Exploitation of Digital Filters to Advance the Single-Phase T/4 Delay PLL System

Yang, Y., Zhou, K. and Blaabjerg, F. (2017) Exploitation of Digital Filters to Advance the Single-Phase T/4 Delay PLL System. In: 2016 IEEE 2nd Annual Southern Power Electronics Conference (SPEC), Auckland, New Zealand, 05-08 Dec 2016, ISBN 9781509015467 (doi: 10.1109/SPEC.2016.7846206)

Abstract

With the development of digital signal processing technologies, control and monitoring of power electronics conversion systems have been evolving to become fully digital. As the basic element in the design and analysis phases of digital controllers or filters, a number of unit delays (z-1) have been employed, e.g., in a cascaded structure. Practically, the number of unit delays is designed as an integer, which is related to the sampling frequency as well as the ac signal fundamental frequency (e.g., 50 Hz). More common, the sampling frequency is fixed during operation for simplicity and design. Hence, any disturbance in the ac signal will violate this design rule and it can become a major challenge for digital controllers. To deal with the above issue, this paper first exploits a virtual unit delay (zv-1) to emulate the variable sampling behavior in practical digital signal processors with a fixed sampling rate. This exploitation is demonstrated on a T/4 Delay Phase Locked Loop (PLL) system for a single-phase grid-connected inverter. The T/4 Delay PLL requires to cascade 50 unit delays when implemented (for a 50-Hz system with 10 kHz sampling frequency). Furthermore, digital frequency adaptive comb filters are adopted to enhance the performance of the T/4 Delay PLL when the grid suffers from harmonics. Experimental results have confirmed the effectiveness of the digital filters for advanced control systems.

• Item Type: Conference Proceedings
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Zhou, Dr Keliang
• Authors: Yang, Y., Zhou, K., and Blaabjerg, F.
• College/School: College of Science and Engineering > School of Engineering > Systems Power and Energy
• ISBN: 9781509015467
• Copyright Holders: Copyright © 2016 IEEE
• First Published: First published in 2016 IEEE 2nd Annual Southern Power Electronics Conference (SPEC)
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher