Search

Speed and selectivity of DC fault protection are critical for High-Voltage DC (HVDC) grids and present significant technical and economic challenges. Therefore, this paper proposes a non-unit protection solution that detects and discriminates DC faults based on frequency domain analysis of the transient period of DC faults. The representation of a generic HVDC grid section and the corresponding DC-side fault signatures in the frequency domain form the basis of a generalized approach for analytically designing a protection scheme based on Wavelet Transform (WT). The proposed solution is adaptive within its design stage and offers general applicability and immunity to system changes, while the protection settings are configured for optimized performance. The scheme is validated through offline simulations in PSCAD/EMTDC and the technical feasibility of the algorithm in the real world is demonstrated through the use of real-time digital simulation (using RTDS) and Hardware-in-the-Loop (HIL) testing. Both offline and real-time simulations demonstrate that the scheme is able to detect and discriminate between internal and external faults at a significantly high speed, while remaining sensitive to high impedance faults and robust to external disturbances and outside noise. [ABSTRACT FROM AUTHOR]

Commutation failure is a serious malfunction in line-commutated high voltage direct current (HVdc) converters which is mainly caused by the inverter ac faults, and results in a temporary interruption of transmitted power and damage to the converter equipment. In this article, a controllable commutation failure inhibitor (CCFI) is developed which obviates the main drawbacks of the existing power electronic based and fault current limiting based strategies. Under normal circumstances, the developed CCFI improves the steady-state stability and the power transfer capability of the inverter ac lines, while it does not cause excessive voltage stress on the converter valves. In addition, it would reduce the risk of commutation failure occurrence, since it does not lead to any voltage drop in the commutation circuit. When a fault occurs at one of the inverter ac systems, its corresponding CCFI limits the fault current depending on the reduced extinction angle. This would not only inhibit the successive commutation failures on the HVdc converter, but also extend the lifetime of components in the inverter ac systems. The practical feasibility of the developed CCFI is assessed through laboratory testing, using a real-time Opal-RT hardware prototyping platform. The obtained results indicate that the developed CCFI can reliably inhibit the commutation failures during various types of faults. [ABSTRACT FROM AUTHOR]

This study presents a method for discriminative detection of direct current (DC) faults on voltage source converter-powered multi-terminal high-voltage direct current transmission systems using two fundamental guiding principles, namely instantaneous current-differential and travelling waves. The proposed algorithm utilises local voltage and current measurements from all transmission lines connected to a DC busbar, and current measurement from the DC side of the converter. The scheme operates at a sampling frequency of 96 kHz, which conforms with IEC 61869-9. No long distance communication is involved while measurements and signal exchange within DC substations are enabled by the utilisation of IEC 61850. Performance is assessed firstly through detailed transient simulation, using verified models of modular multi-level converters, hybrid DC circuit breakers and inductive DC-line terminations. Furthermore, practical performance and feasibility of the scheme are evaluated through laboratory testing, using the real-time Opal-RT hardware prototyping platform. Simulation and experimental results demonstrate that the proposed protection algorithm can effectively, and within a very short period of time (i.e. <1 ms), discriminate between busbar and line faults (internal faults), while remaining stable during external faults. Additionally, it has been demonstrated that IEC 61869-9 is suitable for enabling fast DC protection schemes incorporating travelling waves. [ABSTRACT FROM AUTHOR]

This study presents a method for discriminative detection of direct current (DC) faults on voltage source converter‐powered multi‐terminal high‐voltage direct current transmission systems using two fundamental guiding principles, namely instantaneous current‐differential and travelling waves. The proposed algorithm utilises local voltage and current measurements from all transmission lines connected to a DC busbar, and current measurement from the DC side of the converter. The scheme operates at a sampling frequency of 96 kHz, which conforms with IEC 61869‐9. No long distance communication is involved while measurements and signal exchange within DC substations are enabled by the utilisation of IEC 61850. Performance is assessed firstly through detailed transient simulation, using verified models of modular multi‐level converters, hybrid DC circuit breakers and inductive DC‐line terminations. Furthermore, practical performance and feasibility of the scheme are evaluated through laboratory testing, using the real‐time Opal‐RT hardware prototyping platform. Simulation and experimental results demonstrate that the proposed protection algorithm can effectively, and within a very short period of time (i.e. <1 ms), discriminate between busbar and line faults (internal faults), while remaining stable during external faults. Additionally, it has been demonstrated that IEC 61869‐9 is suitable for enabling fast DC protection schemes incorporating travelling waves. [ABSTRACT FROM AUTHOR]

