Substation DC Research Articles

Optimization of battery charging and discharging strategies in substation DC systems using the dual self-attention network-N-BEATS model.

With the rapid pace of urbanization and industrialization, the demand for electricity has surged, placing immense pressure on power management systems. Substation DC systems play a crucial role in managing these fluctuations to ensure a stable and reliable power supply. However, existing battery charging and discharging strategies often suffer from inefficiencies, which can negatively impact overall system performance and sustainability. In this study, we introduce a novel approach that leverages artificial intelligence and time series predictive analytics through the dual self-attention network-neural basis expansion analysis for time series (DSAN-N-BEATS) model. This model integrates the self-attention network with the neural basis expansion analysis for time series (N-BEATS) model to accurately capture time-series data and optimize battery management. Our experimental results demonstrate that the DSAN-N-BEATS model significantly enhances battery state prediction accuracy, achieving a 95.84% accuracy rate, and improves charging and discharging efficiency by 20% compared to traditional methods. These improvements contribute to the overall reliability and sustainability of power systems. This research provides innovative methods for optimizing battery strategies, supporting sustainable development in the power industry, and enhancing system stability and reliability.

Ground fault detection in substation DC system based on improved differential current method

DC system is the main electrical equipment and control signal system in the substation, and its stability and reliability are directly related to whether the power system can operate safely. This paper firstly introduces the common methods of insulation detection of DC power system in substation and its advantages and disadvantages, and proposes the differential current method based on unbalanced bridge, i.e., using the combination of unbalanced bridge and leakage current sensor to detect the insulation condition of DC system, which makes up for the defects of the traditional differential current method that can only detect the faults of simple branch circuits, and realizes the detection of multi-branch grounding under complex situations. Finally, the feasibility of this method is verified by building a simulation model through simulink.

New Topology Design and On-line Charging and Discharging Technology of Substation DC System

The substation DC system uses battery packs as a backup power source. It needs to be regularly checked for capacity. In the existing topology, batteries are connected in series as a power source. When checking capacity discharge, an additional backup power supply must be built to replace it, which is costly and complicated to operate. To this end, this paper proposes a new battery topology. The previous 54 series batteries were divided into 3 packs, with each consisting of 18 batteries. The three battery packs are connected in parallel to the DC bus through bidirectional DC/DC converters. The automatic charging and discharging control strategies of the battery packs under the new topology are studied. The system can automatically charge and discharge batteries through bidirectional DC/DC converters, and conduct online capacity testing of battery packs. Simulation results show that the designed new topology not only realizes the online verification of battery capacity but also saves the test cost. The power supply reliability of the DC system of the substation is also greatly improved through the redundant structure.

Environmental and Techno-economic Life Cycle Assessment of Energy Storage Systems in Railway supply system

During rush hours, catenary voltage drop is a significant issue on the 1,5kV – DC lines. Indeed, when voltage drop occures between two substations, the trains can't accelerate as they should. Among the solutions that could solve such a problem, the development of a new traditionnal substation in the middle of two others, also the integration of wayside Energy Storage Systems (ESS). This paper deals with the development on Energy Storage Systems (ESS) in the SNCF (French Railway Company) railway network. It aims to study the techno-economic interests of such innovations, also to investigate the environmental impact they could have. The assessment is based on the comparison of a traditional railway 1,5kV–DC substation and a battery-based substation.

A ground fault detection method of substation DC system based on particle filter

A ground fault detection method of substation DC system based on particle filter

Intelligent substation DC transformer control based on fuzzy PID technology

Intelligent substation DC transformer control based on fuzzy PID technology

Intelligent substation DC transformer control based on fuzzy PID technology

Intelligent substation DC transformer control based on fuzzy PID technology

A travelling wave based primary and backup protection for MMC-MTDC transmission system using morphological un-decimated wavelet scheme

The primary protection speed requirement for the HVDC grid is much faster as compared to the conventional HVAC grid. This research article proposes a travelling wave-based primary and backup protection scheme for the multi terminal HVDC transmission system using the morphological un-decimated wavelet decomposition signal processing technique. Depending on the polarity and arrival time information of the first incident travelling wave at both DC transmission line terminals, the fault is identified to be either in the internal zone, forward external zone, or backward external zone of the DC transmission line. Each DC transmission line is covered by its own internal zone as well as forward & backward external zone of its neighbouring line. The internal zone fault identification of the protection scheme sends the primary relay trip signals to associated hybrid DC circuit breakers. But if the primary protection relay fails, then the neighbouring DC substation protection system identifies the fault either in forward external or backward external zone. Then it sends a remote backup trip signal to the DC circuit breaker in the forward or backward external direction with a coordinated time delay.

