Parallel UPS Switching for Soft Start After AC Recovery
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Solution Overview
Problem
Uninterruptible power supplies configured to serve both AC and battery power feeding functions cannot simultaneously perform these functions, making it impossible to gradually reduce battery discharge current while gradually raising AC input voltage when commercial AC power supply recovers, thus preventing a soft start during recovery.
Innovation Solution
A system of uninterruptible power supplies connected in parallel with a control device that switches between AC and battery power feeding modes, allowing gradual switching to AC power feeding mode when commercial AC power supply recovers, ensuring a soft start by successively turning on switches in each uninterruptible power supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the converter is used to serve both AC power feeding function and battery power feeding function, then components such as filter and semiconductor module can be miniaturized, but when AC power supply recovers, the converter cannot be controlled to gradually raise AC input voltage while gradually reducing battery discharge current
Solution Approach 1:
The system segments the power feeding function across multiple uninterruptible power supplies connected in parallel. Each UPS can independently operate in either AC power feeding mode or battery power feeding mode, allowing the system to collectively provide both functions simultaneously. This segmentation enables some UPS units to gradually transition from battery mode to AC mode while others remain in battery mode,从而实现软启动
Solution Approach 2:
The system dynamically adjusts the operating mode of each uninterruptible power supply based on system needs. When AC power recovers, the control device dynamically transitions individual UPS units from battery power feeding mode to AC power feeding mode in a controlled sequence, enabling gradual voltage raising and current reduction without requiring simultaneous dual-function operation in a single converter
2Device complexity
If the converter selectively performs AC power feeding or battery power feeding, then device complexity is reduced, but the ability to perform both functions simultaneously is lost
Solution Approach 1:
The system merges multiple uninterruptible power supplies connected in parallel to collectively provide both AC power feeding and battery power feeding functions. While each individual UPS maintains simple selective operation, the combined system achieves dual-function capability through parallel operation, with some units handling AC power feeding and others handling battery power feeding simultaneously
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
Enables a soft start during AC power supply recovery, maintaining constant power to the load by gradually raising AC input voltage and reducing battery discharge current, thereby suppressing voltage variations and ensuring stable operation.
Implementation Method 1
a power conversion device configured to selectively receive power from one of the AC node and a power storage device, generate AC power, and supply the AC power to the load
Data Source
AI summary
A plurality of UPSs are connected in parallel between an AC power supply and a load. The UPSs each include a first switch connected between the AC power supply and an AC node. During the first power feeding mode, a control device turns on the first switch, and controls a power conversion device so as to receive AC power from the AC node and generate AC power. During a second power feeding mode, the control device turns off the first switch, and controls the power conversion device so as to receive DC power from a power storage device and generate AC power. When the AC power supply recovers during the second power feeding mode, the control device successively switches the plurality of UPSs to the first power feeding mode by successively turning on a plurality of the first switches each of which corresponds to each of the plurality of UPSs.