has three stages (O1–O3), depending on two criticalboundary conditions (C1 and C2). We implement the optimumwith a photovoltaic (PV)-storage system by developing an OVUAcontroller. The proposed approach is demonstrated by dynamicsimulations under different VU conditions and is compared withseveral existing practices. Finally, we discuss the extension of theproposed solution in a multi-IBR system.
Lourenco EM, Tortelli OL, Pal BC, et al., 2022, Fast--decoupled distribution system state estimation, POWER DISTRIBUTION SYSTEM STATE ESTIMATION, Editors: Bosco, Lourenco, Junior, Publisher: INST ENGINEERING TECH-IET, Pages: 185-207, ISBN: 978-1-83953-201-6
Tortelli OL, Lourenco EM, Pal BC, et al., 2022, Fast--decoupled power flow method for active distribution systems, POWER DISTRIBUTION SYSTEM STATE ESTIMATION, Editors: Bosco, Lourenco, Junior, Publisher: INST ENGINEERING TECH-IET, Pages: 163-183, ISBN: 978-1-83953-201-6
Lekshmi DJ, Rather ZH, Pal BC, 2022, Frequency Response Improvement in RE Integrated Low Inertia Power Systems using Synchronous Condensers, 22nd National Power Systems Conference (NPSC), Publisher: IEEE
Nagam SS, Pal BC, 2022, Enhancing Synchronization Stability of a VSC-Grid System using IDA-PBC Controller, 13th International Symposium on Power Electronics for Distributed Generation Systems (PEDG), Publisher: IEEE, ISSN: 2329-5759
Lekshmi DJ, Rather ZH, Pal BC, 2021, A new tool to assess maximum permissible solar pv penetration in a power system, Energies, Vol: 14, ISSN: 1996-1073
With diminishing fossil fuel resources and increasing environmental concerns, large-scale deployment of Renewable Energy Sources (RES) has accelerated the transition towards clean energy systems, leading to significant RES generation share in power systems worldwide. Among different RES, solar PV is receiving major focus as it is most abundant in nature compared to others, complimented by falling prices of PV technology. However, variable, intermittent and non-synchronous nature of PV power generation technology introduces several technical challenges, ranging from short-term issues, such as low inertia, frequency stability, voltage stability and small signal stability, to long-term issues, such as unit commitment and scheduling issues. Therefore, such technical issues often limit the amount of non-synchronous instantaneous power that can be securely accommodated by a grid. In this backdrop, this research work proposes a tool to estimate maximum PV penetration level that a given power system can securely accommodate for a given unit commitment interval. The proposed tool will consider voltage and frequency while estimating maximum PV power penetration of a system. The tool will be useful to a system operator in assessing grid stability and security under a given generation mix, network topology and PV penetration level. Besides estimating maximum PV penetration, the proposed tool provides useful inputs to the system operator which will allow the operator to take necessary actions to handle high PV penetration in a secure and stable manner.
Nsengiyaremye J, Pal BC, Begovic MM, 2021, Low-cost communication-assisted line protection for multi-inverter based microgrids, IEEE Transactions on Power Delivery, Vol: 36, Pages: 3371-3382, ISSN: 0885-8977
Multi-inverter microgrid systems, particularly those with loop topology, offer higher power supply reliability and robustness compared to conventional radial distribution systems. In meshed systems, communication-less protection schemes have proved to be ineffective for multi-inverter microgrids due to bidirectional power flow, and limited and controlled fault currents generated by the voltage source converters interfacing the energy source to the network. This makes communicationassisted line protection schemes preferable for such systems despite the necessity for communication means. While these protection schemes are effective, their reliability depends much on the communication availability. This requires a back-up communication path in case the main one fails bringing up the cost issue that hinders their uptake. This paper proposes a novel and low-cost line protection based on directional blocking strategy that can operate as a main as well as a back-up protection to any protection scheme using communication means between the line terminals. As the main, it requires low-bandwidth communication system. As a back-up, it would share the same communication means with the main one and use those of the healthy lines when the faulted lines fails. Thus saving the cost of back-up communication system.
