Abstract—Electric vehicles (EVs) an

Abstract—Electric vehicles (EVs) and hybrid electric vehicles K Inductance slope when faulted.
L
(HEVs) can reduce greenhouse gas emissions while switched re- Ki Current slope when faulted.
luctance motor (SRM) is one of the promising motor for such
Lmin Minimum of the phase inductance.
applications. This paper presents a novel SRM fault-diagnosis
and fault-tolerance operation solution. Based on the traditional Lmax Maximum of the phase inductance.
asymmetric half-bridge topology for the SRM driving, the central T ∗ Given load torque.
tapped winding of the SRM in modular half-bridge configuration T Instantaneous torque.
are introduced to provide fault-diagnosis and fault-tolerance func- Tav Average electromagnetic torque of one phase when
tions, which are set idle in normal conditions. The fault diagnosis normal.
can be achieved by detecting the characteristic of the excitation 
and demagnetization currents. An SRM fault-tolerance operation Tav Average electromagnetic torque of one phase when
strategy is also realized by the proposed topology, which compen- faulted.
sates for the missing phase torque under the open-circuit fault, and Uin Bus voltage.
reduces the unbalanced phase current under the short-circuit fault ωr Angular velocity.
due to the uncontrolled faulty phase. Furthermore, the current
θon Turn-on angle.
sensor placement strategy is also discussed to give two placement
methods for low cost or modular structure. Simulation results in θoff Turn-off angle.
MATLAB/Simulink and experiments on a 750-W SRM validate the
effectiveness of the proposed strategy, which may have significant I. INTRODUCTION
implications and improve the reliability of EVs/HEVs.
URRENTLY, electric vehicles (EVs) and hybrid electric
Index Terms—Central tapped node, electric vehicles, fault diag- Cvehicles (HEVs) provide a low-pollution and high-
nosis, fault tolerance, switched reluctance motor (SRM), traction efficiency solution to the depletion of fossil fuels and envi-
drives.
ronmental problems, and thus, are under wide development
across the world [1], [2]. Switched reluctance motors (SRMs)
NOMENCLATURE are becoming a mature technology for EV/HEV applications and
D PWM duty cycle. are also considered to have commercial potentials for massive
i ,i ,i Currents for phases A , B, and C. global markets due to their nonreliance on rare earth materi-
a b c
i Phase current peak when faulted. als and a wide torque–speed range, in addition to their robust
max
imax Phase current peak when normal. mechanical structure, low cost and high efficiency [3]–[7]. For
Δi Hysteresis window. EV/HEV applications, high reliability and fault tolerance is crit-
Nr Rotor poles. ically important as they involve human lives.
KL Inductance slope when normal. The SRM drive system is mainly composed by two parts:
K Current slope when normal. power electronics and motors [8]. For EV/HEV applications, the
i
switching devices are prone to failure, especially in harsh envi-
Manuscript received September 29, 2014; revised December 7, 2014 and ronments such as vehicular conditions [9]. Based on the widely
January 28, 2015; accepted March 9, 2015. Date of publication March 18, 2015; used asymmetrical half-bridge drive topology, the power elec-
date of current version September 29, 2015. This work was supported by the
EPSRC of UK (EP/L00089X/1). Recommended for publication by Associate tronics faulty conditions such as short-circuits and open-circuits
Editor J. A. Pomilio. are studied in [10]–[16]. In [11], the bus current is employed to
Y. Hu is with the College of Electrical Engineering, Zhejiang University, distinguish open-circuit faults and short-circuit faults in power
Hangzhou 310027, China, and is also with the Department of Electronic and
Electrical Engineering, University of Strathclyde, Glasgow G1 1XQ, U.K. electronics converters. In [12], two on-line fault-diagnosis meth-
(e-mail: huyihuacumt@126.com). ods based on analysis of bus current or freewheeling current
C. Gan and W. Li are with the College of Electrical Engineering, Zhe- are developed to distinguish short circuits and open circuits. In
jiang University, Hangzhou 310027, China (e-mail: ganchun.cumt@163.com;
woohualee@zju.edu.cn). [13], the switching device fault diagnosis including open cir-
W. Cao is with the School of Electronics, Electrical Engineering and Com- cuit and short circuit is achieved by analysis of phase current
puter Science, Queen’s University Belfast, Belfast BT7 1NN, U.K. (e-mail: without additional hardware investment. The FFT algorithm is
w.cao@qub.ac.uk).
S. J. Finney is with the Department of Electronic and Electrical Engi- also introduced to analyze the power converter supply current
neering, University of Strathclyde, Glasgow G1 1XQ, U.K. (e-mail: stephen. of phase absence fault in [14]. A method to predict the SRM
finney@strath.ac.uk). drive performance under normal and fault operating conditions
Color versions of one or more of the figures in this paper are available online
at http://ieeexplore.ieee.org. is proposed in [15], which uses a genetic-algorithm-based artifi-
Digital Object Identifier 10.1109/TPEL.2015.2414664 cial neural networks, showing a fast and accura