A New Method for Optimal Placement of TCSC using ABC Algorithm in Power Systems

A New Method for Optimal Placement of TCSC using ABC Algorithm in Power Systems

Mohammad Rafee Shaik¹, Dr. A. Srini vasula Re ddy²

1Asst. Professor, Department of Electrical Engineering, College of Engineering Technology , Jijiga University , Jijiga, Somali Regional State, Ethiopia

2Principal & Professor, CM R Engineering College, Hyderabad, Telangana State, India.

Abstract— In power systems because of unce rtainty of the load curve and transfer of power between various utilities and loads create block out situations. In these situations the Flexible AC transmission system (FACTS) controllers play an important role in power system sec urity enhance ment. As the capit al cost of these controllers is high, these controllers must be placed optimally. FACTS devices can regulate the active and reactive power control as well as adaptive to voltage -magnitude control simultaneously because of their flexibility and fast control characteristics. Placement of these devices at optimal location can lead to control in line flow and maintain bus voltages at required level and so improve the voltage profile, to improve load transfer capability, decreasing the losses in the system and o perate the system within stable regions. This paper proposes a systematic method for finding optimal location of TCSC to improve voltage profile of a power system with Artificial Bee Colony (ABC) Algorithm. An OPF with/without TCSC using ABC algorithm is considered for healthy conditions in simulation and compared with existing literature. Effectiveness of the proposed method is demonstrated on IEEE 30 -bus test system.

Keywords— ABC algorithm, FACTS devices, Optimization, TCSC, IEEE 30 bus, Voltage profile

I. IN TRO DUC TION

In recent years power demand has increased substantially while the e xpansion of power generation and transmission has been limited due to limited resources and environmental restrictions. As a consequence some transmission lines are heavily loaded and system stability becomes a power transfer limiting factor. Fle xib le AC transmission system (FACTS) controlle rs are ma inly used for solving various power system steady state control problems. Ho wever recent studies reveal that FACTS controlle rs could be employe d to enhance power system stability in addition to their ma in function of power flow control. It is known that the power flow through an AC transmission line is a function of line impedance, the magnitude and the phase angle between the sending and the receiving end voltages. By proper coordination of FACTS devices in the power system network, both the active and reactive power flo w in the lines can be controlled. FACTS devices imp roves power transmission capacity, voltage profile, enhancing power system stability [5].FA CTS devices include static var compensator (SVC), thyristor controlled series compensator (TCSC), unified power flow controller (UPFC) etc. Like other FA CTS devices, SVC is an expensive device; therefore it is important to find the optima l lo cation and its size in a power system, so that voltage profile may be improved effective ly. In [10], optimal place ment of TCSC based on reactive power spot price is discussed.In [14], a method optimal p lace ment of TCS C for static and dynamic voltage security enhancement has been developed. This paper focuses on the placement of TCS C for improving the voltage profile and reducing the real power losses. TCSC is a series FACTS device which is designed to maintain the vo ltage profile in a power system conditions. In practical powe r systems, all buses have different sensitivity to the power system stability, some buses are mo re and some are less.

II. TCSCMO DELLING

The model of a transmission line with a TCSC connected between the buses i and j. The change in the lin e flows due to series reactance. The real powe r injection at buses i and bus j (Pi (co m)) and Pj(co m)can be e xpressed as

2

P (

)

Δ

[ Δ

cos( ) δ

Δ

sin( δ

)]

2

j j ij i j ij ij ij ij

P (com) =V  G -V V [ G cos ( )- B sin ( )]    

(2) Similarly, the reactance power injected at bus i and j (Qi (co m)) can be e xp ressed as

2

i i ij i j ij ij ij ij

Q (com) = -V B -VV [ G sin ( )- B cos ( )]     

(3)

2

j i ij i j ij ij ij ij

Q (com) = -V B -V V [ G sin ( )- B cos ( )]     

(4) Where,

csc csc

ij 2 2 2 2

csc

( 2 )

G

( )( ( ) )

t ij t ij

ij ij ij ij t

X R X X

R X R X X

  

  

(5)

2 2

csc csc

ij 2 2 2 2

csc

( )

B ( )( ( ) )

t ij ij t ij

ij ij ij ij t

X R X X X

R X R X X

  

    

(6)

III. PROBLEM FO RMULATION

The generation cost function for the real power (P) output of the generators is given as a second order polynomial function as shown below

C_P = α ₂P² + α₁P + α ₀ [US$/h] (7)

Where P is the output in MW and α0, α1 and α2 are cost coefficients. And the cost function of the reactive power (Q) output of the generators is given by:

CQ = β 1 Q + β0[US$/h] (8)

As far as the cost of TCSC devices is concerned, only typical cost functions associated with the total investment and infrastructure costs are considered. Cost function of TCSC is based on the Sie mens AG Database which is shown below.

