Energies

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34 pages, 6053 KB

Open AccessArticle

Optimal Reactive Power Compensation in Offshore HVAC Transmission: Evaluating Onshore and Subsea Reactor Placement

by Frederico Oliveira Passos, Lúcio José da Motta, Gabriel Victor dos S. C. Campos, Lucas Henrique Venâncio, Ivan Paulo de Faria, José Mauro T. Marinho, Vinicius Z. Silva, Carlos A. C. Cavaliere and Rodrigo de Moraes P. da Rosa

Energies 2026, 19(9), 2085; https://doi.org/10.3390/en19092085 - 25 Apr 2026

Viewed by 472

Abstract

The electrification of floating production, storage, and offloading (FPSO) units has emerged as a strategic solution to meet the growing demand for increased oil production while reducing carbon emissions associated with onboard gas turbine generation. Power-from-shore (PFS) systems represent a promising approach to [...] Read more.

The electrification of floating production, storage, and offloading (FPSO) units has emerged as a strategic solution to meet the growing demand for increased oil production while reducing carbon emissions associated with onboard gas turbine generation. Power-from-shore (PFS) systems represent a promising approach to achieving this goal, with transmission technologies based on high-voltage direct current (HVDC) and high-voltage alternating current (HVAC) solutions. Although HVDC is more suitable for long-distance and high-power applications, HVAC systems offer advantages in terms of robustness, simplicity, and operational maturity. Nevertheless, the reactive power compensation requirements arising from the high capacitance of submarine cables remain a major technical challenge. This study investigates and compares several reactive power compensation topologies applied to three distinct PFS systems. The proposed methodology enables a comprehensive evaluation of both onshore and subsea reactor placement strategies under technically and technologically feasible conditions. The results demonstrate that long-distance transmission of 75 MW over 250 km was achieved exclusively through subsea compensation configurations, which maintained efficiencies above 90% and voltage and current profiles within operational limits. Conversely, onshore-only compensation proved to be the most efficient solution for shorter transmission distances. The results demonstrate that the full electrification of an FPSO is technically feasible, with voltage and current profiles remaining within acceptable operational limits. The findings also indicate that mid-cable reactor placement (at 50%) is not the most effective configuration, with superior results observed for placements at 20–80% and 40–70% of the cable length. Overall, the outcomes confirm that subsea reactor placement enables higher power transfer over longer distances, significantly extending the technical boundaries traditionally separating HVDC and HVAC solutions. These results emphasize the need for continued technological development to make subsea shunt reactor installation a viable and reliable option for future FPSO electrification projects. Full article

(This article belongs to the Special Issue Advanced Electric Power Systems, 2nd Edition)

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17 pages, 710 KB

Open AccessArticle

Modeling of Three-Phase Transformers for Naval Applications Considering Transient Analysis

by Marcelo Cairo Pereira, Felipe Proença de Albuquerque, Eduardo Coelho Marques da Costa and Pablo Torrez Caballero

Energies 2026, 19(8), 1877; https://doi.org/10.3390/en19081877 - 12 Apr 2026

Viewed by 372

Abstract

This paper presents a systematic methodology for time-domain modeling of three-phase power transformers aimed at electromagnetic transient analysis in shipboard and embedded electrical systems. Accurate modeling of transformers in such environments is critical, as naval power systems are subject to strict electromagnetic compatibility [...] Read more.

This paper presents a systematic methodology for time-domain modeling of three-phase power transformers aimed at electromagnetic transient analysis in shipboard and embedded electrical systems. Accurate modeling of transformers in such environments is critical, as naval power systems are subject to strict electromagnetic compatibility (EMC) requirements and are particularly susceptible to fast transients caused by switching operations, fault events, and nonlinear loads operating in confined and isolated grids. The proposed approach combines the Vector Fitting (VF) algorithm with Clarke modal decomposition to obtain stable, passive, and causal rational approximations of the frequency-dependent admittance matrix over a wide frequency range. The admittance matrix is first identified from frequency-domain measurements or simulations, capturing the transformer’s terminal behavior across multiple frequency sub-bands. Clarke’s transformation is then applied to decouple the three-phase system into independent modal components—namely the zero-sequence and positive-sequence modes, reducing the original multi-phase problem to a set of independent single-phase systems. This modal decoupling significantly improves computational efficiency without sacrificing accuracy, as each mode can be fitted and simulated independently. Full article

