Brijesh M. Patel, Kalpesh J.Chudasma, Hardik A.Shah
26
Simulation of Single Phase Inverter using PSIM
Software for Solar P.V. System give Constant
Output Voltage at Different Solar Radiation
Brijesh M. Patel, Kalpesh J.Chudasma, Hardik A.Shah
Abstract:This study investigated the detail function of
inverterin small scale distributed power generation, its
modelling and related simulation on P-SIM software. This
model can be used for photovoltaic application or especially for
particular AC module. In this paper work on three basic
requirements for Inverter Modelling Amplification, Inversion
and Voltage regulation under change in atmospheric condition.
1. Introduction
The overview of single phase inverters developed for
small distributed power generators. The functions of
inverters in distributed power generation (DG) systems
include dc–ac conversion, output power quality assurance,
various protection mechanisms, and system controls. Unique
requirements for small distributed power generation systems
include low cost, high efficiency and tolerance for an
extremely wide range of input voltage variations. These
requirementshavedriven the inverter development toward
simpler topologies and structures, lower component counts,
and tighter modular design. Both single-stage and multiplestage inverters have been developed for power conversion in
DG systems. Single-stage inverters offer simple structure
and low cost, but suffer from a limited range of input
voltage variations and are often characterized by
compromised system performance. On the other hand,
multiple-stage inverters accept a wide range of input voltage
variations, but suffer from high cost, complicated structure
and low efficiency [1]. Various circuit topologies are
presented, compared, and evaluated against the requirements
of power decoupling and dual-grounding, the capabilities for
grid-connected or/and stand-alone operations [2].and the
simulation of two stage inverter saw a variation in inverter
output power when there is a small variation in input supply
or variation in solar panel power output due to change in
solar radiation during the day. And result discussion.
2 Discussion on different possible power
conversion topology for PV system or DG system
2.1 Topology of single-phase inverters
DG systems are usually small modular devices
close to electricity users, including wind turbines, solar
energy systems, fuel cells, micro gas turbines, and small
hydro systems, as well as the relevant controlling/ managing
and energy storage systems. Such systems commonly need
dc–ac converters or inverters as interfaces between their
single-phase loads and sources as shown in Fig. 1[7],
which depicts a typical renewable DG system using
photovoltaic (PV) as energy source. DG inverters often
experience a wide range of input voltage variations due to
the fluctuations of energy sources, which impose stringent
requirements for inverter topologies and controls. Functions
of inverters for small DG systems can be summarized as
follow [2, 12].
Fig. 1. Block diagram of a photovoltaic system. [19]
1) Power conversion from variable dc voltage into fixed ac
voltage for stand-alone applications or ac current output
following the grid voltage and frequency for grid-connected
applications. The variable dc voltage can be higher or lower
than the ac voltage in one system, which is observed
normally in a wind-turbine energy system.
2) Output power quality assurance with low total harmonic
distortion (THD), voltage and frequency deviation, and
flickering.
Brijesh M. Patel is working as Assistant Professor, ADIT, New Vallabh
Vidyanagar, India, bmp1412@gmail.com, Kalpesh J.Chudasma and Hardik
A.Shah are working as Associate Professor, ADIT, New Vallabh
Vidyanagar, India,
3) Protections of DG generators and electric power systems
from abnormal voltage, current, frequency and temperature
conditions, with additional functions such as anti islanding
International Journal of Emerging Trends in Electrical and Electronics (IJETEE – ISSN: 2320-9569)
Vol. 4, Issue. 1, June-2013
Brijesh M. Patel, Kalpesh J.Chudasma, Hardik A.Shah
27
protection and electrical isolation if necessary.
4) Control of DG systems and accomplishment of
certain objectives such as maximum power extraction from
wind energy, maximum power point tracking (MPPT) of
PV modules, optimum efficiency for fuel cell systems,
optimal energy flow control [5], etc.
