International Journal of Conceptions on Electrical & Electronics Engineering
Vol. 1, Issue. 2, December 2013; ISSN: 2345 – 9603
Simulation of high power factor single state
LCC resonant inverter
Mohammed Sabah Ul Islam and Dr. S Tara Kalyani
Dept. of Electrical Engineering,
JNTUH,
Hyderabad, India.
msi_4mair@yahoo.com , tarasunder98@yahoo.co.in
Abstract— This paper presents the simulation of high-power
factor (HPF) single-stage inductor-capacitor-capacitor (LCC)
resonant inverter. A half-bridge LCC resonant inverter shares
switches with a power factor- correction circuit to form single
stage. The proposed single stage LCC resonant inverter can
achieve almost unity power factor and ripple-free input current,
and can also realize zero-voltage-switching by operating the
switches above the resonant frequency. The simulated result is
compared with the results of conventional inverter, LLC
resonant inverter and Z-source inverter. Among all these results,
LCC resonant inverter has the high power factor value which is
almost unity. Thus, the proposed single-stage inverter provides
HPF to the utility line and also achieves circuit simplicity, low
cost, and high reliability [1]-[2].
Keywords- Power Factor Correction, High Power Factor, LCC
Resonant Inverter.
I. INTRODUCTION
Without a power-factor-correction (PFC) circuit, the
current drawn by the inverter from the utility line will contain
significant harmonic components and therefore, the inverter
will operate at a poor power factor. By adding active PFC
circuits, line current harmonics can be reduced effectively and
high power factor is achieved, which means that the utility line
can be utilized more efficiently.
each stage, but the disadvantages are, since it has two-powerprocessing-stage topology, it reduces the inverter reliability,
decreases the efficiency, and increases the final cost because
more components are needed in this approach. In order to
avoid these problems, inverters based on single-stage designs
are considered to be desirable and several single-stage inverters
have been proposed [5]-[6]. These kinds of inverters combine the
PFC stage and the inverter stage by sharing switches to form
single stage. A smaller number of devices are more desirable in
terms of efficiency, reliability, and cost.
II.
ANALYSIS OF PFC STAGE
Fig 2 shows the proposed PFC circuit. iCf1 and iCf2 are the
currents flowing through the filter capacitors Cf1 and Cf2 (Cf1 =
Cf2 = Cf ), respectively. The current flowing through the
inductor L is iL. The transformer-type coupled inductor Tc is
modeled as an ideal transformer, which has a turn ratio of 1:1.
The magnetizing inductance Lmc is large enough to maintain a
constant current imc during a switching period. The steadystate operation of the PFC circuit in one switching period Ts
includes eight modes, and the theoretical waveforms.
The input current is controlled to follow the sinusoidal
waveform of the input voltage to provide high-power-factor
(HPF) to the utility line [3]-[4]. The advantage of this twopower-processing stage approach is that it is easy to optimize
Fig 2: Proposed PFC circuit.
Fig 1: Proposed single-stage LCC resonant inverter.
Switches S1 and S2 are operated symmetrically with the
duty ratio equaling to 0.5. To illustrate the steady-state
operation, it is assumed that all the components are ideal. The
ripple components of the dc-link voltage Vd are negligible
because the dc-link capacitor Cd has a large value. It is
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International Journal of Conceptions on Electrical & Electronics Engineering
Vol. 1, Issue. 2, December 2013; ISSN: 2345 – 9603
assumed that the supply voltage vi is constant during the
switching period. Then, the capacitor current iCf1 becomes:
=
(
=
)
gate signal should be applied to S1 before the current changes
its direction. The inductor current iL and the current i2 decrease
linearly as in Mode 2, and approach −IL and zero, respectively
at the end of Mode 3.
