4810 IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 30, NO. 9, SEPTEMBER 2015
Fig. 1. Block diagram of PV-powered centrifugal pump. (a) Conventional two
stage. (b) Conventional single stage. (c) Proposed single stage.
Recently, Makhlouf et al.  have suggested the closed-loop
vector control for the PV pumping system using a single-stage
multilevel pulse width modulation (PWM) converter. While this
system results in low motor losses, it is more complex with
more number of control variables and sensors. Most recently,
Perp´etuo Corrˆea et al.  have published a paper with a stand-
alone PV pumping system. It is also a single-stage system,
wherein the authors have proposed MPPT and minimum losses
point tracking methods of control. However, this system requires
more number of sensors, and results in low bandwidth for PV
Thus, from the previous discussion, it is evident there is a
requirement for a low-cost, low-voltage single-stage power con-
version PV water pumping system with wide bandwidth of PV
operating voltage. Also, the three-level/multilevel inverter with
a low dc-bus voltage could be a better solution as the perfor-
mance of this system improves with the increased number of
levels/steps in the inverter output voltage. Also, many investi-
gations on open-end winding induction motor (OEWIM) with
multilevel inverters are documented in the literature –.
Further various PWM techniques and control schemes –
for OEWIM drive have been analyzed by various researchers. In
short, OEWIM promises to provide effective solutions for drive
application as compared to common neutral IM . Apart from
high reliability and redundancy , , OEWIM has many
good features as discussed in the next paragraph.
One of the most important feature of OEWIM is it uses two
two-level voltage-source inverters (VSIs) to achieve three-level
inversion . It also lowers voltage rating of semiconduc-
tor devices and input dc-bus electrolytic capacitor . This
can be attributed to the fact that dc-bus voltage is designed
based on maximum value of phase voltage instead of line-to-line
voltage. The decoupled PWM technique increases the apparent
switching frequency of switching devices, reducing the ripple
in the motor phase current. Unlike the conventional three-phase
neutral point-clamped three-level inverter, wherein the dc-link
capacitor is constrained to carry load current leading to large
ﬂuctuations of voltage of the dc-neutral point, the dc-link ca-
pacitor of OEWIM carries only the ripple current, thus resulting
a negligible voltage ﬂuctuations . This increases the life and
reliability of the dc-bus capacitor or in other words the relia-
bility of the inverter system, which is of paramount interest for
systems connected to the PV source.
Thus, OEWIM coupled with the PV source could be a good
proposition. This paper presents one such solution for a simple
water-pump application as depicted in Fig. 1(c). The proposed
system has the following features:
1) it is an economical system as it uses a single power con-
2) it has inherent low dc-bus voltage requirement with V/f
control integrated with MPPT and uses three-level (dc–
ac) inversion for better performance of motor;
3) low input dc-bus voltage requirement reduces the voltage
rating of dc-link capacitor and increases bandwidth of PV
operating voltage, it also reduces the voltage rating of the
semiconductor devices used in the inverter;
4) it optimally uses the PV source for all environmental con-
ditions by operating it at MPP, also, it employs V/f control
integrated in the MPPT algorithm which improves the per-
formance of the motor and requires less number of sensors
for its operation;
5) three-level output with the decoupled sample-averaged
zero-sequence elimination (DSAZE) algorithm  fur-
ther improves the performance with reduced motor current
Rest of this paper is divided into four sections. Section II gives
details of modeling of the proposed system. Section III describes
the operation and analysis of the proposed system. Section IV
describes the control strategy and algorithm proposed. Section
V depicts the simulation and experimental results obtained. It
also gives the detailed cost analysis and comparison for the
proposed system with the existing system(s).
II. MODELING OF THE PROPOSED SYSTEM
A proposed conﬁguration of the solar PV-powered pumping
system is shown in Fig. 2, which comprises of: 1) solar PV
array; 2) dual-inverter namely Inverters I and II; 3) three-phase
OEWIM with pump load; and 4) controller block which consists
of MPPT and DSAZE PWM algorithm. These components are
described in detail in the following sections.
