最新刊期
卷 ， 期 2 ， 2024
- 摘要：With the rapid development and technological maturity of China's rail transit electric traction system, its reliability assessment and intelligent monitoring technology have gradually attracted attention. Digital twin, as a virtual characterization technique for actual physical systems based on data and machine learning, can simulate the behavioral characteristics and monitor parameters of actual physical systems. Therefore, introducing digital twin technology into the rail transit electric traction system field can provide development ideas and technical means for the digital and intelligent monitoring and operation & maintenance of these systems. This paper first provides an overview of the current application of digital twin technology in electric traction systems, and then lists the key technologies required in the construction process of digital twin in electric traction systems and the development of these technologies. In the electric traction system field, digital twin and related technologies are still in the theoretical research stage, with only exploratory research on some subsystems available, and the complete system modeling and intelligent monitoring system has not yet formed. Finally, this paper looks forward to the engineering implementation prospects of digital twin technology in the electric traction system field, and discusses the internal technical problems and external objective challenges it may face when applied in engineering, for providing a reference for the subsequent technical research and practice.关键词：digital twin;electric traction system;system modeling;artificial intelligence;data processing
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发布时间：2024-08-02
General
- 摘要：This paper presents an optimization method based on a synchronization strategy for suppressing vibration noise in permanent magnet synchronous motors (PMSM) through square wave harmonic injection, to address the frequency aliasing issue that occurs at the injected harmonic current frequency near the Nyquist frequency in traditional harmonic injection methods. It began with a noise analysis for PMSMs, and elucidates on the suppression mechanism, control calibration, and frequency aliasing associated with traditional harmonic injection methods. In the subsequent sections, the implementation principle of the proposed optimization method based on the synchronization strategy was expounded. The aim was to maintain synchronization between the inverter switching frequency and the injected square wave harmonic current frequency. This synchronization facilitated the enhancement of harmonic current amplitude and stabilization of the harmonic current order. In the final part, an experimental comparison was elaborated, showcasing that the optimization method centered on the synchronization strategy effectively alleviated frequency aliasing. Results indicate an average reduction of 6.4 dB in 48th order noise and 5.6 dB in 96th order noise, surpassing the outcomes obtained with traditional harmonic injection methods.关键词：permanent magnet synchronous motor (PMSM);vibration noise;synchronization strategy;square wave harmonic injection
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发布时间：2024-08-02 - 摘要：To solve the starting problem of permanent magnet traction motors in rotating state, this paper proposes a starting technology based on high-frequency injection (HFI) for initial speed recognition in rotating state. The technical principle and mathematical model of high-frequency injection of pulsating sine wave were studied, and the traditional high-frequency injection was improved to make it suitable for starting in rotating state, simulation calculation was carried out. Besides, a starting strategy for permanent magnet synchronous motor in rotating state was proposed based on high-frequency injection for initial speed recognition, and tests were designed to test and verify the pulsating sine wave high-frequency injection technology and the starting strategy in rotating state. Through research, it concluded that the pulsating sine wave high-frequency injection technology can track the actual position and speed of the rotor with high accuracy; the starting technology based on high-frequency injection in rotating state can accurately identify the speed of the motor when it starts up and effectively solve the motor starting problems under different working conditions. The test verifies the high-frequency injection technology for initial speed recognition and the starting strategy in rotating state.关键词：permanent magnet synchronous motor;high-frequency injection;starting in rotating state;saturated salient pole;polarity identification
