DC/DC Converter Circuit Breaker Layout for HVDC Overvoltage Protection
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Solution Overview
Problem
Existing DC/DC voltage converters for HVDC electrical energy transmission are bulky, expensive, and inefficient due to the need for excessive submodules to handle fault voltages, leading to increased conduction and switching losses, and complex control systems.
Innovation Solution
A DC/DC voltage converter design that includes a circuit breaker device capable of opening when the voltage across the upper half-arm reaches a maximum, reducing the number of submodules required and incorporating a filter module to limit alternating current, thereby protecting against overvoltages and optimizing submodule usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the chains of sub-modules of the upper half-arms are over-sized by adding a large number of sub-modules to support fault voltages, then the converter is protected against overvoltages, but the converter becomes particularly heavy, bulky and expensive
Solution Approach 1:
A circuit breaker device is introduced as an intermediary protective element between the upper half-arms and the first continuous terminal. This circuit breaker acts as a mediator that interrupts current flow during fault conditions, allowing the sub-modules to be sized for normal operation rather than worst-case fault conditions. The circuit breaker absorbs the stress of overvoltages without requiring the sub-modules themselves to be oversized.
2Reliability
If a large number of sub-modules are added to support overvoltages, then sufficient voltage can be supported during faults, but conduction and switching losses increase
Solution Approach 1:
The circuit breaker serves as a protective intermediary that prevents fault voltages from reaching the sub-module chains. This allows the sub-modules to operate within their normal voltage ratings without requiring excessive voltage headroom, thereby reducing the number of sub-modules needed and minimizing associated conduction and switching losses.
3Reliability
If the chains of sub-modules are over-sized to handle fault voltages, then protection is ensured, but the control resources required increase significantly
Solution Approach 1:
The circuit breaker simplifies the control architecture by providing a straightforward overcurrent protection mechanism. Instead of requiring complex control algorithms to manage oversized sub-module chains during faults, the circuit breaker offers a simple, reliable protective action that reduces the computational and control resources needed.
4Reliability
If excessive sub-modules are used to support fault voltages, then converter protection is achieved, but the converter becomes particularly expensive
Solution Approach 1:
The circuit breaker provides an cost-effective protective solution that avoids the need to purchase and install excessive numbers of expensive power electronic sub-modules. By using a dedicated protective device, the system achieves the same level of reliability at a lower overall cost.
5Weight of stationary object
If the number of sub-modules is reduced to eliminate useless components, then weight and cost are reduced, but the converter becomes vulnerable to overvoltages during faults
Solution Approach 1:
The circuit breaker compensates for the reduced voltage headroom in the sub-module chains by providing dedicated overvoltage protection. This allows the system to use minimally sized sub-modules for normal operation while maintaining robust protection capabilities through the circuit breaker intermediary.
Data Source
Figure 1
Figure 2
Figure 3A~3D
AI summary
Disclosed is a voltage converter (10) comprising at least one arm (24) extending between a first DC terminal (16) and a second DC terminal (28) and comprising at least one upper half-arm (24u) and one lower half-arm (24l) that are connected, each half-arm comprising a chain of submodules (30), the converter comprising a filtering module (34) and at least one circuit-breaker device (40) connected between a mid-point of the arm and the first DC terminal, the circuit-breaker device being able to assume an open position and a closed position, the circuit-breaker device being configured to open when the voltage across terminals of the upper half-arm of the at least one arm reaches the maximum voltage that can be generated by the chain of submodules of the upper half-arm.