Search Results (793)

Railway traction power supply systems (TPSSs) are evolving from passive grid-fed infrastructures into active energy systems with local photovoltaic (PV) generation capacity, energy storage systems (ESSs), and converter-based regulation. Unlike conventional microgrids, TPSSs feature single-phase, highly dynamic traction loads; short-duration regenerative braking bursts; and strict constraints on voltage quality, stability, and protection. These characteristics make the energy management of distributed PV-storage-integrated TPSSs a distinct research problem. This review examines the field from three coupled perspectives: supply architecture, power electronic interfaces, and energy management strategies. First, representative integration architectures are classified into substation-side, wayside-distributed, and hybrid multi-port schemes. Second, converter interfaces and flexible traction substations are analyzed as the enabling layer for coordinated control of PV, ESS, the utility grid, and traction feeders. Third, major energy management strategies, including rule-based, optimization-based, hierarchical multi-timescale, and uncertainty-aware methods, are compared. The review further discusses power quality, stability, protection, and battery degradation constraints that shape practical deployments. Finally, research gaps and future directions are identified to further the development of more robust, railway-specific, and implementation-oriented PV-storage energy management. Full article

Shipboard diesel–electric power systems (SDEPSs) are inherently vulnerable to transient instability owing to their compact, isolated, and low-inertia design. Their performance is considerably influenced by dynamic disturbances, which can lead to operational failures and accidents of varying severity. Therefore, this research addresses the critical challenge of transient stability enhancement in SDEPSs during significant dynamic disturbances. Recognizing that traditional automation and protection systems respond only after transient instability occurs, this study introduces an emergency preventive control (EPC) strategy that enables anticipatory control of SDEPS power sources to enhance transient stability. The proposed EPC system integrates hardware and software components to perform real-time monitoring and control based on forecasting system parameters, specifically the relative rotor angles of the power sources. The feasibility and effectiveness of the proposed system are validated through comprehensive computer simulations, demonstrating improvements in transient stability and system resilience by substantially reducing relative rotor angle deviations during the transient event. Overall, the proposed framework can be readily integrated into existing shipboard control architectures, offering an effective means to improve the safety of modern SDEPSs operating under dynamic conditions. Full article

The accumulation of ice on power lines severely affects the safety of power systems. Conventional ice melting methods suffer from poor flexibility and adaptability, accompanied by high power consumption. As a novel technical approach, distributed ice melting deploys modular and movable ice melting units at key sections of overhead ground wires, which generate heat on site according to the actual icing conditions of icing segments, and imposes high requirements on the miniaturization of ice melting equipment as well as the regulation strategy of ice melting current. This study proposes a distributed ice melting method for overhead ground wires based on AC power supply, which can adjust the current in accordance with the specific demands of wire protection and ice melting for different line sections. The feasibility and effectiveness of the proposed method are verified through thermodynamic simulations and experimental tests. The de-icing method injects power–frequency AC into the overhead ground wire through a Scott transformer combined with a series capacitor reactive power compensation structure, enabling on-demand regulation by adjusting capacitor switching strategies and transformer operating modes. This approach balances efficiency and flexibility. Based on a reactive power compensation capacity current control strategy and thermodynamic analysis, an electro-thermal-fluid field coupling simulation model for the experimental ground wire was developed. The current regulation strategies for different environmental and operating conditions were calculated and validated. The simulation results show that, under different conditions, the adjustable current effective values of the de-icing system in this model range from 101 to 380 A (line maintenance current), 304 to 622 A (critical de-icing current), and 661 to 1121 A (maximum de-icing current). Field tests demonstrate that this method can stably achieve AC de-icing and current control. For the experimental JLB40-150 model ground wire, adjusting the injected current to 350 A enables safe operation under line maintenance conditions, with a limit not exceeding 400 A. This paper provides a more efficient, flexible, controllable, and widely applicable method for the de-icing of overhead ground wires. Full article