(This article belongs to the Special Issue Advanced Electric Power Systems, 2nd Edition)

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27 pages, 5112 KB

Open AccessArticle

Persistence-Based Identification of Structurally Critical Transmission Lines Under N − 1 Contingencies

by Manuel Jaramillo, Diego Carrión, Carlos Barrera-Singaña, Luis Tipán, Filippos Perdikos and Jorge González

Energies 2026, 19(4), 956; https://doi.org/10.3390/en19040956 - 12 Feb 2026

Viewed by 416

Abstract

Voltage stability assessment under transmission contingencies is traditionally performed using severity-based indices evaluated on isolated outage scenarios. While effective for identifying extreme events, such approaches provide limited insight into which transmission corridors structurally govern voltage-stress behavior across the full contingency space. This paper [...] Read more.

Voltage stability assessment under transmission contingencies is traditionally performed using severity-based indices evaluated on isolated outage scenarios. While effective for identifying extreme events, such approaches provide limited insight into which transmission corridors structurally govern voltage-stress behavior across the full contingency space. This paper introduces a persistence-based diagnostic framework for voltage stability assessment under exhaustive

N - 1

line contingencies, using the Fast Voltage Stability Index (FVSI) as a base indicator. Rather than ranking lines by instantaneous severity, the proposed methodology identifies dominant transmission lines—defined as those attaining the maximum FVSI in each convergent contingency—and aggregates these outcomes statistically to quantify dominance persistence, conditional severity, and dispersion. A dominance concentration metric (

k_{90}

) is introduced to measure how many transmission corridors are sufficient to explain the majority of dominant voltage-stress events. The framework is applied to IEEE 14, 30, and 118-bus benchmark systems under exhaustive

N - 1

enumeration. Results reveal a clear phenomenon of dominance collapse: as system size increases, dominant voltage-stress outcomes concentrate onto an extremely small set of transmission corridors. While IEEE 14 exhibits partial dominance dispersion (

k_{90} = 2

), both IEEE 30 and IEEE 118 demonstrate near-total dominance collapse (

k_{90} = 1

), where a single corridor governs more than 90% of dominant FVSI events. The proposed approach is fully deterministic, scalable, and independent of control or optimization assumptions, making it well-suited for planning-stage screening, monitoring prioritization, and pre-filtering of large-scale contingency studies. By shifting voltage stability analysis from severity-only screening to persistence-based structural diagnosis, this work provides new insight into vulnerability concentration in modern transmission networks. Full article

(This article belongs to the Special Issue Advanced Electric Power Systems, 2nd Edition)

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23 pages, 2922 KB

Open AccessArticle

Optimisation of Aggregate Demand Flexibility in Smart Grids and Wholesale Electricity Markets: A Bi-Level Aggregator Model Approach

by Marco Toledo Orozco, Diego Morales, Yvon Bessanger, Carlos Álvarez Bel, Freddy H. Chuqui and Javier B. Cabrera

Energies 2026, 19(1), 152; https://doi.org/10.3390/en19010152 - 27 Dec 2025

Viewed by 900

Abstract

The transition toward intelligent and sustainable power systems requires practical schemes to integrate industrial demand flexibility into short-term operation, particularly in emerging electricity markets. This paper proposes an integrated framework that combines data-driven flexibility characterisation with a bi-level optimisation model for an industrial [...] Read more.

