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IJSART - volume 1 Issue
4 –APRIL 2015
ISSN [ONLINE]: 2395-1052
Multimode Power Controllers for Three Phase Matrix
Converters Operating as UPFC
Mr. T .Karthik 1, Mr. M. Nagarajan 2
1, 2
Arignar Anna Institute of Science and Technology, Chennai, India
Abstract- This project presents the design and compares the
performance of linear, decoupled and direct power controllers
(DPC) for three-phase matrix converters operating as unified
power flow controllers (UPFC). A simplified steady-state
model of the matrix converter-based UPFC fitted with a
modified Venturini high- frequency pulse width modulator is
first used to design the linear controllers for the transmission
line active (P ) and reactive (Q) powers. In order to minimize
the resulting cross coupling between P and Q power
controllers, decoupled linear controllers (DLC) are
synthesized using inverse dynamics linearization. DPC are
then developed using sliding-mode control techniques, in
order to guarantee both robustness and decoupled control.
Decoupled linear controllers (DLC) designed by inverse
dynamics linearization.
DPC, which have been successfully used in power
applications, owing to its simplicity and good performance.
This control method, based on sliding-mode control technique.
Keywords- Unified power flow controller, Matrix converter, Direct
power controller.
I. INTRODUCTION
A Unified Power Flow Controller (or UPFC) is an
electrical device for providing fast-acting reactive power
compensation on high-voltage electricity transmission
networks. The UPFC is a versatile controller which can
be used to control active and reactive power flows in a
transmission line. The concept of UPFC makes it possible
to handle practically all power flow control and
transmission line compensation problems, using solid state
controllers, which provide functional flexibility, generally
not attainable by conventional thyristor controlled systems.
The UPFC is a combination of STATCOM and SSSC coupled
via a common DC voltage link. The parameters affecting the
power flow in a transmission line. The parameters usually are
voltage, impedance and phase angle.
II. CONTROL SCHEME OF THE PROPOSED
METHOD
The proposed system is a matrix converter-based
UPFC (MC-UPFC) for power transmission networks is used
to control the P and Q power flow in a transmission line.
Three different types of controllers are designed and tested:
Proportional integral (PI) linear controllers designed by
modified Venturing high frequency MC pulse width
modulator (PWM).
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Fig.1 Control Scheme of the Proposed System
III. DESIGN MATRIX CONVERTER SWITCH
Matrix converter
Directly converts AC to AC rather than AC to DC to
AC as in conventional voltage source PWM AC Drives.
Matrix converters have capability to regenerate power and
suppress input current. The nine MC switches can be
represented as a 3 × 3 matrix
Circuit topology restriction for k ∈ {1, 2, 3} implies that
Based on Matrix, the relationship between load and input
voltages can be expressed as follows:
The input phase currents can be related to the output phase
currents (3), using the transpose of matrix S
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IJSART - volume 1 Issue
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ISSN [ONLINE]: 2395-1052
These terms can both be controlled by changing the
controllable voltage source amplitude VC and phase ρ.
V. MATRIX CONVERTER –UNIFIED
POWER FLOW CONTOLLER
A.MC-UPFC control using PI Controller
The synthesis of PI power controller is based on a
linearized model assuming small variations near the operating
point ρ ≈ π/2, the incremental gain relative to VC is
Fig. 2 Basic scheme of matrix converters
IV. UPFC Power System Steady-State Model
To design slow feedback controllers, a UPFC steadystate model can be used. A single-phase MC equivalent circuit
represented as a controllable voltage source (see Fig.) is
considered, with amplitude VC and phase ρ, in series with
equivalent line inductance L2 (L2 = X2 /ω, X2 = XL2+XL
1_XZL), neglecting line resistance and shunt capacitances,
being VR0 the voltage at the load bus.
Fig.3 Per phase equivalent circuit of the MC-UPFC and
transmission line.
The injected series voltage VC must compensate the
amplitude and phase differences between VS and VR0,as well
as the effects of line impedance XL2 .
From the sending-end complex power, obtained by
the product of the end voltage by the complex conjugate of the
line current in the per phase equivalent circuit, controllable
parts of active and reactive powers, ΔP and ΔQ, are,
respectively
Considering the active power dynamics represented
by a first-order transfer function with time Considering the
active power dynamics represented by a first-order transfer
function with time constant Tl and choosing a PI controller
CP (s) = KP [(1 +sTiP )/sTiP ] to guarantee zero steady-state
error , the block diagram is obtained. To determine the PI
controller parameters, it is chosen to cancel the open-loop pole
with the controller zero (i.e., TiP = Tl ).
B.MC-UPFC control using DLC
To guarantee no cross coupling between P and Q
power controllers, linear controllers are derived in dq
coordinates using inverse dynamics linearization. A UPFC
model is represented by Assuming a reference frame
synchronized to the mains voltages which guarantees VSq = 0,
P and Q will be given by
Based on the desired active and reactive powers,
reference currents can be calculated from, seeking decoupled
control of active and reactive powers. However, designing
closed-loop Id and Iq current controllers, the resulting active
and reactive powers, P and Q, will be sensitive to the values of
the mains voltages VSd and VSq.
To overcome this problem, the synthesis of P and Q
power controllers is obtained by substituting the previously
calculated Id and Iq currents. Active and reactive powers are
obtained as a function of transmission line parameters, load
bus and source voltages.
C.MC-UPFC control using DPC
Sliding-mode control theory enables the derivation of
a direct power control (DPC) method for MC-UPFC to
regulate the P and Q powers in the transmission line.VSd is
imposed by source VS in steady state. From (7), the
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transmission line currents are state variables with a first-order
dynamics dependent on the sources and the line time constant
(L2 /R2). Therefore, line transmission active and reactive
powers have a strong relative degree of one.
The strong relative degree represents the number of
times the control output variable must be differentiated until a
control input appears explicitly in the output dynamics. From
sliding-mode control theory, robust sliding surfaces to control
the P and Q variables with strong relative degree of one can be
obtained considering proportionality to a linear combination of
the errors of the state variables.
ISSN [ONLINE]: 2395-1052
Fig, 7 Matrix converter active (P) and Reactive Power (Q)
VI. CONCLUSION
VI. SIMULATION RESULTS
Fig.4 Matrix converter three phase output voltage
This paper designs and compares three different
control methods for active and reactive power flow using MCs
connected to power transmission lines as UPFC: PI linear
controllers, DLC, and sliding-mode-based nonlinear DPC.
MC-UPFCs need almost no energy storage, which is a clear
advantage in the converter sizing and design, and the proposed
controllers and high frequency filter placement were chosen to
obtain control parameters almost independent of load and filter
characteristics.
Simulation and experimental results show that P and
Q power flow can be effectively controlled using the MCUPFC and one of the three controllers. The nonlinear DPC
methodology show no steady-state errors, no cross coupling,
insensitivity to non-modeled dynamics, fast response times,
and low THD, whereas the simpler PI linear P and Q power
controllers using a modified Venturini high-frequency PWM
show a small cross coupling and slower response times. DLC,
although dependent on system parameters, show no cross
coupling, fast response, and small ripples in steady state, but
higher THD.
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Fig.5 Matrix converter three phase output current
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4 –APRIL 2015
ISSN [ONLINE]: 2395-1052
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