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Power System Voltage and Reactive Power Control by means of Multi-agent Approach
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Energy Procedia
Energy Energy ProcediaProcedia 00 (2011) 000–000 14 (2012) 705 – 710 www.elsevier.com/locate/procedia
2011 2nd International Conference on Advances in Energy Engineering (ICAEE 2011)
Power System Voltage and Reactive Power Control by means of Multi-agent Approach Masato Ishidaa, Takeshi Nagataaa* a
Hiroshima Institute of Technology, 2-1-1, Miyake, Saeki-ku, Hiroshima, 731-5139, Japan
Abstract In order to maintain system voltage within the optimal range and prevent voltage instability phenomena before they occur, a variety of phase modifying equipments are installed in optimal locations throughout the power system network and a variety of methods of voltage and reactive control are employed. The proposed system divided the traditional method to control voltage and reactive power into two sub problems: "voltage control" to adjust the secondary bus voltage of substations, and "reactive power control" to adjust the primary bus voltage. In this system, two types of agents are installed in substations in order to cooperate "voltage control" and "reactive power control". In order to verify the performance of the proposed method, it has been applied to the model network system. The results confirm that our proposed method is able to control violent fluctuations in load.
© 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of the organizing committee 2011 PublishedConference by ElsevieronLtd. Selection and/or Engineering peer-review(ICAEE). under responsibility of [name organizer] of© 2nd International Advances in Energy Keywords：Multi-agent system; distributed system; voltage control; reactive power control; power system;
1. Introduction Numerous studies have been conducted the control of voltage and reactive power. From the viewpoint of system structures, this research can be divided into two categories: one covering centralized systems and the other decentralized. A centralized system [1]-[4] collects all data on the power system at a single point and solves problems of phase modifiers and tap operations of load tap-changing transformers as
* Corresponding author. Tel.:+81-82-921-3121; fax: +81-82-921-8934. E-mail address: [email protected].
1876-6102 © 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of the organizing committee of 2nd International Conference on Advances in Energy Engineering (ICAEE). doi:10.1016/j.egypro.2011.12.887
2706
Masato Ishida and/Takeshi Procedia 14 (2012) 705 – 710 Author name Energy Nagata\ Procedia/ Energy 00 (2011) 000–000
problems of optimization. For problem solving with these kinds of systems, some methods have been proposed that utilize mathematical programming and/or soft computing. Meanwhile, a decentralized system [5]-[8] locally exchanges information among neighboring substations for autonomous control. For this category, some methods have been put forward to harmonize tapping and phase modification of transformers. The proposed system divides the traditional methods to control voltage and reactive power into two sub problems: "voltage control" to adjust the secondary bus voltage of substations, and "reactive power control" to adjust the primary bus voltage. We propose a decentralized system featuring agents and a method that divides all control voltage and reactive power into these two sub problems. In doing so, we intend to clarify what needs to be controlled to obtain more flexible control. Reference [7] describes the results of our previous research focused on the sub problem of "voltage control." In the proposed control method, agents of upper-layer substations change the dead bands of VQC adaptively (i.e., they control the target voltage), based on information collected from agents of lower-layer substations, to enable more flexible control. Reference [8] describes the results of our previous research focused on the method on the sub problem of "reactive power control." In the proposed control method, agents of each substation adjusts the reactive power among the same voltage class, thus keeping the primary voltage within the upper and lower limits and equalizing the voltage distribution, to enable more flexible control. This paper, therefore, focuses a method that adding the reactive power control to the voltage control, and proposes a method that adjusts the primary bus voltage and the secondary bus voltage of substations interconnected in the same voltage class. Listed below are the features of the proposed method: (1) The proposed system divides the traditional methods to control voltage and reactive power into two sub problems: "voltage control" to adjust the secondary bus voltage of substations, and "reactive power control" to adjust the primary bus voltage. (2) The proposed system consists of two kinds of agents: substation agent (SSAgent) and transmission line agent (LineAgent). (3) Each SSAgent corresponds to a substation and is implemented by the computer in each substation, while each LineAgent corresponds to transmission lines which connect to the equi-potential substations and can be implemented by any computer in any substation. (4) In the proposed system, LineAgent cooperates with SSAgent toward a resolution of the voltage control issues. In this paper, we propose a new index, "integrated target voltage range (ITVR)", which coordinates with two sub-problems (voltage control and reactive power control). We conducted a computer simulation by developing the proposed system with Java and applying it to a model power system based on an actual system. From results, we confirmed that the proposed method achieves better performance than the conventional VQC. 2. The Proposed method The method we propose in this paper is intended for the radial system with the branches and the multiple power lines. 