A ground fault detection method of substation DC system based on particle filter

In order to reduce the false alarm rate and false alarm rate of grounding fault detection in substation DC system and improve the efficiency of fault detection, a method of grounding fault detection in substation DC system based on particle filter is proposed. The wavelet threshold denoising method is used to remove the noise of the grounding fault signal of the substation DC system. The wavelet packet decomposition method is used to decompose the grounding fault signal of the substation DC system and extract the characteristics of the grounding fault signal of the substation DC system. Based on the particle filter algorithm, the residual smoothing value is used to detect the grounding fault of the DC system in the substation. The experimental results show that the failure detection rate and false alarm rate of the proposed method are low, which has a good fault detection effect.

Defect Treatment and Cause Analysis of DC Grounding Fault in 500kV Substation

The substation DC system is the most important power source for signal acquisition, protection and control of the power system. During the operation of a DC system, DC faults can occur due to incidental causes. This article briefly studies and analyzes a DC ground fault in a 500KV substation, introduces the method of finding DC ground faults, and the reasons for their formation. The following points are for reference only.

Design of Remote Monitoring System for Substation DC Power Supply under the Background of Big Data

The DC power supply(DPS) system is an important part of the substation. In order to adapt to the current unmanned operation and maintenance mode of the substation and the new requirements of state maintenance and management, it must develop in the general direction of digitalization, programming and intelligence. To ensure the safety and stability of the new operation and maintenance mode of the power system. Through the design and application research of the DPS remote monitoring system of the substation, the real-time data collection of the domestic DPS device is realized, the collected data information is summarized, and the cooperation of the remote control center and related operation and maintenance management teams is requested. The management software effectively analyzes the collected equipment operating parameters and real-time data, extracts fault information and hidden dangerous data required for operation and maintenance, which is helpful for the scientific management and risk prediction of DC power equipment in substations. The operation and maintenance personnel and the DPS system of the substation ensure the operation in a high-quality and healthy state and the safe and stable operation of the entire power network. This paper studies the design principle, structure and function of the DPS remote monitoring system used in the substation. On this basis, in-depth study of battery voltage equalization technology, internal resistance measurement technology and other core technologies related to DPS remote monitoring system design. In order to realize the online monitoring, analysis and diagnosis of the operation information data of DPS devices such as remote charging and discharging operation safety management strategy, DC power information collection and communication network design, the theoretical and technical foundations have been formulated.

Design of remote operation and maintenance platform of substation DC system for field defect handling

The current remote operation and maintenance platform of substation DC system mainly relies on manual use of each independent monitoring device to collect and transmit data for remote operation and maintenance management, which is difficult to realize intelligent operation of substation and also leads to slow response and poor processing performance of operation and maintenance platform. In order to optimize the above-mentioned problems, the remote operation and maintenance platform of substation DC system for on-site defect processing is studied and designed. Based on the framework of the operation and maintenance platform, a combination of balanced and unbalanced bridge-based principle is used to monitor the DC insulation status. The JSON protocol is used to realize the data interaction between the operation and maintenance platform and the management terminals, and to design the DC system defect processing scheme. The Floyd shortest path algorithm is used to plan the operation and maintenance inspection strategy of the platform to achieve fast operation and maintenance of the DC system. The platform performance test results show that the performance index of the designed operation and maintenance platform is significantly improved, and the average request response time is shortened by 28.1%, and the operation and maintenance management effect is better.

Island Detection Communication in IEC61850 Grid Controller by Utilizing 2oo3 Architecture to Improve Redundancy and Reliability

After large-scale photovoltaic (PV) and wind power integration with the national grid, the island grid detection is a crucial technique that identifies when a grid should be considered as dead. This logic is built in an IEC61850 grid controller which mainly depends on the bus bar scheme and fault type. It becomes more complex when the ½ circuit breaker scheme is utilized. The lack of communication redundancy causes island mal-operation due to the substation's DC supply failure. In order to avoid such mal-operation discrepancies, this paper investigates the conventional islanding detection method. Then, an advanced IEC61850 grid controller 2oo3 architecture is proposed for islanding detection, based on SAS redundant communication which improves reliability. However, even if there is an interface communication failure, the power plant control center can still detect the islanding through the proposed IEC61850 grid controller and SCADA IEC60870-5-101/104 gateways integration. This method has the tendency of full supervision of the entire grid and perfect logical judgment by plant operation staff. This feasible and the proposed redundant communication architecture can play a decisive role for power system network stability in order to avoid system blackout.

Grounding fault detection and type determination of substation DC system

The DC system is used as the power supply for all kinds of protection, measurement and control, safety automation and other devices in the substation. It is the fundamental guarantee of power system control and protection. If the substation DC system fails, it will have a destructive impact on the entire substation system and function. Based on this, in order to solve the problems of maloperation and refusal of protection device caused by grounding fault of DC system, a method combining unbalanced bridge method with leakage current sensor is proposed to detect the grounding resistance of bus and branch. On this basis, the neural network optimized by quantum particle swarm optimization is used to determine the fault type. Finally, the effectiveness of the proposed method is verified by MATLAB/Simulink simulation.

