IET Electrical Systems in Transportation最新文献

A novel 40-pulse autotransformer rectifier is proposed to reduce total harmonic distortion (THD) of the input current in aircraft electrical power systems. The 40-pulse rectifier (40PR) includes a passive harmonic reduction circuit (PHMC) with a low kVA rating (about 0.95% of the load power) to enhance the performance of the conventional 40PR. This PHMC is based on 2 harmonic suppression circuits and contains four tapped reactor and 4 auxiliary diodes. 50 Hz simulations of the improved 40PR indicate that THD of the input current and voltage is less than 2%, which meets the IEEE-519 standard. In addition, without using any input and output filters, input current harmonic components at 400–800 Hz are less than the requirements mentioned in the DO-160G and MIL-STD-704F standards. The suggested PHMC can easily be implemented. A prototype is developed to verify the proposed design. A good agreement can be seen in simulation and experimental results.

The precision of equivalent circuit model (ECM)-based state of charge (SoC) estimation methods is vulnerable to the variation of the battery parameters, due to several internal and external factors. In this regard, this study proposes a fuzzy logic method for the approximate estimation of the ECM parameters at different temperatures and SoC levels. The fuzzy inference system is designed to handle the non-linear deviation of the battery parameters from their reference values. On this basis, the extended Kalman filter and smooth variable structure filter are used to estimate the SoC. The two algorithms with fuzzy parameters (FP), namely FP-EKF and FP-SVSF, are tested on a 20 Ah Nickel Manganese Cobalt cell with maximum voltage of 4.2 V. The results show that the maximum root mean square error (RMSE) of the estimated SoC is kept within 1.51% with the FP-EKF and 0.68% with the FP-SVSF. Moreover, the reduction of the maximum absolute error may reach 0.34% with the FP-EKF, and 0.82% with the FP-SVSF, compared to the same algorithms without the proposed FP method. The executable codes are implemented on a low-cost controller, and the average computational time is obtained as 215 μs, which confirms the real-time practicality of the proposed method.

The computational efficiency is a challenging task in the real-time implementation of battery State of Charge (SoC) estimation algorithms in Electric Vehicle (EV) application. This study proposes for the first time a pure hardware architecture of a Smooth Variable Structure Filter (SVSF) to estimate the SoC of a lithium-ion battery in an EV. The proposed embedded architecture is implemented on a Xilinx Zynq-7000 field programmable gate arrays board without using any soft-core, and validated with real-time tests carried out on a 20 Ah NMC battery with nominal voltage about 3.65 V. The whole embedded architecture of the SVSF needs a reduced execution time in the range of 921 ns, and it consumes only 466 mW. The average estimation errors of the SoC and battery voltage at different temperatures are kept within 4.95% and 2.35% respectively. The successful convergence of the algorithm and the accurate results obtained in different circumstances, prove the practicability and computational efficiency of the proposed hardware architecture.

This paper proposes a three-layer framework for energy efficiency evaluation of Shore-to-Ship Charging (S2SC) systems using load-dependent loss models of the components. The considered S2SC system is supplied by the grid but is also supported by On-Shore Batteries (OSB). The presented approach is then used to investigate the impact of the specific design and operational parameters on energy efficiency. Power system architectures for three general S2SC solutions for ac, dc, and inductive charging are defined and compared in terms of energy efficiency. Operational parameters are also considered in the analysis, namely, the grid power ratio, determining the load sharing between the grid and the OSB, as well as the OSB charging profile. A case study is performed with peak charging power of 1 MW, and the most efficient S2SC solutions are identified for both ac- and dc-based onboard power systems. Moreover, it is shown that charging OSB with the highest available power from the grid between the charging breaks would often lead to higher energy efficiency than the maximum utilization of the available charging time. Field data from a real S2SC system is used to verify the estimated energy efficiency by the proposed framework. The analysis of the real case S2SC is then extended to include and verify a projected OSB.

Medium-voltage DC (MVDC) electric railway systems have several advantages over conventional DC and AC railway electrification systems. These advantages include higher capacity, possibility of connecting to power networks at lower voltage, removal of neutral sections, smaller line voltage drops, and longer distances between traction power substations. This paper reviews in depth the arrangements for MVDC railway electrification systems proposed in the technical literature and the topologies used for high-power medium-voltage AC-DC converters. With reference to typical requirements of a MVDC railway electrification system, the pros and cons of the topologies are critically analysed. Moreover, this paper reviews the DC-DC power converter topologies for on-board power electronic traction transformers, required to interface the MVDC power supply with the traction motors. Finally, the review highlights the existing challenges of MVDC electric railway systems and the potential areas of future research.

