Power batteries are the core of electric vehicles, but minor faults can easily cause accidents; therefore, fault diagnosis of the batteries is very important. In order to improve the practicality of battery fault diagnosis methods, a fault diagnosis method for lithium-ion batteries in electric vehicles based on multi-method fusion of big data is proposed. Firstly, the anomalies are removed and early fault analysis is performed by t-distribution random neighborhood embedding (t-Sne) and wavelet transform denoising. Then, different features of the vehicle that have a large influence on the battery fault are identified by factor analysis , and the faulty features are extracted by a two-way long and short-term memory network method with convolutional neural network. Finally a self-learning Bayesian network is used to diagnose the battery fault. The results show that the method can improve the accuracy of fault diagnosis by about 12% when verified with data from different vehicles, and after comparing with other methods, the method not only has higher fault diagnosis accuracy, but also reduces the response time of fault diagnosis, and shows superiority compared to graded faults, which is more in line with the practical application of engineering.
In the induction electric energy transmission system applied to fix point charging of vehicles, the mutual inductance change caused by position deviation or air gap change, and the equivalent load change caused by power demand change will make the output power and efficiency fluctuate, thus affecting the output stability of the system. In order to ensure the reliability of the charging process of the system and at the same time have a strong power output capacity, this paper proposes a load segmental tracking control strategy based on the optimal power efficiency. This control strategy adjusts the equivalent load to track different power efficiency indicator curves according to different mutual inductance states of the system and power demand when the vehicle is static charging, so that it can always maintain the optimal power efficiency state according to different charging conditions and improve the system performance. Finally, simulation and experimental verification are carried out under different states of mutual inductance. The results show that this method can achieve the equivalent load segmental tracking under different mutual inductance states, and always maintain the optimal power efficiency output. INDEX TERMS Efficiency, inductive power transmission, load tracking, optimization, power.
The electric machine emulator (EME), using digital simulation and power electronics to emulate the characteristics of actual machines, can greatly accelerate the testing of electric drives. However, most existing EMEs are based on typical L filter and linear controller, which causes control conflicts and bandwidth limitation. To address this issue, this paper presents an EME based on LCL filter with passive damping for a three-phase permanent magnet synchronous motor. To improve the dynamic emulating accuracy, a dual closed-loop deadbeat predictive current control algorithm is proposed, which is computationally efficient and easy to implement. The system stability is analyzed in the discrete domain, and the parameter constraints of the filter are obtained. Then, two unknown input observers are designed to compensate for the disturbance currents and voltages caused by modeling errors. Moreover, instead of the empirical method, a theoretical one considering the harmonic suppression, bandwidth, stability and resonance is presented for filter design. Finally, the performance of the proposed EME is validated through simulation and experimental results under various conditions such as machine start-up, torque step change, and speed reversal.INDEX TERMS Electric machine emulator (EME), LCL filter, dual closed-loop deadbeat predictive current control, unknown input observer. NOMENCLATURE
The application of inductive power transmission system in trams makes trams get rid of the traditional overhead catenary, but the electromagnetic environment and safety problems brought by the inductive power transmission system also attract the public's attention. In this paper, the model of the wireless charging tram platform is built to analyze the electromagnetic environment when the tram stops at the platform. Then, the shielding shape of the platform is proposed. A mathematical model with the minimum shielding cost as the goal and the magnetic field and installation space as constraints, is proposed for the platform shielding model of wireless charging tram. The three-dimensional finite element simulation software is used to verify the designed platform shield. The results show that the designed platform shield can ensure the electromagnetic radiation at the platform reaches the standard, and the cost is low. The platform shielding scheme designed in this paper provides a theoretical basis for the establishment of electromagnetic protection measures in the practical application of the wireless charging tram.
The inductive power transmission system is applied to urban rail transit. Due to the limitations of the volume and coupling coefficient of the inductive coupling mechanism and the fact that the fluctuation of air gap in its movement will cause the fluctuation of mutual inductance value, DCDC booster link should be added to the side, rectifying side, to improve the output voltage level and stability. At present, most of the existing control strategies are based on the original side information communication. However, in the application of dynamic wireless charging in urban rail transit, the primary and secondary side coils are in the process of relative movement, so it is relatively difficult to establish reliable real-time communication, and it is easy to be interfered by electromagnetic transmission process, resulting in large errors. This paper analyzes the relationship between load and efficiency of IPT system applied to urban rail transit in detail and obtains the optimal load matching strategy of optimal efficiency. At the same time, an independent control strategy is proposed to eliminate the information communication of the primary and secondary sides and realize decoupling control. Finally, a simulation model is built to verify the effectiveness of the control strategy.
As its name indicates, the bearingless switched reluctance motor does not have windings or permanent magnets on the rotor. This has the advantages of simple structure, high reliability and easy control. The sharing-suspension-windings bearingless switched reluctance motor inherits the above characteristics, and has obvious advantages in the research field of bearingless motors with its motor structure of decoupling torque and radial force. In this paper, the sharing-suspension-windings bearingless switched reluctance motor is taken as the research object. The finite element model of the sharing-suspension-windings bearingless switched reluctance prototype is established. The electromagnetic characteristics of the prototype are analyzed. As the premise of motor suspension, the structural decoupling of torque and radial force is analyzed and experimentally verified. Then, the flux-linkage saturation of the motor is derived at the position where the stator and rotor are completely aligned and the stator and rotor are completely unaligned. The torque model of the motor is derived based on the flux-linkage saturation, and the accuracy of the model is verified by the fitting comparison between the theory and the finite element simulation. It lays a theoretical foundation for the subsequent structure optimization design research of the sharing-suspension-windings bearingless switched reluctance motor.
This article proposes a novel space vector pulse width modulation (SVPWM) scheme for multilevel converters in abc coordinate system, in which the reference vector is decomposed into an offset vector and a remainder vector that can be synthesized using two-level SVPWM. The switching state satisfying a specific relationship is first selected as the offset vector such that the common-mode components are eliminated and therefore the phase voltages are decoupled. A dynamic reference point mechanism establishes a one-to-one correspondence between all available vector combinations and one unique variable, i.e., the number of level shifts. This feature further facilitates a general approach to determining the optimum switching states to satisfy different control objectives, such as common-mode voltage rejection. Besides, phase decoupling enables the introduction of carrier-based modulation to simplify implementation, where the duty cycle of the zero vector can be flexibly adjusted while the non-zero vectors remain the same to generate an equivalent output. Consequently, two-level SVPWM-based method and carrierbased PWM are combined to exploit their respective strengths. The proposed scheme achieves overmodulation operation, and provides more flexibility, i.e., redundant switching states and adjustable duty cycles, to optimize switching patterns. Simulation and experimental results validate the proposed algorithm.
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