Download a new strategy to control reactive power of a pms wind

A NEW STRATEGY TO CONTROL REACTIVE POWER OF
A PMS WIND GENERATOR WITH MATRIX CONVERTER
C. Jaya Krishna
PG Student [EPS],
Dept. of EEE
SITS, Kadapa,
Andhra Pradesh, India.
K. Meenendranath Reddy
Assistant professor,
Dept. of EEE
SITS, Kadapa,
Andhra Pradesh, India.
Abstract— In this paper, a new strategy is
proposed to increase the maximum achievable grid-side
reactive power of a matrix converter-fed PMS wind
generator. Unlike conventional back-to-back converters
in which a huge dc-link capacitor makes the control of
the generator and grid-side converters nearly
independent, a matrix converter control the generator
and grid-side quantities simultaneously. Matrix
converter is a direct AC-AC converter topology that is
able to directly convert energy from an AC source to an
AC load without the need of a bulky and limited lifetime
energy storage element.
Due to the significant advantages offered by
matrix converter, such as adjustable power factor,
capability of regeneration and high quality sinusoidal
input/output waveforms, matrix converter has been one
of the AC–AC topologies that receive extensive research
attention for being an alternative to replace traditional
AC-DC-AC converters in the variable voltage and
variable frequency AC drive applications. Different
methods for controlling a matrix converter input
reactive power is investigated. It is shown that in some
modulation methods, the grid-side reactive current is
made from the reactive part of the generator-side
current. In other modulation techniques the grid side
reactive current is made from the active part of the
generator-side current. In the proposed method, which
is based on a generalized SVD (singular valued
decomposition) modulation method, the grid side
reactive current is made from both active and reactive
parts of the generator-side current. In existing
strategies, a decrease in generator speed and output
active and reactive power will decrease the grid-side
reactive power capability. A new control structure is
proposed which uses the free capacity of the generator
reactive power to increase the maximum achievable
grid-side reactive power. Simulation results for a case
study show an increase in the grid-side reactive power at
all wind speeds if the proposed method is employed.
Permanent
Magnet
synchronous
generator(PMSG), Matrix converter, reactive power
control,
singular
value
decomposition
(SVD)
modulation, space vector modulation (SVM).
IndexTerms—
I. INTRODUCTION
In an integrated power system, efficient management
of active and reactive power flows is very important.
Quality of power supply is judged from the frequency and
voltage of the power supply made available to the
G. Venkata Suresh Babu
Associate professor, HOD,
Dept. of EEE
SITS, Kadapa,
Andhra Pradesh, I ndia.
consumers. While frequency is the measure of balance
between power generated (power available) and MW
demand impinged on the system, the voltage is indicative of
reactive power flows. In a power system, the ac generators
and EHV and UHV transmission lines generate reactive
power. Industrial installations whether small or large as also
the irrigation pump motors, water supply systems draw
substantial reactive power from the power grid.
The generators have limited defined capability to
generate reactive power- this is more so in respect of large
size generating units of 210 MW/500 MW capacity.
Generation of higher reactive power correspondingly
reduces availability of useful power from the generators.
During light load conditions, there is excess reactive power
available in the system since the transmission lines continue
to generate the reactive power thereby raising the system
voltage and this causes reactive power flows to the
generators. Particularly in India, the load curves show wide
fluctuations at various hours of the day and in various
seasons of the year. When load demand is heavy, there is
low voltage, which is harmful to the consumers as well as
utility’s installations. Burning of motors occur.
When load demand is very low, high voltage occurs in
the system and this has harmful effect on insulation of
power transformers. Failure of power transformers occur.
For better efficiency, it is necessary to reduce and minimize
reactive power flows in the system. Besides harmful effects,
the reactive power flows also affect the economy adversely
both for the utility and the consumer. If reactive power
flows are reduced i² R power losses as well as i² X losses are
reduced.
