Power Supply Apparatus Phase Control for Harmonic and Circulating Current Reduction
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Solution Overview
Problem
The existing power supply apparatus experiences circulating current and heat generation when the technique from PTL 1 is applied to PTL 2, particularly in the second power feed mode, due to the phase difference between carrier wave signals in the power supply apparatus.
Innovation Solution
A power supply apparatus with a forward converter and a reverse converter, including a first and second switch, and control units that manage power feed modes by adjusting the phase difference between carrier wave signals to 180 degrees in the first and third modes, and matching phases in the second mode to reduce zero-phase harmonic components and circulating current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the phase difference between carrier wave signals is set to 180 degrees to reduce zero-phase harmonic components, then zero-phase harmonic reduction is improved, but circulating current increases in the second power feed mode
Solution Approach 1:
The patent applies dynamics by making the phase difference between carrier wave signals variable rather than fixed. The control device dynamically adjusts the phase difference based on the operating mode: setting it to 180 degrees in first and third power feed modes to reduce zero-phase harmonics, and setting it to 0 degrees in the second power feed mode to prevent circulating current. This dynamic adaptation resolves the contradiction between harmonic reduction and circulating current prevention.
2Object-generated harmful factors
If the phase difference between carrier wave signals is set to 180 degrees, then zero-phase harmonic component is reduced, but wiring heat generation increases due to circulating current
Solution Approach 1:
The control device dynamically adjusts the phase difference between carrier wave signals based on the power feed mode. In the second power feed mode where circulating current causes wiring heat, the phase difference is set to 0 degrees to eliminate circulating current and reduce heat generation. In other modes where harmonic reduction is the priority, the phase difference is set to 180 degrees. This dynamic adjustment resolves the contradiction between harmonic reduction and heat prevention.
Data Source
AI summary
In this uninterruptible power supply apparatus, respective phase differences between first to third carrier wave signals (CS1 to CS3) for a converter (1) and fourth to sixth carrier wave signals (CS4 to CS6) for an inverter (2) are set to 180 degrees in an inverter power feed mode and a bypass power feed mode, and respective phase differences between the first to third carrier wave signals and the fourth to sixth carrier wave signals are set to 0 degree in an overlap power feed mode. Zero-phase current (I01, I02) and circulating current (ICL) therefore can be reduced.