Multiple-fault events can initiate overload propagation and cascading outages, resulting in severe load loss and reduced system resilience. Therefore, beyond conventional protection concepts based on the (n − 1) criterion, there is also a need to address multiple-fault events to minimize loss of load. This paper presents an optimized overload tripping scheme to mitigate cascading outages in high-voltage grids under multiple-fault conditions, where selected line switches or circuit breakers are opened in a controlled manner to isolate limited grid sections, minimize interrupted load, and prevent further overload propagation. The method combines inverse definite minimum time relay modeling with a heuristic graph-search algorithm implemented in pandapower to identify feasible switching actions that minimize load loss while preventing overload propagation. The approach is demonstrated on SimBench high-voltage urban and mixed benchmark grids under double-line fault scenarios. In the urban grid, the proposed scheme reduces the maximum load loss from 34.0% to 2.4%, while in the mixed grid, the reduction is from 50.3% to 5.2%. A SAIFI-inspired resilience proxy is introduced to quantify the reduction in customer/load interruptions, showing a resilience improvement factor of about 3.6 for cascading scenarios. In addition, thermal inertia analysis indicates that corrective switching must be completed within approximately 5 min to remain within line-temperature limits. The analysis is based on quasi-steady-state power-flow and relay simulations; transient stability effects are outside the scope of this study. The results demonstrate that the optimized overload tripping scheme is a promising adaptive protection strategy for improving grid resilience under severe contingency conditions. Full article

Containerized mobile power supplies (CMPS), a critical energy replenishment carrier for all-electric ships, have caused severe economic losses via frequent fire and explosion accidents during temporary port storage in recent years. Existing literature focuses on battery thermal runaway under laboratory conditions and maritime transport risk analysis, but its conclusions are not directly applicable to port temporary storage. Port storage, featuring full-charge quiescent placement and high turnover, differs significantly from maritime transport, while its high-temperature and humid environment is distinct from laboratory settings. Furthermore, no system safety-based risk assessment framework exists, failing to deliver targeted mitigation strategies for practical operations. To address these issues, fault tree analysis (FTA), Bayesian network (BN), and attack–defense game theory were combined to build a systematic safety risk assessment framework. FTA clarified the hazard factors’ correlation mechanism; based on FTA, BN conducted a quantitative evaluation. Extended from BN results, attack–defense game theory identified key risk evolution paths and formulated targeted prevention and control measures. The main conclusions are as follows: Combined with similar accident features and port storage scenario attributes, internal correlations between hazard-inducing factors were clarified via FTA. Based on expert evaluations and BN calculation, the target port’s fire accident occurrence probability was determined as 2.41%, with two core root nodes identified via sensitivity analysis. Two critical risk evolution paths corresponding to IE1 (thermal runaway initiation) and IE2 (failure of protection and emergency response systems) were identified via game theory and traversal method, with occurrence probabilities of 1.50% and 1.77%, respectively. Targeted prevention and control measures adapted to the port storage scenario were proposed based on path triggering mechanisms. These findings provide theoretical support for port enterprises to improve CMPS fire prevention and emergency response capabilities, elevate port safety management levels, and promote the safe development of the all-electric vessel shipping industry. Full article

Due to the controlled characteristics of fault current in doubly fed wind farms and the distributed capacitance effects of transmission lines, traditional distance protection is prone to failure or maloperation during high resistance faults. To improve protection reliability, this paper proposes a novel time–domain distance protection scheme based on the hybrid-π model. First, the improved time–domain fault differential equations are formulated based on the hybrid-π model, incorporating ground capacitance and integrating electrical quantities at both ends of the line. Next, the composite weight matrix integrating transient mutation weights and fitting error weights is introduced and embedded within a nonlinear least-squares framework. This enables the algorithm to adaptively distinguish and suppress unreliable data, simultaneously achieving transient disturbance resistance and rapid steady-state convergence. Finally, a 220 kV double-fed wind power grid-connected system with a 100 km transmission line is built in MATLAB/Simulink for simulation. Different types of faults under various locations and transition resistances are simulated to verify the effectiveness of the proposed scheme. Full article