The generators can produce additional active power. If
the consumer reduces reactive power requirement his
demand KVA is reduced. For energy conservation also there
is need to reduce reactive power demand in the system. It is
therefore very clear that for efficient management of power
system and for improving the quality of electric supply, it is
very essential to install reactive compensation equipment
Because of the advantages of the matrix converter it is used
for the control of the reactive power in this project. A matrix
converter is a direct ac/ac frequency converter which does
not require any energy storage element. Lack of bulky
reactive components in the structure of this all silicon made
converter results in reduced size and improved reliability
compared to conventional multistage ac/dc/ac frequency
converters. Fabrication of low cost and high power switches
and a variety of high speed and high performance digital
signal processors (DSPs) have almost solved some of matrix
converter drawbacks, such as complicated modulation, four
step switching process of bidirectional switches and use of a
large number of switches. Therefore its superior benefits
such as sinusoidal output voltage and input current,
controllable input power factor, high reliability as well as a
small and packed structure make it a suitable alternative to
back-to-back converters.
One of the recent applications of matrix converters is
the grid connection of a variable speed wind generators
variable speed permanent magnet synchronous wind
generators are used in low power applications. The use of
matrix converter with a multiple PMSG leads to a gearless,
compact, and reliable structure with little maintenance
which is superior for low power micro-grids, home and
local applications. The wind generator frequency converter
should control the generator side quantities such as
generator torque and speed to achieve maximum power
from the wind turbine and the grid side quantities such as
grid side reactive power and voltage improve the system
stability and power quality. Unlike back-to-back converters
in which a huge dc link capacitors makes the control of the
generators and grid side quantities simultaneously.
Therefore the grid reactive power of a matrix converter is
limited by the converter voltage gain and the generator side
active or reactive power.
One necessary feature for all generators and
distributed generators connecting to a grid or microgrid is
the reactive power control capability. The generator reactive
power can be used to control the grid or microgrid voltage
or compensate local loads reactive power in either a grid
connected or an islanded mode of operation. In this project
the grid side reactive power capability and control of a PMS
wind generator with matrix converter is improved. For this
purpose in section II, a brief study of matrix converter and
its singular value decomposition (SVD) modulation
technique which is generalized modulation method with
more relaxed constraints compared to similar modulation
methods is presented.
II. MATRIX CONVERTER REACTIVE POWER
CONTROL
Fig.1 shows In a matrix converter, the input and
output phases are related to each other by a matrix of
bidirectional switches such that it is possible to connect any
phase at the input to any phase at the output. Therefore, the
controllable output voltage is synthesized from
discontinuous parts of the input voltage source, and the
input current is synthesized from discontinuous parts of the
output current source or
𝑉𝑂,𝐴𝐵𝐶 = S 𝑉𝑖,𝑎𝑏𝑐
𝐼𝑖,𝑎𝑏𝑐 = ST 𝐼𝑂,𝐴𝐵𝐶
s11 s12 s13
S = (s21 s22 s23 )
s31 s32 s33
{
Skj ∊ 0,1
k, j = 1,2,3
sk1 + sk2 + sk3 = 1
𝑉𝑖,𝑎𝑏𝑐
𝑣𝑖𝑎
𝑖𝑖𝑎
