Analysis of R-SFCL with Parallel Shunt Resistor in MMC-HVDC System

Xiangyu Tan, Li Ren, Siyuan Liang, Yuejin Tang, Ying Xu, Shuqiang Guo and Guilun Chen State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science & Technology, Wuhan, China

Abstract— R-SFCL has a board application prospect in MMC-HVDC system.

However, the R-SFCL will quench due to fault current, which results in temperature

rise and may damage superconducting coils. A shunt resistor in parallel can protect

the superconducting coils, but the influence has not been quantitatively calculated.

This work proposed a novel R-Q curve method to calculate quenching resistance of

R-SFCL. Using this method, the influence of shunt resistor to R-SFCL is analyzed in

terms of current-limiting effect and maximum temperature. Performance of R-SFCL

with different shunt resistance is compared, and the optimal shunt resistance value is

obtained.

Current

Pancake

Submodule

0 200 400 600 800 1000

0.00

0.01

0.02

0.03

0.04

0.05

AC 1360A DC 1460A

AC 1420A DC 1580A

AC 1580A DC 1820A

AC 1920A DC 1950A

R (

Ω/m

)

Q (J/m)

Trendline

0 2 4 6 8 10

0

2

4

6

experiment

R-Q method

FEM

Rsc (

Ω)

time (ms)

MMC1 MMC2SFCL unit

Mechanical DCCB

RSC

RSC

Rshunt

Unit 1 Unit 2

No. Rshunt Turns Tape length

1 without Rshunt24 2.64 km

2 15 Ω 28 3.53 km

3 12 Ω 30 3.89 km

4 10 Ω 36 4.49 km

0 2 4 6 8 10 12

-5

0

5

10

15

20 unlimited

#1

#2

#3

#4

I dc (

kA

)

time (ms)

0 200 400 600 800

80

100

120

140

160 #1

#2

#3

#4

T (

K)

time (ms)

0

1

2

3

4

5

#1 #2 #3 #4

Max

imum

res

ista

nce

(Ω

)

0

20

40

60

80

100

#1 #2 #3 #4

Lim

itin

g r

atio

(%

)

0

1

2

3

4

#1 #2 #3 #4

Tap

e le

ngth

(km

)

0

50

100

150

200

#1 #2 #3 #4

Max

imum

tem

per

ature

(K

)

0

100

200

300

400

Rec

over

y t

ime

(ms)

#1 #2 #3 #40.0

0.5

1.0

1.5

2.0

#1 #2 #3 #4

Rec

over

y t

ime

(s)

Basic structure of R-SFCL

Fig. Configuration of non-inductive pancake and R-SFCL

Parameter Value

Rated voltage 160kV

Critical current 2kA

No. of turns 24

No. of pancakes 16

R-Q curve method to calculate quenching resistance

Tab. Parameters of R-SFCL

Experiments show that there is a corresponding

relation between quenching resistance R and the

accumulated joule heat Q.

Fig. R-Q curve of superconducting tapes. Fig. Calculation result of R-Q method compared with experiment and FEM.

An R-Q method to calculate quenching

resistance is proposed. Result is well fitted with

finite element method (FEM) and experiments.

Analysis of R-SFCL with shunt resistor

Q = Q + q R-Q curveI

R

RSCq = I2R t *L

The R-Q method is coupled with

system simulation to calculation

quenching resistance. And FEM is

used to calculate magnetic file and

temperature.Fig. Calculation process of R-Q curve method

Fig. Structure of MMC-HVDC system with SFCL unit

Tab. Parameters of SFCL units

Four types of SFCL units with different shunt

resistance and tape length are chosen for analysis.

Fig. Fault current during DC pole-to-pole fault

Fig. Temperature of superconducting coils

(a) maximum current-limiting resistance

(b) Current-limiting ratio

(c) Tape length

(d) Maximum temperature

(e) Recovery time to 92K

(f) Recovery time to 77K

All SFCL units have the same current-limiting

ratio. The temperature is reduced by shunt resistor.

Considering the temperature and tape length, No.3

is the most economical scheme.

Fig. Comparison of SFCL units

This paper studies the performance of R-SFCL with a fixed-value shunt resistor

using R-Q method and FEM. Conclusions are as follows:

• The R-Q method is highly fitted with FEM and experiment. Combing the R-Q

method and FEM, system simulation and finite element analysis are separated. The

calculation speed is greatly improved.

• The shunt resistor can reduce the temperature and recovery time, but more tapes

are consumed. When shunt resistance is 12Ω, the maximum temperature is reduced

by 30K, which is the most economical.