International Conference on Electrical, Electronics, and Optimization Techniques (ICEEOT) - 2016
Closed Loop Operation of Three Switch Inverter
Sreesan K.S and Ajmal K.T
Electrical and Electronics Engineering
MEA Engineering College
Perinthalmanna, Kerala, India
Sreesan91@gmail.com
Abstract—The proposed system explains the inverting
operation of DC voltage to AC simply using only three switches.
The power demands increases day by day but the sources are
limited. A micro grid is benign source of power with various
renewable energy resources. The proposed topology has a high
frequency rectified sine modulated switch with two
symmetrically operated line frequency switches in the front end.
The center tapped LF transformer unfolds the voltage to a sine
wave in the output. It has higher power gain and lower
harmonics. Simulation of this three switch inverter topology is
done in MATLAB and the validity is proved.
Keywords— CCM-continues conduction mode, Three switch
inverter
I. INTRODUCTION
The ever increasing power demand in the world is a
symbol of growth in some countries. But the use of nonrenewable fuels deploys the resources and pollution grows
very fast. One solution to avoid the depletion of gasoline fuels
by the use renewable energy resources and which can easily
done with the help some converters and inverters with cells.[1]
Different topology inverters have wide uses in domestic
and industry applications. Some of those are energised by lowv voltage sources like fuel cells and solar cells. In these cases,
the output voltage of the primary side converters has to be
lower than sinusoidal output of the inverter. Therefore in order
to interface fuel cells and solar cells to a high-voltage gain,
high efficient dc-dc converters with lower harmonics, high
conversion ratio and very lesser input current ripple are
required. The Different inverter topologies and variable
control techniques for the advanced mode operation of a micro
grid are reviewed and they are categorised based isolation as
three main classes, i.e. 1) LF transformer based topologies 2)
HF transformer based topologies 3) Transformer-less
topologies.
The HF transformer based topology has some draw
backs such several power stages and it will not block the dccurrent injection to its output…etc. The transformer-less
topology has many draw backs such as 1) Higher DC voltage
requirement 2) large ground leakage current 3) DC current
injection into grid. So series connection of DC sources, safety
hazards and limited duty cycles results.
LF transformer topology has galvanic isolation and
higher power gain and DC current rejection more than other
978-1-4673-9939-5/16/$31.00 ©2016 IEEE
topologies. But the larger size of LF transformer increases the
size of the system and weight.[2]
To overcome these draw backs of conventional
topologies, a voltage source inverter is introduced called three
switch inverter. The operation is explained in the section II
and control part in III and MATLAB simulated.
II.
PROPOSED SYSTEM
A. Three switch inverter circuit description
The circuit diagram of proposed inverter is shown in the
figure (a). Here there are two stages which include a dc-dc
converter stage and a dc-ac unfolding rectified sine wave stage
[3]. The primary side is a buck converter. Switch S is high
frequency rectified sine modulated one and switches S1 and
S2 are line frequency operated.
Fig.1 Proposed system
Fig.2 output waves
The average voltage of the dc-dc converter is a function of
duty cycle and which is given by the equation,
Vc =
ton
× Vdc
T
(1)
The duty cycle is varied in a fully rectified sine wave
manner so that Vc will be rectified sine voltage as shown in
figure (b).
B. Operation
From the fig.(a) the switches S and S1 turned on so that the
capacitor starts to charge as rectified sine wave manner. The
path of current will be positive-S-o-f2-S1-negetive of battery.
In the next half cycle the current flow will be through, Vdc-of1-S2-negetive of battery. The unidirectional voltage in the
capacitor is unfolded using centre tapped transformer and the
output of the transformer will be a sine voltage.
Cmin =
δ
(8)
2 * f s * rc
A. Control of the system
In the control part the sine pulse is transformed to rectified
form and which is compared with a high frequency carrier
wave which produces the pulses for switch S [5]. One part of
sine wave which having line frequency is compared with
ground. The resulting pulse is given to switch S1 and the pulse
is inverted, given to S2.
The list of parameters is given in the table I. Input voltage
requirement is 48V and the modulation index is 0.72 as given
in table.
