DC Power Flow Control in Meshed HVDC Networks
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Solution Overview
Problem
Current HVDC power transmission networks, especially meshed networks, face challenges in efficiently managing power flow and preventing overcurrent issues, which can lead to thermal overload and potential earth faults, particularly in large-scale or long-distance transmission systems.
Innovation Solution
A method and device for controlling power flow in meshed HVDC networks by using DC power flow control devices connected in series to transmission lines, balancing current distribution through parallel connections, and strategically injecting additional DC voltage to relieve heavily loaded lines, thereby optimizing power transmission capacity and reducing losses while avoiding unnecessary overcurrent protection interventions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If power flow is concentrated in fewer transmission lines, then power transmission capacity is maximized, but thermal overload and overcurrent protection issues occur
Solution Approach 1:
The patent implements dynamic power flow control by injecting adjustable DC voltages through controllable voltage sources. The system continuously monitors line loading conditions and dynamically adjusts the injected voltages to redistribute power flow, enabling the network to adaptively balance load distribution and prevent thermal overload while maintaining high transmission capacity
Solution Approach 2:
The patent changes the electrical parameters (DC voltage levels) in the transmission lines by injecting controlled voltages through the power flow control devices. This parameter modification alters the current distribution across the meshed network, allowing heavily loaded lines to have reduced current while maintaining overall power transmission capacity
2Reliability
If DC voltage is injected to balance current distribution, then thermal overload is prevented, but power transmission capacity is reduced
Solution Approach 1:
The patent applies local quality by injecting DC voltages at specific locations (heavily loaded transmission lines) rather than uniformly across the entire network. This localized intervention selectively balances current distribution only where needed, preventing thermal overload on critical lines while maintaining optimal power flow and transmission capacity in other parts of the network
3Loss of energy
If power flow is redistributed to relieve heavily loaded lines, then losses are reduced, but device complexity increases
Solution Approach 1:
The patent implements self-service by designing the power flow control devices to be self-powered through power extraction from the transmission lines they control. The devices extract a portion of the line power to supply their own operational requirements, eliminating the need for external power sources and reducing overall system complexity while enabling intelligent power flow redistribution to minimize transmission losses
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach ensures optimal use of power transmission capacity, reduces losses, and prevents thermal overloads and earth faults by redistributing current flow, ensuring stable operation under various loading conditions and extending the lifespan of transmission lines.
Implementation Method 1
controlling the first DC power flow control device so that the DC current distribution in the first closed path is balanced by injecting an additional DC voltage into the first transmission line
Implementation Method 2
a first converter (32), which is able to transform an AC voltage into a DC voltage and to inject the DC voltage into the first transmission line (20)
Implementation Method 3
a second converter (34), which is able to transform a DC voltage into an AC voltage and to provide the AC voltage to the first converter (32)
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A meshed HVDC power transmission network (10) comprises at least three HVDC converter stations (1, 2, 3) interconnected in a first closed path by at least three transmission lines (16, 18, 20). A first DC power flow control device (30) is series connected to a first (20) of the at least three transmission lines. That first DC power flow control device (30) takes its power from the first transmission line (20) and balances the DC current distribution in the first closed path.