(9)

The objective function (OF) considered here minimizes the generation cost while taking into consideration the cost of FACTS devices, i.e.

(10)

CP, CQ and CFACTS are the costs of active and reactive power productions and the cost of allocated FACTS devices, respectively. The indices n and m are the nu mber of the generators and allocated FACTS devices, respectively.

A. ABC algorithm based optimization method

 The TCSC is injected to all lines in 30 bus system and for each line we find power flow and cost of generation.

 The GA algorithm based optimization procedure is then applied to optimally allocate available FACTS devices. There are two variables per device to be determined, the location and the rating.

 A penalty factor is set to prevent the placement of two series connected devices in the same branch. The penalty factor increases the cost of placing the second device at the same location and discards such solution from further consideration

IV. ARTIFICIALB EECOLONYALGORITHM

In a real bee colony, some tasks are performed by specialized indiv iduals. These specialized bees try to ma ximize the nectar amount stored in the hive using effic ient self-organization. The Artific ial Bee Colony (ABC) a lgorith m, proposed by Karaboga [18] in 2005 fo r real-para meter optimization, is a recently introduced optimization algorithm which simulates the foraging behavior of a bee colony .The minimal mode l of swarm-intelligent forage selection in a honey bee colony which the ABC algorith m simu lates consists of three kinds of bees: employed bees, onlooker bees and scout bees. Half of the colony consists of employed bees, and the other half includes onlooker bees.

Emp loyed bees are responsible for e xploit ing the nectar sources explored before and giving informat ion to the wait ing bees (onlooker bees) in the hive about the quality of the food source sites which they are exp loit ing.

Onlooker bees wait in the hive and decide on a food source to explo it based on the information shared by the emp loyed bees. Scouts either randomly search the environment in order to find a new food source depending on an internal mot ivation or based on possible e xte rnal c lues .All these units and interactions between them are shown as a flowchart in Figure 1.

Fig..1. Flow chart of Artificial Bee Colony Algorithm

V. RES ULT AND DISCUSS ION

ABC based algorithm for optimal powe r flow was applied between all the buses in IEEE 30 bus system. This system comprises of one slack bus, 5 PV buses, 24 PQ buses and 41 lines as shown in fig. 2. After running the algorith m up to 5 iteration at each bus and then the average generation cost was calculated for each bus. The optimal location of the device was chosen based on the minimu m generation cost i.e. between bus number 10 -21. It is found that one TCSCs is required to achieve objective of optimization.

After installing TCSC between bus number 10 & 21 in IEEE 30 bus system, the bus voltage (V), act ive power (P), reactive power (Q) and Bus voltage angle (δ) without TCSC and with TCSC are shown in Table 1 & 2 respectively.

It is observed from Table 1 & 2 that after installing TCSC, the overall voltage profile have been improved throughout the system. Power transfer capability also has been improved between all the buses. In the following tables the improve ment of voltage profile has shown in table 1 without TCSC and in table 2 with TCSC. He re Table 3 shows cost of generation, savings, Power loss percentage without TCSC and with TCSC. Fig. 3 shows cost of

generation with TCSC graphs with GA. Fro m tables 1 & 2 it is clear that TCSC plac ing optima lly successfully increased the voltage profile of the system.

