Power quality enhancement using fuzzy sliding mode based pulse width modulation control strategy for unified power quality conditioner Rajesh Kumar Patjoshi ⇑ , Venkata Ratnam Kolluru, Kamalakanta Mahapatra Electronics and Communication Engg. Dept., National Institute of Technology Rourkela, India article info Article history: Received 4 January 2016 Received in revised form 3 March 2016 Accepted 13 May 2016 Keywords: FSMPWM Power quality Sliding surface Mamdani based fuzzy Chattering effects Fixed switching abstract This paper proposes a fixed switching methodology based on fuzzy sliding mode pulse width modulation (FSMPWM) control strategy for three-phase three-wire unified power quality conditioner (UPQC). The proposed FSMPWM control technique eliminates numerous power quality (PQ) problems such as current harmonics, load unbalance, voltage sag/swell, voltage unbalance, voltage distortion and phase-angle jump existing in the power distribution network. Initially, the design of FSMPWM is based on the imple- mentation of sliding surface by proper extraction of reference current and voltage signals for UPQC. Subsequently, the equivalent control law is formulated for both shunt and series converter. With this consideration, Mamdani fuzzy rule base is designed at the sliding surface for generation of switching pulse. Moreover, the proposed method eliminates the chattering effects by smoothing the control law in a narrow boundary layer for generating fixed switching pulse for both shunt and series converter. The performance of proposed UPQC system has been simulated and analyzed by MATLAB/SIMULINK fol- lowed by real-time experimental studies accomplished with a real-time-hardware-in the loop (HIL) sys- tem in OPAL-RT simulator. Additionally, the efficacy of this proposed technique is compared with a conventional sliding mode controller (CSMC). Ó 2016 Elsevier Ltd. All rights reserved. Introduction UPQC is a custom power device (CPD) utilized for eliminating the PQ problems such as harmonics [1] unbalance, sag and swell and phase-angle jump due to the extensive usage of electronically switched devices and non-linear load [2,3]. This CPD comprises of both shunt and series converters coupled through a common DC- link voltage and deals with harmonics in load current and also imperfections in source voltage [4]. The shunt converter can elim- inate current harmonics and unbalances from the nonlinear load so that perfect sinusoidal current flows through the power network, however series converter can compensate voltage sag/swell, volt- age unbalance, voltage distortion and phase-angle jump present on the source side, so that perfect voltage regulation is maintained across the load [5]. Therefore, UPQC draws the consideration of power engineers to create active and adaptable solutions to PQ issues, which leads to the development of novel topologies and advanced control systems for UPQC. Control system plays an important part in the overall performance of a power conditioner. The quick detection of distur- bance signal and fast extraction of reference signal are the main requirements for perfect compensation. Some advanced control techniques have been reported for UPQC in the literature, which include neural networks, SRF and PSO based controller [6–8]. How- ever, these controllers are mainly used for reference signal gener- ation and not so much useful in generation of pulse width modulation (PWM) signal. PWM controllers such as Hysteresis, tri- angular carrier and space vector modulation (SVM) [9–11] are failed to track the reference signal properly during load and supply side perturbations, therefore compensation capability of UPQC is degraded. Recently, many control techniques like deadbeat control, repet- itive controller and Fuzzy PWM controller [12–14] have been investigated to accomplish the aforementioned demands. Addi- tionally, harmonics elimination method and nonlinear observer strategy are employed to improve the transient response. How- ever, these control techniques utilize average modeling technique of the converter [15]. As the state space equations of converter vary with switching states, power converters suffer from discontinuous control [16]. The inherent switching nature of power converters is compatible with sliding mode controller (SMC) [17,18]. Moreover, the SMC is popular for its stability, robustness, good regulation and frequent switching action under all operating conditions of load and supply voltage. http://dx.doi.org/10.1016/j.ijepes.2016.05.007 0142-0615/Ó 2016 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: rajeshpatjoshi1@gmail.com (R.K. Patjoshi). Electrical Power and Energy Systems 84 (2017) 153–167 Contents lists available at ScienceDirect Electrical Power and Energy Systems journal homepage: www.elsevier.com/locate/ijepes