A. PV Source Model
The PV source was modeled by using PV cell current–voltage
characteristic equation as follows :
ipvcell = iL − i0 e
q (v p v c e ll + i p v c e ll R s )
n k T − 1 (1)
JAIN et al.: SINGLE-STAGE PHOTOVOLTAIC SYSTEM FOR A DUAL-INVERTER-FED OPEN-END WINDING INDUCTION MOTOR DRIVE 4811
Fig. 2. Schematic circuit diagram of the proposed system.
where ipvcell is PV cell current, iL is photocurrent, i0 is diode
saturation current, n is diode quality or ideality factor, k is Boltz-
mann constant, q is electron charge, T is panel operating tem-
perature in Kelvin, Rs is PV cell series resistance, and vpvcell is
PV cell voltage (V).
The output of PV source is connected to inverter with dc-bus
capacitance Cpv . By applying KCL at input of the inverter [from
ipv = ic + iinv ⇒ ipv = Cpv
+ iinv . (2)
Integral solution of (2) is the voltage vpv across capacitance
Cpv , which is used by the PV model to calculate the PV source
current. The inverter current iinv is the current drawn by In-
verters I and II. Further dual inverter has two series connected
equal value capacitors across the dc link. These capacitors share
equal voltage with respect to the common point “o” as shown
in Fig. 2.
B. Modular Three-Level Dual-Inverter Model
Dual inverter used in the proposed conﬁguration is modeled
using switching functions . To model dual inverter, switch-
ing function SW (where W can be A, B, C, A’, B’ or C’ depending
on the phase and number of inverter) requires the logic gener-
ated from the PWM controller. It has value 1 and –1 which
represents turn ON of top and bottom switch, respectively, for
the given leg or phase of the inverter. The modular dual inverter
shown in Fig. 2 consists of six poles (a, b, c, a’, b’, and c’)
and 12 switches (two switches per pole). The value of the pole
voltages in a particular phase can be ±Vpv /2 depending on the
switch (whether top or bottom) is turned ON. If top switch of
phase “a”, S1 is turned ON, the pole voltage vao is +Vpv /2 and
when bottom switch of phase “a”, S4 is turned ON, then the pole
voltage vao is −Vpv /2. Thus, pole voltage of Inverter I can be
vao = SA
; vbo = SB
; vco = SC
Fig. 3. OEWIM model.
Similarly, pole voltage of Inverter II can be given as
va o = SA
; vb o = SB
; vc o = SC
The motor phase voltage vaa is given by
(SA − SA ) −
((SB − SB ) + (SC − SC )) .
Similarly, the other phase voltages vbb , vcc of the inverter
output can be derived for the system. Further, the input inverter
current iinv can also be derived using switching functions. Cur-
rent ﬂowing through Inverter I is given by
(SA + 1)iaa +
(SB + 1)ibb +
(SC + 1)icc .
Current ﬂowing through the Inverter II is given by
(SA + 1)(−iaa ) +
(SB + 1)(−ibb )
(SC + 1)(−icc ). (7)
The net current ﬂowing through the dual inverter is
iaa (SA − SA ) +
ibb (SB − SB )
icc (SC − SC ). (8)
Thus, the previous values of phase voltage and current can be
used by the Simulink model of OEWIM, which is discussed in
the next section.
C. OEWIM Model
An OEWIM  is obtained by opening the neutral point
of the star-connected stator windings of a normal three-phase
IM. The winding diagram of three-phase OEWIM is shown in
For modeling and analysis, the decoupled form of OEWIM
is considered. For transforming the stator (φ = θ) and the ro-
tor parameters (φ = β) to decoupled form, the transformation
4812 IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 30, NO. 9, SEPTEMBER 2015
matrix used is given as follows:
cos φ cos (φ − 2π/3) cos (φ + 2π/3)
sin φ sin (φ − 2π/3) sin (φ + 2π/3)
1/2 1/2 1/2
whereθ is theanglebetweenthestator as-axis andthequadrature
(q) axis, β is the angle between rotor ar-axis and the q-axis, also
β = θ − θr , θr is the angle between rotor ar-axis and stator as-
axis (see Fig. 3), parameter x can be either voltage “v” or current
“i” or ﬂux linkage “λ” and subscript parameter y can be “s” or
“r.” The subscript “s” denotes the parameters of stator and the
subscript “r” denotes the parameters of rotor.