Wind turbines operating under highly variable wind conditions require effective pitch-angle control to ensure maximum energy capture and structural protection. This study examines the performance of a 2.5 MW GEWE-B2.5-100 horizontal-axis wind turbine by quantifying how pitch-angle regulation affects power limitation, rotor-speed stability, and mechanical loading. Using an aerodynamic model, the maximum power point (MPP) was identified at an optimal mechanical angular speed of ω_OPTIM = 240.45 rad/s for V = 10 m/s, and the corresponding pitch-angle adjustments were determined for wind speeds up to 26 m/s, where β increases from 9.28° to 29.06° to maintain safe operation. Three dynamic case studies were conducted. Under sinusoidal wind variations between 10 and 14 m/s, PI-based pitch control limited rotor-speed oscillations to below 0.1%, ensuring stable operation. For exponential wind increases to 24 m/s and 34 m/s, the pitch angle rose to 28.48°, with rotor-speed overshoot remaining minimal at 0.004% and 0.006%, respectively. As stated in the manuscript, “dynamic pitch angle control significantly reduces rotor speed oscillations and mitigates excessive which indirectly contributes to alleviating potential structural stresses”. These results show that pitch-angle control is a key factor in turbine performance, enabling precise power capping at 2.178 MW and ensuring structural safety under extreme wind conditions. The proposed strategy supports reliable integration of large wind turbines into modern power systems. Full article

In weak receiving-end grids, the active support of the valve-side static var compensator and filter (SVF) extends the commutation failure (CF) boundary of LCC-HVDC. However, SVF control state transitions reshape valve-side voltage and harmonic characteristics, causing conventional fixed threshold protection to exhibit concurrent misblocking and failure to operate risks, while SVF zone internal faults are prone to excessive pole-level escalation. This paper proposes a state-aware coordinated protection strategy for symmetric single-pole SLCC-HVDC systems. A normalized commutation margin index, derived from the commutation voltage time integral, characterizes the nonlinear CF boundary under SVF support. SVF control mode, health status, and reactive power margin serve as conditioning variables for adaptive threshold and time window modification. A three-level escalation strategy—local isolation, derated ride-through, and pole-level action—is further designed for SVF zone faults. Validation via RTDS sequence of events records and EMT–protection logic replay co-simulation shows that the proposed index achieves a 100% CF risk prediction rate across five fault scenarios, versus 40% for conventional indices. The method maintains zero failure to operate with a misblocking rate ≤ 10.1% at SNR ≥ 30 dB. The staged response correctly escalates all four SVF zone fault types to the required level, compared with two of four for the fixed threshold baseline. These results confirm effective enhancement of protection robustness, fault ride-through capability, and operational continuity for SLCC-HVDC in weak receiving-end grids. Full article

A large number of reservoirs (or hydropower plants) have been constructed for flood control and energy production in the past several decades in the Yangtze River basin in China. The conventional scheduling rule curves (Scheme A) were designed in the reservoir construction period and did not consider river flow alternation, which needs to be modified to increase comprehensive benefits in the reservoir operation period. In this study, six large-scale cascade reservoirs or mega hydropower systems constructed and operated by the China Yangtze Three Gorges Corporation were selected for this case study. The current joint scheduling plans of cascade reservoirs (Scheme B) were introduced, and a joint scheduling and multi-objective coordinating operation model (Scheme C) was proposed for this mega hydropower system. The Gaussian radial basis functions (GRBFs) were used to fit operation policies of each reservoir, and the Borg multi-objective evolutionary algorithm was selected to optimize three-objective functions for Scheme C. The observed daily flow data series at main hydrometric stations from 2003 to 2025 were used to simulate and compare different operation scheduling schemes. The results show that the performance of joint scheduling of cascade reservoirs (both Schemes B and C) is much better than the single-reservoir scheduling (Schemes A) with overall benefit; Scheme C-best achieves a comprehensive target of decreasing average annual spillway wastewater by 12.82 billion m³ (or a decrease of 28.5%), increasing average annual power generation by 31.02 billion kWh (or an increase of 10.7%), and improving average annual impoundment efficiency rate by 5.0%. The GRBFs can fit reservoir operation policies well, while the Borg multi-objective evolutionary algorithm can quickly converge with high-precision non-dominated solution sets. The proposed joint scheduling and multi-objective coordinating operation model will provide a scientific basis for achieving maximum benefits in flood protection and hydropower generation for the mega hydropower system. Full article

