Power Conversion System Strategies for Fuel Cell Vehicles

Kaushik Rajashekara,　 Fellow IEEE
(Delphi Corporation, Mail Code  ERC 12/ D35, P.O. Box 9005, Kokomo, IN 46904-9005, USA)
Abstract: Power electronics is an enabling technology for the development of environmental friendly fuel cell vehicles, and to implement the various vehicle electrical architectures to obtain the best performance. In this paper, power conversion strategies for propulsion and auxiliary power unit applications are described. The power electronics strategies for the successful development of the fuel cell vehicles are presented. The fuel cell systems for propulsion and for auxiliary power unit applications are also discussed.
Key words: fuel cell; vehicles; propulsion; APUs; power electronics

μ-synthesis for boiler superheated steam temperature system
with different perturbed model

HENG Qing-hai1，MAI Miao1，LU Jing1，HENG Qing-zhu2，HUANG Chun-mei2
(1.Beijing Information Technology Institute, Beijing 100101, China；
2.Tianjin University, Tianjin 300072, China)
Abstract: This paper presents the μ-synthesis problem of the perturbed model of the leading and inertia sections of the superheater of a supercritical once-through 600MW boiler. The strong change (including time constant, gain, even the orders etc.) of the model of the controlled member occurs as the operating conditions are changed extensively. A design method of μ-synthesis PID control system is proposed, the selections of weighting functions are discussed and the μ-synthesis robust PI controllers are solved. Results of the design look as if they were normal PI controllers, but their control quality, robustness and adaptability are better than the latter, and their structures are simple, definite, and useful. The realization of the controllers doesn’t involve extra cost to the control equipment in existence. The results show that the proposed method is valid.
Key words: superheated steam temperature; perturbation; μ-synthesis; robust control

Research on a LCC resonance-based phase-shift-controlled high-frequency link inverter
SUN Xiang-dong, REN Bi-ying, ZHONG Yan-ru
（Xi’an University of Technology, Xi’an 710048, China）
Abstract: A single-phase high frequency（HF）link inverter for soft-switching in which constant-frequency phase-shifted LCC resonant circuit and SPWM control technique are integrated tightly is proposed. The inverter is composed of uni-polarity phase-shift-controlled inverter, LCC resonant circuit, HF transformer, cycloconverter and low-pass filter. Its working principle, control method and working modes in CCM are analyzed in detail for the resistive load，and the experiments are carried out respectively. Their results verify that the circuit topology is right and feasible.
Key words：uni-polarity phase-shifted control；LCC resonance；SPWM；high frequency link；soft-switching

Influences of center frequency and bandwidth on UHF PD detection for transformers
WANG Guo-li1 2, YUAN Peng3, LI Yan-ming3
(1. Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China; 
2. Department of Electrical Engineering, Tsinghua University, Beijing 100084, China; 
3. Xi’an Jiaotong University, Xi’an 710049, China)
Abstract：The selections of center frequency and bandwidth are very important to detection, calibration and pattern recognition of ultra-high-frequency (UHF) partial discharge (PD) signals in transformers. In this paper, an UHF PD detection system and a typical PD models simulated system are developed to study the influences of center frequency and bandwidth on UHF PD detection for transformers. Experimental results show, the selected center frequency should be in the frequency range that the UHF component of PD signals is rich and the noise is not very strong, the bandwidth of the filters should be as wide as possible unless the noise goes high.
Key words: transformer; partial discharge (PD); ultra-high-frequency (UHF); center frequency; bandwidth

Edge element computation of load performance of a claw-pole alternator
WANG Qun-jing, NI You-yuan, ZHANG Xue 
(School of Electrical Engineering & Automation, Hefei University of Technology, Hefei 230009, China)
Abstract: In this paper, calculation of load performance of a 28V, 35A claw-pole alternator is presented using three dimensional finite element method with tetrahedral edge elements. The output current of the alternator at different speed is computed by an iteration method. The magnetic field of the alternator is also computed using three dimensional finite element method with nodal elements. The comparison of two methods shows that the computation using the edge element method requires less memory and less time. So it is appropriate for computing load performance of the alternator. The calculated results are validated by the experimental results. The results of the paper are helpful to computation of load performance and parameters of the claw-pole alternator and to the optimal design of the alternator.
Key words: claw-pole alternator; edge element; nodal element; load performance

