DC Power Transmission System AC Stage Segmentation
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Solution Overview
Problem
Current DC power transmission systems require extensive DC insulation to ground, leading to increased size, cost, and complexity, particularly in applications with limited space such as oil and gas platforms, due to the need for heavy insulation of active and passive components to prevent damage from DC faults.
Innovation Solution
The DC power transmission system incorporates an AC stage with an AC/AC converter and a transformer with electromagnetically coupled primary and secondary windings, reducing the need for high voltage DC insulation by isolating active components from the DC side during faults, and using passive components that require less insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active components and passive components are heavily DC insulated to ground to prevent damage from DC faults, then reliability is improved, but device complexity and size increase significantly
Solution Approach 1:
The converter is divided into an AC stage with active components and a DC stage with passive components. The AC stage processes AC power and is isolated from DC faults by the AC/DC rectifier, while the DC stage handles DC power transmission. This segmentation allows the active components to avoid direct exposure to high-voltage DC faults, reducing insulation requirements.
Solution Approach 2:
The AC/DC rectifier acts as an intermediary between the AC stage and DC stage. It converts AC to DC and provides electrical isolation, preventing DC fault currents from reaching the active components in the AC stage. This intermediary protects the sensitive active components without requiring them to have heavy DC insulation.
2Reliability
If all auxiliary power components including gate drives and sensors are DC insulated with respect to ground, then reliability is improved, but cost and size increase significantly
Solution Approach 1:
Auxiliary components are segmented into two groups: those in the AC stage (gate drives, sensors for active components) and those in the DC stage (protection circuits). The AC stage auxiliary components only require AC insulation levels, which are much lower than DC insulation requirements. This segmentation dramatically reduces the quantity of high-voltage insulation material needed.
3Reliability
If cooling systems and auxiliary support equipment are DC insulated to ground, then reliability is improved, but the system becomes too large for limited space applications
Solution Approach 1:
The cooling system is segmented into an AC-side cooling system for active components and a DC-side cooling system for passive components. The AC-side cooling system does not require high-voltage DC insulation, allowing for more compact design. This segmentation enables the converter to fit within limited space constraints while maintaining adequate cooling and protection.
4Loss of energy
If AC power is converted to DC power using a diode rectifier and then modified by active DC/DC converters, then power transmission efficiency is improved, but the need for heavy DC insulation increases system cost
Solution Approach 1:
The conventional approach is inverted: instead of converting AC to DC and then using active DC/DC converters, the patent uses active AC/AC converters followed by a simple AC/DC rectifier. This inversion places the active power conversion in the AC domain, where insulation requirements are lower, while maintaining power transmission efficiency through controlled rectification.
Solution Approach 2:
The patent changes the operating domain of active power conversion from DC to AC. By performing active power control in the AC stage with lower voltage stress, the system achieves the same power transmission efficiency without requiring high-voltage DC insulation on active components, thereby reducing system cost.
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 configuration reduces the amount of DC insulation needed, minimizing the size and cost of the transmission end converter while maintaining efficient power transmission, and allows for fine control of transmission voltage through parallel power conversion sections.
Implementation Method 1
a transformer with electromagnetically coupled primary and secondary windings
Data Source
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AI summary
A DC power transmission system is configured to generate an electric field including components substantially constant with respect to time and varying with time. The DC power transmission system includes an AC stage (202) configured to receive AC electrical power. The AC stage (202) includes a transformer (208) including primary windings (210) and secondary windings (212) configured to be electromagnetically coupled to, and electrically isolated from, each other. The AC stage (202) also includes an AC/AC converter (206) having substantially no insulating features against the at least one substantially constant component of the electric field. The AC/AC converter (206) is electrically coupled to the primary windings (210). The DC power transmission system also includes an AC/DC conversion stage (204) positioned downstream of the AC stage (202). The AC/DC conversion stage (204) includes an AC/DC rectifier (214) configured to convert AC electrical power to DC electrical power without external control. The AC/DC rectifier (214) is coupled to the secondary windings (212).