=−
=−
(1)
Therefore, the same amount of currents flow through each
capacitor. Since iCf1 = iCf2 + iL, iCf1 = 0.5iL. The ripple
components of the filter capacitor voltages vCf1 and vCf2 are
negligible because the filter capacitors Cf1 and Cf2 have large
values. Thus, vCf1 and vCf2 are considered to be constant during
the switching period Ts, and as the duty ratio equals 0.5, vCf1 =
vCf2 = 0.5vi. CS1 and CS2 (CS1 = CS2 = CS) are the parallel
capacitors of switches S1 and S2, respectively. Prior to Mode 1,
the magnetizing inductor current imc becomes IL, and the
inductor current iL flows with the positive peak value IL
through D4, L, and S2.
Mode 4: At t3, the current i2 arrives at zero and the diode
D4 is turned off. Then, the inductor current is clamped at −IL.
Because the magnetizing inductance Lmc of the coupled
inductor Tc is much greater than that of the inductor L, the
voltage across the inductor L is considered to be zero and the
voltage vTc is fixed to 0.5vi.
Mode 1: At t0, the lower switch S2 is turned off. Then, the
inductor current iL starts to discharge CS1 and charge CS2. The
voltage vS1 across the upper switch S1 decreases and the
voltage vS2 across the lower switch S2 increases. Thus, the
inductor current iL and the transition interval Tt are given by:
Mode 6: At t5, the voltage vS2 across the lower switch S2
becomes zero. Then, the lower diode DS2 is turned on. Since
vCf1 = −vL + vTc + Vd and vCf2 = vL + vTc, the voltage vTc across
the coupled inductor Tc and the voltage vL across the inductor
L are given by:
=
Mode 5: At t4, the upper switch S1 is turned off. Then, the
inductor current iL starts to charge CS1 and discharge CS2. The
voltage vS1 across the upper switch S1 increases and the
voltage vS2 across the lower switch S2 decreases. The transition
interval Tt is the same as in Mode 1. The diode D4 is turned on
at the end of Mode 5.
(2)
=
( )=−
(3)
=
Since the capacitors CS1 and CS2 in parallel with the
switches S1 and S2 have small values, the transition interval Tt
is negligible and the inductor current iL has a constant value.
( )=−
=−
+
(4)
=−
(5)
=
(9)
Then, the inductor current iL increases linearly as follows:
−
( )=− +
( − )
Mode 2: At t1, the voltage vS1 across the upper switch S1
becomes zero. Then, the upper diode DS1 and the diode D1 are
turned on. Since vCf1 = −vL + vTc = 0.5vi and vCf2 = vL + vTc + Vd
= 0.5vi, the voltage vTc across the coupled inductor Tc and the
voltage vL across the inductor L are given by:
−
(8)
=− +
( −
)
(10)
Then, the inductor current iL decreases linearly as follows:
−
( )= +
( − )
=
−
( −
)
(6)
Where IL is the peak value of iL during one switching
period.
Since i2 = iL + i1’ + imc, i1’ = −i2, and imc = IL, the secondary
current i2 of the coupled inductor Tc is given by:
( )=
=
−
( −
)
(7)
Mode 3: At t2, the zero-voltage turn-on of the upper switch
S1 is achieved because the current has already flowed through
the body diode DS1 before the upper switch S1 is turned on.
When the upper switch S1 is turned on, S1 takes over the
current flowing through DS1. To guarantee ZVS at turn on, the
Fig 3: Theoretical waveforms of PFC circuit.
Since i2 = iL + i1’ + imc, i1’ = −i2, and imc = IL, the secondary
current i2 of the coupled inductor Tc is given by:
54 | 6 6
( )=
=
( −
)
(11)
International Journal of Conceptions on Electrical & Electronics Engineering
Vol. 1, Issue. 2, December 2013; ISSN: 2345 – 9603
Mode 7: At t6, the lower switch S2 is turned on. Zerovoltage turn-on of the lower switch S2 is achieved in a similar
way that is described in Mode 3. The inductor current iL and
the current i2 increases linearly as per Mode 6, and approach IL
at the end of Mode 7.
