Leonardo Journal of Sciences
Issue 29, July-December 2016
ISSN 1583-0233
p. 43-54
The sensitivity approach method with optimal placement of thyristor controlled series compensator Messaoud. ZOBEIDI1,*, Fatiha LAKDJA2 and Fatima Zohra GHERBI1 1
Engineering Department. Intelligent Control and Electrical Power System Laboratory (ICEPS), Djillali Liabes University, Sidi-Bel-Abbes, 22000, Algeria 2 The Department of Electrical Engineering, Saida University, Engineering Department. Intelligent Control and Electrical Power System Laboratory (ICEPS), Djillali Liabes University, Sidi-Bel-Abbes, 22000, Algeria. E-mails:
[email protected];
[email protected];
[email protected] * Corresponding author, phone: +213664789057
Abstract The stressed power system, due to the increased loading or severe contingencies leads to situation where the system no longer remains in the secure operating region. The Flexible AC Transmission System (FACTS) can improve the power system transmission network operation. In order to undue costs, optimal placement of the devices FACTS in the power system must be located. The main objective of this manuscript is to locate the optimal placement of the TCSC devices (Thyristor Controlled Series Compensator), using the reactive power loss sensitivity index based approach and LODF (Line Outage Distribution Factor). The method proposed as testing in two different systems of IEEE 6 bus and IEEE 25 bus is modified using Power world simulator software version 18. Keywords Line outage distribution factor; Reactive power loss sensitivity index; Flexible AC Transmission System; Thyristor Controlled Series Compensator
43 http://ljs.academicdirect.org/
The sensitivity approach method with optimal placement of thyristor controlled series compensator Messaoud ZOBEIDI, Fatiha LAKDJA, Fatima Z. GHERBI
Introduction
During the last years, the power system, included problems related to the increased loading or severe contingencies, has lead to situations where the system no longer remains in the secure operating region. The principal objective of the operators is to improve power system security with different levels of difficulty [1]. The security of a power system can be defined as its ability to withstand a set of severe but credible contingencies and to survive transition to an acceptable new steady state condition. In contrast, the insecure cases represent grave threats to the operation of the system [2-3]. The Flexible AC Transmission systems (FACTS) controllers can be help to improve system safety by effectively controlling the line power flows (to reduce the transmission congestion, resulting in an increased loadability) [4-5]. It is defined by the IEEE (Institute of Electrical and Electronics Engineers) as a power electronic based system and other static equipment that provide control of one or more AC transmission system parameters to enhance controllability and increase power transfer capability [6]. The FACTS devices have high cost so it is necessary for optimal placement in the power system. Several papers interested to treat with different methods the optimal location of FACTS controllers. Which have presented the method of optimal location of TCSC, TCPAR and UPFC [2-3]. In this paper, the reduction of total system reactive power losses and the line outage distribution factor method used for determined optimal location of series FACTS device (TCSC). The reduction of total system reactive power losses method is suggested to find optimal placement of FACTS devices, this method based on the sensitivity of the total system reactive power loss with respect to the control variable of the FACTS [7-9]. The line outage distribution factor used again for decide optimal for one only case in the line outage .The LODF says how the flow changes on a line when there is other line outage in the power system [10]. The aim of this study was to test the methods suggested on two different systems of IEEE 6 bus and IEEE 25 bus is modified using Power world simulator software version 18.
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Leonardo Journal of Sciences
Issue 29, July-December 2016
ISSN 1583-0233
p. 43-54
Material and method
Modeling of the series FACTS device TCSC The TCSC consists of an inductance in series with a thyristor valve, shunted by capacitor, this unit is inserted in series on the line of transmission and the figure 1 shows the basic structure of TCSC:
Figure 1. Thyristor controlled series capacitor
Model of injection Figure 2 shows a model of line with TCSC connected between tows buses i and j. TCSC is equivalent a static reactance -jxc, This controllable reactance is directly used the control variable in the power flow equations . j
Let complex voltages at bus-i and bus-j are Vii and Vj
respectively.
