Feasibility Study of Conversion of Double Circuit ac Transmission Line for Simultaneous ac-dc Power Transmission

Electric power consumption has been increasing rapidly across the globe; this increase specially accelerated in the last decade. Consequently, existing transmission lines are becoming overloaded beyond their power transfer capability. The inadequacy of the transmission lines has contributed to power interruptions and instability of the power system. Construction of new transmission lines can be a solution to mitigate these problems. However, to build the whole structure of a new transmission line, a huge investment is required. Besides this, environmental concerns would create further barriers that delay the accomplishment of the project. Therefore, the effective and quickest solution to tackle this problem is enhancing the power transfer capability and stability margin of existing transmission lines. This paper studied the techno-economic feasibility of converting an existing HVAC line into a simultaneous AC-DC power transmission system to enhance power transfer capability as well as to improve power system stability. Using the proposed method, the loadability of Tana Beles to Addis Ababa 400 kV, 476.2 km AC line has increased to more than double which is from 1091.66 MW to 2196.85 MW. The active power loss and corona loss evaluation of the two systems ensured that simultaneous AC-DC system is more efficient than HVAC system. It is also shown that the instability can be effectively improved by simultaneous AC-DC power transmission with fast DC power modulation. From the economic point of view, rather than constructing new HVAC line, converting existing HVAC line into simultaneous AC-DC transmission system has a price reduction of about 107,984,968.56 USD or 32.46% of the new HVAC line cost. Considering a 35-year project life cost analysis, it is observed that the life cycle cost of the simultaneous AC-DC transmission system is about 29.2% lower than the life cycle cost of a new 400 kV HVAC line. Thus, the designed simultaneous AC-DC power transmission system has better technical performance and also is less costly than constructing a new HVAC line.

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“…e total power transfer through the double circuit line before conversion (i.e., original existing AC line) is [12]…”

Section: The Technical Aspectmentioning

confidence: 99%

“…X is the transfer reactance per phase of the double circuit line and δ 1 is the power angle between the voltages at the two ends. As mentioned above to keep sufficient stability margin, the angular difference at the two ends of a long transmission line does not often exceed 30 °[7, [12][13][14][15][16].…”

Section: The Technical Aspectmentioning

confidence: 99%

Techno-Economic Comparisons of HVAC and Simultaneous AC-DC Transmission

Asmare

Gessesse

Getie

2022

Journal of Electrical and Computer Engineering

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“…Experimental verification of the satisfactory working of the proposed system on a laboratory model is reported in [2,3].…”

Section: For the Converted Linementioning

confidence: 99%

“…The idea is extended to bi-polar dc power transmission through a double circuit ac transmission line [3] with power up-gradation and steady state stability improvement. Utilization of built-in short term overload capacity of converters in HVDC may improve the transient stability limit in an ac line operating in parallel with the dc line [4].…”

Section: Introductionmentioning

confidence: 99%

Stability enhancement of power system by simultaneous ac-dc power transmission

Basu

Naeem

2009

IEICE Electron. Express

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Generators may supply power to infinite bus through a single circuit long ac transmission line. The system becomes unstable after the clearance of a fault if the pre fault power transfer or the fault clearance time is high. Conversion of the line for simultaneous ac-dc power flow may keep the system stable with high values of pre fault power and fault clearance time. During the transient period after the clearance of the fault, ac power flow is switched off and the dc power flow is augmented to produce a retarding torque to bring back the generator to its normal speed. Fast control of dc current regulator may be used for this purpose. The circuit breakers are then reclosed and the ac power flow is resumed at its pre fault value without any oscillation. The power swing is low and the system is optimally damped at the end of first swing.

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“…To extend the capability of power transmission and take full advantages of HVDC, the concept of hybrid ac/dc transmission as shown in Fig. 1, was proposed in [4][5][6][7]. The basic idea is pushing ac line close to its thermal limits by superposing dc current on the ac current along existing ac lines, thus featuring the advantages in exploiting existing ac lines, towers, facilities and avoiding new right-of-way.…”

Section: Introductionmentioning

confidence: 99%

A line impedance conditioner to improve zigzag transformer based hybrid Ac/Dc transmission under unbalanced line impedance conditions

Liu

Shi

Wang

et al. 2014

2014 IEEE Energy Conversion Congress and Exposition (ECCE)

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Hybrid ac/dc transmission extends the power transfer capacity of existing long ac lines closer to the thermal limit, by superposing dc current onto ac lines through a zigzag transformer. However, this transformer could suffer saturation under unbalanced line impedance conditions. This paper introduces the concept of hybrid line impedance conditioner (HLIC) as an approach to eliminate the line unbalance, which significantly reduces the design cost of the zigzag transformer and could be integrated into the transformer without requiring high voltage insulation. The topology and operation principle are presented, fully utilizing the capability of full bridge converters to generate a hybrid ac/dc voltage as an active impedance compensator. The selection criterion of the line conditioner key components, especially dc link capacitance is also proposed. Simulation and experimental results are provided. I.978-1-4799-5776-7/14/$31.00 ©2014 IEEE

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Feasibility Study of Conversion of Double Circuit ac Transmission Line for Simultaneous ac-dc Power Transmission

Cited by 14 publications

References 8 publications

Techno-Economic Comparisons of HVAC and Simultaneous AC-DC Transmission

Techno-Economic Comparisons of HVAC and Simultaneous AC-DC Transmission

Stability enhancement of power system by simultaneous ac-dc power transmission

A line impedance conditioner to improve zigzag transformer based hybrid Ac/Dc transmission under unbalanced line impedance conditions

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