Performing Wind System with Rectifier with Near Sinusoidal
Input Current
IRINEL VALENTIN PLETEA, MARIANA PLETEA
Technical University “Gheorghe Asachi” of Iasi,
Faculty of Electronics, Telecommunications and Information Technology,
blv. Carol I, no.11, Iasi, cod 700508,
ROMANIA
Abstract: - The RNSIC-1 (rectifier with near sinusoidal input currents converter), is the foundation of a wind
generator system that is presented. The three inductances that make up a traditional RNSIC–1 converter are
eliminated in the proposed arrangement, and the SCIG generator's leakage inductances fill their place. This is
what makes it new. The wind system's role in the load currents is discussed. Lower power losses, smaller
harmonic input currents, fewer EMI issues, excellent dependability, and cheaper costs are characteristics of the
new wind system. This new wind system could be used for partial variable speed wind turbines (usually 70% to
100% synchronous speed) and lower hydro connector squirrel cage induction generators (SCIG).
Key-Words: - Power converter, AC-DC converter, PWM converter, three – phase rectifiers, squirrel-cage
induction generator, AC-DC power conversion.
Received: August 27, 2022. Revised: August 24, 2023. Accepted: September 21, 2023. Published: October 26, 2023.
1 Introduction
Although the cost of the energy they produce is still
expensive, the development of wind systems has
made some impressive strides in recent years. The
maximum output of a wind system should be
determined by wind speed, [1], [2].
Wind turbines are characterized by a simple
construction and dependability in operation in the
majority of solutions with constant speed.
Yet, the mechanics are put under strain by these
solutions. Induction generators are typically used in
systems with constant-speed wind turbines.
The usage of variable speed systems is a trend
in wind systems. The variety of applications and
generator types have increased as a result of the
development of systems with variable speed, [3],
[4].
A back-to-back PWM converter is used in the
rotor circuit of a double-fed induction generator
(DFIG) drive system for high-power applications.
The generator’s speed typically varies by more
than 30% of the synchronous speed.
Back-to-back systems, however, have the
drawback of using slip rings in the rotor circuit and
necessitating unique protective circuits, [5], [6], [7],
[8], [9], [10], [11].
The variable speed wind turbines are built to
provide the most electricity possible given the wind
speed.
The total installed wind power capacity rose
exponentially over the past few years, rising from
158 GW in 2009 to 283 GW by 2010, [3].
Small-to-medium-scale (1-100 kW) wind
turbines are pervasive, according to the British
Wind Energy Association and the American Wind
Energy Association.
Small-to-medium-sized wind turbines in the US
with 100kW or less in production made up about
20% of installed electricity generating in 2010.
The proposed wind farm in work can be an
economical solution for small and medium wind
turbines power up to several hundred kW.
2 New Wind Systems with a SCIG
and RNSIC – 1 Converter
A new variable–speed wind system is presented in
Figure 1. Electricity supplied by the SCIG is
transmitted over the network using an RNSIC - 1 of
a boost converter and a PWM inverter.
Figure 1 depicts a novel variable-speed wind
system. A boost converter and a PWM inverter
comprise the RNSIC-1, which is used to transmit
SCIG-supplied electricity through the network.
Three capacitive stages are present in a novel AC-
DC converter, [12]. Capacitors C1–C6 that are
permanently connected in parallel to diodes D1–D6
make up the first step. The switches K1, K3, and K5,
WSEAS TRANSACTIONS on POWER SYSTEMS
DOI: 10.37394/232016.2023.18.20
Irinel Valentin Pletea, Mariana Pletea
E-ISSN: 2224-350X
186
Volume 18, 2023
respectively, are connected in series with the
capacitors C11, C31, and C51 in the second stage.
Capacitors C41, C61, and C21 are connected in series
with switches K4, K6, and K2, respectively, to
complete the third step.
(a)
(b)
Fig. 1: (a) Scheme for calculating inductances Lm,
Lst, Lrot, and L1 ; (b) Wind system with SCIG and
RNSIC – 1 converter (without inductance L1)
Figure 1 depicts a novel variable-speed wind
system. A boost converter and a PWM inverter
comprise the RNSIC-1, which is used to transmit
SCIG-supplied electricity through the network.