The dynamic d–q model of an OEWIM is described by
vqs = Rsiqs + ω(Llsids + Lm (ids + idr )) + pλqs (10)
vds = Rsids − ω(Llsiqs + Lm (iqs + iqr )) + pλds (11)
vqr = Rr iqr + (ω − ωr )(Llr idr + Lm (ids + idr )) + pλqr
vdr = Rr idr − (ω − ωr )(Llr iqr + Lm (iqs + iqr )) + pλdr
where Rr is rotor resistance, Rs is stator resistance, Lls is sta-
tor leakage inductance, L’lr is rotor leakage inductance, Lm is
mutual inductance between stator and rotor winding, ω is the
synchronous speed, ωr is the electrical speed of motor, and p
denotes the time derivative. Also, here v qr = v dr = 0, since
rotor bars are short-circuited.
The expression for the electromagnetic torque Tem is given
Lm [iqsidr − idsiqr ] (14)
where P is the number of poles.
The mechanical equation governing the OEWIM-pump drive
is expressed as follows:
Tem = J
rmech + TL (15)
where J is motor inertia (kg · m2
), B is centrifugal load torque
coefﬁcient, TL is load torque (N · m), and ωrmech is instantaneous
angular velocity of motor shaft (rad/s).
III. OPERATION AND ANALYSIS OF THE PROPOSED SYSTEM
The proposed dual inverter is operated by using the decou-
pled PWM strategy. It incorporates simple V/f control for the
efﬁcient operation of system below the rated speed. The pro-
posed PWM strategy requires the information of magnitude and
angle of the reference voltage vector. The magnitude is calcu-
lated and controlled by the MPPT algorithm and the angle “α”
is the function of time and fundamental frequency of reference
Fig. 4. Demonstration and comparison of dc-bus voltage requirement for H-
bridge and dual-inverter systems. (a) Schematic circuit diagram of the two-level
H-bridge inverter with input dc voltage (PV voltage) of “Vpv .” (b) Space vector
locations of voltage vector obtained from two-level inverter. (c) Schematic
circuit diagram of dual-inverter-fed OEWIM drive with input dc voltage (PV
voltage) of “Vpv /2.” (d) Space vector locations of voltage vector obtained from
three-level dual-inverter scheme.
modulating waveform. The reference voltage vector |vsr|ࢬα is
further divided into two decoupled components |vsr|/2 ࢬ α and
|vsr|/2 ࢬ (180 + α). The decoupled components are then given as
the reference vector for Inverters I and II, respectively, as shown
in Fig. 2, for generation of required output voltage. Thus, using
decoupled PWM conﬁguration has the beneﬁt of double output
A. Low Input DC-Bus Voltage Requirement of Dual Inverter
for OEWIM-Pump Drive
To analytically verify the low input dc-bus voltage require-
ment, a comparison between two-level and dual-inverter-fed
OEWIM is done. Both the inverters are compared for generat-
ing the same output voltage vector with different values of input
PV source voltage. The low input voltage requirement of dual
inverter for an OEWIM drive is demonstrated in Fig. 4.
Let the PV source voltage required to generate the rated in-
stantaneous IM phase voltage van is Vpv as shown in Fig. 4(a).
From Fig. 4(a) and (b), the inverter output voltage, van , vbn , and
vcn can be obtained using the inverter pole voltage, vao, vbo , and
vco; and switching functions SA , SB , and SC as follows:
van = vao − vno =
(SB + SC )
where vno is common-mode voltage given by
(vao + vbo + vco) =
(SA + SB + SC )
Thus, the space vector location of reference voltage vector
OA [see Fig. 4(b)] can be generated by the switching functions
SA = 1, SB = −1, and SC = −1. Substituting these values into
(17) will result in the phase voltage, van as 2Vpv /3.
