Xuhui Wen

Fuel cell power system and high power DC-DC converter

This paper discusses the principle and electrical characteristics of the fuel cell, designs an innovative hybrid power system, and proposes a new DC/DC converter scheme to combine the fuel cell with the storage system. An effective converter scheme for the fuel cell is obtained by analyzing the high efficient topology as well as the phase shifted pulse-width modulation. Through comparing several different control modes of converters, a 75-kW prototype system is constructed, moreover, which steady-state operating characteristics are illustrated and discussed in detail. At last, experimental results are also shown to verify the proposed scheme.

Analysis and Evaluation of DC-Link Capacitors for High-Power-Density Electric Vehicle Drive Systems

In electric vehicle (EV) inverter systems, direct-current-link capacitors, which are bulky, heavy, and susceptible to degradation from self heating, can become a critical obstacle to high power density. This paper presents a comprehensive method for the analysis and comparative evaluation of dc-link capacitor applications to minimize the volume, mass, and capacitance. Models of equivalent series resistance that are valid over a range of frequency and operating temperature are derived and experimentally validated. The root-mean-square values and frequency spectra of the capacitor current are analyzed with respect to three modulation strategies and various operating conditions over practical ranges of load power factor and modulation index in EV drive systems. The modeling and analysis also consider the self-heating process and resulting core temperature of the dc-link capacitors, which impacts their lifetimes. Based on an 80-kW permanent-magnet (PM) motor drive system, the application of electrolytic capacitors and film capacitors has been evaluated by both simulation and experimental tests. The inverter power density is improved from 2.99 kW/L to 13.3 kW/L, without sacrificing the system performance in terms of power loss, core temperature, and lifetime.

Analysis and Design of High Power Interleaved Boost Converters for Fuel Cell Distributed Generation System

This article proposes a novel topology of high power interleaved boost converter for fuel cell. With thorough analysis of the operating principle of the converter, eight equivalent sub-circuits are described. According to the waveforms of the inductor current, the operation modes of the converter are classified to six kinds, including CCM (continuous conducting mode) and DCM (discontinuous conducting mode), and the uniform state-space averaged model of the converter in CCM and DCM are developed. Based on the transfer function, the two-loop controllers are designed, and a prototype of 150 kW converter that is controlled by DSP-320F2407 is constructed. The volume and weight of the proposed converter are decreased 1/3 than conventional converter and the efficiency is over 97%. The experimental results show that the converter has excellent electrical characteristics, and it can be applied in the fuel cell distributed generation system

Analysis and design of Bi-directional Z-source inverter for electrical vehicles

A new topology bi-directional Z-source inverter is proposed. It can overcome the uncontrollable and unstable limitations of the Z-source inverter in DCM mode. The operational principle, design guidelines of Z-source networks and power devices are provided. A DC clamp snubber circuit is developed to limit the voltage spike on power device. Power loss analysis and 3-D design for Z-source inverter system are presented. A prototype of 55 kVA bi-directional Z-source inverter is designed to verify the principle and performance of the proposed topology.

High Power Interleaved Boost Converter in Fuel Cell Hybrid Electric Vehicle

This article presents the fuel cell electric vehicle (FCEV) power supply system configuration, and proposes a topology of high power interleaved boost converter for fuel cell. With thorough analysis of the operating principle of the converter, eight equivalent sub-circuits are described. According to the waveforms of the inductor current, the operation modes of the converter are classified to six kinds, including CCM (continuous conducting mode) and DCM (discontinuous conducting mode), and the uniform state-space averaged model of the converter in CCM and DCM are developed. Based on the transfer function, the two-loop controllers are designed, and a prototype of 150 kW converter that is controlled by DSP-TI320F2407 is constructed. The volume and weight of the proposed converter are decreased 1/3 than conventional converter and the efficiency is over 97%. The experimental results show that the converter has excellent electrical characteristics, and it can be applied in the FCEV as well as the fuel cell distributed generation system