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发布时间：2024-08-02 - 摘要：The three-level converter topology stands out as an effective way to reduce the voltage level borne by individual switching devices, which provides a solution for the application of silicon carbide (SiC) devices in high-voltage and high-power traction converters. This paper explores the current harmonic minimum pulse width modulation (CHMPWM) strategy based on the three-level diode neutral-point-clamped (NPC) inverter topology, tailored to meet the specific application requirements of traction inverters. Through a solving process, this study generated the curve of switching angle variations with modulation ratios at different numbers of switching angles, leading to overall optimization of current harmonics under low pulse counts of three-level inverters. Subsequent theoretical analysis revealed the characteristics of current harmonics at diverse orders and the weighted total harmonic distortion (WTHD) at different numbers of switching angles within the CHMPWM framework. Further exploration in this study delved into the pulse generation method of CHMPWM and the modulation mode switching method based on the flux linkage deviation vector of stators. In addition, experimental research was carried out on a small-power experimental platform, to verify the three-level inverter CHMPWM and modulation mode switching strategy. The experimental results showcased the good dynamic and steady performance of the three-level inverter CHMPWM strategy, demonstrating its suitability for the technical application requirements of traction inverters.关键词：three-level inverter;pulse width modulation;current harmonic minimum;synchronous modulation;modulation switching
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发布时间：2024-08-02 - 摘要：Three-level converters have been widely used in high-power rail transit applications due to their advantages. However, they also have an inherent problem of neutral-point voltage imbalance. To address this issue in neutral point clamped (NPC) converters, reduce the output phase current distortion, and improve the system operation stability, this paper proposes a new dual degree of freedom neutral-point voltage balance modulation strategy based on the analysis of neutral-point charge. With respect to this modulation strategy, the authors first introduced the causes of the neutral-point voltage imbalance on the DC side of three-level converters from a mathematical perspective, then, analyzed the impact of voltage vector output sequences on the neutral-point voltage in space vector pulse width modulation (SVPWM), and finally improved the traditional voltage vector output sequence according to the above analysis results, and proposed a new dual degree of freedom neutral-point voltage balance modulation strategy based on the characteristics of the improved sequence. This modulation strategy adjusted the action time of balance factors with dual degree of freedom. Theoretically, the proposed new modulation strategy has more controllable charges and better control effect compared with the traditional method. The simulation and test results prove that the proposed new modulation strategy can control the neutral-point voltage faster and more stably. In summary, the proposed new modulation strategy with dual degree of freedom can effectively solve the neutral-point voltage imbalance problem in three-level converters.关键词：three-level;NPC converters;space vector pulse width modulation;neutral-point voltage balance;balance factor
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发布时间：2024-08-02 - 摘要：Restricted by heat dissipation conditions, the switching frequency of the traction inverters for rail transit typically remains below 1 kHz, to prevent potential shortening of their service lifetime due to excessive switching losses in power devices. Inverter operation in the middle and high-frequency ranges results in a decrease in carrier ratio, leading to amplified output harmonics. This not only lowers output performance but also elevates peak current levels, intensifying power losses within the insulated-gate bipolar transistor (IGBT) and consequently undermining driving safety. Unlike existing modulation strategies to address low carrier ratios, which mostly focus on optimizing output performance while overlooking the suppression of IGBT power losses, this paper presents a multi-objective optimization modulation strategy for traction inverters under five-division frequency. This strategy aims to maintain a low weighted total harmonic distortion (WTHD) in the inverter output while reducing total power losses. Firstly, numerical and phase relationships between the output voltage and current were established based on the inverter load model. A precise discrete calculation model for IGBT power losses was developed based on the data manual provided by the device manufacturer, leveraging the power loss generation mechanism. Subsequently, the switching angles were solved under the premise of ensuring the fundamental amplitude of inverter output voltages aligned with the reference level, to enable multi-objective optimization modulation for inverters, including both inverter output current harmonics and power losses as optimization objectives. Simulation results indicate that within the operating range, the proposed optimization modulation strategy significantly reduced IGBT power losses and remained superior output performance compared to traditional strategies.关键词：converter;power loss;five-division frequency;multi-objective optimization modulation;weighted total harmonic distortion;switching angle
