ISSN 2348–2370
Vol.07,Issue.02,
February-2015,
Pages:0200-0206
www.ijatir.org
Analysis of Matrix Converter Based UPFC
M. NAGA RAJU1, S. MUNI RAJA2
1
Associate professor, P.B.R.Visvodaya Institute of Science and Technology, Kavali, AP, India.
2
PG Scholar, P.B.R.Visvodaya Institute of Science and Technology, Kavali, India.
Abstract: This paper present a Matrix Converter (MC)
based Unified Power Flow Control (UPFC). Matrix
converter directly converts power AC to AC without DC
energy storage link. The absence of DC energy storage link
causes decreases volume and cost. Based on sliding mode
control technique the theriotcal principle of direct power
control established for a matrix converter working as a
UPFC dynamic model having the input filter. MC based
UPFC directly control the shunt side reactive power and
series side active & reactive power by selecting appropriate
matrix converter switching states gives steady state error
tracking zero, steady state and dynamic response are good,
response time fast, presenting faultless steady-state and
dynamic response.
Keywords: Direct Power Control (DPC), Matrix Converter
(MC), Unified Power-Flow Controller, Space Vector
Modulation (SVM), Sliding Mode Control Technique.
I. INTRODUCTION
In last few decades, power demand increases abnormally
it will raises power quality and stability problems. In order
to achieve power quality and stability we have several
FACTS devices. UPFC is the one of the powerful and
versatile FACTS device for power flow in long transmission
line [5-8]. In the last few years, electricity market
deregulation, together with rising economic, environmental,
and social concerns, has increased the difficulty to burn
fossil fuels, and to obtain new licenses to build transmission
lines (rights-of-way) and high-power facilities. This
situation started the development of decentralized electricity
generation (using renewable energy resources) [1]. Unified
power-flow controllers (UPFC) allow the operation of
power transmission networks near their maximum ratings,
by enforcing power flow through well-defined lines [2-4].
These days, UPFCs are one of the most versatile and
powerful flexible ac transmission systems (FACTS)
devices.[5]-[8] The conventional UPFC results from the
mixture of a STATCOM (static synchronous compensator)
& a SSSC (static synchronous series compensator) that
shares a common dc capacitor link[9].
The survival of a dc capacitor bank originates additional
losses, decreases the converter lifetime, and increases its
weight, cost, and volume. In the last few decades, an
increasing attention in new converter types, capable of
performing the same functions but with reduced storage
needs, has arisen [10]. These converters are capable of
performing the same ac/ac conversion, allowing
bidirectional power flow, guaranteeing close to sinusoidal
input and output currents, voltages with variable amplitude,
and adjustable power factor. These minimum energy storage
ac/ac converters have the capability to agree to independent
reactive control on the UPFC shunt and series converter
sides, while guaranteeing that the active power exchanged
on the UPFC series connection is always supplied/absorbed
by the shunt connection. In the last few years, direct power
control techniques have been used in many power
applications, due to their cleanness and good performance.
In this paper, a matrix converter- based UPFC is planned,
using a direct power control approach (DPC-MC) based on
an MC-UPFC dynamic model. In order to design UPFCs,
presenting healthy behavior to parameter variations and to
disturbances, the proposed DPC-MC control method, is
based on sliding mode-control techniques, allowing the realtime selection of sufficient matrix vectors to control input
and output electrical power. Sliding mode-based DPC-MC
controllers can guarantee zero steady-state errors and no
overshoots, good tracking performance, and fast dynamic
responses, while being simpler to execute and requiring less
processing power, when compared to proportional-integral
(PI) linear controllers obtained from linear active and
reactive power models of UPFC using a modified Venturini
high-frequency PWM modulator[11].
II. DIRECT POWER CONTROL (DPC)
Direct Power control (DPC) has become an interesting
control approach of grid-connected converters because it
provides the maximum dynamic capability available in the
system. This non-linear control approach is defined as a
direct control technique because it chooses the best suited
converter’s voltage vector without any modulation
technique [5]. The basic control configuration of DPC has
been shown in Fig.1 Where two cascaded control loops are
described; an internal active and reactive power regulation
loop and an external control loop which establishes the DClink voltage requirements. The inner loop evaluates directly
active and reactive power tracking requirements,
approaching the state of the system toward the reference
values. This section will develop two DPC control strategies
for the 2L-VSI and 3L-NPC VSI.
