Ruichang Qiu

Research on Energy Management for Hybrid EMU

The operation route of EMU is relatively definite, the operating condition can be predicted and planned, and the applicability of logic threshold is relatively good. Therefore, the rule based on logic threshold energy management strategy is adopted as a control strategy in this paper. Depending on the operating characteristics of hybrid EMU, this paper develop the logic threshold energy management control strategy based on rules considering of integrated fuel consumption, and make the simulation model of specific control method and speed control of diesel generator and battery charge and discharge control, then the hybrid energy management strategy of different mode have been achieved.

Characterization and Variable Temperature Modeling of SiC MOSFET

Silicon power semiconductor device is difficult to meet the requirements of high temperature, high pressure and high frequency. Among them, the MOSFET which has the fast switch speed and the simple driving circuit, become the most popular object in SiC power electronic devices. In this paper, we choose the C2M0160120D chip of CREE company, establishing a complete model. And the static characteristics of SiC MOSFET under different temperature points are simulated. The switching characteristics of SiC MOSFET under different driving resistances are analyzed and compared with the experimental results, and the accuracy of the model is verified in this paper.

Performance Comparison of Battery Chargers Based on SiC-MOSFET and Si-IGBT for Railway Vehicles

New type semiconductors, for instance, SiC-based switching devices, have many performance advantages over Si-based devices, including faster switching and lower power dissipation. In this paper, a research of an application of SiC-based MOSFET in a battery charger for railway vehicles is introduced, focusing on the performances of the charger. This battery charger is designed based on a silicon-IGBT-based charger. The new SiC-based battery charger has the same input and output rating with the original charger, but there’s an increase of switching frequency from 15 to 50 kHz. Therefore, a comparison between the two chargers from the aspects of efficiency, volume and power density is provided in this paper. It can provide some technical support for the design and application of high-power-density battery chargers in the auxiliary power system of railway vehicles.

Online Fault Diagnosis of the Hybrid Electrical Multiple Unit Traction Converter

In this paper, the signatures and the diagnosis approach of the failure of switching devices in Hybrid Electrical Multiple Unit (HEMU) traction converter (TC) are developed. In this paper, the distorted voltage and current with such failures are treated as disturbance exerted over normal voltage and current without failures, and a special analytical failure model is built for the expression of voltage and current disturbance. Combined with the failure model, this paper proposes a novel reasoning process to locate malfunctioning switching device. The reasoning process is based on object-oriented colored Petri Net (OOCPN). Digitalized failure signatures are taken as inputs into the OOCPN reasoning machine, what stimulates the brain activities during fault diagnosis of an expert.

The Research on Bi-Directional DC/DC Converter for Hybrid Power System

In the hybrid power system, the bidirectional DC/DC converter, as the driving devices for energy storage element, is the core element of hybrid energy storage system and has the function of stabilizing the intermediate DC link voltage. This paper introduces the working principle and the derivation of bidirectional Buck/Boost converter in the process of modeling. A voltage and current double closed loop control system based on load current prediction is designed. When the load changes constantly, the response speed of the system can be improved. Simulation studies using MATLAB/Simulink show that the established model and control strategy can be used for further research.

Method of Health State Assessment for Satellite Power System Based on Fuzzy Judgment and Variable Weight Layered Evaluation

In order to improve the reliability and safety of satellite power system, the concept of health management is introduced to the research of health state assessment about satellite power supply. Considering the complex characteristics of satellite power system, a health state assessment method based on fuzzy judgment and variable weight layered evaluation is proposed and applied to the assessment of satellite power system. First, the fuzzy comprehensive evaluation method is used to quantify the influence degree of fault modes on the system and obtain the objective corresponding health degree. The method also combines analytic hierarchy process (AHP) with variable weight synthesis to solve variable weights and calculate health degree of the system step by step, which conducts real-time health state assessment for satellite power system. And then, the calculation results are divided into healthy, good, attentive, deteriorative, and morbid 5 levels to characterize the health states of the evaluation object. Finally, the applicability and validity of the method are verified by the concrete calculation example.

Simulation of Aging Characteristics of Power Switch Device Based on Saber

IGBT is a power switch device that is very important in modern power electronics. The reliability of IGBT concerns the security of circuits and even the whole system, while IGBT module’s aging is inevitable, so it is necessary to study the aging of IGBT module. At home and abroad, the measurement of the electrical parameters when the bonding wires fall off is used to identify the aging failure state of IGBT, but the consideration is far from comprehensive, the evaluation is also inaccurate. This paper uses the saturation voltage drop which is easy to measure as a state characteristic parameter and considers the influence of junction temperature and collector current to the saturation voltage and IGBT module’s aging failure to evaluate the aging failure of IGBT module.

Instantaneous Voltage PIR Closed-Loop Control for the Auxiliary Inverter

As an important part of EMU (Electric Multiple Units), the auxiliary power supply system plays an important role in the normal operation of the vehicle. In order to improve the reliability of the auxiliary power supply system, this paper analyses the harmonics of the auxiliary inverter under nonlinear load and suggests that the 6th harmonic voltage components in the DQ synchronous rotating coordinate system can be controlled to achieve the simultaneous control of the 5th and 7th harmonic voltage components in the three-phase static coordinate system. The instantaneous voltage PIR (Proportion Integral Resonance) closed loop control method in DQ synchronous rotating coordinate system is researched to eliminate the voltage aberration caused by harmonics and ensure the quality of output voltage. Finally, the simulation results show that the design has achieved the desired objectives.

Service Life Prediction of Electrolytic Capacitors in Urban Rail Transit Based on Analytical Iteration and GM Model

In the power supply of urban rail transit system, electrolytic capacitors are used in large numbers. They suffer from inevitable ripple currents; such ripple currents generate heat dissipation, which shortens their service life seriously. To increase the reliability of the whole power supply system, the aging process of electrolytic capacitors must be evaluated, so that their service life could be predicted and measures could be taken in advance before their failures. When they are applied into the power supply system, the accuracy of conventional approaches is somewhat lowered, owing to the existence of unpredictable ripple current and ambient temperature variations. In this paper, we build an analytical ripple model to offer online aging monitoring of electrolytic capacitors. After that, a GM model is adopted to predict service life with higher accuracy than conventional approaches.

Stability Analysis Method of Parallel Inverter

In order to further provide theoretical support for the stability of an auxiliary inverter parallel system, a new model which covers most of control parameters needs to be established. However, the ability of the small-signal model established by the traditional method is extremely limited, so this paper proposes a new small-signal modeling method for the parallel system. The new small-signal model not only can analyze the influence of the droop parameters on the system performance, but also can analyze the influence of the output impedance of the inverter, the unbalanced and nonlinear loads, and the power calculation method and cut-off frequency of the low-pass filter on the system performance and stability. Based on this method, this paper carries out a comprehensive analysis on the performance of a parallel inverter system. And the correctness of the modeling method and analysis process of the system performance and stability are verified by the consistency of the simulation and experimental results.