𝑣
= ( 𝑖𝑏 ), Ii,abc = (𝑖𝑖𝑏 )
𝑣𝑖𝑐
𝑖𝑖𝑐
𝑣0𝑎
𝑖0𝑎
𝑉𝑂,𝐴𝐵𝐶 = (𝑣0𝑏 ), I0,ABC = (𝑖0𝑏 )
(1)
𝑣0𝑐
𝑖0𝑐
Where V0, j and I0, j; j = (A, B, C) are the output phase
voltages and currents, respectively; and are the input phase
voltages and currents; and is the switching function of
switch .Lack of an energy storage component in the
structure of a matrix converter leads to an equality between
the input output active power, i.e.,
𝑇
𝑇
𝑝𝑖 = 𝑉𝑖,𝑎𝑏𝑐
. 𝐼𝑖,𝑎𝑏𝑐 = 𝑉𝑖,𝐴𝐵𝐶
. 𝐼𝑖,𝐴𝐵𝐶 = 𝑝𝑜
(2)
Fig.1 Typical three-phase matrix converter schematic diagram
A. SVD Modulation technique
Different modulation techniques are proposed for a
matrix converter in the literature. A more complete
modulation technique based on SVD decomposition of a
modulation matrix is proposed in. Other modulation
methods of a matrix converter can be deduced from this
SVD modulation technique. The technique proposed in has
more relaxed constraints compared to other methods. The
SVD modulation method is a duty cycle method in which
the modulation matrix M, which is defined in (3), is directly
constructed from the known input voltage and output
current and desired output voltage and input current, i.e.,
m11 m12 m13
M = Ave{s} = (m21 m22 m23 )
m31 m32 m33
0 ≤ 𝑚𝑘𝑗 ≤ 1
{𝑚𝑘1 + 𝑚𝑘2 + 𝑚𝑘3 = 1
(3)
𝑘, 𝑗 = 1,2,3
Where mkj is the average of S k j over a switching
period to represent the input and output voltages and
currents in space vector forms, all quantities of the input and
output of the matrix converter are transferred from the abc
reference frame to the αβ0 reference frame by the modified
Clarke transformation of (4). Therefore, the new modulation
matrix Mαβ0 obtained as
𝑉𝑂,αβ0 = 𝑀αβ0 𝑉𝑖,αβ0
𝐼𝑖,αβ0 = MT αβ0 𝐼𝑂,αβ0
𝑀αβ0 = K 𝑀abc KT
1 1
2 2
√3 √3
0
−
2
2
1 1 1
√2 √2 √2
1− −
2
K=√
3
(
)
K-1 = KT or KKT = I
(4)
The last equality means that matrix is a unitary
matrix K or its transpose is equal to its inverse. Considering
the condition set by (3) and using (4), the following basic
form for the Mαβ0 is obtained:
g11 g12 0
g
𝑀αβ0 = K𝑀abc K = ( 21 g 22 0 )
c1′ c2′ 1
T
𝑀
= ( 0 𝛼𝛽2𝑋2 𝑂0 )+(0𝐶
0
1𝑋2′ 0
M0 =
(0𝐶 0)
1𝑋2′ 0
Fig.3 SVD of 𝑀αβ0
M α β maps VI, α β from the input αβ space onto Vo,α β in the
output αβ space and MT α β maps Io,αβ from the output αβ
space onto II, α β in the input αβ space. Each matrix can be
decomposed into product of three matrices as shown in 2
which is called SVD of a matrix.
M = U0 ∑ Ui*
)
(5)
Where Mαβ generates Vo, α β and II, α β from Io, α β
and VI, α β, and Mo generates Vo, 0 and Io, 0 from VI, αβ0 and Io,
αβ0, respectively.
Since, in a three-phase three-wire system, no zerosequence current can flow, the zero-sequence voltage can be
added to the output phase voltages to increase the flexibility
of the control logic. Therefore, in all modulation methods,
the main effort is devoted to selecting suitable in (6) to
control the output voltage and input current and a suitable to
increase the operating range of the matrix converter, i.e.,
(6)
∑ = (𝜎01𝜎0)
2
𝑈0,2𝑋2 = 𝑈01,2𝑋2 𝑈02,2𝑋1
{
𝑈𝑖2𝑋2 = 𝑈𝑖1,2𝑋1 𝑈𝑖2,2𝑋1
UiUi* = U0U0* = I
(7)
Where U i and U o are unitary matrices meaning
that their columns are ortho normal vectors, and
The * operator is conjugate transpose σ1 and σ 2 are
the gains of matrix M in the direction of U i1 and U i2.
As Fig.2 depicts, the SVD of a matrix means that
this matrix will transform the vectors in the direction U i1, 2 X
1 toward the direction of U o1, 2X1 by a gain of σ1 and vectors
in the direction of U i2, 2 X 1 toward the direction of U o2, 2 X 1
by a gain of σ 2 .
As presented in Fig. 3, M α β also has an SVD
decomposition where U i1, 2 X 1 and U i2, 2 X 1 are ortho
normal vectors rotating at a speed equal to the input
frequency.