This paper presents a method for rapid detection of faults on voltage source converter multiterminal HVdc transmission networks using multipoint optical current sensing. The proposed method uses differential protection as a guiding principle, and is implemented using current measurements obtained from the optical current sensors distributed along the transmission line. Performance is assessed through detailed transient simulation using MATLAB/Simulink models, integrating inductive dc-line terminations, detailed dc circuit-breaker models, and a network of fiber-optic current sensors. Moreover, the feasibility and required performance of optical-based measurements is validated through laboratory testing. Simulation results demonstrate that the proposed protection algorithm can effectively, and within very short period of time, discriminate between faults on the protected line (internal faults), and those occurring on adjacent lines or busbars (external faults). Hardware tests prove that the scheme can be achieved with the existing, available sensing technology. [ABSTRACT FROM PUBLISHER]

10.3390/en14051349 5 van der Blij N.H., Purgat P., Soeiro T.B., Ramirez-Elizondo L.M., Spaan M.T.J., Bauer P. Decentralized Plug-and-Play Protection Scheme for Low Voltage DC Grids. The electrical energy industry is undergoing dramatic changes; the massive deployment of renewables, an increasing share of DC networks at transmission and distribution levels, and at the same time, a continuing reduction in conventional synchronous generation, all contribute to a situation where a variety of technical and economic challenges emerge. As society's reliance on electrical power continues to increase as a result of international decarbonisation commitments, the need for the secure and uninterrupted delivery of electrical energy to all customers has never been greater. [Extracted from the article]

Electric Vehicles (EVs) are becoming increasingly available and are expected to be a large part of the load in future power systems. EV chargers are a relatively new type of load and are mainly interfaced with the grid through power electronics. It is therefore important to investigate the impact they have on power system dynamic behaviour. In this paper, two detailed EV charger models (representing a typical slow and fast charger) were investigated. The aim was to test the capability of standard static—and more importantly, dynamic—load models, commonly used in power system studies, to represent the static and dynamic behaviour of EV chargers. Different control parameter settings for two types of EV chargers were investigated, as were the limits of standard power system dynamic load model structures' accurate representation. Typical parameter sets have also been provided for cases where proper representation was possible. [ABSTRACT FROM AUTHOR]

Power-hardware-in-the-loop (PHIL) is a vital technique for realistic testing of prototype systems. While the application of power electronics-based amplifiers to enable PHIL capability has been widely reported, the use of motor-generator (MG) sets as the PHIL interfaces has not been fully investigated. This article presents the realization of the first MW-scale PHIL setup using an MG set as the power amplifier, which offers a promising solution for testing novel systems for the integration of distributed energy resources. Uniquely, this article presents a methodology that introduces augmented frequency and phase control loops that can be integrated to commercially-available MG set's existing frequency controller for precise frequency and phase tracking. Internal model control is used for the controllers design and tuning. The developed control algorithm is tested in a MW-scale MG set that couples a Great Britain (GB) transmission network model simulated in a real time simulator to an 11 kV distribution network. Experimental results are presented, which demonstrate that the proposed control methodology is highly effective in maintaining the synchronization between the simulated and physical systems, thereby capable of enabling the MG set as a PHIL interface. [ABSTRACT FROM AUTHOR]

Microgrids are considered a viable solution for achieving net-zero targets and increasing renewable energy integration. However, there is a lack of conceptual work focusing on practical data analytics deployment schemes and case-specific insights. This paper presents a scalable and flexible physical and digital architecture for extracting data-driven insights from microgrids, with a real-world microgrid utilized as a test-bed. The proposed architecture includes edge monitoring and intelligence, data-processing mechanisms, and edge–cloud communication. Cloud-hosted data analytics have been developed in AWS, considering market arrangements between the microgrid and the utility. The analysis involves time-series data processing, followed by the exploration of statistical relationships utilizing cloud-hosted tools. Insights from one year of operation highlight the potential for significant operational cost reduction through the real-time optimization and control of microgrid assets. By addressing the real-world applicability, end-to-end architectures, and extraction of case-specific insights, this work contributes to advancing microgrid design, operation, and adoption. [ABSTRACT FROM AUTHOR]

