XVI-th International Conference on Electrical Machines, Drives and Power Systems ELMA 2019, 6-8 June 2019, Varna, Bulgaria
978-1-7281-1413-2/19/$31.00 ©2019 IEEE
Modelling and Control of Bidirectional Buck-Boost
Converter for Electric Vehicles Applications
Gergana VACHEVA*, Vladimir DIMITROV* and Nikolay HINOV*
*Technical University of Sofia, Faculty of Electronic Engineering and Technologies, 1000 Sofia, Bulgaria,
E-mail: gergana_vacheva@tu-sofia.bg, dimitrov@tu-sofia.bg,
hinov@tu-sofia.bg
Abstract— The present paper study modelling, design
consideration and control of a bidirectional DC/DC buck-boost
converter for application in hybrid and electric vehicles. The
proposed model includes electric motor, dynamics of the vehicle
and theirs control. A mathematical model of the DC/DC buck-
boost converter is described with differential equations during
the both the boost and buck regions of operation. The control
system is created and realized with proportional-integral
regulator. The proposed solution is realized in visual
environment MATLAB/Simulink. The obtained results
demonstrates that the proposed solution is suitable for different
electric vehicles applications.
Keywords— Bidirectional DC/DC converters, Control,
Electric and hybrid vehicles, Modelling.
I. I
NTRODUCTION
Recently, the usage of the electric vehicle (EVs) in the
modern society is significantly growing. The electric motor,
being able to operate both as a motor during acceleration and
generator during braking allows for a more controlled energy
conversion in the vehicle. To realize the possibility of fully
controlling the energy in both directions the onboard DC/DC
converter must be able to accept both of its ports as potential
energy sources. These converters are called bi-directional
DC/DC converters and their control and analysis are very
important in order to fully utilize the advantages of full electric
propulsion. These converters can operates with fixed
switching frequency and variable duty cycle, which allows
several working modes such as step down function(buck),
step-up function(boost) and the both (buck-boost) [1-3, 4, 5,
6]. These characteristics allows a process of energy storage.
II. M
ATHEMATICAL MODEL
On Figure 1 a schematic of a typical drive system for an
EV is presented. It consists of an electric battery as an energy
storage element and, respectively, an energy source, a
bidirectional buck-boost DC/DC converter, inverter and
permanent magnet synchronous machine. The DC/DC
converter and its modes of operation is the main focus of this
manuscript.
The system is described during the whole commutation
period. When the converter operation in boost mode the
following equations can be obtained for the state variables (1-
4) [8, 9, 10]:
)))(1).(()()((
1
)(
111
1
1
tdtvtiRtv
L
ti
dt
d
CLLL
−−−=
(1)
))()()((
1
)(
2221
2
2
tvtiRtv
L
ti
dt
d
CLLCL
−−=
(2)
))())(1).(((
1
)(
21
1
1
titdti
C
tv
dt
d
LLC
−−=
(3)
−−=
load
C
LC
I
R
tv
ti
C
tv
dt
d
)(
)(
1
)(
2
2
2
2
(4)
When operating in buck mode the equations for the state
variables are (5-8).
()
))(1).()()((
1
)(
111
1
1
tdtvtiRtv
L
ti
dt
d
CLLL
−−−=
(5)
))()()((
1
)(
2221
2
2
tvtiRtv
L
ti
dt
d
CLLCL
−−=
(6)
()
))()(1).((
1
)(
21
1
1
titdti
C
tv
dt
d
LLC
−−=
(7)
M
V
L
1
Q
1
Q
2
L
2
C
1
C
2
Battery
Buck/Boost Converter
Inverter
Permanent
magnet
synchronous
machine
Fig. 1. Investigated topology of a pure electric propulsion vehicle