The transition toward intelligent and sustainable power systems requires practical schemes to integrate industrial demand flexibility into short-term operation, particularly in emerging electricity markets. This paper proposes an integrated framework that combines data-driven flexibility characterisation with a bi-level optimisation model for an industrial demand-side aggregator participating in the short-term balancing market. Flexibility is identified from AMI data and process information of large consumers, yielding around 2 MW of interruptible load and 3 MW of reducible load over a 24 h horizon. At the upper level, the aggregator maximises its profit by submitting flexibility offers; at the lower level, the system operator minimises balancing costs by co-optimising thermal generation and activated flexibility. The problem is formulated as a mixed-integer linear programming model and is evaluated on a real subtransmission and distribution network of a local utility in Ecuador, with ex-post power flow validation in DIgSILENT PowerFactory. Numerical results show that, despite the limited flexible capacity, the aggregator reduces the maximum energy price from USD/MWh 172.32 to 139.59 (about 19%), generating a daily revenue of USD 2475.15. From a network perspective, demand flexibility eliminates undervoltage at the most critical bus (from 0.93 to 1.03 p.u.) without creating overvoltages, while line loadings remain below 50% in all cases and total daily technical losses decrease from 89.46 to 89.10 MWh (about 0.4%). These results highlight both the potential and current limitations of industrial demand flexibility in short-term markets. Full article

(This article belongs to the Special Issue Advanced Electric Power Systems, 2nd Edition)

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15 pages, 1824 KB

Open AccessEditor’s ChoiceArticle

Optimal Determination of Synchronous Condenser Placement and Voltage Setting for Enhancing Power System Stability

by Juseong Lee, Hyeongjun Jo and Soobae Kim

Energies 2025, 18(24), 6474; https://doi.org/10.3390/en18246474 - 10 Dec 2025

Cited by 1 | Viewed by 1241

Abstract

With the increasing share of renewable energy in power systems, the instability of the power systems is becoming increasingly significant. Consequently, power system stability has become a critical issue, and non-transmission alternatives have been examined as potential solutions. Among non-transmission alternatives, the synchronous [...] Read more.

With the increasing share of renewable energy in power systems, the instability of the power systems is becoming increasingly significant. Consequently, power system stability has become a critical issue, and non-transmission alternatives have been examined as potential solutions. Among non-transmission alternatives, the synchronous condenser can enhance power system stability by providing inertia support and reactive power compensation, especially in systems with a high share of renewable energy. The placement and voltage settings of synchronous condensers significantly impact system stability. This paper proposes a methodology for determining the optimal placement and optimal voltage setting of synchronous condensers for enhancing their voltage stability and transient stability; the improved voltage stability index and synchronizing torque coefficient are used for enhancing the voltage stability and transient stability, respectively. A case study with a focus on specific stability aspects and involving scenarios where the size and number of synchronous capacitors are varied while maintaining a constant inertia energy is presented. The results of the case study show that strategically optimizing the placement and voltage setting of synchronous condensers can enhance the stability of a power system significantly. Full article

(This article belongs to the Special Issue Advanced Electric Power Systems, 2nd Edition)

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21 pages, 6897 KB

Open AccessArticle

Performance Analysis of HVDC Operational Control Strategies for Supplying Offshore Oil Platforms

by Alex Reis, José Carlos Oliveira, Carlos Alberto Villegas Guerrero, Johnny Orozco Nivelo, Lúcio José da Motta, Marcos Rogério de Paula Júnior, José Maria de Carvalho Filho, Vinicius Zimmermann Silva, Carlos Andre Carreiro Cavaliere and José Mauro Teixeira Marinho

Energies 2025, 18(14), 3733; https://doi.org/10.3390/en18143733 - 15 Jul 2025

Viewed by 828

Abstract

Driven by the environmental benefits associated with reduced greenhouse gas emissions, oil companies have intensified research efforts into reassessing the strategies used to meet the electrical demands of offshore production platforms. Among the various alternatives available, the deployment of onshore–offshore interconnections via High-Voltage [...] Read more.