Figure 2. Transmission line with TCSC model The real and reactive power flow equations at bus i and bus j with a new line reactance given as follows: Pijc Vi2G ij Vi Vj (G ij cos ij Bij sin ij )
(1)
Pjic Vj2G ij Vi Vj (G ij cos ij Bij sin ij )
(2)
Qijc Vi2 (Bij Bsh ) Vi Vj (G ij sin ij Bij cos ij )
(3)
Qcji Vi2 (Bij Bsh ) Vi Vj (G ij sin ij Bij cos ij )
(4)
45
The sensitivity approach method with optimal placement of thyristor controlled series compensator Messaoud ZOBEIDI, Fatiha LAKDJA, Fatima Z. GHERBI
Hence, the change in the line flows due to series capacitance, the real and reactive power flows injection at bus i and bus j:
Pijc Vi2 G ij Vi Vj (G ij cos ij Bij sin ij )
(5)
Pjic Vj2 G ij Vi Vj (G ij cos ij Bij sin ij )
(6)
Qijc Vi2 Bij Vi Vj (G ij sin ij Bij cos ij )
(7)
Qcji Vi2 Bij Vi Vj (G ij sin ij Bij cos ij )
(8)
The reactive power loss on each line can be formulated as: QL = Qij + Qji
(9) (10)
QL (Bij Bsh )( V V ) 2Vi VjBij cos ij 2 i
where: G ij
Bij
x c rij ( x c 2x ij )
(r x ) r ( x ij x c ) 2 ij
( x c x ij ) r ( x ij x c ) 2 2 ij
2 j
2 ij
2 ij
2
, Bij
x c (rij2 x ij2 x ij x c )
(r x ) r ( x ij x c ) 2 ij
2 ij
2 ij
2
, G ij
rij r ( x ij x c ) 2 2 ij
,
, Vi , Vj : The voltage magnitude at bus i and j, δij : The voltage angle
difference between bus i and j (δi-δj), xc : TCSC capacitive reactance (TCSC is equivalent a static capacitive reactance), xij : The reactance of Transmission line between bus i and j, rij : The resistance of Transmission line between bus i and j, Gij: The susceptance of Transmission line between bus i and j with TCSC, Bij: The conductance of Transmission line between bus i and j with TCSC, Bsh: Shunt susceptance at line i-j, ∆Gij: (Gline-Gij)The change of Transmission line Susceptance, ∆Bij: (Bline-Bij) Transmission line Susceptance, Pijc: is the real power transfer from bus i to bus j with TCSC, Pic, Pjc: the real power injections at bus i and j, Qijc: is the reactive power transfer from bus i to bus j with TCSC, Qic, Qjc: the reactive power injections at bus i and j, QL: The reactive power loss on the line i-j
Method for optimal placement of TCSC Sensitivity approach method This method based on the sensitivity of the total system reactive power loss with respect to the control variables of the TCSC devices. We controlled the parameter of the reactance line for TCSC located between two buses i and j. Loss sensitivity with respect to control parameter of TCSC placed between buses i and j can be giving as [5]: rij2 x ij2 Q L 2 2 a ij Vi Vj 2Vi VjG ij cos ij 2 x ij rij2 x ij2
46
(11)
Leonardo Journal of Sciences
Issue 29, July-December 2016
ISSN 1583-0233
p. 43-54
Application In this example, the Sensitivity approach method for optimal placement of TCSC has been tested on IEEE 6 bus system by using power world simulator software 18,such as, the system consists 3 generators and 3 loads and 8 transmission lines. It shows by figure 3 when the system without TCSC. 50 MW
3
2
A
99 Mvar
5% MVA
60 MW 69 Mvar A
A
97% MVA
A
1
30% MVA
6
86% MVA
A
26%
A
87%
MVA
MVA
A
59%
A
MVA
2%
slack
MVA
21 Mvar
5
70 MW 70 Mvar
A
108 MW 4
A
39% MVA
48% MVA
A
6%
70 MW 70 Mvar
70 MW 70 Mvar
MVA
Figure 3. IEEE 6 bus system modified In the Figure 3, the lines 2-6, 2-5 and 3-6 have most percentage load ability values 97%, 87% and 86% respectively, caused by the increased loading. The obtained results shown on ‘Results and discussion’ section
Line outage distribution factor This method proposed for the optimal site of facts series TCSC, in power system. The line outage distribution factor (LODF) is important linear sensitivity factor, which is based on simplifying the nonlinear power flow equations in to a linear system using the DC assumption. LODFs are used to approximate change in the flow on one line due to the outage of another line, the line outage distribution factor says how the flow changes on a line when there is other line outage in the power system. The definition of the LODF can be giving as it is the change in flow on a line as a percentage of the pre outage flow on another line [10 -11]. (12) Pk ,m Pm where LODF(k,m) : is the line outage distribution factor of branch k with respect to outage
LODFk ,m
branch m; ∆P
(k,m) :
The change of the active power between two lines; Pm: The power flow
after the outage of line m.