Now, consider the three-phase, three-level dual inverter con-
nected to an OEWIM as shown in Fig. 4(c). Let the input PV
source voltage is Vpv /2, which is half of the voltage taken for
two-level H-bridge inverter. Now, the dual inverter output phase
JAIN et al.: SINGLE-STAGE PHOTOVOLTAIC SYSTEM FOR A DUAL-INVERTER-FED OPEN-END WINDING INDUCTION MOTOR DRIVE 4813
OG [see Fig. 4(d)] is given as
vaa = vao − va o − voo (18)
where voo is the common mode voltage [see Fig. 4(c)] which is
[(SA − SA ) + (SB − SB ) + (SC − SC )].
Therefore, vaa is given by
(SA − SA )−
[(SB − SB ) + (SC − SC )]
So, to generate voltage vector
OG [see Fig. 4(d)], the switch-
ing functions required are SA = 1, SB = −1, and SC = −1;
SA = −1, SB = 1, and SC = 1. Substituting these values in
(20), results in the phase voltage of magnitude 2Vpv /3 corre-
sponding to phase aa’.
Hence, to generate the phase voltage of 2Vpv /3, the PV source
voltage required in case of two-level inverter is Vpv and in
case of dual inverter connected to OEWIM is Vpv /2. However,
the DSAZE PWM technique  needs excess 15% of dc-link
voltage to generate the rated motor phase voltage.
IV. CONTROL STRATEGY AND MPPT ALGORITHM
The solar PV-powered-fed dual inverter connected to
OEWIM-pump drive is operated using a simple control strategy,
which simultaneously accomplishes MPPT and DSAZE PWM
integrated together. This integrated algorithm generates the re-
quired PWM control signals for the modular dual inverter. The
ﬂowchart of control algorithm is shown in Fig. 5. The MPPT part
of algorithm facilitates motor-pump drive to extract maximum
available power from the PV source, thereby assuring effective
utilization of the PV source. The DSAZE PWM part of the algo-
rithm incorporates V/f control. It maintains constant rated ﬂux
in the motor which retains the maximum torque capability of the
machine for the given PV power. Thus, in pump drive applica-
tion where torque is proportional to square of speed, maintaining
the maximum torque further helps in maximum utilization of the
A. MPPT Algorithm
One of the simplest, most popular, and commercially used
methods of MPPT, namely, the Hill Climbing algorithm 
is employed in the proposed system. The algorithm ﬁrst senses
the voltage (vpv ) and current (ipv ) of PV array for calculating the
power (ppv ). The calculated and sensed PV power and voltage
are then compared with their previous value to determine the
slope of the operating point. The considered slope then deter-
mines the correction for modulation index (ma). With respect to
sign of the slope (negative or positive), the value of ma is modi-
ﬁed (incremented or decremented) as described in the ﬂowchart
shown in Fig. 5 until the operating point reaches near MPP.
The calculated value of ma is then used by the DSAZE PWM
Fig. 5. Flowchart of the MPPT, DSAZE algorithm used in the proposed
B. DSAZE PWM Algorithm
The magnitude of the reference voltage vector generated by
the MPPT output and angle “α” is decomposed into the in-
stantaneous three-phase reference voltage vas, vbs, and vcs for
Inverter I. The gating time Tgj (j = a, b, c) for top switches of
Inverter I (see Fig. 2) is then obtained by the switching algo-
rithm . This algorithm  requires instantaneous values
of the reference phase voltage for calculating the effective time
(time for which all the active vectors are switched) or turned
ON time for top switches. The position of effective time period
can be adjusted in such a way that the offset time is equal to
Ts/2 within a switching period. This feature is exploited by the
DSAZE PWM technique to eliminate the zero sequence voltage
within a sampling period.
