Synchronous Voltage Reversal control of TCSC– impact on SSR conditions
Hailian Xie Lennart Ängquist
EME/ETS, Royal Institute of Technology, Stockholm
Series compensation
capacitor bank inserted in series with transmission line
aims to increase the power transfer capacity of high-voltage transmission line
fixed capacitor bank may cause a Torsional Interaction Sub-Synchronous Resonance (TI-SSR) problem with thermal power generators
Thyristor Controlled Series Capacitor (TCSC) may solve this problem
EME/ETS, Royal Institute of Technology, Stockholm
TCSC main circuit and generic waveforms
EME/ETS, Royal Institute of Technology, Stockholm
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2-2
0
2
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2-5
0
5
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2-50
0
50
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2-40
-20
0
Line current
Valve current
Capacitor voltage
Apparent reactance
About this paper
describes the laboratory setup of a TCSC model with the SVR (Synchronous Voltage Reversal) control scheme
presents the result from an investigation concerning the impact of the SVR controlled TCSC on SSR in the real-time simulator
EME/ETS, Royal Institute of Technology, Stockholm
Diagram of the real-time simulator
EME/ETS, Royal Institute of Technology, Stockholm
Infinite
bus u2
Source 1 impedanceu1
Line FixedImpedance capacitor
TCSC inductance
TCSC capacitor
Thyristor valve
SVR Control scheme
EME/ETS, Royal Institute of Technology, Stockholm
2
c
t
iL
iv
uc SVR idea: control capacitor voltage zero-crossing instant
TCSC capacitor
SVR boost control system overview
EME/ETS, Royal Institute of Technology, Stockholm
PLL
Boost controller
uc (measured)
kBref + kBm _
pulses
-XC0 Re
Im
SVR trig pulse
generation
TCSC inductance
Thyristor valve
il (measured)
Apparent Z evaluation
Phasor estimation
Method to analyze the system damping
EME/ETS, Royal Institute of Technology, Stockholm
Kel
DelTel
iL LPfilter
Calculate the electrical
torque
In DSP In Matlab
Calculate the spring constant and damping
coefficient
Generate system voltage
u1Control
modulation
Re(ΔTel)Im(ΔTel)
Electrical damping curve (1)
system with fixed series compensation
EME/ETS, Royal Institute of Technology, Stockholm
10 15 20 25 30 35 40 45-15
-10
-5
0
5Del & Kel with fixed series compensation
De
l [p
u t
rq/p
u s
pd
]
10 15 20 25 30 35 40 45-2
-1
0
1
2
3
mech freq [Hz]
Ke
l [p
u t
rq/r
ad
]
Electrical damping curve (2)
system with SVR controlled TCSC
EME/ETS, Royal Institute of Technology, Stockholm
10 15 20 25 30 35 40 45-6
-4
-2
0
2
4SVR control, no PLL, no boost control
De
l [p
u t
rq/p
u s
pd
]
10 15 20 25 30 35 40 45-2
-1
0
1
2
3
mech freq [Hz]
Ke
l [p
u t
rq/r
ad
] KB=1.2KB=1.72
Electrical damping curve (3)
Comparison between SVR and control
EME/ETS, Royal Institute of Technology, Stockholm
10 15 20 25 30 35 40 45-6
-4
-2
0
2
4KB=1.2, no PLL, no boost control
De
l [p
u t
rq/p
u s
pd
]
10 15 20 25 30 35 40 45-2
-1
0
1
2
3
mech freq [Hz]
Ke
l [p
u t
rq/r
ad
] SVR controlbeta control
Electrical damping curve (4)
SVR control with different parameters
EME/ETS, Royal Institute of Technology, Stockholm
10 15 20 25 30 35 40 45-8
-6
-4
-2
0
2
4SVR, KB=1.72, medium boost control with different PLL speed
De
l [p
u t
rq/p
u s
pd
]
10 15 20 25 30 35 40 45-2
0
2
4
mech freq [Hz]
Ke
l [p
u t
rq/r
ad
]
s lowmediumfast
Conclusions
at low boost factor, SVR controlled TCSC can provide much better damping than conventional control scheme that controls the firing angle directly
the damping characteristic of SVR controlled TCSC with respect to SSR is almost independent of the boost factor
the tuning of the boost controller and PLL makes no critical difference on the TCSC SSR behavior
EME/ETS, Royal Institute of Technology, Stockholm
Thank you!Thank you!
EME/ETS, Royal Institute of Technology, Stockholm