DSP implementation of morphological wavelet
for early detection of short-circuited fault in low-voltage system
CHEN Li-an1,2，ZHANG Pei-ming1
(1. Fuzhou University, Fuzhou 350002, China;
2. Xiamen Institute of Tech., Xiamen 361005, China)
Abstract：A novel type of integrated filtering algorithm named as morphological wavelet filter which combined the quadratic B spline wavelet transform and the complex morphological opening filter with multiple structuring elements is proposed in this paper and its application in the short-circuited fault detection in low-voltage system is also presented. This algorithm has the excellent capability in removing various kinds of interference, protecting the properties of short-circuited fault, and decreasing the computational complexity, moreover, it can be implemented on hardware in real-time. The equipment for short-circuited fault detection based on TI TMS320F2812 DSP is also developed in this paper and the real-time implementation of the proposed algorithm has been realized. The simulating results and the actual system experiments show that the proposed morphological filtering algorithm can be used to effectively remove the white noises and impulsive noises in low-voltage system and the validity of the proposed scheme applied in the short-circuited fault detection is successfully demonstrated.
Key words：morphological wavelet filter; short-circuited fault; early detection; DSP

Analysis, design and performance comparison of droop method
of parallel power converters
WEI Tong-zhen1, 2, LI Yao-hua1, ZHU Hai-bin1
（1. Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100080, China;
2. Graduate School of the Chinese Academy of Sciences, Beijing 100039, China）
Abstract: There are mainly two approaches to provide output voltage droop characteristics in droop method: program voltage reference by load current and limiting the DC gain of the voltage loop compensator. In this paper, detailed design guidelines of these two approaches are provided based on mathematical model analysis, and the transient and steady performance of these two approaches are analyzed and compared. It is observed that, for the approach of limiting DC gain, the bandwidth frequency of the output impedance in per unit is approximately equal to the bandwidth frequency of the voltage control loop, while as to the approach of programmable voltage reference, the bandwidth frequency is only about half of that of the voltage control loop. If the load current of the approach of programmable voltage reference is obtained through load current observer, in the worst condition the corresponding bandwidth may decrease to one third of the bandwidth of the voltage control loop. Finally, theoretical analyses are verified by experimental results.
Key words：power converter; droop method; parallel operation

A new mixed control strategy for induction motor drives
LU Zhi-gang, SUN Xu-dong, SU Wei-feng
(Dept. of Electrical Engineering, Tsinghua University, Beijing 100084, China)
Abstract：Field oriented control (FOC) and direct torque control (DTC) are two major control methods for high performance induction motion drives. Research on these two schemes shows that FOC and DTC each has its own advantages and disadvantages. An innovative control strategy, which is an organic combination of the two schemes, is presented in this paper to adopt the other's strong points to offset one's weakness, with the purpose of realizing more flexible and high performance motion control and providing users with more options in various applications. For smooth switching between DTC and FOC, a new “resetable” PI controller is designed to replace the conventional PI controller. Simulation and experiments show that the new “resetable” PI controller can remarkably reduce the fluctuation of mixed control system, and the control performance of DTC and FOC can be maintained.
Key words: induction motor; field oriented control; direct torque control; mixed control

Power system signals processing method based on order morphology
OUYANG Sen
(College of Electric Power, South China University of Technology, Guangzhou 510640, China)
Abstract: The mathematical morphology and order morphology are introduced in this paper, and a new power signal processing method is proposed in this paper. With the morphological operators’ re-combination, analysis of the structure element and the percentile, and combination with threshold method, the effective method based on the order morphology is formed. Furthermore, the efficiency and validity are discussed in detail. Finally, the capability of this method is verified by the simulation and actual calculation results.
Key words: power quality; mathematical morphology; signal processing; order morphology

Effect of spark discharge preionization on dielectric barrier discharge in air
ZHAN Hua-mao1, DING LI-jian1, LI Cheng-rong1, WANG Xin-xin2, LI Ming1, YAO Ji-sha1,
(1. Dept. of Electrical Engineering, North China Electric Power University, Beijing 102206, China;
2. Dept. of Electrical Engineering, Tsinghua University, Beijing 100084, China)
Abstract：One of the approaches to obtain atmosphere glow discharges in air is to decrease the electric field when discharging and prevent the air breaking down in a streamer mode. In this paper, spark discharges produced by an impulse circuit are used to provide initial electrons for a dielectric barrier discharge. The effect of preionization on the dielectric barrier discharge was investigated. The experimental results show that:
1. the spark discharge preionization can ignite the discharge effectively and decrease the electric field when discharging. Under the condition of normal atmosphere, electric fields employed in the reactor decrease by about 25 percent when the preionization method is adopted;
2. higher is the gas pressure, lower is the probability of effectual ignition;
3. under the condition of gas flow, the effect of preionization is more prominent;
4. the preionization is not the only one condition necessary for obtaining atmosphere glow discharge in air. The preionization method metioned in the paper can be used to supply initial electrons for establishing uniform dielectric barrier discharge at low electric field, however, under existing experimental conditions, the decrease is still too little to getting the one atmospheric pressure glow discharge in air.
Key words：atmosphere glow discharge in air; preionization; gas flow

