Basic to gain better control of loads; more accurate

Basic Study of Power electronics

Sadanand  Suthar

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P. T.Science College, Surat, Gujarat, India.



The development of power electronics is state of the
art of power electronics converters are briefly reviewed, before giving an
insight into the deficiencies of the conventional current-source and
voltage-source converters and into the superiority of impedance-source
converters. The design methodology for impedance-source converters target  to replace the traditional design methods.


1. Introduction


Power electronics refers to electric power,
electronics and control systems. Electric power deals with static and rotating
power equipment for generation, transmission and distribution of electric
power; while electronics is concerned with solid-state semiconductor power
devices and circuits together with control systems for power conversion specified
to meet the desired control objectives. Power electronics is one of the main
technologies to realise energy conversion with high efficiency. It is known
that about 70% of electric energy is converted by

power electronics devices before it reaches the
consumer. Nowadays, power electronics has become a fundamental technology
critical for the development of energy conservation, especially for renewable
energy 1.


With the development of semiconductor devices,
different kinds of control strategies have also been developed to realise
specified purposes. For instance, high-accuracy and high-frequency control
methods based on single-chip solutions like Digital Signal Processors, Field Programmable
Gate Arrays or Complex Programmable Logic Devices are applied to meet desired
requirements and to gain better control of loads; more accurate mathematical
methods to model power converters enable gaining better output features,
reducing energy losses and increasing efficiency; and improved control
algorithms are utilised to improve efficiency and robustness, to reduce
complexity and to achieve better output features.


Power electronics
converters fall into four categories, i.e. AC-DC, AC-AC, DC-DC and DC-AC
converters, and they have been invented for and found a wide spectrum of
applications in, for instance, transportation (electric/hybrid electric
vehicles, electric locomotives, electric trucks), utilities (line transformers,
generating systems, grid interfaces for alternative energy resources like solar
panels, wind turbines and fuel cells, energy storage), industry/commerce (motor
drive systems, electric machinery and tools, process control, factory
automation), consumer products (air conditioners/heat pumps, appliances,
computers, lighting, telecommunication equipment, un-interruptible power supplies,
battery chargers) or medicine. Especially in the area of renewable energy
applications, power electronics converters play a more important rôle, which
enable DC micro-grids to realise highefficient

usage of renewable
energy, and stable interfaces between energy storage systems and renewable
energy resources 2,3, as well electrification of distant villages and rural areas 4;
high-voltage direct current (HVDC) systems can be also enabled to replace some long-range
transmission AC transmission systems 5; aircraft power supplies with special
requirements can be realised by specific power converters 6; to list just a few.
Thus, power electronics has established itself as a scientific discipline 7.


To design a new power electronics converter, one
can, on one hand, develop a new control strategy; on the other hand, one can
design a novel power converter topology, so as to achieve specific outputs,
simpler control, higher efficiency, less complexity, lower weight, minimal cost
and better robustness. In fact, a control strategy is specified for a certain
topology, and the topology determines the control system. Therefore, it is of
great significance to coin optimal power-converter topologies to fulfill the
requirements of various applications.


2. State
of the art of impedance-source converters


Inspired by the typical Z-source converter proposed
by Peng, various impedance-source converters have been proposed for different applications,
such as quasi-Z-source converters, trans-Z-source converters or
embedded-Z-source converters. So far, more than 1100 articles on
impedance-source converters have been published in various professional
journals by many scholars 8–12.


Quasi-Z-source converters


The quasi-Z-source converter was proposed by
Anderson and Peng in 2008 for applications in motor systems, renewable energy
systems and micro-grid systems. According to the operational modes voltage type
or current-type and continuous or discontinuous current, quasi-Zsource converters
can be classified into four categories, i.e. voltage-fed quasi-Z-source
inverters with continuous input current, voltage-fed quasi-Z-source inverters
with discontinuous input current, current-fed quasi-Z-source inverters with
continuous input current and current-fed quasi-Z-source inverters with
discontinuous input current, which are

shown in Fig. 2 13. It was found by Cao and Peng 14
that all impedance-networks in Fig. 2 can be derived from the one in Fig. 1.
For instance, the voltage-fed quasi-Z-source inverter with continuous input current
in Fig. 2(a) is equivalent to that in Fig. 3, whose switches S1

and S2 are equivalent to the diode D and the
inverting bridge in Fig. 2(a to d), respectively.



1, A Z-network.

2. Quasi-Z-source inverters 59

3. Equivalent circuit of the converter in Fig. 9 60.


A further analysis derives a set of criteria for
designing impedancesource converters, which leads to a design methodology
dealing with input- and output-impedance matching, and with load-phase
matching. This overcomes the shortcomings of the traditional tedious, manual
and experience-dependent design methods and eases the design of new converters.
With this design methodology, a Z-source half-bridge converter for
electroplating applications and a dual-output Z-source half-bridge converter
for hybrid electric vehicles have been designed.

It is expected that a variety of impedance-source
converters will to be designed in the near future addressing the needs of
specific industrial applications.




Zhang B, Qiu D. Sneak circuits of power
electronic converters. Singapore: John Wiley & Sons; 2014.

 Justo JJ, Mwasilu F, Lee J, Jung JW.
AC-microgrids versus DC-microgrids with distributed energy resources: a review.
Renew Sustain Energy Rev2013;24:387–405.

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Mwasilu F, Justo JJ, Kim EK, Do TD, Jung
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Siwakoti Y, Peng F, Blaabjerg F.
Impedance-source networks for electric power conversion part I: a topological
review. IEEE Trans Power Electron 2015;30(2):699–716.

Siwakoti Y, Peng F, Blaabjerg F.
Impedance-source networks for electric power conversion part II: review of
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Ellabban O, Abu-Rub H. An overview for
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Suganthi J, Rajaram M. Effective
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Kirubakaran A, Jain S, Nemae RK. A
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Anderson J, Peng FZ. Four quasi-Z-source
inverters. In: Proceedings of the IEEE power electronics specialists conference
(PESC 2008); 58(1); 2008. p. 2743–9.

14.  Cao
D, Peng FZ. A family of Z-source and quasi-Z-source DC-DC converters. In:
Proceedings of the Twenty-Fourth Annual IEEE applied power electronics
conference and exposition (APEC 2009); 58(1); 2009. p. 1097–101.