As DSAZE is a center-spaced PWM technique for the dual-
inverter system, the ripple content in current is less and hence
results in the improvement of developed torque. The other
4814 IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 30, NO. 9, SEPTEMBER 2015
Fig. 6. Simulation results showing waveforms at PV source side.
advantage of the DSAZE PWM algorithm for OEWIM drive
is that it requires less memory and computing time for process-
ing. As both the reference voltage vectors for Inverters I and II
are in the phase opposition, the gating time Tgj (j = a, b, c) for
the top switches of Inverter II are directly obtained using the
gating time for Inverter I as follows:
Tgj = Ts − Tgj (21)
where j = a, b, c and Ts is the inverter switching time period(s).
Complement of the respective gating signals for Inverters I
and II are generated for bottom switches for both inverters.
V. SIMULATION AND EXPERIMENTAL RESULTS WITH
A. Simulation Results
The single-stage PV-powered OEWIM drive for pump appli-
cation, shown in Fig. 2, is simulated using MATLAB/Simulink.
A 3.6 kW (20 × 3) PV array feeding power to a 4 kW
OEWIM-pump drive is considered for simulation. The Solarex
MSX60 PV panel parameters under standard test conditions
are Voc = 21 V, Isc = 3.74A, Vm = 17.1 V, Im = 3.5 A, and
Pm = 59.9 W. A dc-bus capacitor (Cpv ) of value 1000 μF is
used at the output of PV source. A four-pole, 400 V, 1430 r/min
IM is used. Further the important parameters of the mo-
tor are Rs = 1.405 W, Rr = 1.395 W, xls = xlr = 1.8344 W,
and xm = 54.0982 W. Simulations are performed by consider-
ing 96 samples per cycle of applied fundamental voltage, irre-
spective of the modulation index. This means that the switching
frequency is a variable quantity. The switching frequency varies
from 1.28 kHz (corresponding to a modulation index, ma = 0.2
with fundamental frequency f = 13.33 Hz) to 4.8 kHz (corre-
sponding to a modulation index, ma ≥ 0.75 with fundamental
frequency f = 50 Hz).
Fig. 6 shows the simulation results of the proposed system
under different environmental conditions for PV source-side
parameters. The increasing and decreasing nature of PV power
with respect to insolation (G) and temperature (T) can be ob-
served with the waveforms of PV power and ma . This veriﬁes the
MPP tracking, further small oscillations in the value of ma near
Fig. 7. Simulation results showing waveforms at motor-pump side.
MPP and small ripple content in a PV power conﬁrms the oper-
ation near optimum voltage. Also, another useful observation in
the simulation results is that the operating voltage of PV array
passes through optimum voltage for every step increase in inso-
lation and temperature. This can be justiﬁed with the matching
values of peak power value during transient tracking and steady
state near MPP as given in the PV power subplot. Further, it can
be noted that PV voltage waveform shows a sudden rise and fall
in the value with the step increase in insolation and temperature.