Based on the electrical isolation between the input
and output, inverters can be classified as isolated inverters
or non isolated inverters. While electrical isolation is
normally achieved using transformers, a choice can be
made between using line-frequency transformers as in Fig.2
or high-frequency transformers as in Fig. 3. The dc-link
voltage of inverters for DG systems may vary over a wide
range. Depending on the input dc voltage range in
comparison to the output ac voltage, inverters can be buck
inverters, boost inverters, or buck-boost inverters. It should
be noted that although the inverters in Fig. 2 and Fig. 3 are
buck inverters by themselves, the whole topologies actually
represent boost or buck-boost inverters due to PWM
operations and voltage step-up in either low frequency or
high frequency.
Traditional full-bridge buck inverters are used in
many existing high power applications with bulky and
heavy line-frequency transformers. However, modern power
electronic converters tend to use “more silicon and less
iron.” This leads to the pursuance of compact designs with
wide input voltage ranges and improved overall efficiency
[3].
A multiple-stage inverter is defined as an inverter with more
than one stage of power conversion, in which mostly one or
more stages accomplish voltage step-up or step-down or
electrical isolation, and the last stage performs dc–ac
conversion.
Fig. 2. Traditional buck inverter and
transformer[17]
line-frequency
Fig. 3 Multiple-stage inverter with a high frequency
transformer.
2.2
Two-Level PWM Control technique
for H bridge inverter control
The H-bridge topology inverter is the most popular singlephase converter in various applications, especially in
higher power rating applications. It consists of two arms
fig4 and outputs a single-phase AC output voltage, V out
to the load. Pulse Width Modulation (PWM) techniques are
used to control the switching devices on and off. During last
few years, PWM technique has been the subject of intensive
research and a large variety of PWM control schemes have
been discussed. Sinusoidal PWM (SPWM) approach is often
used in single-phase applications.
1) dc–dc–ac topologies;
2) dc–ac–dc–ac topologies;
3) dc–ac–ac topologies.
These topologies will also be discussed regarding the
capabilities to meet certain challenging requirements of DG
resource and ac utility [3,8].
Fig.4 single-phase H-bridge inverter
Three different sinusoidal PWM switching
schemes are used commonly for two-level single-phase
inverter. They are bipolar PWM scheme, unipolar PWM
scheme and modified unipolar PWM scheme [3] Figure 5
below shows the bipolar PWM modulation scheme. In
International Journal of Emerging Trends in Electrical and Electronics (IJETEE – ISSN: 2320-9569)
Vol. 4, Issue. 1, June-2013
Brijesh M. Patel, Kalpesh J.Chudasma, Hardik A.Shah
28
order to generate a sinusoidal AC output with desired
amplitude Vm and frequency f, a sinusoidal control
signal Vcontrol at a desired frequency f1 is compared
with a continuous triangular waveform Vcarrier as shown in
Figure 5[13,16]
Fig. 6 unipolar PWM modulation scheme
Fig.5 bipolar PWM modulation scheme
When Vcontrol is greater than Vcarrier, the PWM
output is positive; otherwise the PWM output is negative.
The frequency of carrier waveform Vcarrier establishes
the switching frequency s f of the inverter. The modulation
index i m is defined as
where Vcm is the peak amplitude of the control signal,
while Vcrp is the peak amplitude of the triangle signal
(carrier).
2.3
Overview of Solar Power Conversion
System
The power conversion subsystem for a solar power
system has two main tasks: one is to control the input
terminal conditions to make photovoltaic (PV) modules
operate at a maximum power point (MPP) and to capture
the maximum power for the sun [7]. The other is to
convert the output dc voltage from solar modules to a
suitable ac voltage and meet the utility requirements [5]
Therefore, most of the solar power conversion systems
apply two-stage topology. The most common two-stage
systems [6] consist of a dc-dc solar module-connected
converter and dc-ac PWM inverters as shown in Figure 7
[9,15].
the modulation ratio is defined as:
where f carrier is the carrier frequency.