Development of a High Power Density Motor Made of Amorphous Alloy Cores

In this paper, the development of a permanent-magnet (PM) motor made of amorphous alloy (AA) core is presented. The motor is rated as 20 kW, and base speed is 2500 r/min. A massive produced interior PM motor used in electric vehicle traction application is chosen as the baseline motor. An optimization software package built based on Matlab platform is used to design the stator made of AA, while the rotor is preliminary designed with the help of analytical formulation aiming at lowest core loss in stator teeth and finally tuned by finite-element analysis. The optimized AA motor is 31% smaller in volume than the baseline motor while keeping the continuous power rating unchanged, which means 45% more in power density. To validate the mathematical model beneath the optimization software package, two prototype motors have been manufactured. The first motor is the AA motor, optimized in this paper, and the second motor has exactly the same lamination shape and structural design of motor 1 but its material is nonoriented silicon steel like the baseline motor, instead of AA. The test result show the efficiency of motor 1 is higher than the baseline motor in full speed range, and motor 2 is badly behaved in terms of efficiency. The observation from the test proves that simply replacing the silicon steel with AA does not work under all circumstances, and the optimization experience gained for the AA cannot be used directly in designing a silicon steel motor.

Armature-Reaction Magnetic Field Analysis for Interior Permanent Magnet Motor Based on Winding Function Theory

As the magnets are embedded in a rotor for the interior permanent magnet (IPM) motor, the distribution of the armature reaction magnetic field is different from that of the surface permanent magnet motor (SPM) type. Various methods have been used for the magnetic field solution, including analytical methods based on the winding function and the Laplacian-Poisson equation. However, in the IPM motor, the boundary condition is too complicated for using the Laplacian-Poisson equation. What is more, the equivalent air-gap inverse function presented in literature is not suitable for the IPM motor. A new armature reaction magnetic field model is proposed for the IPM motor, considering the effect of the embedded magnet in the rotor, which is named a pole-cap effect in this paper. The proposed model is derived from the winding function theory, and the rotor magnetic motive force (MMF) function is employed to model the so-called pole-cap effect. The proposed model is used to predict the armature reaction field under a different type of stator MMF, such as different orientation of the excitation current as well as various MMF wavelengths. The calculation result is validated by the finite element analysis (FEA) and shows remarkable advantages over the traditional method. The new model proposed in the paper is quite useful for evaluating various IPM motor performances in an accurate and time-effective manner, such as inductance, stator core losses, and magnet eddy current losses. Complete demonstration of the method to calculate the aforementioned performance indices will be presented in a separate paper, and inductance calculation of a primitive winding is given as an example at the end of this paper.

A new deep field-weakening strategy of IPM machines based on single current regulator and voltage angle control

Field-weakening control is an important issue of wide speed range motor control. In order to achieve higher speed range above base speed, this paper proposes a new field-weakening strategy based on single current regulator (SCR) and voltage angle control (VAC). Some critical problems of existing SCR algorithm are resolved by the new method and a speed range of 8∶1 is achieved in the experiment.

Adaptive-Linear-Neuron-Based Dead-Time Effects Compensation Scheme for PMSM Drives

This paper presents an adaptive-linear-neuron (ADALINE)-based dead-time compensation method for vector-controlled permanent-magnet synchronous motor drives. The proposed strategy is achieved by suppressing the sixth-order current harmonics in the dq-axes synchronous reference frame. Four ADALINEs are employed in the proposed algorithm. Two ADALINEs are used for estimating the sixth-order harmonic components of dq-axes currents and the other two are used for generating the dq-axes compensation voltages. The voltage compensators are self-tuned by minimizing the estimated current distortion by means of the least mean square algorithm. The proposed compensation algorithm does not require any additional hardware or complicated signal processing algorithms. Experimental results validating the proposed compensation method are also presented.

Comparison study of singly-fed electric machine with doubly-fed machine for EV/HEV applications

A doubly fed motor performance is analyzed and experimentally tested. The performance of the doubly fed machine is compared for various operational conditions for variable speed applications. In particular, the possibility of eliminating brushes and slip rings for the doubly fed motor is also discussed and solution presented to highlight the bright future of the brushless doubly fed motor in EV/EHV applications.