Driven by the environmental benefits associated with reduced greenhouse gas emissions, oil companies have intensified research efforts into reassessing the strategies used to meet the electrical demands of offshore production platforms. Among the various alternatives available, the deployment of onshore–offshore interconnections via High-Voltage Direct Current (HVDC) transmission systems has emerged as a promising solution, offering both economic and operational advantages. In addition to reliably meeting the electrical demand of offshore facilities, this approach enables enhanced operational flexibility due to the advanced control and regulation capabilities inherent to HVDC converter stations. Based on the use of interconnection through an HVDC link, aiming to evaluate the operation of the electrical system as a whole, this study focuses on evaluating dynamic events using the PSCAD software version 5.0.2 to analyze the direct online starting of a large induction motor and the sudden loss of a local synchronous generating unit. The simulation results are then analyzed to assess the effectiveness of both Grid-Following (GFL) and Grid-Forming (GFM) control strategies for the converters, while the synchronous generators are evaluated under both voltage regulation and constant power factor control operation, with a particular focus on system stability and restoration of normal operating conditions in the sequence of events. Full article

(This article belongs to the Special Issue Advanced Electric Power Systems, 2nd Edition)

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28 pages, 3540 KB

Open AccessArticle

Dynamic Analysis of the Interconnection of a Set of FPSO Units to an Onshore System via HVDC

by Johnny Orozco Nivelo, Carlos A. Villegas Guerrero, Lúcio José da Motta, Marcos R. de Paula Júnior, José M.d. Carvalho Filho, Alex Reis, José Carlos Oliveira, José Mauro T. Marinho, Vinicius Z. Silva and Carlos A. C. Cavaliere

Energies 2025, 18(14), 3637; https://doi.org/10.3390/en18143637 - 9 Jul 2025

Viewed by 1292

Abstract

In an effort to restrict further increases in climate change, governments and companies are exploring ways to reduce greenhouse gas (GHG) emissions. In this context, the oil industry, which contributes to indirect GHG emissions, is seeking ways to develop solutions to this issue. [...] Read more.

In an effort to restrict further increases in climate change, governments and companies are exploring ways to reduce greenhouse gas (GHG) emissions. In this context, the oil industry, which contributes to indirect GHG emissions, is seeking ways to develop solutions to this issue. One such approach focuses on the connection of offshore oil production platforms to the onshore power grid via high-voltage direct current (HVDC), enabling a total or partial reduction in the number of local generators, which are generally powered by gas turbines. Therefore, this work aims to determine the technical feasibility, based on transient and dynamic stability analyses, of electrifying a system composed of six floating production storage and offloading (FPSO) units connected to a hub, which is powered by the onshore grid through submarine cables using HVDC technology. The analysis includes significant contingencies that could lead the system to undesirable operating conditions, allowing for the identification of appropriate remedial control actions. The analysis, based on real data and parameters, was carried out using PSCAD software. The results show that the modeled system is technically viable and could be adopted by oil companies. In addition to aligning with global warming mitigation goals, the proposal includes a complex system modeling approach, with the aim of enabling further study. Full article

(This article belongs to the Special Issue Advanced Electric Power Systems, 2nd Edition)

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29 pages, 6029 KB

Open AccessArticle

Multi-Mode Operation and Coordination Control Strategy Based on Energy Storage and Flexible Multi-State Switch for the New Distribution Network During Grid-Connected Operation

by Yuechao Ma, Jun Tao, Yu Xu, Hongbin Hu, Guangchen Liu, Tao Qin, Xuchen Fu and Ruiming Liu

Energies 2025, 18(13), 3389; https://doi.org/10.3390/en18133389 - 27 Jun 2025

Viewed by 919

Abstract

For a new distribution network with energy storage and a flexible multi-state switch (FMSS), several problems of multi-mode operation and switching, such as the unbalance of feeder loads and feeder faults, among others, should be considered. This paper forwards a coordination control strategy [...] Read more.