Experimental research of double evaporation-cooling technology
in ship propulsion motor
LI Shi-qing1,2, FU De-ping1, XIONG Nan1
(1. Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100080, China;
2. Graduate School of the Chinese Academy of Sciences, Beijing 100039, China）
Abstract: The principle of close-loop-self-circulating (CLSC) evaporation-cooling is introduced firstly, then the idea of double evaporation-cooling is presented according to the cooling requirements of a ship propulsion motor. Two models of a ship propulsion motor using the evaporation-cooling technology are built, one uses the normal evaporation-cooling technique and the other uses the double evaporation-cooling technique. The experiment using R113 as the cooling liquid is done firstly on the normal evaporation-cooling model. Then there are some experiments on the double evaporation-cooling model. R113 are used as the first cooling liquid in the stator cavity and R113,R11 and R123 is used as the second cooling liquid respectively in the special condenser. The experimental results show that double evaporation-cooling is operable and can meet the cooling requirements of the ship propulsion motor. So the evaporation-cooling technology can have a wider application.
Key words: CLSC evaporation-cooling; double evaporation-cooling; ship propulsion motor

An automatic interleaving method of parallel DC/DC converters
based on distributed control circuits
LIANG Feng, QU Wen-long
(Tsinghua University, Beijing 100084, China)
Abstract: This paper introduces a kind of automatic interleaving method of parallel DC/DC converters. This method adopts distributed control circuits, which makes the system to have the ability of automatic interleaving as well as high tolerance of subsystem failures. The most important characteristic of this method is that no other line between the cells is needed except the input/output buses, so that the system can possess higher stability as compared with some traditional methods. In this paper, the main circuit structure, as well as the block diagram of the control circuit is illustrated.  The principle of the method is described in detail. A three-cell DC/DC converter prototype based on the method has been developed and some experiments have been done. The experimental results show that the method is valid.
Key words: distributed control; automatic interleaving; DC/DC converter; without interleaving bus

A new design principle for variable-pole winding
QIAN Luo-fen
(Jimei University, Xiamen 361021, China)
Abstract: This paper introduces a new principle of design for variable-pole motor’s winding. This principle of the design is based on ampere-conductor-unit in order that it adapts itself to different polar distance. By using it the variable-pole motor’s winding is equivalent to full-pitch-winding, whether the motor’s pole changing or not. By using traditional method of design based winding-unit, the variable-pole motor’s winding is shown with different short-pitch factor in different polar distance. The paper analyzes the cause of the winding short-pitch factor and presents the improved method of design. The paper gives a definition of ampere-conductor-unit, and presents this design principle based on ampere-conductor-unit for variable-pole winding. Then the design method is given with a 8/2 pole changing as example.
Key words: AC electric machine; variable-pole; full-pitch-winding; ampere-conductor wave; ampere-conductor-unit

Stability analysis for cryocooled aluminum stabilized superconducting magnet
LIU Hong-wei1. 2，WANG Qiu-liang1，YU Yun-jia1，BAI Ye1. 2
(1. Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100080, China;
2. Graduate School of the Chinese Academy of Sciences, Beijing 100039, China）
Abstract: Aluminum-stabilized superconductors have been employed in superconducting magnet, such as SMES and detector magnets etc. The stability and homogeneity of temperature in superconducting magnet fabricated by these kinds of conductors are considerably improved due to the advantage of high RRR, and high thermal conductivity at low temperature. The stability anlysis of cryocooled aluminum-stabilized superconducting magnet was performed through numerical simulation. The results were compared with those in helium immersed cooling manner. Measure and opinions were put forward for its design and operation.
Key words: aluminum-stabilized superconductor；cryocooled；current diffusion

Renewable Energies, Present & Future
X. S. Cai,  Fellow IEEE
(E.E. Dept., Tsinghua University, Beijing 100084, China)
Abstract: Fossil fuels are major cause of environmental destruction in pollutions. It has created much needed momentum for renewable energies, which are environmentally benign, generated locally, and can play a significant role in developing economy. As a sustainable energy sources, it can grow at a rapid pace to meet increasing demands for electricity in a cost-effective way.
Key words: global warming; renewable energy; wind; solar; photovoltaic cell; fuel cell; hydrogen power

Application of modular design on automatic bus transfer
LIN Wei-ke, LI Zhi-kang, Huang Yi-zhuang
(Department of Electrical Engineering, Tsinghua University, Beijing 100084, China)
Abstract: With the reference to the typical main connection diagram of mid- and low- voltage substations, the software and hardware design of automatic bus transfer device are simplified properly by applying the decomposition method in Modularization. Universal modules can be established through decomposing function of the software and hardware. The devices made up of these adaptable modules meet the requirement of the typical main connection diagram and operate with high reliability, self-adaptation and good economical performance. Modular design will be widely adopted in automatic bus transfer.
Key words: modularization; automatic bus transfer; universal property