This can be attributed to charging and discharging of PV capac-
itor CP V with excess or deﬁcit PV power, respectively, during
Fig. 7 shows the motor-side parameters for different environ-
mental conditions. Variation on ma with respect to PV power
can also be seen here in the waveform of torque, speed, and
mechanical power output. It can be observed that torque, speed,
and mechanical power output follow ma or the PV power indi-
rectly. Also, it can be easily observed that slip power too follows
ma. Thus, slip power loss increases and decreases with increase
and decrease of PV power, respectively. This may help in keep-
ing small variation in efﬁciency which can be observed from
last subplot of Fig. 7. Also, another important feature that re-
late results of Figs. 6 and 7 is motor phase voltage plot. The
transient variations in PV voltage Vpv during step increase in
insolation can be depicted with a peak value of motor phase
Another typical observation between Figs. 7 and 8 is the rip-
ple contents in the torque waveform and motor phase current
follows ma. It can be observed that torque ripple is more dur-
ing lower insolation and decreases as insolation increases. This
JAIN et al.: SINGLE-STAGE PHOTOVOLTAIC SYSTEM FOR A DUAL-INVERTER-FED OPEN-END WINDING INDUCTION MOTOR DRIVE 4815
Fig. 8. Harmonic spectrum of motor phase current (iaa ) at steady state ob-
tained from simulation under different environmental conditions: (a) at 0.1
insolation and 25 °C; (b) at 0.6 insolation and 35 °C; (c) at 1.0 insolation and
can be attributed to the fact that the increase and decrease of
ripple content in the motor phase current will result in the in-
crease and decrease of the torque ripple, respectively. Further,
it can be noted that the amplitude of motor phase current also
follows ma and total harmonic distortion (THD) of motor phase
current decreases with increase in insolation. Thus, in short,
system performance improves with increase in PV power. This
can be observed in Table I, where the simulation results are
B. Experimental Results
To verify simulation results, a prototype of the proposed sys-
tem is developed. To emulate PV characteristics, a dc power
supply with ﬁxed series resistance is used. The power sup-
ply is operated in constant voltage mode with variable cur-
rent limit. The three-phase OEWIM with speciﬁcations 440 V,
SUMMARY OF SIMULATION RESULTS FOR THE PROPOSED SYSTEM
η (%) Speed
0.1 25 329 240 72.95 352 6.5 4.74 12 11.94
0.3 30 1040 895 86.06 740 11.6 3.62 33.5 8.58
0.6 35 2133 1902 89.17 1026 17.7 3.8 75.25 5.06
0.8 45 2763 2465 89.21 1139 20.65 4.24 109.25 4.28
0.9 50 3072 2735 89.03 1187 22 4.46 128 3.97
1 55 3365 2990 88.86 1229 23.25 4.7 147.5 3.77
Fig. 9. DSAZE PWM modulating waveforms for leg a and a’ of Inverters I and
II: (a) from simulation (Vpv ≈ 320 V and ma = 0.64), (b) from experimental
setup (Vpv ≈ 110 V and ma = 0.5) (x-axis: simulation time (s); y-axis: gate
Fig. 10. α–β plot of three-phase vo1tage input to OEWIM obtained from: (a)
simulation (Vpv ≈ 320 V and ma = 0.64) and (b) experimental setup (Vpv ≈
110 V and ma = 0.5).
1.5 A, 1440 r/min, and 1 hp is used with fan type of cen-
trifugal load which guarantee the operation for water-pump
load proﬁle. The motor is fed from the dual inverter which
uses Semikron insulated-gate bipolar transistor (IGBT) mod-
ule (SKM75GB128DN). Gate pulses required by IGBT module
is generated from dSPACE 2201 and is given via a driver IC
(HCPL 316J). The control algorithm implemented in dSPACE
includes the MPPT and V/f control with DSAZE PWM for the
OEWIM coupled to a centrifugal torque load. This control al-
gorithm can also be implemented using a low-cost Freescale
semiconductor made MC56F8013 signal controller. For track-
ing MPP of the source, a voltage sensor (LV25-P, 600 V rms,
10/25 mA) to sense the terminal voltage and a current sensor
(Tektronix A622, 0–70 A rms, 100 mV/A) to sense the PV cur-
rent are used. The sensed voltage and current are given to the
computing system through the ADC’s of dSPACE. The comput-
ing system internally generates the value of ma required for the
4816 IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 30, NO. 9, SEPTEMBER 2015
Fig. 11. Experimental results for the proposed system on the dc source side, i.e., source voltage, current, power, and the modulation index: (a) under starting
condition, (b) under running condition, and (c) for various emulated environmental conditions.
DSAZE PWM algorithm to calculate Tgj and Tgj for Inverters
I and II, respectively (see Fig. 5).