Three capacitive stages are present in a novel AC-
DC converter, [12]. Capacitors C1–C6 that are
permanently connected in parallel to diodes D1–D6
make up the first step. The switches K1, K3, and K5,
respectively, are connected in series with the
capacitors C11, C31, and C51 in the second stage.
Capacitors C41, C61, and C21 are connected in series
with switches K4, K6, and K2, respectively, to
complete the third step.
The SCIG can operate at partial speed thanks to
the reactive power provided by the RNSIC-1
converter. When the generator speed changes
between 70% and 100%, the capacitive steps enable
an essentially constant magnetizing current. The
RNSIC-1 converter has the benefit of giving an
induction generator stator almost sinusoidal current.
At fixed-speed wind turbines, when the stator
currents have high harmonic content, this benefit is
not realized. The proposed converter in Figure 1
ensures a more balanced load for capacitors and
diodes when compared to the wind system solution
described in [12].
According to Figure 1, a boost DC-DC
converter can be added to the DC connection to
achieve a variable speed dependent on wind speed.
The input PWM inverter connected to the network is
used to apply the output voltage Vd from the RNSIC
- 1 converter, which amplifies the value of Vdc.
According to Figure 1, more IGBT transistors or
GTO transistors can be connected in parallel to
provide a greater power wind system of
approximately 1 to 2 MW. An AC-DC converter
that produces harmonics of low-valued stator
currents in SCIG is shown in Figure 1. Harmonics in
the distribution network's current or voltage do not
affect how this converter operates, [12].
We'll think about a load resistor with rated
current I(1)r and rated value RLr. Where Vmax is the
maximum AC input voltage and Vdc is the rectified
average voltage,
max
33
ref
VV
is the reference
voltage characteristic for three-phase rectifiers with
diodes. The rectifier's rated voltage is
2
1
12
dr ref
V V LC
.
The three L1 inductors shown in Figure 2 are
absent from the RNSIC - 1 in the proposed wind
system in Figure 1. This is one of the system's
primary distinguishing features. The three
equivalent circuits Leq, which are generated from the
SCIG generators, fill their place. The Leq inductors
can be thought of as lacking any loss resistance for
simplicity's sake, and their inductance merely
consists of the stator inductance Lst, rotor inductance
Lrot, and magnetization inductance Lm. A minimal
value of Vmin and a maximum value of Vmax are
represented by the power supplies Vg. About 0.7 is
the ratio between these figures. The stator currents
iR, iS, and iT of the SCIG are kept constant with
THD% values less than 5% when the L1 inductances
are replaced with Leq ones.
Fig. 2: RNSIC-1 converter with six DC capacitors
In Figure 3, the equivalent induction generator
circuit for the induction generator with iron losses
taken into account is shown.
WSEAS TRANSACTIONS on POWER SYSTEMS
DOI: 10.37394/232016.2023.18.20
Irinel Valentin Pletea, Mariana Pletea
E-ISSN: 2224-350X
187
Volume 18, 2023
Fig. 3: The equivalent circuit of the induction
generator in which the iron losses are taken into
account
The induction generator can supply electricity to
the network since the slip speed has a negative
value.
3 Operation of the Introduction
Generator Connected to the
Proposed Wind System
Based on the presence of a remanence Erem in the
rotor, the induction generator's self-excitation
process is shown in Figure 4, [1]. The resistive-
capacitive load for this generator is represented by
the RNSIC-1 converter in Figure 1 with several
capacitive stages. It can be observed that two or
three diodes may be in the pipeline by looking at the
waveforms of phase currents and conduction times
for the diodes D1 through D6 for large current Id in
Figure 5(a) and Figure 5(b).
Fig. 4: Variations of ratio Vm/Vmax as a function of
Img/I(1)r for different values of
s
The waveforms of phase currents and
conduction times for the tiny currents of Id are
shown in Figure 6(a) and Figure 6(b).
The fundamental harmonic of the phase current,
or IR(1), and the phase voltage, for instance, form a
negative angle. The voltage induction capacitive
current delivered by the battery reduces with a
decreasing frequency generator if a single-phase
capacitor is connected to the generator.