2.1. Overview We illustrate basic idea of the proposed method as shown in Fig.1. In the proposed method, the model network is divided into sub-networks (H1) and (H2), which are controlled by the shunt capacitor/shunt reactor (SC/ShR), and sub-networks (V1) through (V4), which are controlled by the under-load tap
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Masato Ishida andname Takeshi Nagata\ / Energy00Procedia 14 (2012) 705 – 710 Author / Energy Procedia (2011) 000–000
switching transformer (LRT). The control of (H1) and (H2) corresponds to the reactive power control, while the control of (V1) through (V4) corresponds to the voltage control. The main functions of these equipments are as follows: 1. SC/ShR (As/s, Cs/s, Ds/s) adjusts and equalizes the primary bus voltage. 2. LRT (Ss/s, As/s, Cs/s, Ds/s) adjusts the secondary bus voltage. The former corresponds to the reactive power control sub-problem intended for the reactive power control sub-network, and the latter corresponds to the voltage control sub-problem intended for the voltage control sub-network. At first, the proposed method adjusts the reactive power among substations to keep the primary bus voltage within the limit and equalize the voltage distribution. Then, it adjusts the voltage at the sending end substation to control voltage in same voltage class. First, SSAgent operates LRT and SC/ShR on the basis of the receiving information from LineAgent. Then, LineAgent regulates the reactive power by collecting the information of substations, estimates in advance the voltage fluctuations following the control, and decides whether SSAgent needs reactive power control. In order to prevent the simultaneous control, which can cause hunting, only one control is allowed at any given moment in time within a single group of substations interconnected to one another. In our approach, it is important to realize the means of coordinating two sub-problems.
Fig. 1. Simple power system network.
2.2. Integrated target voltage range (ITVR) The integrated target voltage range (ITVR) is calculated from the downstream substations to the sending end substation. In order to keep the primary bus voltage of downstream substations into the proper level, the sending end substation must keep this range. To calculate ITVR, we use the target voltage range of each substation. Upper substations must keep the primary bus voltage into the target voltage range. Namely, if upper substation keep the primary bus voltage inside this range, it is assumed that the primary bus voltage of the downstream substations would keep the own target voltage range. Here, we illustrate how to calculate the target voltage range in Fig. 2. The target voltage range of the primary bus voltage of substation-i ( Vimin ,Vimax ) can be represented as follows: ⎫ , V min j + ΔVij } ⎪ ⎬ max + ΔVij }⎪⎭ V imax = min{ V i , V max j min
V imin = max{ V i
where Vi primary bus voltage of substation- i ;
(1) V j primary bus voltage of substation- j ;
4708
Masato Ishida and/Takeshi Procedia 14 (2012) 705 – 710 Author name Energy Nagata\ Procedia/ Energy 00 (2011) 000–000
ΔVij voltage difference of substation- i and j ; The real power system consists of a number of simple networks as shown Fig.2, and the connection of the substation includes the branches. In addition, other transmission lines are connected through the primary bus of substation. Next, we illustrate how to calculate ITVR using a simple model network as shown in Fig.3. In this figure, the node 2 is the secondary bus in the substation, the node 3 is the branch node in the transmission line, the node 6 is the primary bus connecting two transmission lines, and the node 8 is the primary bus at the most downstream substation. ITVR can be calculated from the target voltage ( V8min,V8max ) at the most downstream substation to the upper substations. First, the target voltage range at the node 6 is calculated from the target voltage range at the node 8 by using eq. (1). Then, the target voltage range at the branch node 3 is calculated by the same manner. In this case, as there are two values calculated from the node 6 and 4, these values are integrated by the following equations. min min ⎫ = max{ V 4 , V min 4 + ΔV34 , V 6 + ΔV36 } ⎪ ⎬ max max max max V 3 = min{ V 4 , V 4 + ΔV34 , V 6 + ΔV36 }⎪⎭ min
V3
(2) Finally, the target voltage range at the node 2 is calculated as the same manner of eq. (1). The resultant value is ITVR, which is the index to keep the primary bus voltages of the all downstream substations. ①
Is/s
Js/s
ΔVij = Vi - Vj i
Line01
②
③
j
(Vimin,Vimax) (Vjmin,Vjmax) Fig. 2. Two buses connection model; Fig. 3. Simple model system.