High-voltage direct-current (HVDC) systems are being widely employed in various applications because of their numerous advantages such as bulk power transmission, efficient long-distance transmission, and flexible power-flow control. However, line-commutated-converter-based HVDC systems suffer from commutation failure, which is a major drawback, leading to increased device stress and interruptions in transmitted power. This paper proposes a predictive control strategy, deploying a commutation failure prevention module to mitigate the commutation failures during ac system faults. The salient feature of the proposed strategy is that it has the ability to temporarily decrease the firing angle of thyristor valves depending on the fault intensity to ensure a sufficient commutation margin. In order to validate the performance of the proposed strategy, several simulations have been conducted on the CIGRE Benchmark HVDC model using PSCAD/EMTDC software. Additionally, practical performance and feasibility of the proposed strategy are evaluated through laboratory testing, using the real-time Opal-RT hardware prototyping platform. Simulation and experimental results demonstrate that the proposed strategy can effectively inhibit the commutation failure or repetitive commutation failures under different fault types, fault impedances, and fault initiation times. [ABSTRACT FROM AUTHOR]

In recent decades, the rapid rise in electricity demand has compelled transmission and distribution systems to operate at almost their maximum capacity. This can pose numerous technical challenges such as excessive power losses, voltage and transient instabilities, as well as reduced power quality and reliability. Employment of Flexible Alternating Current Transmission System (FACTS) devices can be an effective approach to obviate such challenges and reinforce the power system functionality. Nevertheless, FACTS devices require a high initial investment, and hence their optimal allocation in terms of various aspects such as type, size and location is of utmost importance. This cannot be achieved without the deployment of optimization techniques. The aim of this paper is to provide a comprehensive review of the existing proposals for the enhancement of power system performance adopting FACTS devices. Adhering to that, an in-depth analysis is carried out, in which the most pertinent options are classified into specific groups based on their optimization objectives. Finally, a comparative analysis is accomplished in which the main attributes and drawbacks of each optimization technique are presented. [ABSTRACT FROM AUTHOR]

This paper introduces a current differential protection scheme, appropriate for application in medium voltage active distribution systems, where it is desired to keep the greatest possible number of loads and DG units energized during a fault. Conventional two-terminal percentage current differential relays are used to form successive, time-current-coordinated, differential protection zones. Multiple time-delayed differential elements in each protection zone guarantee coordination with the zone's lateral protection devices, as well as between successive differential protection zones. Sensitive time-delayed differential elements protect against relatively high-resistance faults, while instantaneous differential elements minimize protection speed whenever possible. Additional emergency differential elements deal with post-fault topology changes and breaker failure conditions enhancing the overall scheme's performance. The proposed scheme is applied to a model of real medium voltage distribution system with distributed generation, considering a ring topology operation. A detailed simulation-based study proves the applicability and enhanced performance of the proposed scheme. [ABSTRACT FROM AUTHOR]

Due to the enhanced price of electricity, the gradual depletion of fossil fuels, and the global warming concerns, power loss minimization through deployment of distributed generators (DGs) has attracted significant attention in recent decades. This paper proposes a genetic algorithm (GA) based strategy for minimization of active and reactive power losses through optimal location and size of DGs. It also quantifies and tallies the total network power losses for the cases with random as well as optimal allocation of DGs. To validate the accuracy of the obtained results from GA, another nature‐inspired optimization algorithm, cuckoo search, is also deployed. The simulation results on IEEE 30 and 118 bus systems indicate that the proposed strategy not only can effectively reduce the total network active and reactive power losses but also lead to the improvement of network voltage profile. [ABSTRACT FROM AUTHOR]