Fig.2. IEEE 30 bus system

Table 1: Bus Data without T CSC Bus no Active Power

(P)

Reactive Power (Q)

Voltage Magnitude (|V|)

Angle (δ)

1 0.8912 1.1541 1.06 0

2 0.5682 -0.6222 1.045 -2.7224

3 -0.0226 -0.0673 1.0253 -2.5936

4 0.0417 -0.6832 1.0167 -4.3402

5 -0.5622 0.1093 1.01 -12.0198

6 0.0312 -0.1785 1.0134 -7.0137

7 -0.1222 -0.1134 1.0042 -10.2313

8 -0.3992 0.3445 1.01 -7.5761

9 -0.0344 -0.1654 1.0532 -11.2273

10 -0.2311 -0.1213 1.0479 -11.2503

11 0.1722 0.2314 1.082 -14.3235

12 -0.3123 -0.2254 1.06 -8.7249

13 0.1298 0.7272 1.071 -7.5378

14 -0.0011 -0.1001 1.0452 -10.5670

15 -0.0195 -0.0742 1.0405 -11.6460

16 0.0294 -0.1006 1.0472 -6.7433

17 0.0100 -0.1432 1.0427 -9.6044

18 0.0085 -0.0711 1.031 -7.7066

19 -0.0301 -0.0849 1.0285 -7.3543

20 -0.0154 -0.0110 1.0326 -7.8190

21 -0.5927 0.5225 1.0355 -14.3763

22 -0.3618 0.7839 1.036 -14.6590

23 -0.5426 0.4076 1.0299 -16.411

24 -0.5686 0.4886 1.0241 -16.6927

25 -0.1115 0.2188 0.9998 -13.1398

26 -0.2156 0.1753 1.0016 -16.6592

27 -0.0056 -0.0504 1.0248 -7.6956

28 0.0530 -0.0577 1.0093 -7.1758

29 0.3041 -0.1448 1.005 -2.8020

30 0.2529 -0.2902 0.9883 -2.4819

Table 2: Bus Data with TCSC

Table 3: Cost of generation using T CSC

Without TCS C With TCS C

Location of TCSC Between buses 10 - 21

Cost of generation ( US $/ hr ) 831.4644 800.9543

S avings in US $/ hr 30.5101

% Ploss 7.34 7.04

Bus no Active Power (P)

Reactive Power (Q)

Voltage Magnitude (|V|)

Angle (δ)

1 0.9199 1.3674 1.06 0

2 0.5897 -0.6686 1.049 -2.7371

3 -0.0364 -0.0731 1.0267 -4.7133

4 -0.0492 -0.0858 1.0178 -5.6464

5 -0.0578 -0.1785 1.01 -6.4955

6 0.0325 -0.1232 1.0145 -6.4971

7 -0.1535 0.3887 1.0053 -8.0472

8 -0.0593 -0.1949 1.01 -8.5118

9 -0.0086 -0.1668 1.0548 -6.0639

10 -0.3281 0.4491 1.0487 -8.3018

11 0.1747 -0.3347 1.092 -6.0951

12 -0.3716 0.7178 1.062 -9.2411

13 0.1622 -0.1005 1.079 -8.0140

14 -0.0014 -0.0892 1.0465 -10.5737

15 -0.0200 -0.1100 1.0423 -10.5611

16 0.0304 -0.1852 1.0482 -10.9620

17 0.0111 -0.0721 1.0439 -10.8988

18 0.0095 -0.0849 1.042 -11.3504

19 -0.0301 -0.0113 1.029 -10.5818

20 -0.0174 -0.0919 1.0336 -6.9296

21 0.0651 -0.0667 1.036 -11.9044

22 -0.0422 0.0592 1.036 -10.8560

23 -0.0520 -0.0028 1.0349 -10.9620

24 -0.0457 0.0145 1.0251 -10.8988

25 -0.0158 -0.0501 1.0102 -11.3504

26 0.0142 -0.1123 1.0016 -10.1214

27 -0.0067 -0.0374 1.0248 -10.5818

28 0.0354 0.0368 1.0093 -6.9296

29 -0.0367 -0.0367 1.005 -11.9044

30 -0.0982 -0.0982 0.9898 -12.8560

Fig. 3 Cost of generation graphs with TCSC (ABC) to with TCSC (GA) VI.CONCLUSION

This paper presents a new approach which can be used to optimally locate the least TCSCs as power flow controllers along system branches in an attempt to enhance both voltage profile and security margin of the system.

IEEE 30-bus test system has been used to evaluate the performance of the proposed approach. Optima lly placing TCSC with optima l cost has been improved the voltage profile and also decreased the cost of generation of power.

This method also decreased the total power losses.

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1

Cost of Generation

Cost of generation Comparison with TCSC(ABC) to with TCSC(GA)

Cost of generation without TCSC

Cost of generation with TCSC (ABC)

Cost of generation with TCSC (GA)

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