JREE: Vol. 7, No. 2, (Spring 2020) 52-63 Research Article Journal of Renewable Energy and Environment Journal Homepage: www.jree.ir A Novel Local Control Technique for Converter-Based Renewable Energy Resources in the Stand-Alone DC Micro-Grids Arash Abedi, Behrooz Rezaie * , Alireza Khosravi, Majid Shahabi Department of Control, Faculty of Electrical and Computer Engineering, Babol Noshirvani University of Technology, Babol, Iran. PAPER INFO Paper history: Received 12 February 2020 Accepted in revised form 12 May 2020 Keywords: DC/DC Converter Stability Analysis Stand-Alone DC Micro-Grid Switching Function ABSTRACT This paper presents a novel local control method for the converter-based renewable energy resources in a stand-alone DC micro-grid based on energy analysis. The studied DC micro-grid comprises the renewable energy resources, back-up generation unit, and battery-based energy storage system, which are connected to the common DC-bus through the buck and bidirectional buck-boost converters. The proposed control method satisfies the stability of the micro-grid output variables, along with current control and voltage regulation by controlling the switching functions of the converters, regardless of the energy resource dynamics. The dynamic component of the switching function is extracted as a control signal using the state-feedback through a mathematical method. The control inputs are designed based on Lyapunov stability theorem to guarantee the stability of output variables (DC-bus voltage and generated currents) in a stand-alone DC micro-grid through an energy analysis. The proposed distributed controller can be easily generalized as a platform with all kinds of the stand-alone DC micro-grids comprising any type or number of distributed generations such as renewable energy resources, fossil-fuel-based generations, and energy storage units. Other features of this local control method are simplicity, celerity, comprehensiveness, and independence of the distributed generations. The dynamic performance assessment of the proposed controller is verified through a simulation in MATLAB/SIMULINK  environment. The results validate the accuracy and stability of the proposed control strategy in various operating conditions. 1. INTRODUCTION 1 Recently the global efforts to reduce the use of fossil fuels, growing energy demand, increased number of renewable energy resources (RERs) [1] and more important advancements in power electronics have led to the modernization of the existing power system [2]. Introduction of AC and DC micro-grids including distributed generations (DGs) such as RERs, energy storage systems (ESS), gas- micro-turbine generators, etc. made it possible for engineers to reshape the conventional power system [3]. The micro-grids are emerging in the modern power system and becoming an attractive choice due to the integration of DGs such as photovoltaics, wind-turbines, storage devices, and controllable loads, which can operate in either isolated or grid-connected mode. However, the issue of reliability and stability has not been accomplished yet within these small- scale distribution grids [4]. In a grid-connected AC micro- grid, the main grid standards for frequency and voltage are utilized, and energy stability is important for power quality [5]. However, in the stand-alone operation mode, the frequency and the voltage must be stabilized and regulated via a control system [6-8]. In a stand-alone micro-grid supplying a residential area, most of the consumptions are DC loads, such as electronic, telecommunication and audio-visual devices. Moreover, the other loads can be supplied either by AC or DC such as air- conditioning or lighting devices [9]. In fact, distributing energy in DC form is in favor of distribution suppliers due to *Corresponding Author’s Email: brezaie@nit.ac.ir (B. Rezaie) the reduced number of converters, limited frequency control challenges, higher efficiency, and minimized costs. Thus, DC micro-grids is a proper choice for providing remote residential areas. Still, in such networks, the voltage regulation, voltage stabilization, and energy management are vital to improve the power quality and provide a reliable and efficient power [10, 11]. Therefore, proposing comprehensive methods for controlling and stability of the stand-alone DC micro-grids is of great importance. Some studies in the literature have been devoted to the DC voltage control strategies and energy management control systems. In [12], the authors employed a three-level control strategy to stabilize the DC-bus voltage in various operation conditions (i.e. load change, generation fluctuations) in a DC micro-grid with variable sources and loads. In this study, a control program based on PI and droop controllers has been presented. However, the stability has not been guaranteed. Augustine et al. [13] developed an adaptive droop control technique to manage the current sharing and voltage regulation in a low voltage DC micro-grid. There are three points to note about this reference. First, in this study, the researchers have not addressed the issues of micro-grid stability. Besides, only two DGs with the same type of converter have been studied. Finally, the authors have neglected the role of energy storage units which is vital in the stand-alone micro-grids with RERs, because the challenges of bidirectional power flow are crucial in energy analysis and stability studies. Dizqah et al. [14] proposed a control strategy based on model predictive control (MPC) to manage the voltage stability and energy flow between wind, solar and battery devices, as well as battery management in a DC micro- grid. Anand et al. [15] presented a decentralized droop