Fig. 5. Waveforms of phase currents for large values
of current Id (a) waveforms of currents iR, iS and iT
(b) DC id
The magnetizing current
(1) sin
mg r
II
has a
nearly constant amplitude without harmonics if you
use a battery with multiple parts. Through the use of
magnetizing inductance, K1–K6 switches are
adjusted to maintain a nearly constant magnetizing
current.
Given that the load resistance RL and the
currents iR, iS, and iT are essentially sinusoidal and
have amplitude, DC Id can be determined using the
equation:
1
1
31 cos
2
d
I
It
(1)
where t1 is the time in Figure 5(b) and Figure 6(b)
that is indicated. Time t1 diode opening equals
then DC Id be canceled, and currents iR, iS, and iT are
only capacitive.
WSEAS TRANSACTIONS on POWER SYSTEMS
DOI: 10.37394/232016.2023.18.20
Irinel Valentin Pletea, Mariana Pletea
E-ISSN: 2224-350X
188
Volume 18, 2023
Fig. 6: Waveforms of phase currents for low values
of current Id (a) waveforms of currents iR, iS and iT
(b) DC id
This circumstance happens when using a boost
converter.
The converter RNSIC – 1 DC capacitors
provide a virtually sinusoidal stator current for
SCIG while also adding 5% to 10% to C0 capacity.
If the capacitor C0 has a smaller capacity, for
example
02 1500CF
, the transient processes
in the wind system are reduced practically in half.
You can get such a period of transient decreased
from 100 ms to about 50 ms. Boost converter
consists of inductance L2, capacitors C0 and Cdc, and
GTO thyristors. Two thyristors that are connected in
antiparallel can be used to implement the switches.
Low currents that pass through these switches mean
that very little electricity is lost as a result. For the
fluctuation range between and, the average currents
that pass through the switches do not exceed (3 -
6%)I(1)r. The aforementioned average values are
required to select the thyristors for the switches.
Without inductances L1, the RNSIC-1
converter's capacitors serve a dual purpose. On the
one hand, they guarantee input currents iR, iS, and iT
that are close to sinusoidal, and on the other, some
capacitors connected in parallel with the capacitors
C0 at Vd enable a better load.
True, there are different DC capacities,
however, they can be used at a rate of 8% to 10% of
the capacitor C0. Compared to those of the AC type,
the DC capabilities are smaller and more affordable.
For the voltages applied capacities in the big current
mode regime, one can formulate the following
relations:
1 4 0C C C
V V V
(2)
3 6 0C C C
V V V
(3)
5 2 0C C C
V V V
(4)
This system is running in SCIG generator mode
at rated speed. If a battery of capacitors with a
specific value is connected to a SCIG generator
control, it can create a network of power. Depending
on the generator's speed, the SCIG generator
operation described in the paper is carried out in
three steps. Figure 7 depicts the power variation P
transmitted throughout three working steps by the
wind turbine of the shaft generator for various
values of wind speed Vw.
Fig. 7: Power delivered to the hub shaft at various
wind speeds
4 System Comparison of Wind
Turbines
Generally speaking, constant speed solutions are
characterized by a simple and reliable construction
of the electrical parts, while the mechanical parts are
subject to higher stresses and additional safety
factors must be incorporated in the mechanical
design. Most fixed-speed turbines use induction
generators. Figure 8a presents a version of the wind
systems, with fixed speed and with partially variable
speed.
This wind turbine has a fixed speed controlled
mechanism, with an asynchronous squirrel cage
induction generator (SCIG), which is directly
connected to the grid through a transformer. This
concept needs a reactive power compensator to
reduce (to eliminate almost entirely) the demand for
WSEAS TRANSACTIONS on POWER SYSTEMS
DOI: 10.37394/232016.2023.18.20
Irinel Valentin Pletea, Mariana Pletea
E-ISSN: 2224-350X
189
Volume 18, 2023
reactive power from the turbine generators to the
grid. A smoother grid connection takes place when
incorporating a soft starter as shown in Figure 8a.
