A Filter-Less Time-Domain Method for Reference Signal Extraction in Shunt Active Power Filters

Abstract

Current distortion degrades power quality and affects system performance, especially for sensitive loads that require pure sinusoidal waves. Owing to its excellent dynamic response, a well-designed active power filter (APF) can achieve a total harmonic distortion (THD) within the acceptable limits defined by IEEE 3002 standards through compensating harmonic distortions. The APF consists of two main modules: a reference signal extraction module and a modulation module. This paper adapts the matrix pencil method, a well-known model-based parameter estimation technique, to the problem of reference extraction. Contrary to conventional time-domain methods such as the synchronous reference frame (SRF) and the reactive power theory (PQ theory) that rely on low-pass filters in their implementations, the proposed method does not use a filter. However, it extracts the reference signal by first decomposing the load current into its constituent frequency components, and then subtracting the pure sine wave synthesized from the obtained fundamental component from the load current. Results on simulated data from MATLAB/Simulink confirm the higher accuracy and fast response time of the proposed method in extracting the reference signal.

Keywords

• active power filter (APF)
• power quality
• reactive power theory (PQ theory)
• synchronous reference frame (SRF) d-q theory
• reference signal extraction