Substation DC system grounding fault prediction method

There may be disturbance and uncertainty in the collection of leakage current in DC system of substation, which leads to the decrease of accuracy and increase of prediction error. Based on this, an improved grey prediction method is proposed to predict DC system branch grounding fault. Firstly, the characteristics of DC system ground fault parameters are collected. Secondly, the improved grey prediction algorithm is used to predict and estimate whether the detection reaches the fault threshold in the future. Finally, the validity of the proposed method is verified by MATLAB modeling.

Analysis of electric-heat characteristics and power storage capacity of emergency power supply in substation based on energy saving and environmental friendly materials

With the continuous increase of DC power system of substation, DC emergency power supply is needed for technical transformation and troubleshooting of DC power supply system. In order to study the ideal backup tool of DC power supply with light weight, small volume and easy to carry, and guarantee safety and stability of the renovation of substation dc system, this paper studies the ternary lithium ion battery with the advantages of large capacity and small volume. The paper intends to master the heating and cooling conditions of ternary lithium-ion batteries in charging and discharging process. Then, the feasibility application in substation emergency power supply of ternary lithium ion battery is analysed. The example results prove that the use of ternary lithium ion battery could meet the demand of using a variety of scenarios of transformer substation, and improve the reliability of dc power supply system.

Comparison of dynamic models for a DC railway electrical network including an AC/DC bi-directional power station

To face environmental issues, SNCF, the French railway, has chosen to improve the energy efficiency of its electrical power system by investigating solutions for regenerative braking. With the contribution of Railenium, a research and test center in railway activities, they aim to recover the braking energy by setting up a reversible inverter in the DC substation ”Masséna”. The issue is to test, implement and compare various control solutions to increase the energy efficiency with minimum impacts on the railway operation. In this paper, a simulation model for studying a reversible power substation is addressed by considering AC and DC equivalent electrical sources. The proposed model provides a reliable tool for analyzing the behavior of the railway electrical network during specially braking mode. In order to validate this model, its simulation results are compared with the ones obtained from Esmeralda, the SNCF professional software. A first configuration is led without the inverter and gives certified Esmeralda results and validates the proposed model despite some gaps in powers and voltages due to differences in input data and models. A second comparison with inverter is presented to highlight the main difference between the proposed model and Esmeralda. In addition, laboratory experimental activities are put forward to investigate the proposed model by using power-hardware-in-the-loop simulations. Finally, a simulation test under MATLAB software with fifty train’s traffic is presented to estimate the energy saving thanks to the installed inverter. For this latter case study, the system sent back to the national AC grid around 6.9% of the total energy consumed by all trains.

DC Substation for DC Grid—Part II: Hierarchical Control Strategy and Verifications

DC substation serves as a multiple-input multiple-output system in dc grid for voltage regulation and power dispatching. Based on the dc substation configurations investigated in Part I, a two-layer hierarchical control strategy is proposed with simultaneous terminal voltage/current control aims. The primary layer is implemented on single-input single-output converters, working for voltage regulation and internal current control. The secondary layer serves for current regulation at the output terminals and substation loss optimization. Hierarchical control of ring-type dc substation is taken as an example, with consideration of dynamic coupling among the internal converters. The proposed control strategy is compared with centralized control and verified through numerical simulations. A downscaled experimental dc grid has been built, and the hierarchical control strategy is implemented on a dc substation prototype with a distributed controller.

Detailed modelling and simulations of an all‐DC PMSG‐based offshore wind farm

A detailed modelling method and corresponding simulations for an all-DC offshore wind farm equipped with a permanent magnet synchronous generator (PMSG) are elaborately discussed and conducted. This all-DC wind farm is designed in series-connected topology with an offshore DC substation and a voltage-sourced converter−high-voltage direct current (VSC-HVDC) transmission system. Some major components including wind turbine, synchronous generator, VSC, and isolated full bridge converter are all modelled based on the complete electrical models and engineering parameter settings. Containing the start process of the system, the simulations under various wind speed conditions and the specific faults analysis under different situations are carried out in the MATLAB/SimulinkTM environment. Simulation results reveal the comprehensive operating characteristics of this all-DC offshore wind farm and its system response to faults.

DC Substation for DC Grid—Part I: Comparative Evaluation of DC Substation Configurations

DC grid has been deemed as the enabling technology for future power systems. Within the dc grid, multi-terminal dc node (MTDN) serves as the key component for voltage/power conversion and fault protection. Configurations of MTDN are explored in this paper. The similarity of MTDN to a classical ac substation is first identified, and three series of “dc substation” have been developed on the basis of classical ac substation structures. To evaluate the influence of different “power conversion technology” and “system structure” on dc substation performance, the proposed configurations are compared under a four-terminal dc node case. Potential applications of dc/dc converters in dc substation are investigated, and each configuration is evaluated in terms of system cost, efficiency, and reliability.