Current Diversion System for MVDC Converter Fault Protection
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Solution Overview
Problem
Existing medium voltage DC (MVDC) and high voltage DC (HVDC) converter systems face challenges in remote locations due to increased stress on components from short circuits, leading to premature service life reduction and the need for oversized, costly components, as well as interruptions in current flow that affect downstream loads.
Innovation Solution
The implementation of a current diversion system using switching devices and transformers to divert current away from critical components during faults, reducing the load on semiconductor-based devices and capacitors, and allowing the use of less rugged and less expensive switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If circuit breakers are opened to isolate faults in remote power conversion assemblies, then protection against short circuits is achieved, but current flow to downstream loads is interrupted for an indeterminate period
Solution Approach 1:
The invention divides the power conversion assembly into separate rectifier and inverter portions that can operate independently. The rectifier portion can continue converting AC to DC even when the inverter portion is isolated due to a fault, maintaining current flow to downstream loads while protecting against short circuits.
Solution Approach 2:
The invention introduces a fault isolation mechanism that acts as an intermediary between the rectifier and inverter portions. This allows the system to isolate faults while maintaining operational continuity through the intermediate DC link, preventing complete system shutdown.
2Reliability
If oversized and more robust components are used in remotely positioned power conversion assemblies, then protection against accelerated reductions in service life is improved, but device cost and complexity increase
Solution Approach 1:
The invention extracts the fault protection function from the main power conversion path by providing separate fault isolation mechanisms. This allows the use of standard, less robust components in the main power conversion path while still achieving reliable protection against short circuits and extended service life.
Solution Approach 2:
The invention implements protective measures in advance by providing fault isolation capabilities that prevent short circuits from causing damage to components. This beforehand protection eliminates the need for oversized, more robust components, allowing the use of standard components with adequate service life.
3Reliability
If devices positioned in series with the principle current path are used to limit current flow, then protection against short circuits is achieved, but device complexity and cost increase due to additional components
Solution Approach 1:
Instead of placing protective devices in series with the current path, the invention inverts the approach by providing fault isolation capabilities that protect components without requiring series devices in the main current path. This reduces device complexity while maintaining current flow limitation and protection capabilities.
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 extends the service life of semiconductor-based devices, reduces the capacitance requirements in DC links, and minimizes the need for circuit breakers by diverting fault currents, thereby maintaining system operation and reducing costs.
Implementation Method 1
The at least one second switching device can be configured to transmit electric current only from the third terminal to the fourth terminal. Transmitting electric power from the DC transmission system can comprise transmitting DC current through the at least one second switching device and at least partially bypassing at least a portion of the plurality of cells
Data Source
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AI summary
An electrical system (100) includes an AC power source (102) and a power converter (120) including at least one first terminal (156; 158) and at least one second terminal (159). The first terminal is configured to receive voltages with a DC component and the second terminal is configured to receive voltages that have a non-zero time average value including AC and DC components. The electrical system also includes an AC power transmission subsystem 110) coupled to and extending between the AC power source (102) and the power converter (120). The electrical system (100) further includes a current diversion system (150) including a plurality of first switching devices (160) coupled to the AC power transmission subsystem. The current diversion system also includes a second switching device (170) including a third terminal (172) coupled to the first terminal and a fourth terminal (174) coupled to the second terminal. The second switching device (170) is configured to transmit current only from the third terminal (172) to the fourth terminal (174).