Shared Transformer Pre-Charging for Poly-Phase DC Link Capacitors
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Solution Overview
Problem
Existing pre-charging strategies for poly-phase power converters, particularly H-bridge rectifiers, require multiple separate pre-charge circuits, leading to high costs and system complexity due to high current spikes during connection to the grid.
Innovation Solution
A pre-charging arrangement using a single transformer and circuit breaker system to pre-charge DC link capacitors of poly-phase power converters, reducing the need for multiple circuits and simplifying the system design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple separate pre-charge circuits are used for each H-bridge DC bus, then the pre-charging function is achieved, but the system complexity and cost increase substantially
Solution Approach 1:
The patent merges multiple separate pre-charge circuits into a single shared pre-charge circuit that serves all H-bridge DC buses. The pre-charge transformer's secondary windings are connected in parallel to multiple DC buses through a single contactor, eliminating the need for separate pre-charge circuits for each bus while maintaining the pre-charging function for all buses.
Solution Approach 2:
The single pre-charge transformer and contactor assembly performs multiple functions: it pre-charges multiple different DC buses (CB1, CB2, CB3) that would otherwise require separate dedicated circuits. This universal pre-charge unit can serve any number of DC buses by simply connecting them to the same pre-charge circuit through the shared contactor.
2Reliability
If multiple separate pre-charge circuits are used for each H-bridge DC bus, then the pre-charging function is achieved, but the cost increases due to multiple transformers and circuit breakers
Solution Approach 1:
The patent combines multiple expensive components (transformers, circuit breakers, contactors) into a single shared pre-charge assembly. Instead of having one transformer per DC bus, a single transformer with multiple secondary windings serves all buses, dramatically reducing component count and manufacturing cost while maintaining the pre-charging function.
3Device complexity
If a single pre-charge circuit is used for multiple DC buses, then the system complexity and cost are reduced, but the current distribution to multiple buses must be managed
Solution Approach 1:
The patent introduces an intermediary mechanism - a single pre-charge contactor with multiple connections - that manages the distribution of pre-charge current to multiple DC buses. The contactor acts as a mediator that can connect or disconnect any combination of DC buses from the pre-charge transformer, simplifying current management compared to multiple independent circuits.
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
The solution allows for a substantial reduction in cost, size, and complexity by using a single pre-charge unit for multiple DC buses, effectively managing high current spikes during connection to the grid.
Implementation Method 1
an AC power supply (12), in particular a single-phase AC power supply, connected via a transformer (14), having a primary side (14A) and a secondary side (14B)
Data Source
AI summary
A pre-charging arrangement (10) for a poly-phase power converter (20), optionally an H-bridge converter, is arranged for being supplied by a poly-phase AC power supply (40) via an input filter (30), wherein the poly-phase power converter (20) is arranged to be connected to and disconnected from the poly-phase AC power supply (40) by a first circuit breaker (35). The pre-charging arrangement (10) includes an AC power supply (12) connected via a transformer (14), having a primary side (14A) and a secondary side (14B), between a first common point (39) of the input filter (30) and a second common point (29) of the poly-phase power converter (20) for pre-charging DC link capacitors (25) of the poly-phase power converter (20), and a second circuit breaker (15) for connecting and disconnecting the pre-charging arrangement (10).