47
The sensitivity approach method with optimal placement of thyristor controlled series compensator Messaoud ZOBEIDI, Fatiha LAKDJA, Fatima Z. GHERBI
The criteria for optimal location of TCSC The TCSC should be place in the line have most positive the reactive power loss sensitivity factors [9]. The TCSC should be place in the line have most positive factors Line outage distribution factor [10].
Results and discussion
IEEE 6 bus system modified The reduction of total system reactive power losses method used to find optimal placement of TCSC on modified IEEE 6 bus system, the results obtained as show in Table 1. Table 1. Sensitivity index of modified IEEE 6 bus system Line Sensitivity index 1-5 -0.7 6-5 -1.1 2-3 -2.7 4-5 -4.2 3-5 -15.0 2-4 -18.1
Line Sensitivity index 2-5 -29.7 2-1 -40.4 1-4 -43.1 2-6 -57.7 3-6 -236.6
According to the results obtained in Table 1, it can be seen that the most positive value the sensibility index in the line (1-5).This line selected for installing of TCSC. 50 MW
3
2
A
88 Mvar
3% MVA
60 MW 64 Mvar A
A
86% MVA
A
1
15% MVA
6
84% MVA
A
22%
A
68%
MVA
MVA
A
60%
A
MVA
5%
slack
MVA
109 MW 31 Mvar
5
70 MW 70 Mvar
A
4
A
65% MVA
39% MVA
A
70 MW 70 Mvar
3%
70 MW 70 Mvar
MVA
Figure 4. IEEE 6 bus system modified with TCSC placed in the line 1-5 The figure 4 shows the transmission network system after placing TCSC in line 1 –
48
Leonardo Journal of Sciences
Issue 29, July-December 2016
ISSN 1583-0233
p. 43-54
5.we notice the loading of lines 2-5, 2-6 ,3-6 decrease, from 87 % to 68% , from 97% to 86% , from 86% to 84% respectively. Table 2. The power flow with and without TCSC Line Bus from-Bus To Without TCSC With TCSC 1 1-5 36.7 63.1 2 1-4 43.4 31.4 3 2-5 11.8 3.7 4 2-1 27.1 14.0 5 2-3 2.9 1.9 6 2-6 27.7 22.4 7 2-4 34.8 39.8 8 3-6 43.6 44.1 9 3-5 19.3 14.0 10 4-5 5.2 1.4 11 5-6 0.6 5.1
The table 2 indicates that the power flow before and after sitting the TCSC, which represents by the graph (figure 5), it’s can be seen good results for the power flow ( balanced distribution of power flow )
Figure 5. The power flow with and without TCSC
IEEE 25 bus system modified In this transmission network system, it used the line outage distribution factor method to find the optimal location of TCSC, The critical line outages were computed by line outage distribution factor for a single line outage case. Modified IEEE 25 bus system with line (5-17) outage shows in Figure 6 and 7.
49
The sensitivity approach method with optimal placement of thyristor controlled series compensator Messaoud ZOBEIDI, Fatiha LAKDJA, Fatima Z. GHERBI 25 MW 8 Mvar
30 MW 10 Mvar
15 MW 5 Mvar
25
15
20 MW 7 Mvar
24
A
9%
3
A
23
15 MW
MVA
A
MVA
25 MW 8 Mvar
40%
sl a ck
MVA
60 MW 20 Mvar
10 MW
5 Mvar
70% 186 Mvar MVA
MVA
17
12
A
22%
56%
A
MVA
5 18 5 Mvar 15 MW
A
MVA
10%
A A
MVA
11
32%
A
15%
MVA
MVA A
5 MW 0 Mvar
0% 2
7
MVA
8
A
A
47% A
42%
10
5%
MVA
25 MW 0 Mvar
9 A
16% 15 MW 5 Mvar
MVA
13 Mvar
-2 Mvar
30%
MVA
133 MW
A
MVA
33%
233 MW
97%
A
MVA
3 Mvar
A
MVA
MVA
6
10 MW
6%
15%
183 MW 22 Mvar
18%
A
100 MW
A
0 Mvar
A
83 MW 28 Mvar
19
1
13
15 MW
4
A
44%
5 Mvar
MVA
71%
MVA
MVA
16% 15 MW
MVA
A
13%
A
52%
5 Mvar
A
42%
30 MW 10 Mvar
A
37% MVA
A
MVA
20 MW 7 Mvar 25 MW 8 Mvar
A
200 MW 65 Mvar
50 MW 17 Mvar
52%
MVA
MVA
16
MVA A
20
A
27%
8%
MVA
22% 14
21
A
MVA
24%
A
25 MW 8 Mvar
45%
MVA A
A
MVA
22
A
21%
MVA
34%
20 MW 7 Mvar
MVA
15 MW
15 MW
5 Mvar
5 Mvar
MVA
Figure 6. IEEE 25 bus system modified without open the line 17-5 In the figure 7, it is observed that the line (19-5) is overloaded when the line 5-17 is opened. Table 3. LODF % of the 25 bus system Line LODF % 5-10 100 1-19 30.8 8-7 25.4 4-19 19.4
According to the results obtained in Table 3, it can be seen that the most positive value the sensibility index in the line (1-5).This line is selected for installing of TCSC. The figure 8 shows the system with TCSC placed in line (5-10), the overloading of the line (5-19) decreases from 107% to 95% and the line (19-4), from 89% to 79%.