𝑔11 𝑔12
𝑞𝑑 0
(
) = (𝑈𝑜𝑑 𝑈𝑜𝑞 ) (
) (𝑈𝑖𝑑 𝑈𝑖𝑞 )
𝑔21 𝑔22
0 𝑞𝑞
𝑐𝑜𝑠𝜃𝑖 − 𝑠𝑖𝑛𝜃𝑖 𝑇
𝜃𝑜 −sin 𝜃𝑜
𝑞𝑑 0
= (sin
)
(
)
×
(
) (8)
sin 𝜃𝑜 𝑐𝑜𝑠𝜃𝑜
0 𝑞𝑞
𝑠𝑖𝑛𝜃𝑖 𝑐𝑜𝑠𝜃𝑖
By substituting (8) into (5), 𝑀𝑎𝑏𝑐 is obtained as
𝑀𝑎𝑏𝑐 = K𝑀αβ𝑜 KT = KT𝑀αβ K + KT𝑀𝑜 K
= 𝑀𝑎𝑏𝑐αβ + 𝑀𝑎𝑏𝑐,𝑜
= P(θo)T(0𝑞𝑑𝑞0 ) P(θi) + 𝑀𝑎𝑏𝑐,𝑜
𝑞
Fig. 2 Concept of SVD of a matrix
2
P(θ) = √ (
3
2𝜋
2𝜋
) cos(θ+ )
3
3
2𝜋
2𝜋
−sin θ –sin(θ− ) –sin(θ+ )
3
3
cos θ cos(θ−
)
(9)
Where P(θ) is the modified Park transformation
matrix. It can be proved that if the following limitation on
𝑞𝑑 and 𝑞𝑞 is held, there exists a 𝑀𝑎𝑏𝑐,𝑜 matrix for which the
condition of (3) is correct. Therefore there may be many
solutions for matrix
|𝑞𝑑 | + |𝑞𝑞 | ≤
1
}⇒
0 ≤ 𝑚𝑘𝑗 ≤ 1
{𝑚𝑘1 + 𝑚𝑘2 + 𝑚𝑘3 = 1
(10)
𝑘, 𝑗 = 1,2,3
There may be many solutions for matrix 𝑀𝑎𝑏𝑐,𝑜 ;
however, the following solution requires simple
calculations:
√3
𝑐 𝑐2 𝑐3
𝑐2 𝑐3 )
𝑐1 𝑐2 𝑐3
𝑀𝑎𝑏𝑐,𝑜 = (𝑐11
Ck = min{ M abc, αβ(i,k)}
+ {1 + ∑𝑗 min{ M abc, αβ(i, k)}
۰
1−max{𝑀 𝑎𝑏𝑐,𝛼𝛽(𝑖,𝑘)}+ min{ M abc,αβ(i,k)}
3− ∑𝑗 max{ M abc,αβ(i,k)}+ ∑𝑗 min{ M abc,αβ(i,k)}
(11)
. The constraint obtained in (10) is an inherent constraint of
a matrix converter which is more relaxed than the constraint
of conventional modulation methods. Therefore, the use of
the SVD modulation technique can improve the
performance of a matrix converter when the input reactive
power control is needed. All of the existing modulation
methods can be deduced from this simple and general
method by choosing a perfect 𝑞𝑑 , 𝑞𝑞 , θi, θo. On the other
hand, equation(9) shows that if the input and output
quantities are transferred onto their corresponding
synchronous reference frames, the SVD modulation matrix
becomes a simple, constant, and time-invariant matrix.
Therefore, as shown in Fig.5, the SVD modulation
technique models the matrix converter as a dq transformer
in the input–output synchronous reference frame.
Fig.4 Matrix converter steady state and dynamic dq transformer model
reactive current and power of a matrix converter. All
modulation techniques can be modeled by the SVD
modulation method. Therefore, this method can be used to
study the reactive power capability and control of a matrix
converter. According to Fig. 3, the input reactive power of a
matrix converter can be written in a general form as
𝑄𝑖 = imag{Si} = 𝑉𝑖𝑞 𝐼𝑖𝑑 - 𝑉𝑖𝑑 𝐼𝑖𝑞
= 𝑞𝑞 𝑉𝑖𝑞 𝐼𝑜𝑑 - 𝑞𝑞 𝑉𝑖𝑑 𝐼𝑜𝑑
= 𝑄𝑖𝑑 + 𝑄𝑖𝑞
(12)
Where Si is the input complex power, 𝑄𝑖𝑑 is the part of the
input reactive power made from, 𝐼𝑜𝑞 and 𝑄𝑖𝑞 is the part of
the input reactive power made as of 𝐼𝑜𝑞 . Therefore, the
following three different strategies of synthesizing the input
reactive power of a matrix converter can be investigated:
 Strategy 1: Synthesizing from the reactive part of
the output current (i.e., 𝑄𝑖𝑞 );
 Strategy 2: Synthesizing from the active part of the
output current (i.e., 𝑄𝑖𝑑 );
 Strategy 3: Synthesizing from the active and
reactive parts of the output current (𝑄𝑖𝑑 +𝑄𝑖𝑞 ).