Copyright @ 2015 IJATIR. All rights reserved.
M.NAGA RAJU, S.MUNI RAJA
(6)
(7)
SP (ep , t) > 0, then the P (ep , t) value ought to be
decrease it describes that it has negative time derivative.
Fig.1. Direct power conversion.
A. Power Control
The power control computes immediate active and
reactive-power values. The definition of instantaneous
power is still a source of argument between researchers.
Among the theories that have been successively planned
over the last years, this work retains the ―original‖ threewire system’s definition. This way, immediate active and
reactive power is defined as follows:
(1)
Here vα-β and iα-β are the line voltage and current in
static αβ coordinates high and mighty power conservation in
Clark’s transformations. It is possible also to represent
immediate active and reactive power using Park’s
transformations where vd-q and id-q, are the line voltage
and current in the rotating dq reference frame. From the
computation point of view, Clark’s transformation uses easy
linear relations whereas Park’s transformation exploits
trigonometric functions and requires to known the grid
phase location [7].
III. SPACE VECTOR MODULATION
A. Line Active and Reactive Power Sliding Surfaces
The line power flow in DPC controllers are derived from
sliding mode control theory.
P = Real power
Q = Reactive power
ep = Active power error
eq = Reactive power error
Pref = Actual transmitted active power
Qref = Actual transmitted reactive power
(2)
(3)
According to sliding surfaces Sp, (ep,t), & Sq, (eq,t), must
be proportional to above errors.
(4)
(5)
Kp & Kq = proportional gains these are choose appropriate
switching frequency.
B. Line Active and Reactive Power Direct Switching
Laws
Based on ep, eq we select matrix converter switching states.
So control speed is high.
Likewise SP (ep , t) < 0 , then. P (ep , t) > 0.
1. If SP (ep , t) > 0 => P (ep , t) < 0 => P < Pref , then
choose
a
vector
appropriate
to increase P.
2. If, SP (ep , t) < 0 => P (ep , t) > 0 => P > Pref , then
choose a vector appropriate to decrease P.
3. If, SP (ep , t) = 0 then choose a vector which does
not considerably change the active power.
The same process should be applied to the reactive power
error. To decide a vector, from (4) and (12), and taking into
consideration Pref and in Vd steady state, the following can
be written:
(8)
From (7), considering Vd and Pref constant, if Sp (ep,t)>0,
then it must be P (ep , t) < 0. From (8), if Kp Vd is positive,
then
> 0, meaning that P must rise. From the
equivalent model in coordinates presented in (1), if the
chosen vector has,
VLd > VR0d – L2Iq + R2Id , then ,
> 0 , the selected vector being suitable to boost the
active power (reaching condition). Reactive power Qref &
Vd in steady state
(9)
From (9), if, SQ (eQ , t) > 0, then, Q (eQ , t) < 0 , which still
implies,
meaning that Q must rise. Also, from
kQVd(
) < 0 which signify that if kQVd is positive,
then
must be negative as shown in Fig.2.
Considering the current dynamics written in coordinates
then, to make sure the reaching condition, the chosen vector
must have VLq < VR0q + L2Id + R2Iq to guarantee,
meaning the voltage vector has a component
suitable to boost the reactive power. To ease vector
selection (Table I), sliding surfaces SP (ep , t) and SQ (eQ , t)
should be changed to αβ coordinates. In this DPC control
system we using table I. In this table group I have six
vectors which are not used because they require extra
algorithms to calculate these vectors. And group III used for
near zero errors. We using only group II having 18 vector
combinations. In order to organize the errors ep & eq we
using two hysteresis comparator each having three levels
International Journal of Advanced Technology and Innovative Research
Volume.07, IssueNo.02, February-2015, Pages: 0200-0206
Analysis of Matrix Converter Based UPFC
such as -1, 0, &1.In this system 9 output voltage error
By using above table I based on error combinations the
combination are derived. Totally 18 error combinations are
system generate corresponding output. Calculation for the
used
remaining eight active and reactive power error
combinations Table II is obtained by generalize the table I.