When a train runs at high speed, affected by the structural characteristics of the catenary, the contact force changes periodically with span and dropper spacing. However, as the running speed of the train increases, the periodic signal of the contact force changes owing to the fluctuation of the catenary and the vibration of the pantograph, which directly affects the stable contact between the pantograph and catenary. Therefore, based on the simulation research method, this study uses the time–frequency transformation method to investigate the influence of changes in the catenary structure on the periodic signal of the contact force. First, the structural design of the catenary structure of the existing railway line is carried out by changing the length of the stitch wires and the dropper spacing, and the stiffness and stiffness curvature variation when the arrangement of the stitch wires and dropper varies are analysed. Then, the relationship between the stiffness, stiffness curvature variation, and contact force variation is analysed. Finally, the wavelet transform method is used to transform the contact force, and variations in the key amplitude component of the contact force are analysed when the structural parameters are changed, and the relationship between the period and the key amplitude component is obtained. By analysing the time–frequency characteristics of the contact force, technical support for improving the speed of the train can be provided.

This study proposes a bounded rational charging guidance strategy based on mental account theory, which guides users to charge in an orderly manner by formulating real-time charging prices. Firstly, an orderly guidance framework for fast-charging EVs under the traffic-grid coupling network is constructed, and the influencing factors of various dimensions when users make charging decisions are analysed. Secondly, considering the bounded rational behaviour of users when making charging decisions, a multifactor bounded rational charging model for EV users based on mental account theory is proposed so as to obtain different charging costs for users when selecting charging stations. On this basis, a real-time charging price strategy based on the Stackelberg game model is constructed, with the goal of maximising the economic benefits of charging station operators while reducing the charging cost of EV users as much as possible. Finally, the particle swarm optimisation algorithm is used to solve the game model so as to solve the real-time charging price under various constraints. The simulation of an example verifies the rationality of the proposed real-time charging price formulation method and the superiority of the bounded rational charging guidance strategy.

To achieve the UK net-zero emissions target by 2050, transformations to decarbonise the energy system will be essential. A transition from generating electricity by burning fossil fuel to renewable energy sources (RESs) is one of the most effective ways, in addition to customer transformation, in which people are willing to participate to reduce energy consumption. The railway sector accounts for 0.5% of carbon emissions in the United Kingdom. In order to meet the net-zero goal, more railway routes must be electrified, as only 38% of railway routes are electrified at present. Furthermore, clean energy is necessary. Therefore, schemes for integrating RESs into the AC high-speed railway power supply system are proposed and simulated in a case study. Power losses in the power system are comprehensively studied and compared. Owing to the fluctuation of traction load, the power quality issue is inevitable. Thus, the voltage unbalance factor is adopted to measure the severity of the imbalance. The results from the case study demonstrate that the proposed scheme in which the RES is connected to a three-phase railway power network generates the smallest power losses among all proposed schemes. Moreover, it also requires lower investment expenditure and provides the most significant cost saving in the long run. The results also reveal that the VUFs of all schemes based on a 400 kV transmission system are below the United Kingdom's stringent limit of 1.5%. Furthermore, the CO₂ emissions are reduced significantly with RES integration by half for the case study with the 120 MW RES. Although the other proposed schemes had higher losses and lifetime costs, the differences are not significant. Each scheme has its advantages and disadvantages. Several factors need to be considered to choose the suitable scheme, such as the size of land available etc.

With the increase of train speed in electrified railways, the increasingly violent interaction of pantograph–catenary (PC) makes the PC detachment arc an extrusive phenomenon, especially in the double-pantograph–catenary (DPC) system. Despite a large number of research studies have focussed on the PC arc in a single pantograph system, the studies of PC arc in the DPC system are relatively insufficient. In this paper, the arcing phenomenon in the DPC system is studied by combining it with DPC dynamics. First, through analysing the PC interaction in the double pantograph coupled model, the contact force and vertical displacement of PC are obtained, which are used to analyse the detachment state and fit the detachment trajectory. Then, a dynamic PC detachment arc model is established by extending the black-box arc model and introducing the detachment trajectory. Next, a circuit model of CRH380BL electric multiple units (EMUs) with a DPC system is established to simulate the dynamic arc model. Finally, the characteristics of arc and their coupling transient influences are analysed under different initial design parameters of the DPC system and the correlation of arc characteristic and arc influence is discussed. The validity of the DPC arc model is verified by experiment results.

The move towards More-Electric Aircraft (MEA) and Engine (MEE) systems has resulted in system integrators exploring the use of Direct Current (DC) for primary power distribution to both reduce energy conversion stages and enable parallelling of non-synchronised engine off-take generation. A prevalent challenge of utilising DC systems is the safe management of arc faults. Arcing imposes a significant threat to aircraft and can result in critical system damage. Series intermittent arc faults in DC systems are particularly challenging to detect due to the lack of a zero current crossing coupled with the intermittency caused by in-flight vibrations. Additionally, several state-of-the-art arc fault detection methodologies fail to address the handling of aircraft system-specific conditions such as dynamic loading and stability requirements. This paper addresses these unique MEA/MEE issues through the proposal of a new generalised real-time arc fault detection methodology (WaSp) based on time–frequency domain-extracted features applied to a feed-forward Artificial Neural Network (ANN). The paper outlines the analysis of arc fault time–frequency domain features. Simulation-based case studies emulating a range of on-board EPS conditions are presented and show the proposed system has the potential for highly accurate and generalised detection performance with fast detection times.