Modular Converter Cell Fault Isolation Using Protected Sub-Cells
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Solution Overview
Problem
Modular power converters face challenges in protecting converter cells from internal short-circuit faults, particularly in Si-IGBT industrial power modules, which can lead to module explosions and affect the entire converter cell, necessitating a solution to isolate faulty sub-cells without shutting down the entire converter cell.
Innovation Solution
A converter cell design with multiple sub-cells, each comprising parallel power modules and capacitors, incorporates protection elements that can be adjusted from a closed to an open circuit connection to isolate faulty sub-cells, allowing the remaining healthy sub-cells to continue operating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If converter cells use Si-IGBT industrial power modules with low stray inductance for cost-effective scaling, then manufacturing cost and scalability are improved, but the risk of module explosion and catastrophic failure increases
Solution Approach 1:
The converter cell is divided into multiple independent sub-cells (first sub-cell, second sub-cell, third sub-cell), each with its own power modules and protection elements. This segmentation allows a fault in one sub-cell to be isolated without affecting the others, thereby maintaining reliability while using cost-effective Si-IGBT modules with low stray inductance.
Solution Approach 2:
Protection elements are pre-configured in each sub-cell to detect and respond to internal faults before they can cause module explosion or affect adjacent sub-cells. The protection elements are positioned and configured in advance to provide immediate isolation upon fault detection, preventing catastrophic failure.
2Reliability
If the entire converter cell is shut down when one sub-cell experiences an internal fault, then system safety is improved, but productivity and operational continuity deteriorate
Solution Approach 1:
The converter cell is segmented into independent sub-cells with individual protection elements. When an internal fault is detected in one sub-cell, only that specific sub-cell is isolated by opening its protection element, while the other sub-cells continue to operate. This maintains system safety by isolating the fault while preserving productivity by keeping healthy sub-cells operational.
Solution Approach 2:
Each sub-cell has its own localized protection mechanism rather than a global shutdown system. The protection elements are configured to provide localized isolation, ensuring that safety measures are applied only where needed (in the faulty sub-cell) rather than affecting the entire converter cell, thus maintaining operational continuity of healthy sections.
3Reliability
If protection elements are added to enable individual sub-cell isolation, then reliability and fault isolation capability are improved, but device complexity increases
Solution Approach 1:
The converter cell is divided into multiple sub-cells, each equipped with its own protection element. This segmentation approach actually reduces overall complexity by localizing protection functions to simple, identical units rather than requiring a complex centralized protection system. Each protection element has the same simple function, making the system easier to design and maintain despite having multiple components.
Solution Approach 2:
Each sub-cell is designed with identical protection elements and the same internal structure. This homogeneity allows for standardized manufacturing and simplifies the overall system design, as the same protection mechanism is replicated across all sub-cells rather than requiring unique complex protection circuits for each sub-cell.
4Power
If multiple parallel power modules are used in each sub-cell for current scaling, then power handling capability and cost-effectiveness are improved, but the impact of a single module failure on the entire converter cell worsens
Solution Approach 1:
Power modules are organized into multiple sub-cells rather than having all modules in a single converter cell. Each sub-cell contains parallel power modules for current scaling. When a module fails, the protection element isolates only the affected sub-cell, allowing other sub-cells with their parallel modules to continue operating, thus maintaining reliability while preserving power scaling capability.
Data Source
Figure 1
Figure 2~2A
Figure 3a~3b
AI summary
The present disclosure relates to a converter cell comprising a first sub-cell (SB, SB1) and at least a second sub-cell (SB2, SB3, SB4), each sub-cell comprising: an energy storage module (ESM) comprising: a primary DC terminal (ESM+); a secondary DC terminal (ESM-), at least one power converter module (PCM); each sub-cell (SB, SB1, SB2, SB3, SB4) further comprising: a primary connection element (CE-1) configured to electrically connect a primary DC connection terminal (DC+) of the power converter module (PCM) with the primary DC terminal (ESM+) of said energy storage module (ESM); a secondary connection element (CE-2) configured to electrically connect a secondary DC connection terminal (DC-) of the power converter module (PCM) with the secondary DC terminal (ESM-) of said energy storage module (ESM); wherein the converter cell is configured to connect to a main connection element (30), and further configured to, in response to an internal fault such as a short-circuiting, isolate at least one sub-cell of the first sub-cell (SB, SB1) and said at least a second sub-cell (SB2, SB3, SB4) by means of at least one protection element at least adjustable from a closed circuit connection to an open circuit connection, wherein said at least one protection element includes: a primary protection element (12-1, 13-1, 14-1, 23-1, 24-1, 34-1) configured to, in closed circuit connection, electrically connect the primary connection element of said at least one sub-cell and the primary connection element of one other of said first sub-cell (SB, SB1) and said at least a second sub-cell (SB2, SB3, SB4). A modular power converter, method, and control unit are also disclosed.