Power Converter Fault Current Dissipation via Switch Recirculation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing fault protection systems for DC power converters, such as those in high voltage direct current (HVDC) grids, often rely on dedicated protection devices like solid state circuit breakers (SSCBs) that add weight, cost, and complexity, and may not adequately protect against line-to-line faults.
Innovation Solution
The system dynamically controls power converters to dissipate fault current by keeping at least one internal switch closed, allowing a portion of the fault current to recirculate through the power source before activating a primary protection device, thereby reducing the load on less robust protection devices and enabling the use of lighter, less costly solutions like fast mechanical disconnects (FMDs).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dedicated DC circuit breakers (SSCB or HCB) are included to protect against faults, then fault protection capability is improved, but system weight, cost, and complexity increase
Solution Approach 1:
The power converter is designed to perform multiple functions: normal power conversion and fault current dissipation. By equipping the power converter with switchable topology capability, it can actively participate in fault protection rather than requiring separate dedicated protection devices, thereby reducing system complexity while maintaining protection capability
Solution Approach 2:
The power converter uses its own internal switches and energy storage elements to dissipate fault current without requiring external dedicated protection devices. The converter serves itself by redirecting fault current through its internal circuitry, eliminating the need for additional SSCB or HCB components
2Reliability
If all internal switches of the power converter are opened to isolate the fault, then fault isolation is improved, but the ability to dissipate fault energy is reduced
Solution Approach 1:
The switch topology is dynamically reconfigured during fault conditions rather than simply opening all switches. The controller selectively closes specific switches to create a dissipation path, allowing the system to adapt its structure in real-time to both isolate the fault and dissipate energy effectively
Solution Approach 2:
The power converter acts as an intermediary between the fault location and the protection device. By introducing controlled switch states, it creates a intermediate path that allows fault energy to be dissipated through the power source while still isolating the protected circuit
3Reliability
If robust protection devices are used to handle entire fault current, then fault protection reliability is improved, but system weight and cost increase
Solution Approach 1:
The power converter performs partial fault current handling by dissipating a portion of the fault energy through its internal switches. This partial action reduces the burden on the downstream protection device, allowing it to be less robust and lighter while the power converter compensates for the reduced protection capability
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A control unit (42) of an electrical system (10) comprising a converter (35) is described. Upon detection of a fault current (26) caused by a line-to-line fault (20) in the output of the converter, the control unit (42) causes at least one of the switches (34) of the converter to be switched-on and conducting to allow some of the fault current (26) to flow through the at least one switch (34), before activating a protection device (38) arranged in the output of the converter to create an open circuit and break the fault (20).