The output here taken is the resistive load. All the
components are connected according to the circuit diagram.
The parameters of the circuit components are as follows:















Mode 8: At t7, the primary current i1 arrives at –IL and the
diode D1 is turned off. Then, the inductor current iL and the
current i2 are both clamped at IL. This mode ends one period Ts
of the switching frequency fs. Referring to the voltage
waveforms of vL and vTc, the volt-second balance law gives the
following equations:
=
(
)
(12)
=
( −
)
(13)
Equations (12) and (13) give the current transition time as
follows:
=
=
=
(14)
Series resonant inductor(Lr )=450nH
From Mode 2 and Mode 3, the peak current IL is given by:
=
=
(15)
The input voltage vi of the inverter is:
=
(16)
where Vm and ω are the peak amplitude and angular
frequency, respectively. From Kirchhoff’s current law and (2),
ii = iCf1 + i1 = iCf2 + i2 = 0.5(i1 + i2) and imc = IL. Then, the input
current ii is given by:
=
=
Input power supply (V)=220Vrms
Frequency (f)=50Hz
Switching frequency (fs)=80KHz
Duty ratio=50%
Ideal transformers
Diode bridge rectifier (IN4007)
Mosfet (1RF 250N)
Resistor (Ri )=100Ω
Load Resistor (RL)=88mΩ
Filter capacitors(Cf1=Cf2=Cf )=0.1µF
DC link capacitor Cd =560nF
DC blocking capacitor Cb =7µF
Parallel resonant capacitor Cp =1µF
Series resonant capacitor Cs =264nF
Inductor (L)=315µH
IV. BLOCK DIAGRAM OF LCC RESONANT INVERTER
Based on the above mentioned parameters the simulation
is done to find the power factor of the circuit along with the
input output waveforms. The schematic shown in figure 6 is
the block diagram representation of HPF single stage LCC
Resonant inverter. It consists of input ac power supply, ideal
transformer, bridge rectifier with a filter diode, Mosfet
switches along with a pulse generator for triggering the gate
terminals, main LCC resonant inverter circuit, transformer and
output resistive load.
(17)
Thus, the input current does not contain any highfrequency harmonics. The real input power Pi is determined
as:
= ∫
(
)=
(18)
From (16)–(18), the power factor PF is given by:
=
=
,
32
Fig 6: Block diagram of LCC Resonant inverter.
=1
,
√2 16√2
Thus, the proposed PFC circuit gives unity power factor in
theory.
III.
SIMULATION OF HPF SINGLE-STAGE LCC RESONANT
INVERTER
The simulation of proposed inverter circuit shown in fig.1
is done in MATLAB SIMULINK. The half-bridge LCC
resonant inverter circuit shares the switches with a power
factor- correction circuit.
A 220 Vrms AC supply is given to the coupled inductor
(Tc) which is modeled as an ideal transformer which acts like
step-down transformer. The output terminals of transformer
are connected to a bridge rectifier which also has a DC link
capacitor. These are connected to the Mosfet switches and the
conduction starts when the gates are triggered with positive
and negative pulses through pulse generator circuit. Till here
it’s a PFC circuit. These switches are shared by both PFC
circuit and the resonant inverter circuit.
Now, LCC inverter circuit with its resonant circuit (LC) is
connected to switches and the other two terminals are
connected to the step-up transformer and finally connected to
the resistive load.
This block diagram is modeled in the MATLAB to form a
simulink model that can be simulated and the output load and
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International Journal of Conceptions on Electrical & Electronics Engineering
Vol. 1, Issue. 2, December 2013; ISSN: 2345 – 9603
power factor can be measured. The simulink model circuit
components are given the values as shown above. Now, the
simulation of the circuit is started for a specific time period
and with the help of scope the current and voltage waveforms
of different components can be viewed and measured.