Based on control laws the P, Q controllers were calculated
but not dependent on system parameter.
TABLE II: Vectors Selection for Different Error StateSpace Vectors Combinations
Fig. 2. (a) Sector for input voltages. (b) State space
vector selection for output voltage for corresponding
input voltage.
TABLE I: Output Voltage/Input Current State-Space
Vectors And Switching Combinations
C. Direct Control of Matrix Converters Input Reactive
Power
In this system UPFC can be compensate reactive power at
the matrix converter input. Sliding surface SQi (eQi ,t) is give
reactive power error. Reactive power error e Qi =Qiref - Qi &
its first-order time derivative
(10)
To get a suitable switching frequency, KQi has been
chosen, levels (-1 and +1) levels chosen by using one
hysteresis comparator. To complete a stability condition
(11)
From (11), it is seen that the control input, the iq matrix
input current, must have sufficient amplitude to impose the
sign of Q (eQ , t) . Supposing that there is enough amplitude,
(10) and (11) are used to create the criteria (12) to choose
the adequate matrix input current vector that imposes the
needed sign of the matrix input-phase current related to the
output-phase currents by
 If, Qi (eQi , t) > 0 => Qi (eQi , t) < 0 then select
vector with current iq < 0 to Boost Qi.
 If SQi (eQi , t) < 0 => Qi (eQi , t) > 0 then select
vector with current iq > 0 reduce Qi .
The sliding mode is reached when vectors useful to the
converter have the necessary iq current for satisfy amplitude
condition of stability. Corresponding input currents also
produce error combinations. So we construct table III for
simplicity as shown in Fig.3.
International Journal of Advanced Technology and Innovative Research
Volume.07, IssueNo.02, February-2015, Pages: 0200-0206
M.NAGA RAJU, S.MUNI RAJA
In this model
Where Vs = Sending end sinusoidal voltage
Vr = Receiving end sinusoidal voltage
Gs = Sending end generator
GR = Receiving end generator
ZL = Load impedance
L2 = Series inductance
R2 = Series Resistance
In the second diagram represents 3- Φ equivalent circuit
matrix UPFC transmission model as shown in Fig.4.
Vc = Controllable voltage source
VR0 = Load bus voltage
Fig.3. (a) Sector allocation for Output currents (b) statespace vectors for input currents.
Let consider symmetrical and balanced 3- Φ system and
apply KCL to the equivalent circuit as shown in Fig.5. Then
Considering the previous example, with the input voltage
we get AC line currents in dq coordinates.
at sector Vi1 and sliding surfaces signals Sα(ep,t)>0and S(
eQi,t) <0 both vectors +9 or -7 would be appropriate to
organize the line reactive & active powers errors.
 For vector +9 gives to •SQi(eQi,t) >0 .
 For vector -7 originates •SQi(eQi,t) <0.
 For vector +9 Reactive power sliding surface =
SQi(eQi,t) selected as CQi =-1.
 For vector -7 SQi(eQi,t) is selected as CQi= +1.
If the active & reactive power errors are zero then the
group III is selected.
(12)
TABLE III: State-Space Vectors Selection, For Input
Voltages Located At Sector Vi1
Fig. 5. 3-Φ equivalent circuit of the matrix UPFC and
transmission line.
(13)
(14)
And also get active and reactive power sending end
generator side in dq coordinates.
(15)
IV. PROPOSED SYSTEMS
A. General Architecture
Let
VRod and Vsd = Vd , Vsq= 0
(16)
(17)
From the equation 4 & 5 we derived Active and reactive
powers Pref, Qref Active and reactive currents Idref, Iqref/.
Fig.4. Transmission network with matrix converter
UPFC as shown in diagram.
B. Matrix Converter Output Voltage and Input Current
Vectors
In this diagram having UPFC system having 3-phase
Transformers having windings Ta, Tb, Tc respectively &
having nine bidirectional switches. Each having turned ON
& turn OFF capability. The system wants one filter to
establish smooth input currents as shown in Fig.6.