Line02
④
⑥
⑧
⑤
⑦
⑨
2.3. Voltage difference between substations The proposed method achieves the equalizing voltage distribution by keeping the range of voltage difference between the secondary bus voltage at the sending end substation and the primary bus voltage at the lower substations. The constraint of voltage difference between substations can be represented as follows: (3) V si = V s − Vi ≤ ΔV where Vsi voltage difference between substations; Vs secondary bus voltage at sending end substation s ; Vi primary bus voltage at downstream substation i ; ΔV defined value (0.2 p.u.); 3. Simulation 3.1. Conditions of the simulation This simulation serves two purposes. One is to keep the voltage within the accepted range at same voltage class, or, between the specified upper and lower limits permissible. The other is to even out the distribution of the primary bus voltage.
Masato Ishida andname Takeshi Nagata\ / Energy00Procedia 14 (2012) 705 – 710 Author / Energy Procedia (2011) 000–000
To confirm how our proposed system works, we conducted a computer simulation using the model system illustrated in Fig. 1 above. As the figure shows, the model system consists of a total of five substation, with Substation B at 275 kV, Substations A, C, D at 275/77kV, and Substation S ( 500/275 kV) as the reference station. Substation A, C, D, and S are installed LRT and SC/ShR. The load data which is based on the actual power system are shown in Fig.4 (1440 steps at one minute in a day). In the simulation, the limit of the bus voltage V min = 0.95 and V max = 1.05 , the initial value of the target voltage range is V 0min = 0.98 and V 0max = 1.02 , and the voltage difference is ΔV = 0.2 . Here, only one typical example is shown due to the page limits.
Fig.4. Load data. (a) substation S, A, B ; (b)substation C, D
3.2. Simulation result Fig.5 shows the result of the secondary bus voltage at Substation S of the proposed method (vertical: voltage (p.u); transverse: minute). The primary bus voltage of each substation for VQC is shown in Fig.6, and the proposed method is shown in Fig.7. The conventional method (VQC) controls the secondary bus voltage according to the control law which is decided from the secondary bus voltage of the transformer and the reactive power through the transformer [7]. As shown in Fig.6, the conventional method doesn't keep the primary bus voltage in the limit of the bus voltage. However, the proposed method controls the primary bus voltage adequately as shown Fig.7. In addition, by the proposed method, it turns out that the voltage of each substation is more close to the center, and the voltage differences are also small. 4. Conclusion This paper introduced a new concept to improve the traditional control of voltage and reactive power. The proposed system divides the traditional problem of this control into two sub-problems, "voltage control" to adjust a substation's secondary bus voltage and "reactive power control" to adjust a substation's primary bus voltage. In the proposed system, LineAgent cooperates with SSAgent toward a resolution of the voltage control issues. Although the simulation employed a rather simple model, the results confirm that our proposed method is able to control violent fluctuations in load. The remaining problems to solve in the future include refinement of cooperating method, application to Smart grids voltage control, and other practical implementation issues.