Strategy1. Synthesizing From the Reactive Part of the
Output Current
If in the SVD modulation technique, θi is set to the
input voltage phase angle as shown in Fig. 5, the output
voltages will also be aligned with the d-axis of the output
synchronous reference frame which is defined by, and the
generalized modulation technique will be the same as the
Alesina and Venturini modulation technique with a more
relaxed limitation on 𝑞𝑑 and 𝑞𝑞 .
Fig.6 Modeling the SVM modulation method by SVD modulation
technique
In this case, controls the voltage gain and controls
the reactive current gain of the matrix converter. Therefore,
the input reactive power is limited by the voltage gain and
the output reactive power as given by
𝑞
𝑄𝑖 = 𝑄𝑖𝑞 = 𝑞 Qo
𝑞𝑑 = 𝐺𝑣 =
𝑞𝑑
𝑣𝑜
𝑣𝑖
(10) ⇒ |𝑄𝑖 | ≤
Where 𝐺𝑣 =
Fig.5 Modeling of Alesina and Venturini modulation method by SVD
modulation technique
Several control strategies based on different
modulation techniques can be used to control the input
1−𝑞𝑑
𝑞𝑑
𝑣𝑜
𝑣𝑖
|𝑄𝑜 | =
1−𝐺𝑣
𝐺𝑣
|𝑄𝑜 |
(13)
where is the voltage gain of the
matrix converter and Q o is the output reactive power. is the
voltage gain of the matrix converter and is the output
reactive power.
Strategy2. Synthesizing From the Active Part of the
Output Current
If 𝑞𝑞 is set to zero, as shown in Fig. 6, the output
voltage will be aligned with the d-axis of the output
reference frame and the input current will be aligned with
the d-axis of the input reference frame. Therefore, the SVD
modulation technique will be the same as the SVM
modulation technique. In this case, 𝑞𝑑 controls the voltage
gain 𝜙𝑖 and controls the input reactive current of the matrix
converter. Therefore, the input reactive power is limited by
the voltage gain and the output active power as given by
𝑉 = 𝑞𝑑 𝑉𝑖𝑑 = 𝑞𝑑 𝑉𝑖 𝑐𝑜𝑠∅𝑖
{𝑜
⇒
𝐼𝑖 = 𝑞𝑑 𝐼𝑜𝑑 = 𝑞𝑑 𝐼𝑜 𝑐𝑜𝑠∅𝑜
√3
𝐺𝑣 = 𝑞𝑑 𝑐𝑜𝑠∅𝑖 ≤
𝑐𝑜𝑠∅𝑖
2
⇒ |𝑄𝑖 | ≤
3
4
√ −𝐺𝑣2
𝐺𝑣
|𝑃𝑜 |
(14)
Strategy3. Synthesizing From Both the Active and
Reactive Parts of the Output Current
The two previous strategies do not yield the full
capability of a matrix converter. To achieve maximum
possible input reactive power, both active and reactive parts
of the output current can be used to synthesize the input
reactive current. To increase the maximum achievable input
reactive current in a matrix converter for a specific output
power, its input current should be maximized.
𝑉𝑜 = 𝑀𝑉𝑖
|𝑞𝑑 |, |𝑞𝑞 | ≤ √3 /2
Subject to:{
(15)
𝐺𝑣 ≤ 𝑘 = |𝑞𝑑 | + |𝑞𝑞 | ≤ 1
where k is positive parameter which is used to vary the
matrix constraint. K can be changed from its minimum
possible value (𝑘 = 𝐺𝑣 ) to its maximum value (k = 1) to
change the gain of the matrix converter and control its input
reactive power.