50
Leonardo Journal of Sciences
Issue 29, July-December 2016
ISSN 1583-0233
p. 43-54 25 MW 8 Mvar
30 MW 10 Mvar
15 MW 5 Mvar
25
15
20 MW 7 Mvar
24
A
23
3
5 Mvar
75%
MVA
A
MVA
25 MW 8 Mvar
58%
sl a ck
MVA
13
60 MW 20 Mvar
10 MW 15 MW 5 Mvar
51% 212 Mvar MVA
MVA
33%
107%
A
MVA
5
MVA
18
17
12
5 Mvar 15 MW
A
38%
6
237 MW
A
MVA
10 MW
A
MVA
16%
187 MW 23 Mvar
19%
A
105 MW
A
0 Mvar
A
87 MW 57 Mvar
19
1
A
13%
MVA
5 Mvar
MVA
4
A
89%
16% 15 MW
MVA
MVA
15 MW
A
42%
30 MW 10 Mvar
A
A
57%
MVA
A
MVA
20 MW 7 Mvar 25 MW 8 Mvar
A
42%
200 MW 65 Mvar
50 MW 17 Mvar
53%
A
MVA
16
MVA A
MVA
12%
MVA
23% 14
20
A
31%
MVA
22%
A
21
54%
MVA A
A
25 MW 8 Mvar
A
26%
MVA
MVA
22
A
13% 35%
20 MW 7 Mvar
40%
80%
MVA A
3 Mvar
A
MVA
11
49%
34%
-1 Mvar
A
A
45%
MVA
MVA
MVA A
5 MW 0 Mvar
13% 2
MVA
7
8
A
9
10
A
55%
A
6% 15 MW 5 Mvar
MVA
137 MW
A
30 Mvar
15%
MVA
MVA
25 MW 0 Mvar
40%
15 MW
15 MW
5 Mvar
5 Mvar
MVA
Figure 7. IEEE 25 bus system modified with line (5-17) is open 25 MW 8 Mvar
30 MW 10 Mvar
15 MW 5 Mvar
25
15
20 MW 7 Mvar
24
A
12% MVA
MVA A
3
A
23
A
MVA
25 MW 8 Mvar
54%
sl a ck
MVA
13
60 MW 20 Mvar
10 MW 15 MW 5 Mvar
56% 212 Mvar MVA
MVA
MVA
5
237 MW
A
A
47% MVA
A A
MVA
11
52%
36%
-10 Mvar
95% A
53%
MVA
MVA
MVA A
5 MW 0 Mvar
17% 2
7
MVA
8
A
A
55% A
39%
10
21%
MVA
25 MW 0 Mvar
9 A
9% 15 MW 5 Mvar
MVA
32 Mvar
95%
5 Mvar 15 MW
A
41% MVA
137 MW
A
18
17
12
3 Mvar
MVA
A
MVA
6
10 MW
28%
11%
187 MW 23 Mvar
22%
A
104 MW
A
0 Mvar
A
87 MW 51 Mvar
19
1
76%
MVA
MVA
5 Mvar
MVA
4
A
79%
16% 15 MW
MVA
MVA
15 MW 5 Mvar
A
A
13%
A
56%
MVA
42%
30 MW 10 Mvar
MVA A
41%
A
MVA
20 MW 7 Mvar 25 MW 8 Mvar
MVA A
200 MW 65 Mvar
50 MW 17 Mvar
A
54%
20
A
30%
MVA
16
MVA
14
21
A
11%
MVA
23%
25 MW 8 Mvar
52%
22%
A
MVA
22
A
25%
A
36%
20 MW 7 Mvar
MVA
15 MW
15 MW
5 Mvar
5 Mvar
MVA
Figure 8. IEEE 25 bus system modified with TCSC in line 5-10 In Figure 9, The TCSC placed in the line (1-19), the lines (1-19) and (5-19) are load ability with limit 103% and 112%. Form figure 10, we can see stressed power system. In figure 11, the TCSC placed in line (4-19), and the loading of line (1-2) increases
51
The sensitivity approach method with optimal placement of thyristor controlled series compensator Messaoud ZOBEIDI, Fatiha LAKDJA, Fatima Z. GHERBI
from 108% .This line is not optimal placement for improvement the power system security. 25 MW 8 Mvar
30 MW 10 Mvar
15 MW 5 Mvar
25
15
20 MW 7 Mvar
24
A
11%
A
55%
MVA
23
3
76%
MVA
A
MVA