Regardless of the aerodynamic power control
principle related to a fixed-speed wind turbine, wind
fluctuations are transformed into mechanical
fluctuations and, further, into electrical power
fluctuations. Thus, the main disadvantages of this
solution are: it does not support speed control, it
requires a stiff grid and its mechanical construction
must be able to support a high mechanical stress
produced by the wind.
Fig. 8: Variants of wind systems with constant
speed and partial variable speed. (a) Fixed speed
wind turbine with direct grid-connected squirrel-
cage induction generator; (b) Double-fed induction
generator using back-to-back PWM converter.
To surpass these issues, the tendency of modern
wind turbine technology is, without any doubt,
directed toward variable-speed concepts. The
Variable-speed systems offer a great number of
advantages, [3], [4], [5], [6], [7], [8], [10], [11]:
- the turbine can be adjusted to the local
conditions or imperfections related to blade
characteristics;
- reduced aerodynamic noise at a low wind speed
by decreasing the turbine speed;
- the useful energy captured on partial load is
maximized through the optimal speed operation;
- reduced power fluctuations;
- reduced lengthy stress on the rotor blades and
the transmission system.
The doubly fed induction generator that uses a
back-to-back PWM converter in the rotor circuit
(Scerbius drive) has been for a long time a standard
drive option for high-power applications involving a
limited speed range according to Figure 8b.
The stator is directly connected to the grid,
while a partial-scale power converter controls the
rotor frequency and thus the rotor speed. The power
rating of this partial-scale frequency converter
defines the speed range (typically ± 30% around
synchronous speed). The smaller frequency
converter makes these concepts economically
attractive. In this situation, the power electronics
enable the wind turbine to act as a dynamic power
source to the grid. However, its main disadvantages
are the use of slip-rings and the protection of
schemes/controllability in the case of grid
malfunctions.
The main advantage of the RNSIC - 1 converter
is that it provides the stator current practically
sinusoidal for the induction generator. This
advantage is not obtained in the case of fixed-speed
wind turbines, where the stator currents have high
harmonics. Compared with the wind system solution
presented in [14], the converter suggested in Figure
1b ensures a more balanced load for capacitors and
diodes.
To obtain a variable speed that depends on the
wind speed, a boost DC-DC converter can be
inserted in the DC connection, according to Figure
4. The output voltage Vd from the RNSIC - 1
converter increases the value of Vdc and applies the
input of the PWM inverter, connected to the
network.
When the performance of the various wind
turbine topologies is compared, a discrepancy
between cost and grid performance is revealed.
Specifically, the wind system presented in the
study, the double-feed induction generator (DFIG),
the brushless double-fed induction generator
(BDFIG), and the permanent magnet synchronous
generator (PMSG) are the only variable speed wind
systems to which further reference is made.
1. For equal power, SCIG is the simplest generator
that might have an RNSIC-1 converter on the
soil surface (without L1 inductances). This
indicates that the type with SCIG, [5], requires
less reinforced concrete for the pillars
supporting the wind system, [13].
2. The investment in the SCIG system is smaller as
a result of the aforementioned factors, [9].
3. A 30% speed synchronism variation of speed
limiters is possible with DFIG.
The usage of slip-rings and the controllability of
the protective schemes in the event of grid
faults, however, are its principal shortcomings.
About 30% of the power from the DFIG
generator can be contained in the three-phase
transformer. It is required because voltages on
the rotor rings must be kept to a minimum, even
if DFIG is directly connected to the grid, [4],
[5].
WSEAS TRANSACTIONS on POWER SYSTEMS
DOI: 10.37394/232016.2023.18.20
Irinel Valentin Pletea, Mariana Pletea
E-ISSN: 2224-350X
190
Volume 18, 2023
4. Due to its reduced cost and improved
dependability when compared to the standard
DFIG, the BDFIG exhibits commercial promise
for the generation of wind power. The BDFIG is
also thought to run at a speed between 30% of
synchronous speed. Many studies propose a
ride-through BDFIG control technique for low-
voltage applications. Additionally, a three-phase
transformer with a nominal power of 30% of the
generator's power is needed for this BDFIG
generator.
5. One of the highest levels of reliability can be
found in SCIG with an RNSIC-1 converter,
[12].
6. Low power losses are present in the paper's
description of the wind system. The stator
currents of SCIG are essentially sinusoidal, and
DC capacitors are minimal in size.