This paper presents a novel load shedding scheme with consideration of the active power ramping capability of Distributed Energy Resources (DERs) to address the challenges due to low inertia and diverse types of DERs in microgrids. In the paper, it is demonstrated that due to the small inertia in microgrids, even with sufficient reserve power, the frequency could rapidly drop to a low level and trigger the DERs’ under frequency protection (thus the total system collapse), if the reserve active power is not ramped up at a sufficient rate. The proposed load shedding scheme addresses this challenge by considering not only the DERs’ reserve, but also their speed in injecting active power to the system to determine the amount of load should be shed, so that critical frequency thresholds are not violated. The proposed load shedding scheme is tested using a realistic real time hardware-in-the-loop arrangement. The results show that the proposed scheme can correctly detect the cases when the DERs’ responses are too slow and trigger the required load shedding actions, thus effectively containing the frequency above the critical threshold. [ABSTRACT FROM AUTHOR]

• The paper examines the role of LV monitoring in MV fault localisation. • Secondary substations provide ground to ICT technologies for this purpose. • An algorithm deploying sparse LV measurements has been developed. • The distributed devices do not require time synchronisation reducing cost. • The results of this study demonstrate the robustness of the technique. A medium voltage (MV) faulted section location technique depending solely on unsynchronized low voltage (LV) measurements in distribution systems is introduced in this paper. The proposed method identifies the faulted MV feeder segment when an unsymmetrical MV fault occurs. It exploits parameters including voltage magnitude, angle and sequence components captured via distributed non-synchronized monitoring devices connected at secondary substations. In this study, the characterization of a system's LV profile during MV faults was achieved throughout both software simulations and physical testing. The latter was conducted in the 11 kV and LV distribution network of the Power Networks Demonstration Centre (PNDC) of the University of Strathclyde. The tests were performed for both 11 kV radial and ring network configurations. Modelling and simulations implemented using the DigSILENT PowerFactory package, complemented the hardware level testing and provided the opportunity for further examinations, such as the impact of MV laterals connection, distributed energy resources on both MV and LV side as well as the presence of unbalanced loads. Finally, the paper evaluates the effectiveness of the proposed faulted section location technique under various physical and simulated fault scenarios, loss of communications and noise interference. [ABSTRACT FROM AUTHOR]

This paper presents the development of a novel data-driven fault detection and classification scheme for DC faults in multi-terminal HVDC transmission system which incorporates superconducting cables and modular multi-level converters. As the deployment of superconducting cables for bulk power transmission from remote renewable generation is progressively increasing in the future energy grids, many fault-related challenges have been raised (i.e., fault detection, protection sensitivity/stability). In this context, the applications of Artificial Intelligence techniques have started to be considered as a powerful tool for the development of robust fault management solutions. The proposed artificial intelligence-based method utilizes local current and voltage measurements to detect and classify all types of faults on the DC cables and DC buses, without the requirement of measurements exchange among different DC substations. The performance of the proposed scheme has been assessed through detailed transient simulation analysis and the results confirmed its effectiveness against a wide range of fault conditions (i.e., various fault types, fault locations and fault resistances). Furthermore, the feasibility of the developed scheme for real-time implementation has been validated using real-time software in the loop testing. The results revealed that the proposed algorithm can correctly, and within a very short period of time (i.e. less than 2 ms) detect and classify the faults within the protected zone and concurrently remain stable during external faults. Additionally, the generalization capability of the algorithm has been verified against influencing factors such as the addition of noise, highlighting the robustness of the presented scheme. • The deployment of DC Superconducting Cables in HVDC systems has started to be considered a promising solution for bulk power transmission from remote renewable generation units. • The inherent fault current limiting capability and the unique electro-thermal properties of the SCs have introduced many fault management issues in power systems. • For the protection of SCs in meshed HVDC systems, schemes with increased sensitivity, discrimination capability and high operational speed are required. • Artificial-Intelligence-based protection schemes overcome the limitations of existing protection methods in the data-rich power systems, providing fast, and accurate fault detection and classification. • XGBoost-based fault detection and classification algorithm performs effectively under various faults occurred on SCs and DC busbars, providing a reliable protection solution and accelerating the uptake of superconducting technology. [ABSTRACT FROM AUTHOR]