The widespread adoption of photovoltaic systems in residential electrical installations has increased the importance of Automatic Transfer Switches (ATSs) for ensuring power continuity during grid outages. However, many low-cost ATS solutions available on the market prioritize economic efficiency over operational safety, leading to significant risks under fault conditions. This paper investigates a real overvoltage incident in a residential three-phase installation equipped with a photovoltaic inverter and an ATS, which resulted in the failure of multiple electronic loads. The study reconstructs the event and demonstrates that the loss of the neutral conductor during backup operation caused severe phase voltage imbalance, generating overvoltage conditions across lightly loaded phases. A simplified electrical model is used to explain current paths and voltage redistribution under asymmetric loads, highlighting the critical role of correct neutral switching in ATS design. Two commercially available ATS architectures, one based on a changeover-contact mechanism and one employing four-pole miniature circuit breakers, are experimentally evaluated. The evaluation reveals major design deficiencies, including the absence of protective elements for control circuits, reliance on mechanical end-position limiters, and the use of switching devices not intended for frequent source transfer. These shortcomings introduce risks such as uncontrolled actuator operation, overheating, mechanical damage, and potential fire hazards. To overcome these limitations, a new ATS architecture was developed using a phase-monitoring relay, interlocked ABB contactors, and dedicated fuse protection for all control circuits. Detailed laboratory measurements were conducted to characterize contactor switching times and internal relay command delays. By optimizing the command sequence, the proposed ATS achieves predictable, fault-tolerant operation with competitive transfer times, representing a meaningful safety improvement over the evaluated commercial alternatives. The proposed solution is scoped to three-phase residential installations equipped with a hybrid photovoltaic inverter providing a dedicated backup output, operating within TN-S or TN-C-S earthing systems with a maximum grid connection capacity of 21 kW. Full article

To address the issue that substations are prone to failures during flood disasters, which further cause large-scale and prolonged power outages, a coordinated optimal allocation strategy of flood control resources is proposed to enhance power grid resilience. Firstly, the failure and network features for substations are constructed considering the uncertainty of flood depth. Subsequently, a representative set of failure scenarios for transmission and distribution (T&D) substations is generated based on feature selection. Secondly, accounting for the coupling relationship between the availability status of T&D substations and the operation strategies of active distribution networks, a transmission-distribution coordinated stochastic optimization model is established to optimize the allocation of flood control resources. The objective is to minimize the system’s expected comprehensive costs incurred by substation structural damage and load shedding constrained by the pre-disaster substation protection constraints and the operation constraints in T&D networks during flood disasters. Finally, numerical case studies based on the improved T24D40 system are conducted. The results demonstrate that the feature-selection-based scenario generation method enables the critical substations with high failure rates and network importance to gain higher protection priority. More importantly, compared with separate decision-making and with limited coordinated decision-making for T&D substation protection schemes, the proposed model, which could effectively maximize the utilization efficiency of flood control resources, reduces the system’s expected comprehensive costs by 32.1% and 8.9%, respectively. Full article

The fault response of inverter-based resources (IBRs) is strongly influenced by their control strategies, which may significantly change the directional information available to line relays during non-ground faults. As a result, conventional directional elements designed according to the fault characteristics of conventional power systems may exhibit poor adaptability in IBR-connected systems. In particular, zero-sequence directional elements cannot be applied to non-ground faults, whereas negative-sequence-based schemes may be adversely affected by the fault-control behavior of IBRs. To address this problem, this paper proposes a directional element for non-ground faults on AC lines in systems with IBRs. First, the positive-sequence measured impedance at the relay locations is analyzed under typical fault conditions, and the dependence of available directional information on the phase characteristic of the IBR fault current is clarified. Then, a control–protection coordinated method is introduced to regulate the fault-current phase of the IBR during faults so that stable and consistent positive-sequence directional features can be established at both line terminals. On this basis, a unified directional criterion is formulated. Finally, PSCAD/EMTDC simulations are carried out to verify the proposed method, and dynamic model experiments are conducted to validate its engineering feasibility. The results show that the proposed element correctly identifies the fault direction under both three-phase and phase-to-phase fault conditions. Additional tests considering measurement noise and opposite-side grid-strength variation further demonstrate the robustness of the proposed criterion. Compared with conventional directional elements, the proposed method improves the adaptability of non-ground fault-direction identification in IBR-connected AC lines. Full article

