Series Compensators for UPS Ring Bus Fault Current
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Solution Overview
Problem
Static uninterruptible power supplies (UPSs) in ring bus architectures face challenges in fault current limitation and power transfer efficiency, particularly due to the limitations of large chokes which isolate but also impede power delivery and voltage regulation, and introduce common-mode failure points.
Innovation Solution
Incorporating series compensators with capacitors and bypass switches between chokes and the ring bus to dynamically adjust impedance for steady-state power transfer and fault current limitation, allowing for reduced reactive power consumption and increased reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large chokes are used to isolate static UPSs in ring bus architectures, then fault current limitation is improved, but power transfer efficiency deteriorates and common-mode failure points are introduced
Solution Approach 1:
The patent applies dynamics by making the impedance characteristic adjustable rather than fixed. The series compensator with capacitor and bypass switch dynamically changes the impedance state: during normal operation the capacitor is connected to provide low impedance for efficient power transfer, and during fault conditions the bypass switch opens to disconnect the capacitor, allowing the choke to limit fault current. This dynamic switching resolves the contradiction between efficient power transfer and fault current limitation.
Solution Approach 2:
The patent changes the electrical parameter (impedance) of the series compensator based on operating conditions. By varying the capacitance parameter through the bypass switch mechanism, the system achieves low impedance during normal operation for efficient power transfer and high impedance during faults for current limitation, thereby resolving the technical contradiction.
2Productivity
If series compensators with capacitors are used for steady state power transfer, then power transfer efficiency is improved, but fault current limitation capability deteriorates
Solution Approach 1:
The bypass switch provides dynamic control to switch between two operational states: normal operation where the capacitor is connected for efficient power transfer, and fault condition where the switch opens to disconnect the capacitor, enabling the choke to limit fault current. This dynamic switching capability allows the system to maintain both efficient power transfer and fault current limitation capabilities at different times.
Solution Approach 2:
The patent extracts the capacitor from the circuit during fault conditions by opening the bypass switch, removing the element that would otherwise prevent effective fault current limitation. This selective extraction allows the choke to perform its fault current limitation function without being counteracted by the capacitor's low impedance characteristic.
3Reliability
If bypass switches are added to series compensators for fault current limitation, then reliability is improved, but device complexity increases
Solution Approach 1:
The bypass switch serves multiple functions: it controls the capacitor connection during normal operation for efficient power transfer and disconnects the capacitor during faults for current limitation. This multi-functionality justifies the added complexity by providing both power transfer optimization and fault protection capabilities within a single component.
Solution Approach 2:
The patent combines the fault protection function with the existing series compensator structure. The bypass switch is integrated into the series compensator circuit, merging the fault current limitation capability with the power transfer function rather than adding a separate dedicated fault protection device, thereby minimizing the increase in overall device complexity.
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 enhances power transfer efficiency, increases the number of UPSs that can be connected, extends ring bus length, and improves reliability by reducing fault current and clearing time, while maintaining voltage regulation and preventing common-mode failures.
Implementation Method 1
each series compensator of the plurality of series compensators comprises: a capacitor; and a bypass switch electrically coupled in parallel with the capacitor to bypass the capacitor
Implementation Method 2
a plurality of chokes, each choke of the plurality of chokes electrically coupled between a respective static UPS of the plurality of static UPSs and the ring bus
Data Source
Figure 1
Figure 2~3
AI summary
A system is provided. The system includes a plurality of uninterruptible power supplies (UPSs) (302), a ring bus (306), a plurality of chokes (308), each choke of said plurality of chokes electrically coupled between a respective UPS of said plurality of UPSs and the ring bus, and a plurality of series compensators (510), each series compensator of the plurality of series compensators electrically coupled between an associated choke of the plurality of chokes and the ring bus.