A unipolar PWM modulation scheme is shown in
Figure 6 where the two switch pairs in H-bridge
inverter are not always switched simultaneously as in the
bipolar scheme. Instead, the switching of the two arms is
controlled by two control signals. Therefore, the output
voltage changes between 0 and +Vd or between 0 and - Vd
in half fundamental period. Two control reference signals
are used in this scheme. The output voltage from the bipolar
PWM scheme does not have zero state, which means the
output voltage of the inverter only changes between +Vd
and - Vd. This scheme requires only one control reference
signal, but the performance is poor[14]
Fig 7 two-stage solar power conversion system [11]
2.4
Simulation of single phase inverter
topology
Linear regulator often plays important role in implementing
power supply capable of constant voltage/current control. It
always provides lost of advantage such as low ripple
noise, low EMI, good regulation, easy control strategy.
However due to bulky size, low efficiency switch mode
technique has become inevitable development trend for
raising the power density, power efficiency and dynamic
International Journal of Emerging Trends in Electrical and Electronics (IJETEE – ISSN: 2320-9569)
Vol. 4, Issue. 1, June-2013
Brijesh M. Patel, Kalpesh J.Chudasma, Hardik A.Shah
performance. The full bridge converter is one of the isolated
converter topology that use in high power rating. The block
diagram of it is shown in fig 8. The feedback signal of
voltage is given to control circuit using PI-controller
block for control and protection purpose.
29
2.6 Converter control scheme using
PI-controller
The control scheme essentially consisting of
only one sensor with simple structure when compared with
classical boost converter which requires both voltage and
current sensors. Here, DC voltage of load is fed back and
compared with Vdc reference voltage. If, there is reduced dc
voltage then there is difference between ref. voltage & O/P
voltage. This difference is in the form of error, which is
given to PI-Controller. PI- controller stabilizes this error and
give the modulated single output for PWM scheme. Signals
from PI- controller is compared with high frequency signal
reference signal as shown in fig9[2]
F
Fig 9 Comparison between Pi Output Signal and Carrier signal
Fig. 8 Single Phase Inverter Topology with p-sim software
2.5 Closed loop converter control system
Control system should be able to adjust duty cycle in time
in order to regulate the output voltage with input voltage
and load variation. Voltage mode and current control mode
control technique adapted to design switching power
supply. As the speed of the processors increase and large
load changes frequently encountered in system transition
from one sleep mode to active mode, the faster transient
response of DC-DC power supply has been more
important. The transient response of voltage mode control
technique, when the input voltage is changing because it has
only one feedback loop. The input voltage varying after the
variation of output voltage occurs. In fact, the transient
response of voltage mode control is slow for any variation
of power stage. The basic principle of following
circuits in the boosting up the voltage are, charging &
discharging reactive component into a load, controlling the
level of charge & consequently output voltage by switching
the DC supply in & out of the circuit at very high
frequencies. They include a freewheeling diode to protect
the switch from inductor’s very reverse current and this also
ensures that the generated inductor energy is applied to
load capacitor are connected in parallel with load, to filter
the voltage ripple & to maintain constant output voltage.
Inductor is used in series with the load to filter the current
ripple.
Fig 10 Converter output 230v DC
To set the gain and time-constant there are three
methods given below:
(i) Analytical method
(ii) Empirical method
(iii) Trial and error method
PI-controller is designed by trial and error method for
line and load regulation. Most of industries used this method
for tuning of PI-controller. PI-proportional integral, where
integral term yields zero steady- state error in tracing
constant set point & proportional term yields output is
proportional to input. Integral control filters higher
frequency sensor noise; it is slow in response to current
error. On the other hand, the proportional term responds
immediately to the current error, yet it cannot achieve
without an unacceptably large gain. PI controller
reduces very high transient error. PWM technique is used
International Journal of Emerging Trends in Electrical and Electronics (IJETEE – ISSN: 2320-9569)
Vol. 4, Issue. 1, June-2013
Brijesh M. Patel, Kalpesh J.Chudasma, Hardik A.Shah
for generating gate pulses of IGBTs. The duty cycle is
varied according to output voltage. To increase the output
voltage increases the duty ratio. Main drawback of this
system is slow transient response of output voltage. If
input voltage changes from 20v to 17v due to solar radiation
as shown in table, the output voltage of the converter will
also changes and error will generated accordingly the
control circuit and this error signal after comparing with
triangular wave is used for triggering the four IGBT and it
will maintain the output voltage of converter to 230v dc
constant. Now this 230v dc is converted to 230v AC with A
unipolar PWM modulation scheme is shown in Figure6.4
where the two switch pairs in H-bridge inverter are not
always switched simultaneously as in the bipolar scheme.