International Journal of Advanced Technology and Innovative Research
Volume.07, IssueNo.02, February-2015, Pages: 0200-0206
Analysis of Matrix Converter Based UPFC
From the above analysis 27 possible switches patterns is
there. The possible combinations lie in between alpha, beta
co-ordinates. In this DPC-MC approaches select any one of
these 27 vectors at any Any instant.
C. Implementation of the DPC-MC as UPFC
Fig.6. Transmission network with matrix converter
UPFC.
If we neglecting the damping resistance effect. Then we get
equations.
Fig.7. Control scheme circuit.
(18)
Where Vid = Input voltage in d-component
Viq = Input voltage in q-component.
Iid = Input current in d-component
Iiq = Input current in q-component
Vd = Matrix converter voltage in d-component
Vq = Matrix converter voltage in q-component
Id = Matrix converter current in d-component
Iq = Matrix converter current in q-component
Skj = Matrix converter bidirectional switches
Skj = 1 for switch closed
Skj = 0 for switch open
From the above block diagram represents it can seen that
control Active &Reactive Power possible only sending end
generator side & currents is essential to calculate as shown
in Fig.7. Sα(ep, t) and Sβ(eQ, t). In order to control the MC
input reactive power require current in input for calculation
SQi(eQi, t) and results as shown in Figs.8 to 15. At any time
the matrix converter choose appropriate vector selection
from table II and II.
(19)
The MC topological constraint imply
kj = 1.
Relationship between load voltages and input voltages.
(20)
Relationship between load currents and input currents,
using the transpose of matrix S
(21)
Fig.8. Matlab/Simulink diagram for MC based UPFC
employ SVM technique.
International Journal of Advanced Technology and Innovative Research
Volume.07, IssueNo.02, February-2015, Pages: 0200-0206
M.NAGA RAJU, S.MUNI RAJA
Fig.12. Reactive Shunt power response with UPFC.
Fig. 9. Matlab/Simulink diagram for MC.
Fig.13. Total harmonic distortion for MC based UPFC.
Fig.10. Matlab/Simulink diagram for MC based UPFC
control circuit.
Fig.11. Active and reactive series power responses for
P&Q step (change in Pref =0.4 p.u& change in Qref =0.2
p.u) with UPFC.
Fig.14. Active and reactive power response for model
without UPFC.
Fig.15. Total harmonic distortion for transmission line
without UPFC.
International Journal of Advanced Technology and Innovative Research
Volume.07, IssueNo.02, February-2015, Pages: 0200-0206
Analysis of Matrix Converter Based UPFC
[10] R. Strzelecki, A. Noculak, H. Tunia, and K. Sozanski,
V. CONCLUSION
Based on sliding mode control technique this thesis
―UPFC with matrix converter,‖ presented at the EPE Conf.,
derived advanced nonlinear direct power controllers, for
Graz, Austria, Sep. 2001.
matrix converters linked to power transmission lines as
[11] J. Monteiro, J. Silva, S. Pinto, and J. Palma, ―Unified
UPFCs. By using the proposed direct power control the
power flow controllers without DC bus: Designing
thesis presented simulation results shows that active and
controllers for the matrix converter solution,‖ presented at
reactive power flow can be gainfully controlled. End results
the Int. Conf. Electrical Engineering, Coimbra, Portugal,
display steady-state errors zero, no cross-coupling,
2005.
inconsiderateness to non modeled dynamics and quick
response times, thus confirm the expected presentation of
the existing nonlinear DPC attitude. PI linear active and
reactive power controllers compared to obtain DPC-MC
results using a modified Venturini high-frequency PWM
modulator. Apart from of showing a suitable dynamic
response, the PI performance is inferior when compared to
direct power control. In addition, modulator and PI
controllers take longer times to compute. Obtain results
display that DPC is a strong nonlinear control contestant for
line active and reactive power flow. It ensures transmissionline power control in addition to sending end reactive power
or power factor control.
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International Journal of Advanced Technology and Innovative Research
Volume.07, IssueNo.02, February-2015, Pages: 0200-0206