Fig. 9 gives the waveform for Tga and Tga obtained from
simulation and experimental setup. The complementary nature
of Tga and Tga can be observed in the waveforms. This veri-
ﬁes the utilization of the decoupled PWM strategy. Further, as
proved decoupled PWM also reduces the required value of dc-
bus voltage which can be depicted from Fig. 10. In this ﬁgure,
the plots of phase voltage vector in αβ plane obtained from
simulation and experimental results were shown. Requirement
of low dc-bus voltage can be easily veriﬁed with the given input
values of ma and input PV voltage of the inverter as mentioned
in Fig. 10(a) and (b). The synchronization of change in ma
after one complete cycle can be depicted from zoom-in part
of Fig. 10(a). If this synchronization between MPPT and V/f
control is disturbed in the ﬁeld, then it may result in a poor per-
formance of the system. This can be taken care of by assuring
proper synchronization between MPPT and V/f control under
all ﬁeld conditions. The other drawback in the ﬁeld may be the
inverter failure. If an inverter fails, a rewiring would enable the
healthy inverter to deliver partial load. In other words, the fault
tolerance with OEWIM is more compared to the conventional
two-level VSI drive. Also, the power cable required to connect
the OEWIM and inverter is double compared to the conventional
two-level VSI drive. However, this drawback in the ﬁeld can be
taken care by minimizing the distance between inverter and the
Fig. 11 gives the experimental results for the parameters at the
input side of inverter. Increasing value of modulation index and
input power conﬁrms the MPP tracking which can be seen in
Fig. 11(a). Oscillations near MPP can be observed in Fig. 11(b).
More number of oscillations in ma near MPP can be attributed
to sharp power–voltage characteristics of input source and the
algorithm used. However, operation near MPP can be observed
in the waveform of source power. Also, to emulate various en-
vironmental conditions in the PV system, the current limit of
programmable power supply is changed from 0.3 to 0.5 A and
again back to 0.3 A. This would nearly emulate the increasing
and decreasing insolation in the PV array system. Fig. 11(c)
shows experimental results obtained from developed test setup
for this condition. The increasing and decreasing value of ma
Fig. 12. Experimental results for the proposed system at motor-pump side,
i.e., motor phase voltage and current: (a) under starting condition and (b) under
Fig. 13. Motor aa’—phase current and its harmonic spectrum: (a) under
starting condition and (b) under running condition.
and source power shows MPP tracking for various environmen-
tal conditions. As fan type load has approximately similar char-
acteristics to centrifugal water pump load, so nearly the same
performance is accepted with actual water pump load systems.
Fig. 12 shows the experimental results for the parameters at
the inverter output. Implementation of V/f control can be veri-
ﬁed by variable frequency operation under starting and running
conditions. At starting when the value of ma is low, the operating
frequency is kept low and near MPP when ma value becomes
high frequency of phase voltage also increases. The motor “aa”
phase current waveform along with its harmonic spectrum under
starting and running conditions is shown in Fig. 13(a) and (b),
respectively. The harmonic spectrum under starting and running
conditions is comparative with the harmonic spectrum of cur-
rent at low and high insolation (see Fig. 8), respectively. Another
important thing is that the typical pattern of ripple in the cur-
rent waveform shown in Fig. 13 is matching with the simulation
results given in Fig. 8.
JAIN et al.: SINGLE-STAGE PHOTOVOLTAIC SYSTEM FOR A DUAL-INVERTER-FED OPEN-END WINDING INDUCTION MOTOR DRIVE 4817
COST COMPARISON BETWEEN THE PROPOSED SYSTEM WITH TWO BASIC
TOPOLOGIES AVAILABLE IN THE LITERATURE FOR PUMP APPLICATION
Item / part no. Using conventional induction motor Using OEWIM
2-stage 2-level  1-stage 2-level
PWMs PWMs PWMs
4 3 6
ADCs ADCs ADCs
3 2 2
Flash / RAM Flash / RAM Flash / RAM
Medium Less Less
Controller MC56F8013 MC56F8013 MC56F8013
$ 4 $ 4 $ 4
2 1 1
$ 120 $ 60 $ 60
1 1 1
$ 23.68 $ 23.68 $ 23.68
Miscellaneous $ 20 $ 10 $ 20
Sub-total $167.68 $97.68 $107.68
DC- link capacitors
4 4 2
$ 155.84 $ 155.84 $ 77.92
6 (900V, 28A)/
6 (900V, 28A)/
12 (400V, 20A)/
$ 31.68 $ 31.68 $ 39.36
Driver circuit $ 26 $ 26 $ 52
Sub-total $213.52 $213.52 $169.28
1 NA NA
$ 25.6 — —
3 NA NA
$116.88 — —
1 NA NA
$ 5.44 — —
Diode/ D22–25–12 1 NA NA
$ 6.16 — —
Driver circuit $ 5 NA NA
Sub-total $ 159.08 — —
TOTAL $540.28 $311.20 $276.96
∗ Switches are chosen with respect to the availability of the devices with nearest rating.