For a new distribution network with energy storage and a flexible multi-state switch (FMSS), several problems of multi-mode operation and switching, such as the unbalance of feeder loads and feeder faults, among others, should be considered. This paper forwards a coordination control strategy to address the above challenges faced by the FMSS under grid-connected operations. To tackle the multi-mode operation problem, the system’s operational state is divided into multiple working modes according to the operation states of the system, the positions and number of fault feeders, the working states of the transformers, and the battery’s state of charge. To boost the system’s operational reliability and load balance and extend the power supply time for the fault load, the appropriate control objectives in the coordination control layer and control strategies in the equipment layer for different working modes are established for realizing the above multi-directional control objectives. To resolve the phase asynchrony issue among the fault load and other normal working loads caused by the feeder fault, the off-grid phase-locked control based on the V/f control strategy is applied. To mitigate the bus voltage fluctuation caused by the feeder fault switching, the switching control sequence for the planned off-grid is designed, and the power feed-forward control strategy of the battery is proposed for the unplanned off-grid. The simulation results show that the proposed control strategy can ensure the system’s power balance and yield a high-quality flexible power supply during the grid-connected operational state. Full article

(This article belongs to the Special Issue Advanced Electric Power Systems, 2nd Edition)

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23 pages, 4508 KB

Open AccessArticle

Investigation of Frequency Response Sharing-Induced Power Oscillations in VSC-HVDC Systems for Asynchronous Interconnection

by Ke Wang, Chunguang Zhou, Yiping Chen, Yan Guo, Zhantao Fan and Zhixuan Li

Energies 2025, 18(11), 2928; https://doi.org/10.3390/en18112928 - 3 Jun 2025

Cited by 3 | Viewed by 1270

Abstract

Low-frequency power oscillations (LFPOs) may occur in voltage source converter-based high-voltage direct current (VSC-HVDC) systems when providing frequency support to asynchronously interconnected power grids. This phenomenon has been observed in the LUXI back-to-back (BTB) VSC-HVDC project in China and results from insufficient damping, [...] Read more.

Low-frequency power oscillations (LFPOs) may occur in voltage source converter-based high-voltage direct current (VSC-HVDC) systems when providing frequency support to asynchronously interconnected power grids. This phenomenon has been observed in the LUXI back-to-back (BTB) VSC-HVDC project in China and results from insufficient damping, which may threaten the stability of the overall power system. To better understand and address this problem, this study investigates the root causes of LFPOs and evaluates how different parts of the system affect damping. A combined approach using small-signal modeling and the damping torque method is developed to analyze the damping behavior of DC power in VSC-HVDC systems. Results show that LFPOs are caused by the interaction between VSC-based frequency control and the dynamic response of synchronous generators (SGs). The turbine and governor systems in SGs help stabilize the system by providing positive damping, whereas the DC voltage-controlled VSC station introduces negative damping. The findings are supported by detailed simulations using a modified IEEE 39-bus test system, demonstrating the effectiveness of the proposed analysis method. Full article

(This article belongs to the Special Issue Advanced Electric Power Systems, 2nd Edition)

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20 pages, 3285 KB

Open AccessArticle

Rapid Resilience Assessment and Weak Link Analysis of Power Systems Considering Uncertainties of Typhoon

by Wenqing Ma, Xiaofu Xiong and Jian Wang

Energies 2025, 18(7), 1731; https://doi.org/10.3390/en18071731 - 31 Mar 2025

Cited by 2 | Viewed by 1080

Abstract

The secure operation of the renewable-integrated power system is affected by extreme weather conditions such as typhoons. In order to meet the operational requirements of the system, it is necessary to dynamically evaluate the resilience of the renewable-integrated power systems based on meteorological [...] Read more.