The common root characteristic of CO₂ and air pollutants in the power industry, both derived from fossil fuel combustion, provides a natural basis for their synergistic emission reduction. However, existing studies suffer from the lack of a multi-pollutant synergistic evaluation system and an imperfect emission reduction technology database, which hinder their ability to support low-cost and high-efficiency emission reduction practices in the industry. Targeting the minimization of synergistic emission reduction costs and the maximization of emission reduction effects, this study integrated the process and economic parameters of 11 power generation technologies and 55 pollutant control technologies to establish a full-chain energy conservation and emission reduction technology database for the power industry, through literature research, industry surveys, and data mining. Based on the definition of pollution equivalent in the Environmental Protection Tax Law, we innovatively developed an air pollutant equivalent normalization evaluation method and constructed a two-dimensional coordinate system comprehensive evaluation system for CO₂ and air pollutants, enabling quantitative analysis and visual evaluation of the synergistic emission reduction effects of various technologies. The results show that new energy power generation technologies such as nuclear power and wind power, as well as O₂/CO₂ cycle combustion, ammonia-based desulfurization, and SNCR-SCR combined reduction technologies, exhibit excellent synergistic emission reduction performance for CO₂ and multiple pollutants. In contrast, some conventional pollutant control technologies, such as the limestone-gypsum method and traditional electrostatic precipitation, have significant CO₂ emission increase antagonistic effects. This study also completed the two-dimensional classification of 66 emission reduction technologies based on “emission reduction efficiency-economic cost”, identified application scenarios for different types of technologies, and proposed optimized paths for synergistic emission reduction adapted to the development of the power industry. The research findings fill the gap in quantitative standards for multi-pollutant synergistic emission reduction, provide theoretical support and detailed technical references for emission reduction technology selection and environmental policy formulation in the power industry, and help the industry achieve the dual development requirements of the “double carbon” goal and air quality improvement. Full article

With the advancement of new-type power systems and smart grids, the structure of power protection and control systems has become increasingly complex, and their reliability exhibits dynamic evolution, multi-factor coupling, and full life cycle characteristics. Against this background, this paper presents a review of the evolution of reliability analysis methods for power protection and control systems. Early research has focused on parametric modeling based on statistical data and structural logic combination analysis, establishing a static reliability analysis framework grounded in the relationship between component failure probability and system structure. Subsequently, to characterize temporal process features such as state transitions, fault dependencies, and maintenance recovery, dynamic modeling methods such as state-space models and dynamic fault trees were developed and applied. In recent years, with the continuous accumulation of full life cycle operational data, multi-source information fusion and data-driven technologies have gradually been introduced into reliability research, promoting the expansion of the analysis framework from stage-based evaluation to full-process evolutionary modeling. On this basis, the modeling concepts, applicable scenarios, and inherent limitations of different methods are summarized and compared. Furthermore, the development trend of an integrated reliability analysis system that deeply combines mechanism models with data-driven methods is discussed, aiming to provide a theoretical foundation for the improvement of reliability analysis systems. Full article

Medium-voltage (MV) networks are increasingly relying on grid-forming inverter-based resources (IBRs) due to the worldwide transition towards renewable energy sources. This transformation poses considerable challenges for traditional protection schemes that were initially developed for systems powered by inertia-based generation. Key challenges include the low and controlled contributions of fault current, two-way power flows, diminished system inertia, and swiftly changing transient behaviors. These elements weaken the effectiveness of standard protection methods such as overcurrent, distance, and differential protection schemes. A critical review of recent advancements in adaptive protection schemes, impedance-based techniques, virtual synchronous machines, and enhancements in inverter control is provided. However, despite these advancements, current solutions frequently lack validation in real-world scenarios, encounter difficulties in detecting high-impedance faults, and face scalability issues. There remains a demand for protection strategies that are resilient, coordinated, and specifically designed to address the distinct dynamics of MV systems dominated by grid-forming inverters. Full article