ABSTRACT:
The Generalized Unified Power Flow Controller
(GUPFC) is a Voltage Source Converter (VSC) based Flexible AC Transmission
System (FACTS) controller for shunt and series compensation among the multiline
transmission systems of a substation. The paper proposes a full model
comprising of 60-pulse Gate Turn-Off thyristor VSC that is constructed becomes
the GUPFC in digital simulation system and investigates the dynamic operation
of control scheme for shunt and two series VSC for active and reactive power
compensation and voltage stabilization of the electric grid network. The
complete digital simulation of the shunt VSC operating as a Static Synchronous
Compensator (STATCOM) controlling voltage at bus and two series VSC operating
as a Static Synchronous Series Capacitor (SSSC) controlling injected voltage,
while keeping injected voltage in quadrature with current within the power
system is performed in the MATLAB/Simulink environment using the Power System
Block set (PSB). The GUPFC, control system scheme and the electric grid network
are modelled by specific electric blocks from the power system block set. The
controllers for the shunt VSC and two series VSCs are pre-sented in this paper
based on the decoupled current control strategy. The performance of GUPFC scheme
connected to the 500-kV grid is evaluated. The proposed GUPFC controller scheme
is fully validated by digital simulation.
KEYWORDS:
60-Pulse GTO Thyristor Model VSC, UPFC, GUPFC,Active
and Reactive Compensation, Voltage Stability
SOFTWARE: MATLAB/SIMULINK
BLOCK DIAGRAM:
Figure 1. Three-bus system with
the GUPFC at bus B5 and B2
EXPECTED SIMULATION RESULTS:
Figure 2. Sixty-pulse VSC output
voltage
Figure 3. Simulated results of the GUPFC .shunt
converter operation for DC voltage with Qref = 0.3pu; 0.5 pu
Figure 4. Simulated results of the GUPFC series
converter operation Pref=8.7pu; 10pu, Qref=-0.6pu; 0.7pu
Figure 5. Simulated results of the GUPFC series
converter operation Pref=7.7pu; 9.0pu, Qref=-0.5pu; 0.9pu
Figure 6. Digital simulation results for the
decoupled current controller schemes for the shunt VSC in a weak power system
CONCLUSION:
The
paper presents and proposes a novel full 60-pulse GTO voltage source converter
that it constructed becomes GUPFC FACTS devices. It comprises the full 60-pulse
VSC-cascade models connected to the grid network through the coupling
transformer. These full descriptive digital models are validated for voltage
stabilization, active and reactive compensation and dynamically power flow
control using three decoupled current control strategies. The control
strategies implement decoupled current control switching technique to ensure
controllability, minimum oscillatory behaviour, minimum inherent phase locked
loop time delay as well as system instability reduced impact due to a weak
interconnected ac system and ensures full dynamic regulation of the bus voltage
(VB), the series voltage injected and the dc link voltage Vdc. The 60-pulse VSC
generates less harmonic distortion and reduces power quality problems in
comparison to other converters such as (6,12,24 and 36) pulse. In the
synchronous reference frame, a complete model of a GUPFC has been presented and
control circuits for the shunt and two series converters have been described.
The simulated results presented confirm that the performance of the proposed
GUPFC is satisfactory for active and reactive power flow control and
independent shunt reactive compensation.
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