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Frequency and fundamental signal measurement algorithms for distributed control and protection applications

Roscoe, Andrew J. and Burt, G.M. and McDonald, J.R. (2009) Frequency and fundamental signal measurement algorithms for distributed control and protection applications. IET Generation Transmission and Distribution, 3 (5). pp. 485-495. ISSN 1751-8687

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Increasing penetration of distributed generation within electricity networks leads to the requirement for cheap, integrated, protection and control systems. To minimise cost, algorithms for the measurement of AC voltage and current waveforms can be implemented on a single microcontroller, which also carries out other protection and control tasks, including communication and data logging. This limits the frame rate of the major algorithms, although analogue to digital converters (ADCs) can be oversampled using peripheral control processors on suitable microcontrollers. Measurement algorithms also have to be tolerant of poor power quality, which may arise within grid-connected or islanded (e.g. emergency, battlefield or marine) power system scenarios. This study presents a 'Clarke-FLL hybrid' architecture, which combines a three-phase Clarke transformation measurement with a frequency-locked loop (FLL). This hybrid contains suitable algorithms for the measurement of frequency, amplitude and phase within dynamic three-phase AC power systems. The Clarke-FLL hybrid is shown to be robust and accurate, with harmonic content up to and above 28% total harmonic distortion (THD), and with the major algorithms executing at only 500 samples per second. This is achieved by careful optimisation and cascaded use of exact-time averaging techniques, which prove to be useful at all stages of the measurements: from DC bias removal through low-sample-rate Fourier analysis to sub-harmonic ripple removal. Platform-independent algorithms for three-phase nodal power flow analysis are benchmarked on three processors, including the Infineon TC1796 microcontroller, on which only 10% of the 2000 mus frame time is required, leaving the remainder free for other algorithms.

Item type: Article
ID code: 19142
Notes: The culmination of much of my PhD research, this paper was well received by reviewers and passed quickly through to publication. The underpinning ideas and methods have also led to much of my subsequent work, particularly conference papers on other topics such as Fourier analysis for power measurement and power quality, and phasor measurement unit (PMU) design.
Keywords: fourier analysis, distributed control, distributed power generation, electric current measurement, frequency locked loops, harmonic distortion, power generation control, power generation protection, power system measurement, voltage measurement, Electrical engineering. Electronics Nuclear engineering, Energy Engineering and Power Technology, Control and Systems Engineering, Electrical and Electronic Engineering
Subjects: Technology > Electrical engineering. Electronics Nuclear engineering
Department: Faculty of Engineering > Electronic and Electrical Engineering
Professional Services > Corporate Services Directorate
Depositing user: Strathprints Administrator
Date Deposited: 21 May 2010 12:30
Last modified: 12 Dec 2015 14:10

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