7. Even though PMSGs (with NdFeB magnets) are
more expensive than induction generators, they
will gain popularity as energy costs rise. the
price of the magnet is sufficiently low. In wind
systems, PMSGs will outperform induction
generators, [3]. The ability to vary the generator
speed between 0% and 100% of synchronous
speed is a benefit of PMSG, [3].
8. The limited range
40%
to only synchronous
speed is a drawback of wind systems with SCIG
and RNSIC-1 converters (without inductances
L1).
5 Experimental Results
Terminals R, S, and T were connected by a SCIG.
After that, the RNSIC-1 converter (without
inductances, L1 is regarded as null) was introduced.
According to Figure 1, the converter comprises 6
capacitors connected in series with switches K1–K6
for stages II and III and 6 capacitors connected in
parallel with diodes D1–D6. A DC motor with
variable speed is used to power the SCIG induction
generator between (0.7 and 1) synchronous speeds.
This generator of electricity operates with a
changing load resistance. The capacitor Cdc will
always have a voltage of 651 V thanks to the use of
the variable speed generator.
A prototype of a wind system with RNSIC -1
was subjected to investigation, lifting it out its
advantages, Figure 11.
The prototype is made up of the following
elements:
1. An induction generator with the following
parameters:
rated power 11 kW;
the value of the maximum phase stator
voltage Vmax = 311V;
the nominal stator current Igr = 24.2 A;
the maximum stator frequency is fmax = 50
Hz;
the minimum stator frequency is fmin = 35
Hz;
the stator leakage inductance is Lst = 0.010
H;
the rotor leakage inductance (referred to as
the stator) is Lrot = 0.010 H;
the magnetization inductance is Lm = 0.140
H.
2. An RNSIC – 1 converter with three capacitive
steps. Capacitors C1 - C6, have the value C = 55 µF,
and the other six capacitors which make up steps 2
and 3 have a capacity equal to 40 µF. The capacitor
C0 out of RNSIC -1 has a value of 3000 µF and
includes the contribution of approx. 165 µF - 245
µF.
3. The boost converter is composed of capacitors C0
and Cdc, the inductor L2 of 10 mH, the diode D2 and
the switch K.
4. A three-phase PWM voltage inverter with how
intelligent PS 12017 + power supply + mode control
HEF 4752, debited energy SCIG generator is
transmitted mains supply R, S, and T.
5. An oscilloscope TPS 2024 with 4 inputs current /
voltage electrical isolation between channels + a
soft harmonic analysis.
6. A DC motor of 12 kW with variable speed acting
SCIG model.
The magnetization inductance Lm depends on
the limits of the magnetization current. In general,
this current has a value between (0.35 – 0.45) of the
rated current. In what concerns the stator leakage
inductance Lst and the rotor leakage inductance Lrot
(referred to as the stator) are smaller than the
magnetization inductance Lm, having values of (0.05
– 0.10) Lm.
With the boost, the converter can adjust ceded
power for the load between zero and the maximum
value depending on wind speeds. The nominal
voltage Vdc can be computed with a (1% - 2%) error
due to the complexity of the equivalent inductance
Leq using the following equation:
max
2
max
33
12
dc
st rot
V
VL L C
(5)
To provide the practically sinusoidal iR, iS, and
iT currents, the following condition must fulfilled for
the RNSIC -1 converter.
WSEAS TRANSACTIONS on POWER SYSTEMS
DOI: 10.37394/232016.2023.18.20
Irinel Valentin Pletea, Mariana Pletea
E-ISSN: 2224-350X
191
Volume 18, 2023
2
max
0.08 0.12
st rot
L L C
(6)
Some experimental data is presented in Table 1
depending on the ratio
maxs
.
This ratio varies between 1.0 and 0.7. Table 1
presents a total capacity Ctot for one phase,
corresponding capacitive steps, namely 2x55, 150,
and 190 µF. The
mg gr
II
ratio, depending on the
maxm
VV
ratio is presented in Figure 4. If we had
adopted an RNSIC – 1 with more capacitive steps,
the variation of the magnetization current Img from
the average value would have been even smaller.