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发布时间：2024-08-02 - 摘要：This paper presents an estimation method of rotor position at low speeds for permanent magnet synchronous motors (PMSM), using a high frequency (HF) square wave voltage injection technique at a low switching frequency. This method utilized variations in q-axis current resulting from the voltage injection to estimate rotor position errors. A Luenberger state observer was incorporated to estimate rotor position based on changes in q-axis current, along with a straightforward design principle provided for the zero and pole points of the Luenberger state observer. The experimental results show that the proposed sensorless control algorithm is effective in accurately tracking actual values in the rotor speed and position estimation at low switching frequency.关键词：permanent magnet synchronous motor (PMSM);sensorless control;low switching frequency;high frequency (HF) square wave voltage injection;Luenberger state observer
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发布时间：2024-08-02 - 摘要：In order to meet the requirements of high-power traction electric drive applications for high precision and fast response of motor output torque, this paper proposes a three-level drive control method for traction motors based on indirect stator quantities control (ISC). Firstly, a dynamic flux weakening control method based on the characteristics of ISC control and the model of induction motor, was proposed to ensure the high dynamic response of motor torque in the high-speed flux weakening region; then, in order to effectively solve the problem of neutral-point potential imbalance in traditional three-level algorithms, according to the different effects of different switch vectors on the neutral-point potential of the neutral point clamped (NPC) three-level inverter, a new neutral-point potential balance control strategy with high balance accuracy and strong anti-interference performance was proposed based on precise calculation of charge cycle balance and principles of proportional integral (PI) controller. Finally, this method was tested through simulation research and the back-to-back testing with a high-power induction motor for rail transit. The test results show the control method proposed in this paper has advantages of high dynamic response, high neutral-point potential balance, and high torque control accuracy.关键词：traction motor;indirect stator quantities control;flux weakening control;neutral-point potential balance
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发布时间：2024-08-02 - 摘要：In light of the characteristics of frequent starting and stopping of urban rail transit vehicles, a control strategy was proposed for achieving precise stopping, enhancing ride comfort, reducing losses and saving energy through pure electric braking of asynchronous motors to zero speed. Within the full-speed range of vehicle operation, a dual-drive technology based on data and model was utilized to predict the maximum available deceleration of the vehicle. In the low-speed range of vehicle electric braking, a deceleration controller was designed to adjust the torque command value for motor braking in real-time. A discretized closed-loop full-order rotor flux observer was employed to identify the operating frequency of the motor, enabling the use of the identified frequency value to replace the frequency value collected by the speed sensor to complete the stopping process. Finally, the effectiveness of the above research strategy was validated through a hardware-in-the-loop simulation platform and vehicle operation tests.关键词：urban rail transit;zero-speed electric braking;model and data dual drive;deceleration controller;full-order rotor flux observer;hardware-in-the-loop simulation platform
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发布时间：2024-08-02 -
A study on high-performance single-phase phase-locked loop method based on synchronous sampling SDFT
摘要：In the traction drive control system of electric locomotives and rolling stock, the grid-side converter obtains phase information through a phase-locked loop and carries out precise control. The voltage amplitude and frequency of the traction power supply network fluctuate, and the network voltage often has serious distortion and contains a large number of harmonics, so the complex grid environment puts forward high requirements for the performance of phase-locked loops. In combination with synchronous sampling, this paper proposes a high-performance phase-locked loop method based on SDFT. The performance of this method was verified through digital simulation and semi-physical simulation tests. The test results show that, compared with several other mainstream phase-locked loop methods, this method has high steady-state phase-locking accuracy, fast dynamic response speed, and strong harmonic suppression and anti-bias capability, and is suitable for application in the field of rail transit.关键词：four-quadrant converter;synchronous sampling;SDFT;phase-locked loop;harmonic suppression;disturbance immunity- 2208
