Parallel UPS Bypass Switching for Balanced RMS Load Sharing
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Solution Overview
Problem
Existing UPS systems face challenges in achieving balanced load sharing during bypass mode due to manufacturing differences and cable variations, leading to uneven load distribution and potential overloading, which can result in protection circuit tripping and load drop.
Innovation Solution
A system with a controller that dynamically adjusts the operation of bypass switches in parallel UPSs to interrupt input current, ensuring equivalent Root Mean Square (RMS) current distribution by controlling the duration of interruptions based on monitored input current, reducing the need for cable length adjustments and additional components like chokes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple UPSs are coupled in parallel to provide enhanced scalability and redundancy, then power capacity and backup capability are improved, but load sharing becomes unbalanced due to manufacturing differences and cable variations
Solution Approach 1:
The controller continuously monitors the input current of each UPS and dynamically adjusts the bypass switch timing to balance load sharing. This feedback mechanism compensates for manufacturing differences and cable variations, ensuring each UPS carries an equivalent RMS current while maintaining system redundancy
Solution Approach 2:
The system changes the timing parameter of bypass switch operation for each UPS based on monitored current levels. By adjusting when each bypass switch interrupts current, the system dynamically balances the load distribution across parallel UPSs despite hardware variations
2Ease of operation
If traditional load sharing methods using cable length adjustments and chokes are used, then load balance can be achieved, but system size, weight, cost, and complexity increase
Solution Approach 1:
The patent replaces mechanical/passive load balancing methods (cable length adjustments and choke inductors) with an active electronic control system. The controller dynamically manages bypass switch timing to achieve load balance, eliminating the need for additional physical components and reducing system complexity
Solution Approach 2:
The invention extracts and removes the need for additional balancing components (chokes, cable length variations) by implementing intelligent control of existing bypass switches. This extraction approach simplifies the system while maintaining load sharing balance
3Device complexity
If bypass switches continuously conduct without interruption, then system simplicity is maintained, but load sharing imbalance occurs leading to protection circuit tripping
Solution Approach 1:
The controller implements periodic interruption of bypass switch conduction based on monitored current levels. Each UPS's bypass switch is dynamically opened and closed in a periodic manner to balance the RMS current contribution, preventing overload and protection circuit tripping while maintaining overall system operation
Data Source
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AI summary
According to aspects, embodiments herein provide a power system comprising a first Uninterruptible Power Supply (UPS) configured to operate in parallel with a plurality of UPSs, the first UPS including an input configured to receive input power, an output configured to provide output power to a load, a bypass circuit interposed between the input and output and including a bypass switch, the bypass switch positioned to couple the input and the output in a bypass mode and decouple the input and the output in an on-line mode, and a controller coupled to the first UPS and configured to monitor an input current through the bypass circuit, and control the bypass switch of the first UPS to interrupt the input current through the bypass circuit of the first UPS for a delay during the bypass mode such that each UPS provides a balanced output current to the load.