Grid phase and harmonic detection using cascaded delayed signal cancellation technique

Abstract

Power converters are indispensable in modern energy conversion and utilization systems. For their control, there are two interesting topics: one is grid phase detection for their grid-tied operation; the other is harmonic detection for power quality improvement. Both problems involve sequence separation and signal detection, which is always challenged by voltage unbalance, harmonics and other disturbances. It is revealed in this thesis that the solution to the two problems can be rooted in the same technique, namely cascaded delayed signal cancellation (CDSC), which can isolate the positive-sequence fundamental signal from arbitrary harmonic patterns. It can be further renovated to extract any harmonic. Based on it, an advanced phase-locked loop system can be built for rapid, accurate and frequency adaptive grid phase and harmonic detection. For the practical implementation of the system, an effective discretization error reduction method is also developed. All system performances are verified by experiments.