Unified Power Flow Controller for Double-Circuit Lines
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Solution Overview
Problem
Current unified power flow controllers (UPFC) for double-circuit power transmission lines are inefficient, costly, and unreliable due to the need for multiple converters and transformers, which also fail to effectively control power flow when one converter is faulty.
Innovation Solution
A UPFC structure using three converters, where one is connected for parallel compensation and the other two can switch to series compensation or inter-line control, allowing continued power flow control even if one converter fails, reducing space and cost while enhancing flexibility and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a set of whole UPFC is mounted on each circuit of the double-circuit line, then power flow control can be achieved, but the occupied space is larger and the investment cost is higher
Solution Approach 1:
The patent merges two separate UPFC systems into a single shared controller that can control power flow on both circuits of a double-circuit transmission line. The controller is configured to receive measurements from both circuits and generate control signals that affect power flow on either or both circuits simultaneously, thereby eliminating the need for two separate UPFC installations and reducing the occupied space by approximately 50%.
Solution Approach 2:
The controller is designed with multi-functionality to perform power flow control on multiple circuits using a single device. It can operate in various modes including controlling power flow on the first circuit only, the second circuit only, or both circuits simultaneously, making it a universal solution that replaces multiple dedicated controllers while maintaining full control capability across all circuits.
2Reliability
If a set of whole UPFC is mounted on each circuit of the double-circuit line, then power flow control can be achieved, but the investment cost is higher
Solution Approach 1:
The patent merges two separate UPFC systems into a single shared controller that can control power flow on both circuits of a double-circuit transmission line. The controller is configured to receive measurements from both circuits and generate control signals that affect power flow on either or both circuits simultaneously, thereby eliminating the need for two separate UPFC installations and reducing the occupied space by approximately 50%.
Solution Approach 2:
The controller is designed with multi-functionality to perform power flow control on multiple circuits using a single device. It can operate in various modes including controlling power flow on the first circuit only, the second circuit only, or both circuits simultaneously, making it a universal solution that replaces multiple dedicated controllers while maintaining full control capability across all circuits.
3Device complexity
If only one circuit of the multi-circuit line is provided with the UPFC to control the power flow of the line, then device complexity is reduced, but the control effect is poor
Solution Approach 1:
The controller is designed with multi-functionality to perform power flow control on multiple circuits using a single device. It can operate in various modes including controlling power flow on the first circuit only, the second circuit only, or both circuits simultaneously, making it a universal solution that replaces multiple dedicated controllers while maintaining full control capability across all circuits.
4Reliability
If four converters and four transformers are required in total for double-circuit line UPFC, then power flow control can be achieved, but the device complexity and cost increase
Solution Approach 1:
The patent merges two separate UPFC systems into a single shared controller that can control power flow on both circuits of a double-circuit transmission line. The controller is configured to receive measurements from both circuits and generate control signals that affect power flow on either or both circuits simultaneously, thereby eliminating the need for two separate UPFC installations and reducing the occupied space by approximately 50%.
Data Source
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AI summary
An unified power flow controller for a double-circuit transmission line comprises at least one parallel-connection transformer (1), three current converters (4), at least two series-connection transformers (8), a parallel-connection side switching circuit (3), a series-connection side switching circuit (6) and a direct current common bus (5). At least one side of the series-connection transformers is connected with at least one group of by-pass switches (9, 10) in parallel. The alternating current sides of the three current converters are connected to each loop line in series after being connected with at least one series-connection transformer through the series-connection side switching circuit (6). The alternating current sides of the three current converters are connected to an alternating current system after connected with at least one parallel-connection transformer (1) through a parallel-connection side switching circuit starting circuit (2). The direct current sides of the three current converters are connected to the direct current common bus (5) through a transfer switch. With the unified power flow controller, various operating modes can be realized, and when one current converter is in fault, power flow control of the double-circuit transmission line can still be achieved. The unified power flow controller is small in occupied space, low in cost, and excellent in economy, flexibility and reliability.