Applications Simulation Simulation: Transactions of the Society for Modeling and Simulation International 1–11 Ó The Author(s) 2017 DOI: 10.1177/0037549716686165 journals.sagepub.com/home/sim Direct power control of a grid-connected photovoltaic system using a fuzzy-logic based controller Hassan Feshki Farahani 1,2 and Farzan Rashidi 3 Abstract In this paper a fuzzy logic-based controller is proposed for direct powercontrol of three-phase grid-connected photo- voltaic (PV) inverters. To demonstrate the effectiveness of the control method, a typical grid-connected PV inverter is implemented and the performance of the proposed technique is compared to a traditional proportional–integral (PI) controller. Numerical simulation results illustrate that the proposed fuzzy controller performs well in independently reg- ulating the active and reactive output powers. Moreover, comparisons of simulation results between fuzzy and PI con- trollers show advantages of the fuzzy-based technique in terms of transient response characteristics, such as fast response, small overshoot, acceptable steady-state fluctuation, and high robustness. Keywords Direct power control, active and reactive powers, inverter direct current link voltage, grid-connected photovoltaic sys- tem, fuzzy control 1. Introduction In recent years, voltage source inverters (VSIs) have been used in different renewable energy applications, such as photovoltaic (PV) systems, wind energy, distrib- uted generation, etc. These converters provide sinusoidal grid currents, constant direct current (DC) link voltage, and the unity power factor using proper controllers. 1–5 Furthermore, they have been widely used in various application, such as active power filters, 6,7 microgrid networks, 8,9 and so on. Various kinds of control methods are investigated for alternating current (AC)/DC conver- ters in the literature, most of which are based on voltage-oriented control (VOC), 10 direct power control (DPC), 5,11,12 and DC control. 6,8 The VOC strategy can decompose the converter current to two components: the active and reactive components. In Rioual et al., 13 active power is controlled and regulated using the current refer- ence in a positive sequence synchronous frame. Song and Nam 14 propose a dual current control approach to control negative and positive sequence currents ade- quately. An improved method using a proportional–inte- gral (PI) controller to overcome the control complexity is presented by Etxeberria-Otadui et al. 15 Another kind of three-phase VSI is DPC, which has many advantages, such as easy to implement, strong robustness, quick response, and so on. 16,17 Use of the DPC method is reported in different literature. Xu et al. 18 pro- pose a simplified control strategy based on DPC with con- stant switching frequency. In Zhi et al., 19 a direct power controller is used to the control active and reactive power of DC/AC converters. Some of the literature focuses on the improvement of steady-state performance via proposing a duty cycle control, 20,21 applying improved switching tables, 9,22 and space vector modulation (SVM). 5 In some researches, the fuzzy controller is applied for the DPC of VSIs. 23–25 An approach to control the three-phase pulse width modula- tion (PWM) rectifier based on DPC is proposed by Lamterkati et al. 26 In Hu et al., 27 a fuzzy proportional– integral–differential (PID) controller for a grid-connected PV inverter is proposed and compared with the traditional PID controller. Noguchi et al. 28 introduced DPC based on 1 Department of Engineering, Asthian Branch, Islamic Azad University, Ashtian, Iran 2 Department of Engineering, Central Tehran Branch, Islamic Azad University, Tehran Iran 3 Department of Electrical and Computer Engineering, University of Hormozgan, Iran Corresponding author: Hassan Feshki Farahani, Department of Engineering, Astian Branch, Islamic Azad University, Ashtian, Iran, P.O. Box: 3961813347, Iran. Email: hfeshki@aiau.ac.ir