Day-ahead Optimal Scheduling of Loads and Dispatchable Resources in a Hybrid AC/DC Microgrid of an Industrial System

Abstract

Industrial systems are usually characterized by high energy consumption and presence of sensitive loads which require high levels of Power Quality. Based on the grid architecture of an actual Italian industrial facility, this paper proposes the installation of a hybrid AC/DC microgrid. The hybrid microgrid includes dispatchable and non-dispatchable renewable generation units, battery storage systems and controllable loads. An optimization model is formulated to solve the problem of the day-ahead optimal scheduling of the microgrid. The model aims to optimize the operation of dispatchable resources, controllable loads and storage systems minimizing the daily costs of the energy imported from the AC grid and the costs required by the dispatchable generators while satisfying operational constraints such as those related to the production process of the industry facility. Different case studies are investigated in order to show the feasibility and effectiveness of the proposed procedure.

A cost minimization strategy for the control of hybrid AC-DC microgrids in industrial systems

“…In this application it is assumed that the real time control procedure follows the scheduling procedure proposed in [9]. The scheduling procedure is performed off-line, a day ahead, and it is finalized to schedule the controllable loads and the daily periods in which the battery can charge or discharge.…”

“…The scheduling problem presented in [9], analogously to the real time control proposed in this paper, is formulated as a non-linear optimization problem aimed at minimizing the cost of the electrical energy. Focusing on the real time operation (very short time predictive control), a centralized control system (CCS) performs a proper algorithm and sends, in real time, the set-points of the powers to the controllers of the BESSs, micro-turbines and AC/DC interfacing converter.…”

“…To meet this dual requirement, hybrid AC-DC Gs have been proposed in the recent literature [4][5][6][7][8][9]. In particular, these papers focused on the energy management, control and operation, since hybrid AC-DC Gs result more complex than the individual AC or DC Gs.…”

“…In [7], based on the modified droop method, a strategy of the control of the interconnection between AC and DC Gs is proposed for an optimal sharing of the load demand among the different AC and DC sources in islanding mode. Eventually, in [8] and [9], the optimal day ahead scheduling of a hybrid AC-DC G was proposed with the aim of minimizing the daily energy cost. In this paper, a hybrid AC-DC G obtained by modifying an actual industrial power system, which is characterized by the presence of AC loads, DC loads, dispatchable and no dispatchable energy sources, is considered.…”

“…A control strategy for the very short time predictive control is proposed to obtain an optimal management and operation of the hybrid G. In particular, the control strategy refers to the gridconnected mode and it is aimed at minimizing the daily costs of the electrical energy taken by the grid and the cost required by the operation of dispatchable generators (e.g., in case of micro-turbine, the fuel cost). Unlike [8] and [9], where the cost minimization of the electrical energy is performed by a day ahead scheduling of the controllable resources, the proposed strategy refers to the real time management of the controllable resources and the interfacing converter. The proposed strategy is able to ensure a cheap and correct operation of the hybrid G. Among different electrical energy tariffs, this paper focuses on the real time pricing (RTP) scheme, which is adopted in order to increase the presence of responsive loads connected to distribution grids [10].…”