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发布时间：2024-08-02 - 摘要：Power electronic transformers (PET) incorporating cascaded H-bridge (CHB) converters as the front-stage topology represent an important development trend for future train traction. Minimizing low-order harmonics in CHB converters holds immense importance in enhancing the control performance of PETs. However, the factors affecting low-order harmonics in CHB converters differ from those in conventional four-quadrant converters. There is still a lack of detailed research on the underlying mechanisms and suppression strategies. This paper delved into the generation mechanisms of low-order harmonics in CHB converters on the traction network side, highlighting that low-order harmonics were related to the module count and topology of H-bridge cascades, in addition to DC voltage fluctuations, device dead-zones and switching voltage drops. According to the findings, a low-order harmonic suppression algorithm was designed, taking into account DC voltage fluctuations and circuit topology characteristics. Furthermore, a comprehensive optimization strategy for suppressing low-order current harmonics in CHB converters was suggested, integrating the dead zone effects and voltage drop impacts. In the final section, an experiment using a low-power experimental platform was detailed. The experimental results verify the accuracy of the theoretical analysis and the effectiveness of the optimized suppression solution.关键词：cascaded H-bridge (CHB) of traction converter;low-order harmonic analysis;harmonic suppression strategy;DC voltage fluctuation;device dead-zone;switching voltage drop
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发布时间：2024-08-02 - 摘要：According to the characteristics of plateau diesel locomotives, i.e. high operating altitude, complex heat dissipation conditions and high lightweight requirement, this paper introduces the main circuit structure, working principle and design method for the traction converter of Fuxing plateau dual-source power centralized diesel multiple units(DMU). For high operating altitude, the in-cabinet electrical insulation performance was strengthened by the altitude correction method; for complex heat dissipation conditions, a reasonable cooling scheme was selected and the detailed thermal design for the loss and heat dissipation capability of the whole cabinet was carried out to ensure its heat dissipation capability; for high lightweight requirement, the modular layout and finite element structural simulation method were used to ensure the structural strength and realize lightweight design at the same time. The tests show that the traction converter can meet the requirements of all performance indicators.关键词：dual-source;plateau;environmental adaptability;diesel;traction converter;main circuit;structural strength;test
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发布时间：2024-08-02
Converting and Control
- 摘要：The inter-turn short circuit of stator winding is one of the main faults affecting the safe and stable operation of permanent magnet traction motors. Affected by operating conditions, power supply and motor body imbalance, existing methods are difficult to achieve online accurate evaluation of inter-turn short circuit of permanent magnet traction motors. This has become a key technical problem that urgently needs to be solved for the widespread application of permanent magnet motors. Therefore, this paper proposed a grading evaluation method for inter-turn short circuit in permanent magnet traction motors based on multi-feature fusion of deep Gaussian processes. Firstly, by establishing a fault model for inter-turn short circuit in permanent magnet traction motors, features such as current unbalance, third harmonic currents and second harmonic feature of dq currents were extracted. Then, a doubly stochastic deep Gaussian processes (DSDGP) method was adopted to fuse and train the extracted features, achieving online grading evaluation of inter-turn short circuit degradation in permanent magnet traction motors. Finally, the algorithm was validated through permanent magnet motor inter-turn short circuit tests and field cases. The results show that the proposed method achieves an evaluation accuracy of over 95% under the condition of multi-feature fusion. Compared with classification methods such as support vector machine (SVM) and back-oropagation neural network (BPN), it exhibits high accuracy and suitability for engineering practical environments with variable operating conditions and small samples, addressing industry challenges in early fault detection and severity evaluation of inter-turn short circuits in permanent magnet traction motors.关键词：permanent magnet traction motor;multi-feature fusion;inter-turn short circuit;graded evaluation;deep Gaussian processes
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发布时间：2024-08-02 - 摘要：To improve the accuracy of grounding fault diagnosis in the permanent magnet traction system of high-speed EMUs, this paper proposed a new grounding detection method suitable for permanent magnet traction systems. By combining the topology structure of the grounding detection circuit, the characteristics of grounding voltage under different grounding conditions were analyzed. Based on this analysis, measures such as optimizing the decision algorithm for grounding voltage exceeding limits, adopting step-by-step detection of each axis inverter, and adding diagnostic nodes for permanent magnet contactors were proposed. This method can accurately diagnose the specific grounding points on the motor side, transformer side and inverter side, thereby improving the accuracy of fault point localization. The feasibility of this method was verified by hardware-in-the-loop simulation and ground unit test results.关键词：high-speed EMUs;traction system;grounding detection;hardware-in-the-loop simulation;unit test
