Bidirectional Chopper Frequency Control for UPS Switching Loss
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Solution Overview
Problem
Conventional uninterruptible power supply apparatuses experience efficiency reduction due to switching loss in switching elements and increased ripple current, which shortens the lifespan of the power storage device.
Innovation Solution
The apparatus employs a control circuit to drive the first switching element at a higher frequency during normal conditions and the second switching element at a lower frequency during power failures, reducing switching loss and extending the lifespan of the power storage device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the switching frequency is reduced to decrease switching loss, then the efficiency is improved, but the ripple current increases and the temperature of the power storage device increases, reducing the lifetime of the power storage device
Solution Approach 1:
The patent applies dynamics by making the switching frequency adjustable rather than fixed. The control circuit dynamically changes the switching frequency of the bidirectional chopper based on system conditions, allowing optimization between switching loss and ripple current effects on the power storage device.
Solution Approach 2:
The patent changes the parameter of switching frequency to resolve the contradiction. By adjusting the switching frequency parameter according to different operating conditions, the system can reduce switching loss when appropriate while avoiding excessive ripple current that would harm the power storage device.
2Loss of energy
If the switching frequency is reduced to decrease switching loss, then the efficiency is improved, but the ripple current flowing in the power storage device increases
Solution Approach 1:
The control circuit dynamically adjusts the switching frequency based on operating conditions, making the system adaptive. This dynamic control allows the system to operate at higher frequencies when ripple current is acceptable and at lower frequencies when switching loss is the primary concern.
Solution Approach 2:
The switching frequency parameter is changed according to system state. The control circuit monitors conditions and adjusts the frequency parameter to balance between reducing switching loss and limiting ripple current generation.
Data Source
AI summary
In an uninterruptible power supply apparatus, a bidirectional chopper (5) includes a first IGBT (Q1) for storing DC power generated by a converter (2) into a battery (22) and a second IGBT (Q2) for supplying DC power of the battery to an inverter (8). A control circuit (7) drives the first IGBT at a first frequency (fH) in a sound state of a commercial AC power supply (21) and drives the second IGBT at a second frequency (fL) lower than the first frequency in response to occurrence of a power failure of the commercial AC power supply. Switching loss produced in the second IGBT thus can be reduced.