DC Transmission System with Series Converter Modules
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Solution Overview
Problem
Existing AC power transmission systems face inefficiencies due to capacitance-related charging currents, which reduce load carrying capability and increase losses over long distances, particularly in sub-sea electrical equipment applications.
Innovation Solution
A DC transmission and distribution system with a system DC link configured for carrying power from a source to loads, utilizing DC-to-AC power converter modules coupled in series and controlled by a controller to manage current, allowing for efficient power delivery and redundancy features like modular redundancy and bypass capabilities to handle faults without the need for expensive circuit breakers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If AC transmission is used for long distance power transport, then power can be transmitted over the cable, but capacitance causes charging current to flow which reduces load carrying capability
Solution Approach 1:
The patent changes the fundamental transmission parameter from AC to DC, eliminating the capacitance-related charging current problem that limits AC transmission distance and load carrying capability. DC transmission does not suffer from capacitive charging currents, allowing for more efficient long-distance power transport.
2Loss of energy
If cable design voltage is increased to minimize line losses and voltage drop, then transmission efficiency improves, but charging current also increases
Solution Approach 1:
By transitioning from AC to DC transmission, the patent eliminates the charging current phenomenon entirely. This allows the system to increase voltage for minimizing line losses without the adverse effect of increased charging current that plagues AC systems.
3Power
If conventional converter topologies with series connection of semiconductor devices are used, then high voltage conversion is achieved, but device complexity and reliability concerns increase
Solution Approach 1:
The patent segments the high voltage DC link into multiple lower voltage series-connected converter modules. Each module operates at a manageable voltage level (e.g., ±10kV to ±30kV), eliminating the need for complex series connections of high-voltage semiconductor devices while achieving the same overall voltage conversion capability.
Solution Approach 2:
The patent introduces dynamic voltage sharing control among series-connected converter modules, allowing the system to adaptively balance voltages across modules. This dynamic control simplifies the converter structure by eliminating the need for complex protective devices while maintaining reliable high-voltage operation.
4Power
If series connection of several semiconductor devices is used to handle high voltages, then voltage handling capability is achieved, but system reliability decreases due to more failure points
Solution Approach 1:
The patent implements dynamic voltage sharing control that actively monitors and balances voltages across series-connected converter modules. This dynamic control prevents voltage imbalances that could lead to device failure, significantly improving system reliability while maintaining high voltage handling capability.
Solution Approach 2:
The patent incorporates feedback control mechanisms that monitor the operating conditions of each converter module and adjust their voltage contributions accordingly. This feedback system ensures reliable operation by preventing any single module from being over-stressed, thereby maintaining high system reliability at high voltage levels.
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
The system enhances reliability and efficiency by reducing the need for complex sub-sea components, minimizing space requirements, and adapting power delivery to meet varying load demands while maintaining system stability and reducing capital investment.
Implementation Method 1
DC to alternating current (AC) power converter modules coupled in series to the system DC link
Data Source
AI summary
A direct current (DC) transmission and distribution system includes a system DC link configured for carrying power from a source to a plurality of loads {16} and DC to alternating current (AC) power converter modules coupled in series to the system DC link on a load side of the system DC link