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发布时间：2024-08-02 - 摘要：In the variable frequency drive system, the high dv/dt and transient overvoltage generated by the high-speed switch of the power device will make the motor insulation parts withstand high electrical stress, accelerate the aging of the motor insulation materials, and then increase the probability of insulation failure and harm the overall reliability of the drive system. Compared with the traditional offline monitoring method, online monitoring of motor insulation states can improve the real-time monitoring performance and reduce the loss of shutdown maintenance. Therefore, this paper presents a method of online monitoring of AC motor grounding insulation based on inverter switch oscillating current. First, the authors established an AC motor insulation equivalent circuit, analyzed the influence of insulation aging on the impedance of AC motor, and simulated the insulation aging process by connecting external capacitors in parallel. Then, the influence of the motor grounding insulation parameters on the switch oscillating current under pulse width modulation (PWM) was analyzed, and proposed an online monitoring method with the frequency domain deviation of switch oscillating current as the aging characteristic index. This test shows that this method can effectively monitor the aging state of the motor grounding insulation without affecting the normal operation of the motor.关键词：AC motor;insulation aging;online monitoring;current response;inverter;high-speed train
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发布时间：2024-08-02 - 摘要：The precise junction temperature monitoring is of paramount importance for enhancing the reliability of insulated gate bipolar transistor (IGBT) modules and extending the lifespan of devices. This paper introduces a method for monitoring junction temperature of IGBT modules based on turn-off voltages (TOV), which highlights resistance to load currents. The study initially verified the rationality of using TOVs as a temperature-sensitive electrical parameter. The deep neural network (DNN) technology was subsequently employed to eradicate the dependence of TOVs on load currents, facilitating accurate junction temperature prediction under varying operational conditions. The proposed method was validated through a single-phase pulse width modulation (PWM) experiment. The findings reveal an error range of ±5 ℃ for this method, demonstrating the feasibility of optimizing junction temperature monitoring through DNN utilization.关键词：insulated gate bipolar transistor (IGBT);junction temperature monitoring;deep neutral network (DNN);temperature-sensitive parameter;turn-off voltage (TOV)
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发布时间：2024-08-02 - 摘要：The paper presents a fault diagnosis and analysis algorithm centered on variational mode decomposition (VMD), sample entropy, and TOPSIS, to address the challenge of frequent misoperations of relay protection systems triggered by oscillating current in the incoming lines of metro traction power supply systems. Using a real-time digital simulation experimental platform, the improved incoming line protection algorithm was compared with traditional reverse current protection algorithms in the application scenario of metro relay protection devices. The experimental analysis verified the practicality and effectiveness of the proposed approach in engineering applications. The study findings highlight the algorithm’s capacity in identifying special oscillating current in DC incoming lines, offering a valuable means to enhance relay protection reliability.关键词：metro traction power supply system;resonant current of DC incoming line;short-circuit current;incoming line protection;variational mode decomposition (VMD)
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发布时间：2024-08-02 - 摘要：The safety and reliability of traction inverters are critical for the stable operation of high-speed EMU vehicles. To identify the operating status of the inverter, this paper proposed a fault diagnosis method based on the analysis of motor vibration signals combined with the vehicle system dynamics. In this method, the motor vibration signal is taken as the monitoring object, and the characteristic signal of abnormal motor vibration caused by current distortion during inverter failure is detected for judgement. Taking the traction transmission system of CRH2 EMU as an example, a simulation model of a three-level traction inverter circuit based on space vector pulse width modulation strategy was established to simulate the structural fault modes of the inverter. The simulation results indicate that inverter faults significantly affect the harmonic content of the output current on the AC side, especially the 5th, 7th, 11th, and 13th harmonic currents. These harmonics currents are converted into pulsating torques at frequencies of 6P(1-s) and 12P(1-s) after input to the traction motor, acting on the motor and causing corresponding harmonic components in its output vibration. Analysis of vibration signals of the traction motor during the actual operation of high-speed EMU reveals that under normal circumstances, the vibration signals do not contain obvious harmonic frequency components, while the presence of inverter faults leads to a very significant content of this frequency in vibration signals. Therefore, the vibration signal analysis method proposed in this paper can effectively monitor and diagnose the operating status of the traction inverter and has a certain engineering application value.关键词：high-speed EMUs;traction inverter;motor vibration;current harmonics;fault diagnosis;simulation