This optimization problem can be solved with
different solvers. However, in this section, a closed form
formulation is derived to simplify computations of the
control system. It is proved in Appendix A that if , , and are
chosen as given in (16), the input current gain of the matrix
converter will be equal to its maximum achievable value for
a given parameter , voltage gain and output power factor
√3 𝑘 + √4𝐺𝑣2 + 𝑘 2 − 4𝐺𝑣 𝑘 sin |∅𝑜 |
𝑞𝑑 = 𝑚𝑖𝑛 {𝑘,
,
}
2
2
𝑞𝑞 = 𝑠𝑖𝑔𝑛(∅𝑖 )𝑠𝑖𝑔𝑛(∅𝑜 )𝑚𝑖𝑛 {𝑘
− 𝑞𝑑 ,
𝑞𝑑 𝐺𝑣 𝑠𝑖𝑛∅𝑖
√3
,
}
2 √𝑞 2 − 𝐺𝑣2 𝑐𝑜𝑠 2 ∅𝑜
𝑑
𝛿𝑖 = −𝑠𝑖𝑔𝑛(∅𝑖 )𝑡𝑎𝑛 −1 √
𝛿𝑜 = 𝑡𝑎𝑛−1 {
𝑞𝑞
𝑞𝑑
Fig.7 Maximum achievable current gain of different techniques versus
voltage gain and output power factor (a) Strategy 1. (b) Strategy 2. (c)
Strategy 3
Fig.8 Maximum input reactive power of different techniques versus output
active and reactive power. (a) Strategy 1. (b) Strategy 2. (c) Strategy 3
Since MT transforms 𝐼𝑜 from the output space onto the input
space, to maximize 𝐼𝑖 the free parameter θi must be chosen
such that 𝐼𝑜 is located as close as possible to the direction
over which the MT gain is maximum that is given below. It
is a positive parameter which is used to vary the matrix
converter constraint can be changed from its minimum
value (i.e., K = 𝐺𝑣 ) to its maximum possible value (i.e., K =
1) to change
Max|𝐼𝑖 | = 𝑚𝑎𝑥
{|MTIo|}
𝑀
𝑡𝑎𝑛𝛿𝑖 }
𝑞𝑑2 − 𝐺𝑣2
𝐺𝑣2 − 𝑞𝑞2
(16)
Figs. 7 and 8 present the maximum current gain
and input reactive power in a matrix converter which can be
achieved by the three strategies described in this section. As
depicted in these figures, the maximum current gain and
input reactive power, which can be achieved by the
proposed strategy (i.e., strategy 3), are more than that
obtained by the other two.
III. PMS WIND GENERATOR REACTIVE POWER
CONTROL
The three methods of controlling the input reactive
power of a matrix converter described in the previous
section can be used to control the reactive power of a PMS
wind generator. A gearless multi-pole PMS wind generator,
which is connected to the output of a matrix converter, is
simulated to compare the improvement in the matrix
converter input or grid-side reactive power using the
proposed strategy. The control block diagram of the system
is shown in Fig.9. The simulations are performed using Mat
lab software. To control the generator torque and speed,
generator quantities are transferred onto the synchronous
reference frame such that the rotor flux is aligned with the
d-axis of 𝑑𝑞0 the reference frame. Therefore, 𝐼𝑔𝑞 will
become proportional to the generator torque, 𝐼𝑔𝑑 and can be
varied to control the generator output reactive power.
Usually, 𝐼𝑔𝑑 is set to zero to minimize the generator
current and losses. However, in this section, the effect of
𝐼𝑔𝑑 on the input reactive power is also studied, and a new
control structure is proposed which can control the
generator reactive power to improve the reactive power
capability of the system.
Fig. 9. Simplified control block diagram of a PMSG.
Fig.12 Generator direct axis current 𝐼𝑔𝑑 (A) for ωm = 1 rad/sec
The next result is the Terminal voltage which is shown
below.
Fig. 10 Proposed control structure which uses and matrix converter
synchronously to control the grid-side reactive power
IV. SIMULATION RESULTS
The proposed control structure is simulated with a
simple adaptive controller (SAC) on a gearless Multi pole
variable-speed PMS wind generator and the results are
presented to verify its performance under different operating
conditions. The simulations are performed using Mat lab
software. The simulation parameters used for this circuit
given in the previous chapter.