25 MW 8 Mvar
103%
sl a ck
MVA
13
60 MW 20 Mvar
10 MW 15 MW 5 Mvar
MVA
30%
45% 261 Mvar
112%
A
MVA
13%
5
MVA
18
17
12
5 Mvar 15 MW
A
39%
6
240 MW
A
MVA
10 MW
A
MVA
MVA
190 MW 22 Mvar
18%
A
107 MW
A
0 Mvar
A
90 MW 14 Mvar
19
1
A
13%
MVA
5 Mvar
MVA
4
A
19%
16% 15 MW
MVA
MVA
15 MW 5 Mvar
A
42%
30 MW 10 Mvar
A
A
39%
A
MVA
20 MW 7 Mvar 25 MW 8 Mvar
A
200 MW 65 Mvar
50 MW 17 Mvar
54%
MVA
MVA
16
MVA A
20
A
29%
10%
MVA
23% 14
21
A
MVA
23%
A
25 MW 8 Mvar
49%
MVA A
A
MVA
22
A
23%
MVA
35%
20 MW 7 Mvar
A
39%
A
3 Mvar
A
MVA
11
50%
33%
-10 Mvar
77%
MVA A
44%
MVA
MVA
MVA A
5 MW 0 Mvar
13% 2
MVA
7
8
A
9
10
A
56%
5% 15 MW 5 Mvar
MVA
140 MW
13%
MVA
MVA
25 MW 0 Mvar
A
28 Mvar
A
42%
15 MW
15 MW
5 Mvar
5 Mvar
MVA
Figure 9. IEEE 25 bus system modified with placed TCSC in (1-19) 25 MW 8 Mvar
30 MW 10 Mvar
15 MW 5 Mvar
25
15
20 MW 7 Mvar
24
A
13%
A
57%
MVA
23
3
75%
MVA
A
MVA
25 MW 8 Mvar
58%
sl a ck
MVA
13
60 MW 20 Mvar
10 MW 15 MW 5 Mvar
51% 212 Mvar MVA
MVA
17
12
A
39%
MVA
5
5 Mvar 15 MW
238 MW A
39%
A A
MVA
11
50%
34%
-1 Mvar
81%
MVA A
45%
MVA
MVA A
5 MW 0 Mvar
17% 2
7
MVA
8
A
A
53% A
43%
10
16%
MVA
25 MW 0 Mvar
9 A
7% 15 MW 5 Mvar
MVA
30 Mvar
107% 18
MVA
138 MW
A
A
MVA
3 Mvar
MVA
A
MVA
6
10 MW
32%
16%
188 MW 23 Mvar
19%
A
105 MW
A
0 Mvar
A
88 MW 56 Mvar
19
1
A
13%
MVA
5 Mvar
MVA
4
A
89%
16% 15 MW
MVA
MVA
15 MW 5 Mvar
A
42%
30 MW 10 Mvar
A
A
42%
A
MVA
20 MW 7 Mvar 25 MW 8 Mvar
A
200 MW 65 Mvar
50 MW 17 Mvar
53%
MVA
MVA
16
MVA A
20
A
31%
12%
MVA
23% 14
21
A
MVA
22%
A
25 MW 8 Mvar
54%
MVA A
A
MVA
22
A
26%
MVA
35%
20 MW 7 Mvar
MVA
15 MW
15 MW
5 Mvar
5 Mvar
MVA
Figure 10. IEEE 25 bus system modified with TCSC in (7-8)
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Leonardo Journal of Sciences
Issue 29, July-December 2016
ISSN 1583-0233
p. 43-54
Conclusion
The optimal placement of TCSC is important for improving the security of power system, the method which are suggested sensitivity based approach and line outage distribution factor .The results obtained was tested on modified IEEE 6 bus and modified IEEE 25 bus systems , where the lines (1-5) and (5-10) are the optimal location respectively.
References
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The sensitivity approach method with optimal placement of thyristor controlled series compensator Messaoud ZOBEIDI, Fatiha LAKDJA, Fatima Z. GHERBI
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54
Electrical,
Electronics
and