One way to turn off the generator sitting idle
SCIG consists of decoupling the stator windings
from the mains and introducing a continuous current
through these windings.
Figure 9 and Figure 10 illustrate the variation of
the iR stator current and of the Vd voltage at the
output of the RNSIC – 1 converter for two different
functioning cases. In the first case, corresponding
Figure 8(a) and Figure 8(b) switch from
max 0.95
s
to
max 0.75
s
. In the second
case, according to Figure 9(a) and Figure 9(b),
switching from
max 0.75
s
to
max 0.95
s
.
Table 1. System operation for the three
capacitive steps
According to the experimental findings shown
in Figure 8 and Figure 9, the wind system suggested
in Figure 1 can be employed as a partially variable-
speed system (usually 30% around synchronous
speed).
The main advantages of the wind system
proposed in Figure 1 are:
The SCIG generator has a lower size than a
DFIG generator with the same power.
Compared with the system proposed in
Figure 1, the back-to-back PWM converter
requires a three-phase transformer in the
rotor circuit. The transformer may have a
power output of 30 % of the DFIG and is
required to be restricted to the ring-rotor
circuit.
The proposed system has greater
reliability.
The rotation frequency of SCIG from
Figure 1 can be up to 30% higher than the
synchronization frequency.
Fig. 9: Experimental results for the transition
between the first functioning step, with
ωS/ωmax=0.95 and Ctot=110μF and the second
functioning step with ωS/ωmax=0.75 and Ctot=190μF
(a) stator current iR and (b) voltage Vd
Figure 9 shows the whole picture of the
suggested wind system, which must be taken into
account, and the DC motor drive system and SCIG
generator.
WSEAS TRANSACTIONS on POWER SYSTEMS
DOI: 10.37394/232016.2023.18.20
Irinel Valentin Pletea, Mariana Pletea
E-ISSN: 2224-350X
192
Volume 18, 2023
Fig. 10: Experimental results for the transition
between the third functioning step with
ωS/ωmax=0.75 and Ctot=190μF and the first
functioning step, with ωS/ωmax=0.95 and Ctot=110μF
(a) stator current iR and (b) voltage Vd
Fig. 11: Experimental system of RNSIC-1 (without
inductances L1), capacitor C0, inductance L2, and
capacitor Cdc.
6 Conclusions
We have introduced a brand-new wind system with
an RNSIC-1 converter in this study. The three L1
inductances of an RNSIC-1 are dropped, and the
leakage inductances of the SCIG generator fill their
place. The three inductances L1 are more expensive
than the one capacitor RNSIC, cheaper harmonic
stator currents, less power losses, and cheaper costs
are all characteristics of the new wind system. This
wind system can also be utilized for a small hydro
hookup with a SCIG and a wind turbine with a
partially variable speed (often between 70% and
100% synchronous speed). The effectiveness of the
suggested wind system with RNSIC - 1 converter
has been demonstrated in laboratory tests.
References:
[1] M.Kazmirkowski, R.Krishnan, F.Blaabjerg,
Control in power electronics: selected
problems (Academic Press, 2002).
[2] B.K.Bose, "Global Energy Scenario and
Impact of Power Electronics in 21st Century”.
IEEE Tran. Ind. Electron., vol.60, no.7,
pp.2638-2651, July 2013.
https://doi.org/10.1109/TIE.2012.2203771.
[3] V. Yaramasu, B. Wu, S. Alepuz and S. Kouro,
"Predictive Control for Low-Voltage Ride-
Through Enhancement of Three-Level-Boost
and NPC-Converter-Based PMSG Wind
Turbine", IEEE Trans. Ind. Electron., vol. 61,
no.12, pp. 6832-6843, Dec.2014.
https://doi.org/10.1109/TIE.2014.2314060.
[4] B.C.Rabelo, Jr.W.Hofmann, J.L.da Silva,
R.G.de Oliveira, S.R.Silva, "Reactive power
control design in doubly fed induction
generators for wind turbines", IEEE Trans.
Ind. Electron., 56, no.10, pp. 4154–4162,
October 2009.
https://doi.org/10.1109/TIE.2009.2028355.