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发布时间：2024-08-02 - 摘要：In order to realize reliable diagnosis of early faults of stator winding turn-to-turn short circuits of traction motors, a fault diagnosis method based on steady-state response current of step excitation was proposed in this study. Firstly, on the basis of a three-phase stator winding turn-to-turn short-circuit model of traction motors, a step excitation was applied to any two phases of the stator winding to derive the response current expressions in three cases, and a new fault characteristic component was proposed on the basis of the change characteristics of the steady-state value of the response current. Then, a simulation model of the faulty motor was established to analyze the impact of short-circuit resistance and fault severity on the response current, and to investigate the validity and reliability of the fault characteristic components for the diagnosis of early turn-to-turn short-circuit faults. Finally, an experimental platform was built to analyze the impact of turn-to-turn short-circuit faults on the fault characteristic components when the motor is inherently asymmetric. The simulation and experimental results show that the fault characteristic component can represent the early turn-to-turn short-circuit fault and its severity, and can filter out the impact of the inherent asymmetry of the motor. The diagnosis method based on the steady-state response current of step excitation is easy to operate and the results are highly reliable. This method holds great significance for the protection of the traction system and offers great value for engineering applications.关键词：traction motor;stator winding turn-to-turn short circuit;fault diagnosis;step response
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发布时间：2024-08-02 - 摘要：This paper introduces a simplified junction temperature curve method for insulated gate bipolar transistors (IGBTs), through the utilization of the discrete integral principle. By quantifying junction temperatures within the fundamental wave period, this approach enables the conversion of junction temperature fluctuation curves containing detailed junction temperature information into simplified representations containing only key junction temperature information. The proposed method exhibited high calculation accuracy, as well as the capacity to rapidly determine maximum and minimum junction temperatures and their corresponding occurrence times, thus greatly reducing the calculation burden. A simulation analysis of junction temperature fluctuations at different fundamental wave frequencies proved the effectiveness in reflecting junction temperature fluctuations and high calculation accuracy of the proposed method. Furthermore, a comparison with other junction temperature calculation methods highlighted the obvious advantages of the proposed method in terms of calculation speed, and its particular suitability for calculations on long time scales. Finally, the accuracy of the proposed method was verified by measuring junction temperature fluctuations in a power assessment test.关键词：junction temperature fluctuation within fundamental wave period;simplified junction temperature curve;IGBT;equivalent sinusoidal half-wave loss;equivalent thermal circuit method
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发布时间：2024-08-02 - 摘要：Transient disconnection between pantographs and catenaries during train operation on electrified railways, known as pantograph-catenary contact loss, can cause issues like over-current, creating safety hazards and consequential disruptions to operational order. This paper introduces the main circuit structure and control method of grid-side rectifiers of the prevailing traction electric drive systems for EMU. The analysis investigated the system impacts of pantograph-catenary contact loss, emphasizing the reasons for over-current occurrences during contact recovery, leading to the establishment of a rapid online identification method and a response strategy. Following developing a full-digital real-time simulation model of the electric drive systems for traction, which includes an arc model, accuracy verification was conducted firstly through waveform comparisons with actual measurements. This model was subsequently used to verify the proposed identification method and response strategy for pantograph-catenary contact loss.关键词：high-speed railway;pantograph-catenary contact loss;traction system;arc;four-quadrant;high-speed EMU
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发布时间：2024-08-02
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