The input supply voltage shows a smooth sinusoidal wave
with the voltage of 300V. The current waveform shows the
input current rating of 0.05A. The input current is ripple free
with reduced switching losses. The output voltage for the
resistive is measured as 90V and the output current of 1mA.
The power factor for the HPF single stage LCC resonant
inverter is measured as 0.995, which is almost unity. The
waveforms of input and output voltage are shown below:
Fig 8: Block diagram of LLC resonant inverter.
Fig 7: Simulated waveform of LCC Resonant inverter.
From the waveforms we can observe that for input 220V
the output is 90V and for input current almost of almost 0 we
get output as 1mA.
Also we can compare the result of LCC resonant inverter
with conventional inverter, LLC resonant inverter and z-source
inverter.
V. BLOCK DIAGRAM OF RESONANT INVERTER
The figure 8 shows the schematic of a block diagram of
LLC resonant inverter where the LCC inverter circuit has been
changed with other inverter circuit which is LLC resonant
inverter. The LLC inverter is connected in order of capacitor,
inductor and inductor.
Fig9: Simulated waveform of LLC Resonant inverter.
From the simulated waveforms we can see that for input
220V and current, the circuit gives very less output voltage
and low current. With this the power factor decreases and
cannot be used in high power applications. The figure 10
shows the block diagram of conventional inverter circuit for
the HPF single stage circuit. In this, no inverter is connected
on the second part of the circuit.
This block diagram is modeled in simulink and the
component values are the same as in the case of LCC resonant
inverter method.
The simulation is done (fig.9) and the current and voltage
values of different components are viewed and measured. The
power factor value in this method of simulation is measured as
0.6536.
Fig 10: block diagram of conventional invereter.
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International Journal of Conceptions on Electrical & Electronics Engineering
Vol. 1, Issue. 2, December 2013; ISSN: 2345 – 9603
obtained shown in fig.13. The load voltage obtained in this
inverter is 10V which is very low and load current obtained is
0.00012A. The power factor rating obtained is 0.9686 which is
also near to unity power factor but due to the low output load
voltage it cannot be used in the applications of LCC resonant
inverter.
VI. CONCLUSION
We can see that the unity power factor and the high load
voltage is obtained by the HPF single-stage LCC resonant
inverter when compared to conventional inverter, LLC
resonant inverter and Z-source inverter.
Fig11: Simulated waveform of Conventional Resonant inverter.
The simulation is done (fig.11) and the load voltage is
measured as 12V only. From the input current waveform we
can see the signal contains fluctuation and harmonics with
0.04A current and the output current obtained is 0.00015A.
Also the power factor generated by the circuit is 0.3335. So, to
improve the power factor and efficiency of the circuit, LCC
inverter has been implemented.
Hence, by using a LCC resonant inverter we can get power
factor of almost unity and ripple-free input current, and can
also realize zero-voltage-switching by operating the switches
above the resonant frequency, hence the switching losses is
reduced.
TABLE I.
The last inverter is the Z-Source resonant inverter. The
figure 12 shows the block diagram of Z-Source resonant
inverter. The Z-Source topology is very simple to describe:
two-port networks that consist of capacitors Ca and Cb and a
split inductor La and Lb connected in X shape.
Inverter Type
P.F.
1)
Conventional resonant inverter
0.3365
2)
LLC resonant inverter
0.6536
3)
Z-source inverter
0.9686
4)
LCC resonant inverter
0.9995
Thus, the proposed single-stage inverter not only provides
HPF to the utility line, but also achieves circuit simplicity, low
cost, and high reliability compared to the conventional HPF
inverters.
Hence, from the above conclusion it is clear that the high
power factor single stage LCC resonant inverter is better than
the conventional and LLC and Z-Source inverter.
REFERENCES
[1]
Fig 12: Block diagram of Z-source inverter.
[2]
[3]
[4]
[5]
[6]
Fig13: Simulated waveform of Conventional Resonant inverter.
This inverter circuit is simulated in MATLAB simulink.
The current and voltage values along with the waveforms are
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