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Z-Source Resonant Converter with Power Factor Correction
for Wireless Power Transfer Applications
Abstract:
In this paper the Z-source converter is introduced to power factor
correction (PFC) applications. The concept is demonstrated through a
wireless power transfer (WPT) system for electric vehicle battery
charging, namely Z-source resonant converter (ZSRC). Due to the Zsource network (ZSN), the ZSRC inherently performs PFC and regulate
the system output voltage simultaneously, without adding extra
semiconductor devices and control circuitry to the conventional WPT
system such as conventional PFC converters do. In other words, the ZSN
can be categorized as a family of the single stage PFC converters. In
addition, the ZSN is suitable for high power applications since it is
immune to shoot-through states, which increases reliability and adds a
boost feature to the system. The ZSRC-based WPT system operating
principle is described and analyzed in this paper. Simulations, and
experimental results based on a 1-kW prototype with 20-cm air gap
between the system primary and secondary side are presented to validate
the analysis, and demonstrate the effectiveness of the ZSN in the PFC of
the WPT system.
Existing System:
 The conventional boost PFC converter offers high efficiency, high
power factor (PF), high power density, and low cost.
 Nevertheless, the boost capacitor ripple current is very high.
 As the power level increases, the system input rectifier losses
significantly degrade the efficiency and require efforts to deal with
heat dissipation.
 Because of this, the boost PFC converter is good for low to medium
power range, up to approximately 3.5 kW.
 For power levels above that, designers typically parallel discrete
semiconductors, or use expensive diode semiconductor modules,
which increases the overall system cost.
 Additionally, the boost converter switch is operated under hard
switching conditions and because of this, the converter has high
switching losses, which limit the switching frequency range of the
system.
 Finally, the boost diode (Db) reverse recovery produces high
electromagnetic interference (EMI), which might cause unexpected
shoot-through states that damage the system, or that trigger protection
and cause an unexpected system shut down.
 In order to overcome some of these drawbacks, a new PFC converter
is introduced in this paper.
Circuit Diagram:
(Boost-converter-based OBC)
Disadvantage:
 System reliability is low.
 Number of semiconductor devices are high when compared to
proposed system.
 The size and cost of the boost PFC converter will increase because of
the extra heat sink for the power semiconductors, and additional
control circuitry for the switch.
Proposed System:
 This paper proposes to use the Z-source Network (ZSN) as a new
converter for PFC applications.
 The ZSN in the ZSRC adds the unique feature of inherent PFC
without adding extra switches as conventional PFC converters do.
 It can do this since it provides immunity to the H-bridge inverter
shoot-through states, which not only increases the system reliability,
but adds a control variable to the system that can be used to shape the
input current as a sinusoidal waveform and in phase with the input
voltage.
 To regulate the output voltage, the proposed ZSN-based OBC uses
the active state duty cycle, which is a conventional control variable
used in SRCs.
 Because of the ZSN, the ZSRC can perform PFC and DC/DC
conversion in one stage.
 This means that we can categorize the ZSN as a family of the single
stage PFC converters.
Circuit Diagram:
(Proposed ZSN-based OBC: Z-source resonant converter)
Advantage:
 The ZSN has a lower failure and degradation rate compared to the
conventional boost PFC converter, thus a better lifetime.
 Adding the ZSN to the OBC increases the system reliability since the
ZSN can handle shoot-through states.
 Has been widely used mainly for voltage regulation applications.
References:
[1] Yilmaz, M.; Krein, P.T., "Review of Battery Charger Topologies,
Charging Power Levels, and Infrastructure for Plug-In Electric and
Hybrid Vehicles," in Power Electronics, IEEE Transactions on, vol.28,
no.5, pp.2151-2169, May 2013.
[2] Modern Trends in Inductive Power Transfer for Transportation
Applications- Covic, G.A.; Boys, J.T., "Modern Trends in Inductive
Power Transfer for Transportation Applications," in Emerging and
Selected Topics in Power Electronics, IEEE Journal of, vol.1, no.1,
pp.28-41, March 2013.
[3] Musavi, F.; Edington, M.; Eberle, W., "Wireless power transfer: A
survey of EV battery charging technologies," Energy Conversion
Congress and Exposition (ECCE), 2012 IEEE, vol., no., pp.1804, 1810,
15-20 Sept. 2012.
[4] Ekemezie, P.N., "Design of a power factor correction ac-dc
converter," AFRICON 2007, vol., no., pp.1, 8, 26-28 Sept. 2007.
[5] Rajappan, Suja C.; John, Neetha, "An efficient bridgeless power
factor correction boost converter," Intelligent Systems and Control
(ISCO), 2013 7th International Conference on, vol., no., pp.55,59, 4-5
Jan. 2013