Instead, the switching of the two arms in Fig.12 is
controlled by two control signals. Therefore, the output
voltage changes between 0 and +230 or between 0 and 230 in half fundamental period as shown in fig13. Two
control reference signals are used in this scheme as shown
in fig11. and also in table show the variation in output
voltage and power using this control topology when the
input supply voltage changes due to variation in solar
radiation.
30
Vin
Delta
Vinverter
Power
Delta
Delta
D.C
Vin
A.C Volt Amp
(watt)
Vinverter
P
Volt
Volt
%
%
22
10 %
259.7
1.29
335.01
12.09
25
21.5
7.5 %
252
1.26
317.52
8.87
19
21
5%
245
1.22
298.9
5.8
12
20.5
2.5 %
237.08
1.18
280.72
2.8
5.6
19.5
2.5 %
230.39
1.15
264.94
0.0462
0.26
19
5%
229.7
1.148
263.69
0.39
0.73
18.5
7.5%
229.35
1.146
262.83
0.54
1.06
18
10 %
230.45
1.152
265.48
0.43
0.06
IL
Fig 11 switching of the two arms using unipolar PWM
modulation scheme
Fig 12 output current and voltage waveform of
sim software
inverter in p-
2.7 Simulation result and discussion
In fig 12 and
table 1 show the simulation result of
inverter with above topology so we can see the variation in
inverter output power when there is a small variation in
input supply or variation in solar panel power output
due to change in solar radiation during the day.
3. Conclusion
Fig. 11
Switching signal of the two arms of PWM modulation scheme
Table 1 variation in inverter o/p power when there is a
Small variation in input supply
These inverter topologies can be used for
photovoltaic applications and particular inverters for the
AC-Module. The task for such an inverter is to amplify
the photovoltaic-module low voltage up to the higher-level
voltage of the grid and to convert it from DC into AC. and
maintain it constant as there is a variation in atmospheric
International Journal of Emerging Trends in Electrical and Electronics (IJETEE – ISSN: 2320-9569)
Vol. 4, Issue. 1, June-2013
Brijesh M. Patel, Kalpesh J.Chudasma, Hardik A.Shah
condition or in solar radiation during the whole day.
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[1]Mr. B.M. Patel was born in visnagar, India, in 1986. He received his B.
E. degree from L.C.I.T. Bhandu, and M.E. from B.V.M College V.V.
Nagar under S.P. University. Presently he is working asAssistant Professor
in A.D. Patel institute of technology New V.V Nagar
[2]Mr.H.A.Shah was born in umreth, India, in 1979. He received his B. E.
degree from B.V.M, V.V. Nagar, and M.E. from M.S. University,baroda.
Presently he is working as Associate Professor in A.D. Patel institute of
technology New V.V Nagar
[3] Mr.K.J Chudasma was born in umreth, India, in 1974. He received his
B. E. degree from B.V.M, V.V. Nagar, and M.E. from B.V.M. College
V.V.Nagar under S.P. University. Presently he is working as Associate
Professor in A.D. Patel institute of technology New V.V Nagar
International Journal of Emerging Trends in Electrical and Electronics (IJETEE – ISSN: 2320-9569)
Vol. 4, Issue. 1, June-2013