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Masato Ishida and Takeshi Nagata\ / Energy Procedia 14 (2012) 705 – 710 Author name / Energy Procedia 00 (2011) 000–000
Fig.5. Secondary bus voltage in substation S;
Fig.6. Primary bus voltage of substation A through D. (Conventional method)
Fig.7. Primary bus voltage of substation A through D (Proposed method ）
References [1] N. I. Santoso and O. T. Tan: "Neural-net based real-time control of capacitors installed on distribution systems", IEEE Trans. on Power Delivery, Vol 5, No. 1, pp. 266-272, 1990. [2] C. J. Bridenbaugh, D. A. DiMascio, R. D’Aquila: “Voltage Control Improvement Through Capacitor and Transformer Tap Optimization”, IEEE Trans. on Power Systems, Vol. 7, No. 1, pp. 222-227, 1992. [3] J. E. Mendoza, D. A. Morales, R. A. Lopez, E. A. Lopez, J. -C Vannier, and C. A. Coello: “Multiobjective Location of Automatic Voltage Regulators in a Radial Distribution Network Using a Macro Genetic Algorithm”, IEEE Trans. on Power Systems, Vol. 22, No. 1, pp. 404-412, 2007. [4] Y. Liu and X. Qui: "Optimal reactive power and voltage control for radial distribution system", in Proc. IEEE Power Engineering Society Summer Meeting, pp 85-90, 2000. [5] J-young Park, S. Nam, and J-keun Park: “Control of a ULTC Considering the Dispatch Schedule of Capacitors in a Distribution System”, IEEE Trans. on Power Systems Vol. 22, No. 2, pp. 755-761, 2007. [6] M. E. Baran, and I. M. El-Markabi: "A Multiagent-Based Dispatching Scheme for Distributed Generators for Voltage Support on Distribution Feeders", IEEE Trans. on Power Systems, Vol. 22, No. 1, pp. 52-59, 2007. [7] T. Nagata, H. Saiki, M. Utatani, Y. Nakachi and R. Hatano: "A Multi-agent Cooperative Voltage and Reactive Power Control", IEEJ Trans. PE, Vol. 128, No. 11, pp. 1313-1319, 2008. [8] T. Nagata, D. Kunisa, H. Saiki and R. Hatano: "Multi-agent Based Distributed Reactive Power Control Method", IEEJ Trans. PE, Vol. 129, No. 8, pp. 1039-1046, 2009.
Energy Procedia
Energy Energy ProcediaProcedia 00 (2011) 000–000 14 (2012) 705 – 710 www.elsevier.com/locate/procedia
2011 2nd International Conference on Advances in Energy Engineering (ICAEE 2011)
Power System Voltage and Reactive Power Control by means of Multi-agent Approach Masato Ishidaa, Takeshi Nagataaa* a
Hiroshima Institute of Technology, 2-1-1, Miyake, Saeki-ku, Hiroshima, 731-5139, Japan
Abstract In order to maintain system voltage within the optimal range and prevent voltage instability phenomena before they occur, a variety of phase modifying equipments are installed in optimal locations throughout the power system network and a variety of methods of voltage and reactive control are employed. The proposed system divided the traditional method to control voltage and reactive power into two sub problems: "voltage control" to adjust the secondary bus voltage of substations, and "reactive power control" to adjust the primary bus voltage. In this system, two types of agents are installed in substations in order to cooperate "voltage control" and "reactive power control". In order to verify the performance of the proposed method, it has been applied to the model network system. The results confirm that our proposed method is able to control violent fluctuations in load.
© 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of the organizing committee 2011 PublishedConference by ElsevieronLtd. Selection and/or Engineering peer-review(ICAEE). under responsibility of [name organizer] of© 2nd International Advances in Energy Keywords：Multi-agent system; distributed system; voltage control; reactive power control; power system;
1. Introduction Numerous studies have been conducted the control of voltage and reactive power. From the viewpoint of system structures, this research can be divided into two categories: one covering centralized systems and the other decentralized. A centralized system [1]-[4] collects all data on the power system at a single point and solves problems of phase modifiers and tap operations of load tap-changing transformers as
* Corresponding author. Tel.:+81-82-921-3121; fax: +81-82-921-8934. E-mail address: [email protected].