The secure operation of the renewable-integrated power system is affected by extreme weather conditions such as typhoons. In order to meet the operational requirements of the system, it is necessary to dynamically evaluate the resilience of the renewable-integrated power systems based on meteorological forecast information to guide operators to make reasonable risk prevention and control decisions. A rapid assessment method for power system resilience is proposed to address the uncertainty of extreme weather caused by typhoons. First, with a focus on the impact of typhoon disasters on power system components, corresponding failure probability models are constructed by taking typhoon meteorological forecast information as input and considering the uncertainty of typhoon meteorological forecast. Error probability circles and average absolute errors of intensity forecasts are included in the sampling of typhoon scenarios. Second, for the resilience assessment process, the impact increment method is used to reduce the dimensionality of multiple fault state analysis in the power system, and resilience indexes are calculated by screening the contingency set based on depth-first traversal through a backtracking algorithm. The weak links in the power system are identified through sensitivity analysis of load loss. Finally, the effectiveness of the proposed method is verified using the modified IEEE RTS-79 power system. Full article

(This article belongs to the Special Issue Advanced Electric Power Systems, 2nd Edition)

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26 pages, 1887 KB

Open AccessArticle

Enhancing Frequency Event Detection in Power Systems Using Two Optimization Methods with Variable Weighted Metrics

by Hussain A. Alghamdi, Midrar A. Adham, Umar Farooq and Robert B. Bass

Energies 2025, 18(7), 1659; https://doi.org/10.3390/en18071659 - 26 Mar 2025

Cited by 1 | Viewed by 873

Abstract

This research presents a novel technique that refines the performance of a frequency event detection algorithm with four adjustable parameters based on signal processing and statistical methods. The algorithm parameters were optimized using two well-established optimization techniques: Grey Wolf Optimization and Particle Swarm [...] Read more.

This research presents a novel technique that refines the performance of a frequency event detection algorithm with four adjustable parameters based on signal processing and statistical methods. The algorithm parameters were optimized using two well-established optimization techniques: Grey Wolf Optimization and Particle Swarm Optimization. Unlike conventional approaches that apply equally weighted metrics within the objective function, this work implements variable weighted metrics that prioritize specificity, thereby strengthening detection accuracy by minimizing false-positive events. Realistic small- and large-scale frequency datasets were processed and analyzed, incorporating various events, quasi-events, and non-events obtained from a phasor measurement unit in the Western Interconnection. An analytical comparison with an algorithm that uses equally weighted metrics was performed to assess the proposed method’s effectiveness. The results demonstrate that the application of variable weighted metrics enables the detection algorithm to identify frequency non-events, thereby significantly reducing false positives reliably. Full article

(This article belongs to the Special Issue Advanced Electric Power Systems, 2nd Edition)

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16 pages, 2157 KB

Open AccessArticle

High-Voltage Measurement Infrastructure Based on Optical Technology for Transmission Lines

by Mauro Augusto da Rosa, Clayrton Monteiro Henrique, Gabriel Santos Bolacell, Hermes Irineu Del Monego and Paulo César Rodrigues de Lima Junior

Energies 2025, 18(4), 830; https://doi.org/10.3390/en18040830 - 11 Feb 2025

Cited by 3 | Viewed by 1752

Abstract

This paper introduces a singular measurement infrastructure for real-time monitoring of transmission lines, applied to a 230 kV section of the Brazilian grid. The system aimed to expand the scope of monitoring variables using new concepts of optical sensing. Thus, variables are captured [...] Read more.

This paper introduces a singular measurement infrastructure for real-time monitoring of transmission lines, applied to a 230 kV section of the Brazilian grid. The system aimed to expand the scope of monitoring variables using new concepts of optical sensing. Thus, variables are captured not only in the electrical domain but also in the mechanical, thermal, and environmental domains through optical technologies and meteorological measurement sensors strategically positioned along the transmission line. The system relies on new features, including a high-voltage polymeric insulator instrumentalized with optical fiber sensors to measure line electrical current, conductor temperature, mechanical strain, and an electro-optical signal processing unit fed by a solar system. The correlations between the monitored variables provide more complete information about what happens in the transmission line compared to the analysis of purely electrical quantities. For instance, the Spearman coefficient of 0.9909 highlights the strong correlation between anchoring force and ambient temperature. This new way of monitoring systems opens the doors to a multivariate power system analysis. Full article

(This article belongs to the Special Issue Advanced Electric Power Systems, 2nd Edition)

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