[5] H. Li and Z. Chen, “Overview of different
wind generator systems and their
comparisons”, IET Renewable Power
Generation, vol, 2, No. 2, pp. 123-128, 2008.
https://doi.org/10.1049/ietrpg:20070044.
[6] A.D.Hansen, F.Iov, F.Blaabjerg, L.H.Hansen,
"Review of contemporary wind turbine
concepts and their market penetration", J.
Wind Eng., 2004, 28, (3), pp. 247–263.
https://doi.org/10.1260/0309524041590099.
[7] Z. Chen, E. Spooner, ”Grid power quality
with variable-speed wind turbines", Trans.
Energy Convers., 2001, 16, (2), pp. 148–154.
https://doi.org/10.1109/60.921466.
[8] J.B.Ekanayke, L.Holdsworth, W.Xue Guang,
N.Jenkin, "Dynamic modeling of doubly fed
induction generator wind turbines", IEEE
Trans. Power Syst., 2003, 18, (2), pp. 803–
809.
https://doi.org/10.1109/TPWRS.2003.811178.
[9] Z. Chen, J.M.Guerrero, F.Blaabjerg, "A
review of the state of the art of power
electronics for wind turbines", IEEE Trans.
Power Electron., 2009, 24, (8), pp. 1859–
1875.
https://doi.org/10.1109/TPEL.2009.2017082.
WSEAS TRANSACTIONS on POWER SYSTEMS
DOI: 10.37394/232016.2023.18.20
Irinel Valentin Pletea, Mariana Pletea
E-ISSN: 2224-350X
193
Volume 18, 2023
[10] M. Zhao, Z. Chen, F.Blaabjerg, "Load flow
analysis for variable speed offshore wind
farms", IET Renew. Power Gener., 2009, 3,
(2), pp. 120–132. https://doi.org/10.1049/iet-
rpg:20070094.
[11] P. Rodriguez, A.Timbus, R.Teodorescu,
M.Liserre, F.Blaabjerg, "Reactive power
control for improving wind turbine system
behavior under grid faults", IEEE Trans.
Power Electron., 2009, 24, (7), pp. 1798–
1801.
https://doi.org/10.1109/TPEL.2009.2014650.
[12] D.Alexa, I.V.Pletea, A.Sîrbu and A.Lazar,
"Wind energy conversion into electricity by
means of the rectifier with near sinusoidal
input current-1converter", IET Renewable
Power Generation, Volume 7, Issue 5,
September 2013, pp.475–483.
https://doi.org/10.1049/iet-rpg.2012.0158.
[13] D.Alexa, A.Sirbu, I.V.Pletea, C.Filote,
R.Chiper, "Variants of rectifier with near
sinusoidal input currents—a comparative
analysis with the conventional diode
rectifier", IET Power Electron., 2011, 4, (6),
pp. 632–641. https://doi.org/10.1049/iet-
pel.2010.0020.
[14] D.Alexa, A.Sirbu, I.V.Pletea, T.C.Goras,
"Hybrid rectifier with near-sinusoidal input
currents", IEEE Trans. Ind. Electron., 2012,
59, (7), pp. 2947–2958.
https://doi.org/10.1109/TIE.2011.2169641.
[15] J.M. Miller, "Ultracapacitor applications”,
(The Institution of Engineering and
Technology, London, 2011), ISBN-13 : 978-
1849190718.
Contribution of Individual Authors to the
Creation of a Scientific Article (Ghostwriting
Policy)
The authors equally contributed in the present
research, at all stages from the formulation of the
problem to the final findings and solution.
Sources of Funding for Research Presented in a
Scientific Article or Scientific Article Itself
No funding was received for conducting this study.
Conflict of Interest
The authors have no conflict of interest to declare.
Creative Commons Attribution License 4.0
(Attribution 4.0 International, CC BY 4.0)
This article is published under the terms of the
Creative Commons Attribution License 4.0
https://creativecommons.org/licenses/by/4.0/deed.en
_US
WSEAS TRANSACTIONS on POWER SYSTEMS
DOI: 10.37394/232016.2023.18.20
Irinel Valentin Pletea, Mariana Pletea
E-ISSN: 2224-350X
194
Volume 18, 2023
