Control Strategy of Solar/Wind Energy Power Plant with Supercapacitor Energy Storage for Smart DC Microgrid Suwat Sikkabut 1,2 , Nisai H. Fuengwarodsakul 1 , Panarit Sethakul 2,3 , Phatiphat Thounthong 2,3 1 Sirindhorn International Thai-German Graduate School of Engineering 2 Renewable Energy Research Centre, Thai-French Innovation Institute 3 Department of Teacher Training in Electrical Engineering, King Mongkut’s University of Technology North Bangkok, Bangsue, Bangkok, 10800 Thailand e-mail: suwatsi@kmutnb.ac.th , phtt@kmutnb.ac.th Serge Pierfederici, Melika Hinaje Babak Nahid-Mobarakeh, Bernard Davat Groupe de Recherche en Électrotechnique et Électronique de Nancy, Université de Lorraine, 2 avenue de la Forêt de Haye, 54516 Vandoeuvre lès Nancy, France e-mail: Serge.Pierfederici@ensem.inpl-nancy.fr Melika.Hinaje@ensem.inpl-nancy.fr Babak.Nahidmobarakeh@ensem.inpl-nancy.fr Bernard.Davat@ensem.inpl-nancy.fr Abstract—This paper presents an original control algorithm for a hybrid energy system with a renewable energy source: a photovoltaic (PV) array and a wind turbine (WD). A single storage device, a supercapacitor (SC) module, is in the proposed structure. The very fast power response and high specific power of a SC complements the insufficient power output of the main sources to produce the compatibility and performance characteristics needed in a load. To verify the proposed principle, a hardware system is realized with analog circuits and with numerical calculation (dSPACE) for the energy control loops. Experimental results with small-scale devices, namely, a wind turbine generator (500 W), a photovoltaic array (800 W, 31 A) manufactured by the Ekarat Solar Company and a SC module (100 F, 32 V), illustrate the excellent energy- management scheme during load cycles. I. INTRODUCTION Renewable energy sources are expected to become competitive with conventional energy sources in the near future. Nevertheless, they are not very reliable. For example, the PV source is not available during the night or during cloudy conditions, and wind power variation due to haphazardly varying wind speed is still a severe problem for distributed network. Other sources such as fuel cells (FCs) may be more reliable but have economic issues associated with them. Because of this, two or more renewable energy sources are required to ensure a reliable and cost-effective power solution. Such a combination of different types of energy sources into a system is called a hybrid power system. A combination of PV and WD sources forms a good pair with promising features for distributed generation applications. Moreover, an electric energy storage system is also needed to compensate the gap between the output from the PV source, the WD source, and the load. At the moment, the supercapacitor (or “ultracapacitor”) device has received wide consideration as an auxiliary power source. SCs are attractive as they have a higher power density (kW/kg) than batteries. They do not require special charging circuitry, and have a long operational lifetime which is usually considered to be unrelated to the number of charge/discharge cycles [1]. For the power electronic control structure, there are still some aspects of control methods to be studied, particularly in the area of dynamics, robustness, stability, and efficiency. Some nonlinear control approaches for the power electronics applications have been widely studied [2]-[3], in which differential flatness theory (nonlinear approach) allowed an alternate representation of the system, where trajectory planning and nonlinear controller design is clear-cut. These ideas have been used lately in a variety of nonlinear systems across various engineering disciplines including: reactive power and dc voltage tracking control of a three-phase voltage source converter [2] and current control for three phase three- wire boost converters [3]. In this paper, we present an innovative control approach called differential flatness to manage energy in the proposed system. This paper is focused on a special control strategy and control law. This method enables the management of transient power demand and power peaks, particularly in future smart DC distributed system, in light of PV, WD and SC constraints. It will provide a new contribution to the field of the cogeneration system. The general structure of the studied system, the new control algorithm of the hybrid source, realization of the experimental bench, and experimental validation are presented in the following sections. This work was partially supported by the annual Thai government statement of expenditure year 2011, by Thai-French Innovation Institute (TFII), and by Faculty of Technical Education, King Mongkut’s University of Technology North Bangkok. 978-1-4673-1792-4/13/$31.00 ©2013 IEEE 1213 Authorized licensed use limited to: King Mongkut's University of Technology North Bangkok. Downloaded on December 07,2020 at 09:28:45 UTC from IEEE Xplore. Restrictions apply.