Liu Y, Singh AK, Zhao J, et al., 2021, Dynamic state estimation for power system control and protection, IEEE Transactions on Power Systems, Vol: 36, Pages: 5909-5921, ISSN: 0885-8950
Dynamic state estimation (DSE) accurately tracks the dynamics of a power system and provides the evolution of the system state in real-time. This paper focuses on the control and protection applications of DSE, comprehensively presenting different facets of control and protection challenges arising in modern power systems. It is demonstrated how these challenges are effectively addressed with DSE-enabled solutions. As precursors to these solutions, reformulation of DSE considering both synchrophasor and sampled value measurements and comprehensive comparisons of DSE and observers have been presented. The usefulness and necessity of DSE based solutions in ensuring system stability, reliable protection and security, and resilience by revamping of control and protection methods are shown through examples, practical applications, and suggestions for further development.
Pawar B, Batzelis E, Chakrabarti S, et al., 2021, Grid-forming control for solar PV systems with power reserves, IEEE Transactions on Sustainable Energy, Vol: 12, Pages: 1947-1959, ISSN: 1949-3029
This paper presents a grid-forming control (GFC) scheme for two-stage photovoltaic (PV) systems that maintains power reserves by operating below the maximum power point (MPP). The PV plant in GFC mode behaves like a voltage source that supports the grid during disturbances in full or limited grid-forming mode as per the reserve availability. This is a model-free method that avoids the estimation of MPP power in real-time commonly done in the literature, which makes it simpler and more reliable. The proposed control also features an enhanced current limitation scheme that guarantees containment of the current overshoots during faults, which is not trivial in voltage-sourced GFC inverters. A thorough investigation is done, exploring various generation mixtures of synchronous machines (SM), GFC and grid-following (GFL) inverters, and all common disturbances, e.g., load change, faults and irradiance transients. The results show very favorable dynamic performance by the GFC inverters, far superior to GFL inverters and directly comparable to SMs. It is found that replacing SMs with GFC inverters may improve the frequency profile and terminal voltage during disturbances, despite losing out in the mechanical inertia and the strict inverter overcurrent limits.
Hatziargyriou N, Milanovic J, Rahmann C, et al., 2021, Definition and classification of power system stability - revisited & extended, IEEE Transactions on Power Systems, Vol: 36, Pages: 3271-3281, ISSN: 0885-8950
Since the publication of the original paper on power system stability definitions in 2004, the dynamic behavior of power systems has gradually changed due to the increasing penetration of converter interfaced generation technologies, loads, and transmission devices. In recognition of this change, a Task Force was established in 2016 to re-examine and extend, where appropriate, the classic definitions and classifications of the basic stability terms to incorporate the effects of fast-response power electronic devices. This paper based on an IEEE PES report summarizes the major results of the work of the Task Force and presents extended definitions and classification of power system stability.
Liu J, Singh R, Pal B, 2021, Distribution system state estimation with high penetration of demand response enabled loads, IEEE Transactions on Power Systems, Vol: 36, Pages: 3093-3104, ISSN: 0885-8950
Demand-side operations incentivize utility customers to take part in various grid services. A demand response enabled load (DREL) is a flexible grid asset that schedules electricity consumption in response to a time-of-use (TOU) energy price. Consequently, its energy profile differs from that of a conventional load that is insensitive to price. This difference may cause new challenges for distribution system state estimation (DSSE). It is well known that DSSE often needs to use pseudo-measurements based on historic load profiles to increase system observability. However, historic profiles of conventional loads are not representative of DREL behaviors. The inaccuracy impacts DSSE results and other DSSE-dependent operations. In this paper, we propose an online pseudo-measurement generation approach for DSSE with DRELs. We formulate an optimization model to represent DRELs self-adjusting actions. Sampling-based stochastic optimization techniques are proposed to account for uncertainties in DRELs. A set of representative DREL behavior data corresponding to the samples are used to characterize DREL pseudo-measurements. Case studies with modified IEEE 123-bus test system verify the validity of the proposed work.
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