Published in IET Power Electronics Received on 27th May 2011 doi: 10.1049/iet-pel.2011.0371 ISSN 1755-4535 Real-time implementation of adaptive fuzzy hysteresis-band current control technique for shunt active power filter Y. Suresh A.K. Panda M. Suresh Department of Electrical Engineering, NIT Rourkela, India E-mail: ysuresh.ee@gmail.com Abstract: Optimising the performance of power system networks using conventional methods is quite difficult because of the complex nature of systems that are highly non-linear and non-stationary. In this study a hybrid adaptive fuzzy hysteresis current controller for shunt active power filter (SAPF) is proposed. The conventional adaptive hysteresis concept is hybridised with fuzzy logic controller (FLC), which facilitates discarding of uncertainty in the system. In fact, conventional proportional- integral (PI) controllers for shunt active filter are based on a linearised model that fails to react under transient events. On the other side, FLC has widened its applicability to many engineering fields and offers satisfactory results for a wide variety of operating conditions. It helps in fulfilling the need for perfection, such as stability and robustness for every system. All this motivated to adopt FLC for SAPF applications. By incorporating an adaptive fuzzy hysteresis band, active power filter (APF) gains outstanding compensation ability under steady-state and transient conditions. To validate the proposed approach, the system is implemented on a real-time digital simulator and adequate results are reported for its verification. 1 Introduction Electrical power is perhaps the most essential raw material used by commerce and industry today. It is an unusual commodity because it is required as a continuous flow. From the consumers’ point of view continuity of supply is an important aspect but in the present day, owing to the presence of non-linear loads continuity seems to be distractive and it is all because of power quality problems. It is important to realise that the electrical load is not static. Differences in duty cycle of equipment and variations in working pattern contribute to a constantly changing load pattern. This results in generating harmonics. Today, harmonics is a buzz word heard from electrical utilities to customers. Although harmonic voltages and currents are, by themselves, imperceptible, the physical phenomena that accompany them are perceivable [1]. The adverse effects of harmonics in electrical power systems are very real and failures related to voltage and current harmonics very often occur without warning. To reduce this harmonic propagation, active and passive filters are introduced. However, passive filters have demerits like fixed compensation characteristics [2], parallel and series resonance with source voltage harmonics and filtering characteristics strongly affected by source impedance. In addition, they are also bulky in nature and they lose their effective performance with passage of time. Owing to these reasons active filters have been proposed as a solution to passive filter problems. Interesting features of active filters are that they are smaller in size and capable of attenuating the harmonic currents in power systems by injecting equal but opposite compensating currents [3–5]. In spite of these features, successful control of active filters requires an accurate current reference that results in exact compensation and it became our key objective to develop an appropriate controller for APF. However, this article deals completely with controller diagnosis. On the other hand, to achieve significant compensation with fast control action, hysteresis controllers are used. In fact, among the various PWM techniques, the hysteresis-band current control PWM method is popularly used because of its simplicity of implementation [6]. Besides fast response current loop and inherent-peak current limiting capability, the technique does not need any information about the system parameters. In spite of this merit, current control with fixed hysteresis band has the disadvantage that the PWM frequency varies within a band because peak-to-peak current ripple is required to control all points of the fundamental wave. Indeed, this results in increasing the switching losses in the system. To avoid these limitations an adaptive hysteresis controller is developed by the author [7]. An attractive feature of the technique is; that the band can be programmed as a function of the load and the supply parameters to optimise the PWM performance. Performing such actions results in a drastic reduction of switching loss in the system. An in-depth assessment of the control technique can be found in the above reference. It is noted that, the authors had introduced the adaptive hysteresis current control for 1188 IET Power Electron., 2012, Vol. 5, Iss. 7, pp. 1188–1195 & The Institution of Engineering and Technology 2012 doi: 10.1049/iet-pel.2011.0371 www.ietdl.org