Optimal Energy Management in a Standalone Microgrid, with Photovoltaic Generation, Short-Term Storage, and Hydrogen Production

Abstract

This paper addresses the energy management of a standalone renewable energy system. The system is configured as a microgrid, including photovoltaic generation, a lead-acid battery as a short term energy storage system, hydrogen production, and several loads. In this microgrid, an energy management strategy has been incorporated that pursues several objectives. On the one hand, it aims to minimize the amount of energy cycled in the battery, in order to reduce the associated losses and battery size. On the other hand, it seeks to take advantage of the long-term surplus energy, producing hydrogen and extracting it from the system, to be used in a fuel cell hybrid electric vehicle. A crucial factor in this approach is to accommodate the energy consumption to the energy demand and to achieve this, a model predictive control (MPC) scheme is proposed. In this context, proper models for solar estimation, hydrogen production, and battery energy storage will be presented. Moreover, the controller is capable of advancing or delaying the deferrable loads from its prescheduled time. As a result, a stable and efficient supply with a relatively small battery is obtained. Finally, the proposed control scheme has been validated on a real case scenario.

Redox Flow Batteries: A Literature Review Oriented to Automatic Control

“…One of the main advantages of its use is that is a clean ESS, being water vapor the residue that comes out. In terms of efficiency, typical values oscillate between 40% and 60% [34,35]. Most losses are in the form of heat, so in the case of an application in which it is necessary to capture waste heat in a cogeneration system, efficiencies can reach 85% [36].…”

Voltage H∞ Control of a Vanadium Redox Flow Battery

“…To compute the equilibrium points for the dynamic system defined by (5) and (6), it is necessary to forceẋ cell = 0 andẋ tank = 0 and isolate the value of x cell and x tank . Because (5) and (6) depend on i cell and q cell , there is no solution, but i cell = 0, q cell = 0, x cell = 0, and x tank = 0, which is clearly not of interest.…”

“…This results in the impossibility to satisfy the constant demand of energy. For that reason, trying to solve this problem, the use of energy storage systems (ESS) is having a great impact within the energy field [2][3][4][5][6]. There are different types of ESS according to the methodology used to convert and store the energy, which are mechanical, electrical, or electrochemical systems.…”

A Model Predictive Control-Based Energy Management Scheme for Hybrid Storage System in Islanded Microgrids

“…Analytical methods can be implemented either offline [18]- [20] or online using techniques like model predictive control (MPC) [21]- [27]. The offline methods are usually employed when the system under consideration is large, distributed [18] or when complex non-linear optimisation problems have to be solved [19], [20].…”

“…In [24], MPC was applied to an isolated power grid with battery storage for reducing operating costs of the grid. Finally, the work in [27] uses MPC to improve demand response capabilities in a microgrid to improve the PV power utilisation. Recent works pertaining to application of MPC in electric systems, have focussed on implementing them in large scale networks, using online distributed optimisation techniques to reduce operational costs [28], [29].…”