Published in IET Power Electronics Received on 2nd September 2007 Revised on 5th April 2008 doi: 10.1049/iet-pel:20070375 ISSN 1755-4535 Generalised single-phase p-q theory for active power filtering: simulation and DSP-based experimental investigation V. Khadkikar 1 A. Chandra 1 B.N. Singh 2 1 Department of Electrical Engineering, Ecole de technologie Superieure, Montreal, Canada 2 Phoenix International, A John Deere Company, Fargo, ND, USA E-mail: vkhadkikar@gmail.com Abstract: The single-phase p-q theory for the purpose of active power filtering in the case of single-phase loads is dealt with here. A simple modification is proposed to develop a generalised single-phase p-q theory that can be utilised under the condition of distorted utility voltage. A systematic study is presented by realising both direct and indirect current control techniques. The simulation as well as the digital signal processor (DSP) (DS1104 of dSPACE) based experimental results are discussed. The developed single-phase shunt active power filter (APF) prototype is tested under different operating conditions with different loads to evaluate the full capabilities of the proposed generalised theory for practical uses. The shunt APF reduces the source current total harmonics distortion (THD) from 27.2 to 3.4% under a distorted supply voltage with a THD of 16.2%. 1 Introduction Power electronics-based devices/equipments are a major key component of today’s modern power processing, at the transmission as well as the distribution level because of the numerous advantages offered by them. These devices, equipments, nonlinear load and so on, draw non-sinusoidal currents from the utility. Therefore a typical power distribution system has to deal with ‘harmonics’ in addition to ‘reactive power support’. Active power filters (APFs), such as shunt APFs, series APFs, hybrid APFs, unified power quality conditioner (UPQC) and so on, have made it possible to mitigate some of the major power quality problems [1, 2]. The shunt APFs are generally utilised to compensate load current related problems, such as reactive power, current harmonics, current unbalance, neutral current and so on. The existing literature shows significant development in APF system performance for three-phase systems. Recently, a lot of attention has been given to compensate power quality problems in single-phase systems. The most significant issues for a single-phase system are – reactive power and current harmonics, which are the major concerns for a modern power distribution system, since these issues play a vital role in giving rise to the other power quality problems. A single-phase APF can be installed at low- and medium-power applications, such as triac-based controllers for heating applications, uninterruptible power supplies, AC voltage regulators, switch mode power supplies, electronic fluorescent lamp ballasts, electric arc furnaces [1–3], electric traction [4, 5] and so on. Three or more single-phase APF modules can also used in multilevel or multicell configurations for three-phase medium-power applications, such as motor drive applications [6, 7]. A typical single-phase shunt APF system consists of a four-switch bridge inverter structure with a self-supporting DC bus as shown in Fig. 1. To tackle power quality problems in a single-phase system, several control strategies are available [3–5, 8–10]. Among them the p-q theory, originally developed for three-phase systems by Akagi et al. [11], is one of the most suitable theories to generate instantaneous reference signals for APFs. The p-q theory has satisfactory steady-state and dynamic response, but was limited to three-phase systems. Lui et al. [12] have successfully extended the concept of instantaneous active and reactive power separation in a  b coordinates for a single-phase system, although the major attention was IET Power Electron., 2009, Vol. 2, No. 1, pp. 67–78 67 doi: 10.1049/iet-pel:20070375 & The Institution of Engineering and Technology 2008 www.ietdl.org