1876-6102 © 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of the organizing committee of 2nd International Conference on Advances in Energy Engineering (ICAEE). doi:10.1016/j.egypro.2011.12.887
2706
Masato Ishida and/Takeshi Procedia 14 (2012) 705 – 710 Author name Energy Nagata\ Procedia/ Energy 00 (2011) 000–000
problems of optimization. For problem solving with these kinds of systems, some methods have been proposed that utilize mathematical programming and/or soft computing. Meanwhile, a decentralized system [5]-[8] locally exchanges information among neighboring substations for autonomous control. For this category, some methods have been put forward to harmonize tapping and phase modification of transformers. The proposed system divides the traditional methods to control voltage and reactive power into two sub problems: "voltage control" to adjust the secondary bus voltage of substations, and "reactive power control" to adjust the primary bus voltage. We propose a decentralized system featuring agents and a method that divides all control voltage and reactive power into these two sub problems. In doing so, we intend to clarify what needs to be controlled to obtain more flexible control. Reference [7] describes the results of our previous research focused on the sub problem of "voltage control." In the proposed control method, agents of upper-layer substations change the dead bands of VQC adaptively (i.e., they control the target voltage), based on information collected from agents of lower-layer substations, to enable more flexible control. Reference [8] describes the results of our previous research focused on the method on the sub problem of "reactive power control." In the proposed control method, agents of each substation adjusts the reactive power among the same voltage class, thus keeping the primary voltage within the upper and lower limits and equalizing the voltage distribution, to enable more flexible control. This paper, therefore, focuses a method that adding the reactive power control to the voltage control, and proposes a method that adjusts the primary bus voltage and the secondary bus voltage of substations interconnected in the same voltage class. Listed below are the features of the proposed method: (1) The proposed system divides the traditional methods to control voltage and reactive power into two sub problems: "voltage control" to adjust the secondary bus voltage of substations, and "reactive power control" to adjust the primary bus voltage. (2) The proposed system consists of two kinds of agents: substation agent (SSAgent) and transmission line agent (LineAgent). (3) Each SSAgent corresponds to a substation and is implemented by the computer in each substation, while each LineAgent corresponds to transmission lines which connect to the equi-potential substations and can be implemented by any computer in any substation. (4) In the proposed system, LineAgent cooperates with SSAgent toward a resolution of the voltage control issues. In this paper, we propose a new index, "integrated target voltage range (ITVR)", which coordinates with two sub-problems (voltage control and reactive power control). We conducted a computer simulation by developing the proposed system with Java and applying it to a model power system based on an actual system. From results, we confirmed that the proposed method achieves better performance than the conventional VQC. 2. The Proposed method The method we propose in this paper is intended for the radial system with the branches and the multiple power lines. 2.1. Overview We illustrate basic idea of the proposed method as shown in Fig.1. In the proposed method, the model network is divided into sub-networks (H1) and (H2), which are controlled by the shunt capacitor/shunt reactor (SC/ShR), and sub-networks (V1) through (V4), which are controlled by the under-load tap
3707
Masato Ishida andname Takeshi Nagata\ / Energy00Procedia 14 (2012) 705 – 710 Author / Energy Procedia (2011) 000–000
switching transformer (LRT). The control of (H1) and (H2) corresponds to the reactive power control, while the control of (V1) through (V4) corresponds to the voltage control. The main functions of these equipments are as follows: 1. SC/ShR (As/s, Cs/s, Ds/s) adjusts and equalizes the primary bus voltage. 2. LRT (Ss/s, As/s, Cs/s, Ds/s) adjusts the secondary bus voltage. The former corresponds to the reactive power control sub-problem intended for the reactive power control sub-network, and the latter corresponds to the voltage control sub-problem intended for the voltage control sub-network. At first, the proposed method adjusts the reactive power among substations to keep the primary bus voltage within the limit and equalize the voltage distribution. Then, it adjusts the voltage at the sending end substation to control voltage in same voltage class. First, SSAgent operates LRT and SC/ShR on the basis of the receiving information from LineAgent. Then, LineAgent regulates the reactive power by collecting the information of substations, estimates in advance the voltage fluctuations following the control, and decides whether SSAgent needs reactive power control. In order to prevent the simultaneous control, which can cause hunting, only one control is allowed at any given moment in time within a single group of substations interconnected to one another. In our approach, it is important to realize the means of coordinating two sub-problems.