A. SIMULATION RESULTS FOR SPEED ωm =
1rad/sec
In the above Figure there are PMS wind generator
block, input and output terminals and the matrix converter
blocks are there. Figures 11, 12, 13 and 14 depict the
simulation results for the proposed control structure for
generator speed ωm = 1 rad/sec. The controller used in these
simulations for the grid-side reactive power control is a
simple adaptive controller (SAC). It can be seen from these
figures that the controller increases 𝑖𝑔𝑑 to track the desired
grid side reactive power, if the maximum achievable grid
side reactive power for 𝑖𝑔𝑑 = 0 is not sufficient. An increase
in 𝑖𝑔𝑑 will decrease the generator terminal voltage and
increase the generator losses.
Fig.13 Generator Terminal voltage Vtg (v) for ωm = 1 rad/sec
Fig.14 Generator power losses plosses, g (kw)
B. SIMULATION RESULTS FOR SPEED ωm =
4.5rad/sec
The following is the required simulation circuit for
ωm = 4.5 rad/sec
Fig.11 Matrix converter grid side reactive power Qs for PMS wind
generator speed ωm = 1 rad/sec
Fig.15 Matrix converter grid side reactive power Qs for PMS wind
generator speed ωm = 1 rad/sec
Fig.16 Generator direct axis current 𝐼𝑔𝑑 (A) for ωm = 4.5 rad/sec
Fig.17 Generator Terminal voltage Vtg (V) for ωm = 1 rad/sec
The next result is the Terminal voltage which is shown
below for ωm = 4.5 rad/sec .
induction generator,” Proc. IEEE IECON, vol. 2, pp. 906–
911, Nov. 1997.
[3] L. Zhang and C.Watthanasarn, “A matrix converter
excited doubly-fed induction machine as a wind power
generator,” in Proc. Inst. Eng. Technol. Power Electron.
Variable Speed Drives Conf., Sep. 21–23, 1998, pp. 532–
537.
[4] R. CárdenasI, R. Penal, P. Wheeler, J. Clare, and R.
Blasco-Gimenez, “Control of a grid-connected variable
speed wecs based on an induction generator fed by a matrix
converter,” Proc. Inst. Eng. Technol. PEMD, pp. 55–59,
2008.
[5] S. M. Barakati, M. Kazerani, S. Member, and X. Chen,
“A new wind turbine generation system based on matrix
converter,” in Proc. IEEE Power Eng. Soc. Gen. Meeting,
Jun. 12–16, 2005, vol. 3, pp. 2083–2089.
[6] M. Chinchilla, S. Arnaltes, and J. C. Burgos, “Control of
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wind-energy systems connected to the grid,” IEEE Trans.
Energy Convers., vol. 21, no. 1, pp. 130–135, Mar. 2006.
[7] K. Ghedamsi, D. Aouzellag, and E. M. Berkouk,
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.
Fig.16 Generator power losses plosses, g (kw)
V. CONCLUSION
In existing strategies, a decrease in the generator
speed and output active and reactive power will decrease the
grid-side reactive power capability. A new control Structure
is proposed which uses the free capacity of the generator
reactive power to increase the maximum achievable gridside reactive power. Simulation results for a case study
show an increase in the grid side reactive power at all wind
speeds for the proposed method is employed.
REFERENCES
[1] P. W.Wheeler, J. Rodríguez, J. C. Clare, L.
Empringham, and A.Weinstein, “Matrix converters: A
technology review,” IEEE Trans. Ind. Electron., vol. 49, no.
2, pp. 276–288, Apr. 2002.
[2] L. Zhang, C. Watthanasarn, and W. Shepherd,
“Application of a matrix converter for the power control of
a variable-speed wind-turbine driving a doubly-fed
K. Meenendranath reddy has 4 years
of experience in teaching in Graduate
and Post Graduate level and he
Presently working as Assistant
Professor in department of EEE in
SITS, kadapa.
G.Venkata Suresh Babu has 12 years
of experience in teaching in Graduate
and Post Graduate level and he
Presently working as Associate
Professor and HOD of EEE department
in SITS, kadapa.