07-05-2013, 02:35 PM
High efficiency contactless energy transfer system with power electronic resonant converter
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Abstract.
A novel Inductive Contactless Energy Transfer (ICET) system is presented in this paper. The energy is transferred using a rotatable
air gap transformer and a power electronic converter. To minimize total losses of the system a series resonant circuit is applied, assuring zero
current switching condition for IGBT power transistors. The analytical expression of the transfer dc voltage gain is given and discussed. The
developed ICET system is characterized by high efficiency and fast FPGA based controller and protection system. The resonant frequency is
adjusted by extreme regulator which follows instantaneous value of primary peak current. Simulated and experimental results which verify
and illustrate operation of developed 3 kW laboratory model are presented.
Introduction
The contactless energy transfer systems have been recently
gaining popularity and investigated widely [1–16]. This innovative
technology creates new possibilities to supply mobile
devices with electrical energy because elimination of cables,
and/or slip-rings as well as plugs and sockets increases reliability
and maintenance-free operation of such critical systems
as in aerospace, biomedical, electric vehicles and robotics applications.
The core of contactless energy transfer system is
inductive or capacitive coupling and high switching frequency
power electronic converter. The capacitive coupling is used
in low power range (sensor supply systems) whereas inductive
coupling allows transferring power from a few mW up to
hundred kW [1, 4].
This paper reports on a new developed Inductive Contactless
Energy Transfer (ICET) system with a rotatable air gap
transformer and IGBT transistors based resonant power electronic
converter. Thanks to the careful design of all systemcomponents,
the high total efficiency (93%) is achieved. Other
important features of the presented ICET system are: operation
of high-switching frequency IGBT transistor based resonant
converter at zero current switching (ZCS) conditions,
low cost single board FPGA based controller, reliable and fast
operation, robustness to magnetic coupling factor changes of
the main circuit. Simulation and experimental results of 3kW
prototype system operated with 60 kHz switching frequency
are presented.
Topology of Inductive contactless energy
transfer (ICET) system
The topology of the investigated experimental ICET system is
shown in Fig. 1(a). The core of the system is a rotatable transformer
with adjustable air gap. This air gap can be enlarged,
for testing purposes, up to 30 mm. At the energy feeding input
there are: a three-phase diode rectifier and a full bridge IGBT
converter. At the secondary side a load module Ro with diode
bridge rectifier is connected. This solution has the following
advantages: secondary circuits can be movable relatively to
primary, control and power supply system is located on the
primary side and is electrically separated from the secondary
circuit. The system can also be easily expanded by connecting
on secondary DC output DC/AC inverters for variable
frequency three-phase loads [10, 16, 17]. For high power applications
the supply diode rectifier can be replaced by high
switching frequency boost rectifier operating with unity power
factor [18].
Control and protection scheme
The block scheme of the ICET control and protection system
implemented in FPGA Stratix II is shown in Fig. 3. The
clock frequency of the FPGA is 100 MHz and the resonant
switching frequency is 60 kHz. The inverter output current i1
is measured and sent to A/D converters via operation amplifiers.
A 12-b A/D converter, AD9433 is used in the designed
system. The analog input signal is 5 V (VDD), hence maximum
amplitude corresponds to 2.5 V. The FPGA device is
Stratix II EP2S60F1020C3ES.
Conclusions
This paper presents an Inductive Contactless Energy Transfer
(ICET) system with rotatable air gap transformer and series
resonant power electronic converter operating at 60 kHz
switching frequency.
The control and the protection system have been implemented
in FPGA Stratix II EP2S60F family.