Fig. 1. Simple power system network.
2.2. Integrated target voltage range (ITVR) The integrated target voltage range (ITVR) is calculated from the downstream substations to the sending end substation. In order to keep the primary bus voltage of downstream substations into the proper level, the sending end substation must keep this range. To calculate ITVR, we use the target voltage range of each substation. Upper substations must keep the primary bus voltage into the target voltage range. Namely, if upper substation keep the primary bus voltage inside this range, it is assumed that the primary bus voltage of the downstream substations would keep the own target voltage range. Here, we illustrate how to calculate the target voltage range in Fig. 2. The target voltage range of the primary bus voltage of substation-i ( Vimin ,Vimax ) can be represented as follows: ⎫ , V min j + ΔVij } ⎪ ⎬ max + ΔVij }⎪⎭ V imax = min{ V i , V max j min
V imin = max{ V i
where Vi primary bus voltage of substation- i ;
(1) V j primary bus voltage of substation- j ;
4708
Masato Ishida and/Takeshi Procedia 14 (2012) 705 – 710 Author name Energy Nagata\ Procedia/ Energy 00 (2011) 000–000
ΔVij voltage difference of substation- i and j ; The real power system consists of a number of simple networks as shown Fig.2, and the connection of the substation includes the branches. In addition, other transmission lines are connected through the primary bus of substation. Next, we illustrate how to calculate ITVR using a simple model network as shown in Fig.3. In this figure, the node 2 is the secondary bus in the substation, the node 3 is the branch node in the transmission line, the node 6 is the primary bus connecting two transmission lines, and the node 8 is the primary bus at the most downstream substation. ITVR can be calculated from the target voltage ( V8min,V8max ) at the most downstream substation to the upper substations. First, the target voltage range at the node 6 is calculated from the target voltage range at the node 8 by using eq. (1). Then, the target voltage range at the branch node 3 is calculated by the same manner. In this case, as there are two values calculated from the node 6 and 4, these values are integrated by the following equations. min min ⎫ = max{ V 4 , V min 4 + ΔV34 , V 6 + ΔV36 } ⎪ ⎬ max max max max V 3 = min{ V 4 , V 4 + ΔV34 , V 6 + ΔV36 }⎪⎭ min
V3
(2) Finally, the target voltage range at the node 2 is calculated as the same manner of eq. (1). The resultant value is ITVR, which is the index to keep the primary bus voltages of the all downstream substations. ①
Is/s
Js/s
ΔVij = Vi - Vj i
Line01
②
③
j
(Vimin,Vimax) (Vjmin,Vjmax) Fig. 2. Two buses connection model; Fig. 3. Simple model system.
Line02
④
⑥
⑧
⑤
⑦
⑨
2.3. Voltage difference between substations The proposed method achieves the equalizing voltage distribution by keeping the range of voltage difference between the secondary bus voltage at the sending end substation and the primary bus voltage at the lower substations. The constraint of voltage difference between substations can be represented as follows: (3) V si = V s − Vi ≤ ΔV where Vsi voltage difference between substations; Vs secondary bus voltage at sending end substation s ; Vi primary bus voltage at downstream substation i ; ΔV defined value (0.2 p.u.); 3. Simulation 3.1. Conditions of the simulation This simulation serves two purposes. One is to keep the voltage within the accepted range at same voltage class, or, between the specified upper and lower limits permissible. The other is to even out the distribution of the primary bus voltage.
Masato Ishida andname Takeshi Nagata\ / Energy00Procedia 14 (2012) 705 – 710 Author / Energy Procedia (2011) 000–000
To confirm how our proposed system works, we conducted a computer simulation using the model system illustrated in Fig. 1 above. As the figure shows, the model system consists of a total of five substation, with Substation B at 275 kV, Substations A, C, D at 275/77kV, and Substation S ( 500/275 kV) as the reference station. Substation A, C, D, and S are installed LRT and SC/ShR. The load data which is based on the actual power system are shown in Fig.4 (1440 steps at one minute in a day). In the simulation, the limit of the bus voltage V min = 0.95 and V max = 1.05 , the initial value of the target voltage range is V 0min = 0.98 and V 0max = 1.02 , and the voltage difference is ΔV = 0.2 . Here, only one typical example is shown due to the page limits.