Line Commutated Converter (LCC) based High-Voltage Direct Current (HVDC) technology has been in operation with a high level reliability and little maintenance requirements for more than thirty years. The current-source based or classical LCC-HVDC systems are being considered for buried cable transmission as well as overhead transmission. The fault analysis and protection of LCC-HVDC system is a very important aspect in terms of power system stability. This paper proposes a novel protection scheme for LCC-HVDC systems, in which the difference between propagation processes of traveling wave under internal and external faults is used as a criterion for detection of fault incidents in HVDC transmission lines. In order to quantify and intensify this difference, Teager Energy Operator (TEO) is used which has the ability to reflect the instantaneous energy of a signal. The main feature of the proposed scheme in comparison with the existing ones is that it operates faster, since it does not require to extract any harmonic or high frequency component; moreover, a 2-ms sampling window is sufficient for its algorithm which only deals with simple calculations. In order to validate the effectiveness of the proposed protection scheme, several fault events under different fault resistances and fault locations were simulated on a test network using PSCAD/EMTDC software. Also, the performance of the proposed scheme under real fault events was tested using four field data cases. Both simulation data and field data test results indicated that the proposed protection strategy has the ability to accurately discriminate between internal and external faults and detect the faulted pole in the bipolar systems even under high-impedance fault conditions. [ABSTRACT FROM AUTHOR]

This paper addresses the challenge of fault localization in power grids which incorporate Superconducting Cables (SCs) and presence of inverter-connected generation, by proposing a novel data-driven fault location scheme. The developed fault location algorithm utilizes the transformation of time domain fault current and voltage signatures, to time–frequency domain and exploits the advantages of a Convolutional Neural Network (CNN) to estimate the fault position along SCs. The proposed algorithm has been tested using a verified model of SC, and the results revealed that it can provide precise fault localization for a wide range of fault scenarios, including different fault types, fault resistance values and fault inception angles. Furthermore, the proposed scheme robustness has been verified against different influencing factors accounting for very small increments of fault location, additive noise and different value of sampling frequency. For validation purposes, the effectiveness of the CNN-based algorithm has been compared with other data-driven algorithms and the relevant advantages have been highlighted. • The deployment of Superconducting Cables in power systems has introduced many fault related challenges, accounting for fault detection and location. • The identification of accurate fault position on Superconducting Cables is a very important task for the wider adoption of such technology, due to their complex configuration and the lack of standardization in the repair procedure. • The limitations of the conventional fault locations schemes, resulting from quenching of Superconducting Cables, renders the utilization of AI-based techniques a very promising solution. • Time to time-frequency domain transformations are utilized as powerful feature extraction tools in fault location applications. • CNN-based algorithms provide accurate fault location estimation on Superconducting Cables, remaining unaffected by quenching phenomenon. [ABSTRACT FROM AUTHOR]

With the high penetration of Renewable Energy Sources (RES) in power systems, the short-circuit levels have changed, creating the requirement for altering or upgrading the existing switchgear and protection schemes. In addition, the continuous increase in power (accounting both for generation and demand) has imposed, in some cases, the need for the reinforcement of existing power system assets such as feeders, transformers, and other substation equipment. To overcome these challenges, the development of superconducting devices with fault current limiting capabilities in power system applications has been proposed as a promising solution. This paper presents a power system fault analysis exercise in networks integrating Superconducting Cables (SCs). This studies utilized a validated model of SCs with second generation High Temperature Superconducting tapes (2G HTS tapes) and a parallel-connected copper stabilizer layer. The performance of the SCs during fault conditions has been tested in networks integrating both synchronous and converter-connected generation. During fault conditions, the utilization of the stabilizer layer provides an alternative path for transient fault currents, and therefore reduces heat generation and assists with the protection of the cable. The effect of the quenching phenomenon and the fault current limitation is analyzed from the perspective of both steady state and transient fault analysis. This paper also provides meaningful insights into SCs, with respect to fault current limiting features, and presents the challenges associated with the impact of SCs on power systems protection. [ABSTRACT FROM AUTHOR]