Redundant Front-End Converter Control for DC-Link Bus Bar Limits
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Solution Overview
Problem
The existing electric drive systems with redundant feeding units require larger and more expensive DC-link bus bars to handle the total current capacity, increasing costs due to the need for excessive materials like copper, especially when only one feeding unit fails.
Innovation Solution
A control system that limits over-current and overload by creating a trip signal to disconnect the feeding system partially from power electronic components, allowing for a redundant feeding system without increasing the DC-link bus bar's current capability and reducing hardware requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundant feeding units are implemented to ensure process continuity, then system reliability is improved, but the DC-link bus bar must be dimensioned for higher current capacity leading to increased material costs
Solution Approach 1:
The patent implements dynamic current sharing control where the operational feeding unit's current contribution is dynamically adjusted based on the status of redundant units. When one feeding unit fails, the control system dynamically redistributes the load current among remaining units, allowing the DC-link bus bar to be dimensioned for normal operating current rather than peak redundant current capacity.
Solution Approach 2:
The control system changes the operating parameters of the feeding units by implementing current limiting and trip signal mechanisms. When over-current or overload conditions are detected, the system automatically trips the affected feeding unit and adjusts the current parameters of operational units, allowing the bus bar to operate within safe current limits without requiring excessive material capacity.
2Power
If the DC-link bus bar is dimensioned to carry total current from all feeding units, then current capability is sufficient, but system cost increases due to excessive material usage
Solution Approach 1:
The patent applies partial action by designing the DC-link bus bar with current capability sufficient for normal single-unit operation rather than excessive capacity for all redundant units operating simultaneously. The control system ensures that only the necessary current capacity is provided, avoiding over-engineering the bus bar for worst-case scenarios that never occur in practice.
3Power
If feeding units operate in parallel with full current capacity, then power delivery is maximized, but over-current protection requirements increase system complexity
Solution Approach 1:
The control system provides self-service protection by automatically monitoring current levels and generating trip signals when over-current or overload conditions are detected. The system autonomously manages the protection function without requiring external complex protection devices, as the control system itself performs the protective function by disconnecting faulty feeding units and adjusting operational parameters.
Data Source
AI summary
An electric drive for driving at least one power converter and/or electric motor, having a mains supply connection for providing electric power to the electric drive, a redundant feeding system comprising at least two feeding units, namely a first non-regenerative front end or active front end and a second non-regenerative front end or active front end, power electronics components for connecting the mains supply connection to the feeding system, a control system for controlling the feeding system, and a DC-link connection for connecting the electric drive to a DC-link. The disclosure further discloses a method for operating a corresponding electric drive.