Fig.4. Load data. (a) substation S, A, B ; (b)substation C, D
3.2. Simulation result Fig.5 shows the result of the secondary bus voltage at Substation S of the proposed method (vertical: voltage (p.u); transverse: minute). The primary bus voltage of each substation for VQC is shown in Fig.6, and the proposed method is shown in Fig.7. The conventional method (VQC) controls the secondary bus voltage according to the control law which is decided from the secondary bus voltage of the transformer and the reactive power through the transformer [7]. As shown in Fig.6, the conventional method doesn't keep the primary bus voltage in the limit of the bus voltage. However, the proposed method controls the primary bus voltage adequately as shown Fig.7. In addition, by the proposed method, it turns out that the voltage of each substation is more close to the center, and the voltage differences are also small. 4. Conclusion This paper introduced a new concept to improve the traditional control of voltage and reactive power. The proposed system divides the traditional problem of this control into two sub-problems, "voltage control" to adjust a substation's secondary bus voltage and "reactive power control" to adjust a substation's primary bus voltage. In the proposed system, LineAgent cooperates with SSAgent toward a resolution of the voltage control issues. Although the simulation employed a rather simple model, the results confirm that our proposed method is able to control violent fluctuations in load. The remaining problems to solve in the future include refinement of cooperating method, application to Smart grids voltage control, and other practical implementation issues.
5709
710 6
Masato Ishida and Takeshi Nagata\ / Energy Procedia 14 (2012) 705 – 710 Author name / Energy Procedia 00 (2011) 000–000
Fig.5. Secondary bus voltage in substation S;
Fig.6. Primary bus voltage of substation A through D. (Conventional method)
Fig.7. Primary bus voltage of substation A through D (Proposed method ）
References [1] N. I. Santoso and O. T. Tan: "Neural-net based real-time control of capacitors installed on distribution systems", IEEE Trans. on Power Delivery, Vol 5, No. 1, pp. 266-272, 1990. [2] C. J. Bridenbaugh, D. A. DiMascio, R. D’Aquila: “Voltage Control Improvement Through Capacitor and Transformer Tap Optimization”, IEEE Trans. on Power Systems, Vol. 7, No. 1, pp. 222-227, 1992. [3] J. E. Mendoza, D. A. Morales, R. A. Lopez, E. A. Lopez, J. -C Vannier, and C. A. Coello: “Multiobjective Location of Automatic Voltage Regulators in a Radial Distribution Network Using a Macro Genetic Algorithm”, IEEE Trans. on Power Systems, Vol. 22, No. 1, pp. 404-412, 2007. [4] Y. Liu and X. Qui: "Optimal reactive power and voltage control for radial distribution system", in Proc. IEEE Power Engineering Society Summer Meeting, pp 85-90, 2000. [5] J-young Park, S. Nam, and J-keun Park: “Control of a ULTC Considering the Dispatch Schedule of Capacitors in a Distribution System”, IEEE Trans. on Power Systems Vol. 22, No. 2, pp. 755-761, 2007. [6] M. E. Baran, and I. M. El-Markabi: "A Multiagent-Based Dispatching Scheme for Distributed Generators for Voltage Support on Distribution Feeders", IEEE Trans. on Power Systems, Vol. 22, No. 1, pp. 52-59, 2007. [7] T. Nagata, H. Saiki, M. Utatani, Y. Nakachi and R. Hatano: "A Multi-agent Cooperative Voltage and Reactive Power Control", IEEJ Trans. PE, Vol. 128, No. 11, pp. 1313-1319, 2008. [8] T. Nagata, D. Kunisa, H. Saiki and R. Hatano: "Multi-agent Based Distributed Reactive Power Control Method", IEEJ Trans. PE, Vol. 129, No. 8, pp. 1039-1046, 2009.