Lijun Diao

Optimized Design of Discrete Traction Induction Motor Model at Low-Switching Frequency

By low-switching frequency of power devices, as well as synchronization between control strategies and pulse-width modulation (PWM) pulse update, the control and calculation frequency of the high-power ac traction drive control system of metro vehicle is low, which leads to some problems of instability in a high-speed region and conflict with the control timing of the digital signal processor (DSP) in the conventional discrete traction induction motor model. This paper analyzed the defects of the conventional discrete model at low-switching frequency and proposed an optimized discrete model based on in-depth study of model pole trajectory, which solved the contradiction among stability in high-speed region, the computational load, and the control timing. The proposed model is also applied for the rotor flux observer design of field-oriented control. Simulation and experimental results are given to demonstrate the steady-state and dynamic performance of the proposed model.

Distributed Auxiliary Inverter of Urban Rail Train—Load Sharing Control Strategy Under Complicated Operation Condition

Paralleling is the development tendency of the auxiliary inverter. This paper analyzes the problems of the parallel process in detail. First, for inherent contraction between voltage regulation performance and current sharing performance, the paper adopts the resistive droop method. Second, the paper improves dynamic performance and reliability of the droop method by improving power calculation and introducing the whole cycle adaptive droop method. Third, in order to solve the unshared current problem caused by inconsistent parameters, the paper increases active power proportion droop coefficient, and introduces voltage compensation strategy to compensate voltage drop caused by increased proportion droop coefficient. Fourth, the auxiliary parallel system has complicated load characteristics; the paper proposes voltage compensation strategy to compensate voltage drop caused by the pump load. This paper utilizes three-phase total reactive power to droop frequency and active power of each phase to droop amplitude, unbalanced current can be shared. This paper introduces special virtual impedance technology to solve the harmonic current sharing problem caused by the nonlinear load. Finally, the effectiveness of above theory is fully verified by simulation and experiment.

A novel traction power supply system for urban rail transportation

This paper presents the design of a novel traction power supply system for urban rail transportation based on multiple-paralleled H-bridge modules. A quasi-sinusoidal voltage output is generated by the novel system with phase-shift control mechanism and the voltage combination of the zig-zag connected transformers on AC line side. As a result, the harmonic components on line side can be greatly eliminated resulting in a higher power factor. Moreover, the power flow of the novel system is bidirectional and the power generated during the braking of vehicles can be fed back into the AC electric grid, saving much of it.

Maximum Adhesion Force Control Simulated Model of Electric Locomotive

When the traction torque of the electric locomotive exceeds the maximum adhesion force torque, the wheel will have slip/skid phenomena. To fulfill the maximum adhesion force control, a full-order state observer for estimating the adhesion torque was designed. To make DSP programming convenient, a simple control algorithm for slip velocity reference generator was proposed. Then, the simulated control model based on FOC (Field Oriented Control) was built in SIMULINK/MATLAB, and its effectiveness was verified by some specific simulation experiment and waveforms.

Taking Traction Control to Task: High-Adhesion-Point Tracking Based on a Disturbance Observer in Railway Vehicles

Railway vehicles have been based on a wheel-rail system since the systems origination. Therefore, the adhesion-coupling behavior between wheel and rail is the fundamental element of railway traction [1]. However, low vehicle wheel-rail adhesion caused by high humidity, rain, snow, oil, or decomposing leaves is a common problem that can cause damage to some elements of the traction system and decrease traction performance [2]. It may even give rise to safety problems and reduce comfort, not to mention delays and their corresponding economic impact. Good traction control to ensure the system is working at high adhesion point is therefore critical and mandatory for the traction control units (TCUs) [2]-[6].

Extended Kalman Filter based on inverse Γ model of induction motor

Most analyses of induction motor drives make use of a conventional T-form of equivalent circuit. This model is actually more complex than necessary for analysis in the linear regime. On the other hand, it is inadequate for use when the machine parameters are changed. Inverse Gamma model is simple model for induction motor, and is particularly appropriate for analysis of vector control. A research on Extended Kalman Filter based on inverse Gamma model is carried on. The change of motor parameters is taken on the state noises of EKF and it makes more precision for vector control. Speed Estimate own simple open loop structure and reduce the computation of the EKF. The speed estimator is filtered out amplifying noise generated by the pure differentiator and can satisfy dynamic and steady state need. The experiment is setup based on DSP. The experimental results give satisfy steady performance at wide speed range.

Control and Implementation of Reversible Multi-modular Converter with Interleaved Space Vector Modulation

Reversible multi-modular converter has such merits as bidirectional energy flow, unity power factor, high power and high reliability. The Interleaved space vector modulation technique is developed to acquire a high equivalent switching frequency, and reduce the harmonic current injected into AC grid. This paper introduces a new reversible multi-modular converter, which is preferred to be the interface between AC grid and DC bus. Then, the Interleaved space vector modulation technique is demonstrated. Furthermore, a novel parallel control scheme for the reversible multi-modular converter is presented. Results are validated by simulation experiments.

Suppression and Modeling Analysis of Auxiliary Converter Rectifying Voltage Output

To solve the problem of excessively high resonant voltage in shift-phase full bridge convertor rectifying voltage output, this paper first analyzes the composition of the voltage, indicating that the voltage is composed of three parts, and analyzes emphatically two parts of the three. Secondly, in the paper is selected the most practical topology of RCD snubber, and models rectifying voltage output according to circuit equivalent theory. Moreover, reasonable parameters of RCD snubber are also presented in the paper. At last, the paper presents the simulation result in MATLAB, adopting the model and RCD parameters derived above. The topology and parameters are subjected to a prototype equipment to testify its effectiveness.

Analysis and design for reducing voltage stress in output rectifier of LFLRV SIV DC-DC converter

This paper presents a full-bridge full-wave DC-DC converter used in 35kVA power grade auxiliary static inverter (SIV) of first low-floor light rail vehicle (LFLRV) in China, where reducing voltage stress in output rectifier diodes is so important for the converter reliability. DC-bias function of high frequency transformer is analyzed and a sensorless digital dc-bias control method by DSP and CPLD without capacitor is given. Voltage spike caused by the secondary winding resonance is analyzed and three output RCD snubber circuit modes are given and compared, the dissipation of each snubber mode is deeply described. Lastly, engineering design methods are additionally given to reduce voltage stress.

An Efficient DSP–FPGA-Based Implementation of Hybrid PWM for Electric Rail Traction Induction Motor Control

Low switching frequency is always used in an electric rail traction induction motor control system, in order to reduce switching losses and increase system reliability. But under low switching frequency, the conventional single pulse width modulation (PWM) technique for the whole speed region will produce a large number of harmonic components, which in turn cause motor heating, torque ripple, and other adverse effects. In this paper, a hybrid PWM technique formed by merging carrier-based asynchronous and synchronous modulation and optimal synchronous modulation is proposed to achieve low losses and total harmonics based on very low switching frequency. A simple low-cost and low-power digital signal processor (DSP) and field programmable gate array (FPGA) hybrid hardware structure is then adopted for implementing the technique, which fully utilizes advantages and resources of each processor. Total harmonic distortion of the system can hence be reduced by operating with the high-precision hybrid PWM, while not compromising the multirate and multitask processing requirements of traction control. Detailed implementations in both DSP and FPGA with high accuracy, low usage of resources, and computational burden are then described, focusing particularly at the smooth transitions among different PWM schemes. Simulations and experiments are eventually performed with results captured for validating the presented hybrid PWM technique.