When switches S and S1 or S2 operate a rectified sine wave
appears across the primary of the transformer. A boosted
voltage induced in the secondary [4].
The main advantage of this topology is its capability to
working in any desired frequency (50Hz or 60Hz) with three
switches where only one switch operates at higher frequency.
So the losses are reduced and requirement of cooling is needed
only for one switch.
III. DESIGN OF PARAMETERS
Maximum and minimum power of the converter given
by,[7]
Pmax = Vc * I mx
(2)
Pmin = Vc * I min
(3)
TABLE I.
Voltage conversion ratio,
μVdc =
Vc
Vdc
(4)
Parameters
Vdc
Capacitor voltage,
Vc = 0.637 * μVdc
(5)
Minimum value of inductance for CCM,
Lmin = Vc *
1−δ
2 * f s * I o min
(6)
The maximum inductor ripple current,
ΔI L max
Fig.3 Block diagram of pulses for switches
1−δ
= Vc *
fs * L
Minimum value of capacitance,
(7)
PARAMETER VALUES
Specifications
48V
Vc
22V, m=0.72
Vr
0.3V
Iomin
0.5A
Iomax
50A
fs
5kHz
FF
50Hz
L
250µH
C
220µF
B. open loop control
Fig.4 Open loop control of Three switch inverter
IV.
MATLAB SIMULATION
The circuit diagram is simulated in the MATLAB with
given parameters. The simulated diagram is as shown in
figure.
Fig.7 Pulses for switches S, S1 and S2
Fig.5 Output voltage of transformer
Fig.6 Voltage across the capacitor
Fig.8 THD measurement
A. Closed loop control
Fig.9 Closed loop control
References
[1]
[2]
[3]
[4]
[5]
Fig.10 Closed Loop Output Voltage with stepping
The closed loop control is done by using PI
controller. The inductor current, capacitor voltage and load
voltages are measured.
V. CONCLUSION
The simulation of the three switch inverter has been
carried out for open loop control using SPW modulation
technique. The simulation results validate the operation of the
inverter circuit. The results are obtained as expected and in
accordance to the theoretical analysis of the inverter.
[6]
[7]
Y.-H. Liao and C.-M. Lai, “Newly-constructed simplified single-phase
multistring multilevel inverter topology for distributed energy
resources,” IEEE Trans. Power Electron., vol. 26, no. 9, pp. 2386–2392,
Sep. 2011. (references)
R.-J. Wai, C.-Y. Lin, Y.-C. Huang, and Y.-R. Chang, ‘‘Design of
highperformance stand-alone and grid connected inverter for distributed
generation applications,’’ IEEE Trans. Ind. Electron., vol. 60, no. 4, pp.
1542---1555, Apr. 2013.
D. Menese, F. Blaabjerg, O. Garcia, and J. A. Cobos, ‘‘Review and
comparison of step-up transformerless topologies for photovoltaic ACmodule application,’’ IEEE Trans. Power Electron., vol. 28, no. 6, pp.
2649---2663, Jun. 2013.
M.F Rahman, L.Zhaong “A new transformerless, photovoltaic array to
utility grid interconnection” in 1997
Y. Xue, L. Chang, S. B. Kjaer, J. Bordonau, and T.
Shimizu,‘‘Topologies of single-phase inverters for small distributed
power generators: An overview,’’ IEEE Trans. Power Electron., vol. 19,
no. 5, pp. 1305---1314,Sep. 2004.J. Clerk Maxwell, A Treatise on
Electricity and Magnetism, 3rd ed., vol. 2. Oxford: Clarendon, 1892,
pp.68-73.
Q. Li and P.Wolfs, ‘‘A review of the single phase photovoltaic module
integrated converter topologies with three different DC link
configurations,’’ IEEE Trans. Power Electron., vol. 23, no. 3, pp. 1320--1333, May 2008.I.S. Jacobs and C.P. Bean, “Fine particles, thin films
and exchange anisotropy,” in Magnetism, vol. III, G.T. Rado and H.
Suhl, Eds. New York: Academic, 1963, pp. 271-350.
N. Mohan, T. Undeland, and W. Robbins, Power Electronics:
Converters, Applications and Design, 2nd ed. New York: Wiley, 1995.