C. Cost Analysis
A brief cost analysis has been carried out (see Table II) for the
three topologies presented in Fig. 1. The cost values presented
in Table II are only for the inverter and converter. The IM-pump
and the PV panel costs are assumed to be nearly similar (since
the same power rating is considered) for all the three topologies.
When compared to a two-stage system, the proposed one is a low
cost because of the nonrequirement of an extra dc–dc converter.
Also, the lower cost of the proposed system compared to the
conventional single-stage two level is because of the requisition
of low-voltage dc-link capacitors and switching devices.
In this paper, an integrated single-stage solution of PV-fed
pump drive is presented. The proposed system has the feature
of low dc-bus voltage requirement, MPPT integrated with V/f,
three-level inverter operation and low cost. Analytical proof for
low dc-bus voltage requirement in the proposed system is pre-
sented. Implementation of V/f with MPPT can be veriﬁed with
simulation and experimental results. Thus, a high-performance
integrated solution is proposed. Low cost of the proposed sys-
tem can be attributed to the requirement of low voltage dc-link
bus capacitor, low voltage rating switches, and less number of
sensors for the integrated control operation which is presented
in Table II. Thus, in all, this paper presents one of the effective
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Sachin Jain is currently working as an Assistant Pro-
fessor at the National Institute of Technology (NIT-
W),Warangal, India. Before joining NIT-W, he was
working as an Senior Design Engineer in the R&D
Department of the Solar Energy Business Group of
Schneider Electric at Bangalore. His research inter-
ests include power electronics applications in non-
conventional energy conditioning, power quality, and
Athieshkumar T received the B.Tech. and M.Tech
degrees from the VR Siddhartha Engineering Col-
lege, and the National Institute of Technology
(NITW), Warangal, India, respectively.
He is currently working as an Engineer in VEM
Technologies, Hyderabad. His areaof interests in-
clude photovoltaic pumping systems, integration of
renewable energy sources to power electronic con-
verters, and switching-mode power supplies.
Ramsha Karampuri received the B.Tech. and
M.Tech degrees from S.R.I.T, J.N.T. University, and
V.N.I.T., Nagpur, India, respectively. He is currently
working toward the Ph.D. degree in electrical engi-
neering from the National Institute of Technology
(NITW), Warangal, India.
His research interests include power electronics
and drives, and application of power electronics to
non-conventional energy conditioning.
V. T. Somasekhar(M’11) received the Graduate de-
gree from the Regional Engineering College Waran-
gal (currently, the National Institute of Technology),
Warangal, India, in 1988, the Postgraduate degree
from the Indian Institute of Technology, Bombay, In-
dia, in 1990, and the Doctoral degree from the Indian
Institute of Science, Bangalore, India, in 2003.
From 1990 to 1993, he was a Research and De-
velopment Engineer with Perpetual Power Technolo-
gies, Bangalore, and a Senior Engineer with Kirloskar
Electric Company, Ltd., Mysore, India. Since 1993,
he has been with the National Institute of Technology,Warangal, India, where
he is currently a Professor. His research interests include multilevel inversion
with open-end winding induction motors, ac drives, and pulse width-modulation