Predictive control for hydrogen production by electrolysis in an offshore platform using renewable energies

Abstract

Predictive control Wave energyWind energy a b s t r a c t An Energy Management System (EMS), based on Model Predictive Control (MPC) ideas, isproposed here to balance the consumption of power by a set of electrolysis units in an offshore platform. In order to produce renewable hydrogen, the power is locally generated by wind turbines and wave energy converters and fully used by the electrolyzers. The energy generated at the platform by wind and wave is balanced by regulating the operating point of each electrolysis unit and its connections or disconnections, using an MPC based on a Mixed-Integer-Quadratic-Programming algorithm. This Predictive Control algorithm makes it possible to take into account predictions of available power and power consumption, to improve the balance and reduce the number of connections and disconnections of the devices. Two case studies are carried out on different installations composed of wave and wind energies feeding a set of alkaline electrolyzers. Validation using measured data at the target location of the platforms shows the adequate operation of the proposed EMS.

Evaluation of a Long Term System coupled with a Short Term System of a hydrogen-based microgrid

“…This equation considers, in prediction and control horizons of N and N u samples respectively, the error between the predictions of H 2 produced (Ĥ i ) and the desired values (H ̅ i ), while also penalizing the number of connections and disconnections. Besides, Q Hi and Q δi are the weighting factors for the error and the control action, respectively [15].…”

“…Two objectives must be fulfilled to maximize H 2 production considering the limitation of the available power and operational constraints [15]:  To maximize H 2 production, the difference between the values of the prediction (Ĥ i ) and its desired values (H ̅ i ) is minimized for all the electrolyzers along the prediction horizon (N).…”

“…This high-level control provides continuous (α i ) and discrete (δ i ) values of the electrolyzers [15]. These values are then used as inputs in the low-level control system which is explained in the section below.…”

“…More specifically, MPC has been used [13] to solve the problem of connections/disconnections of the electrolyzers and its integration with storage devices such as batteries or ultracapacitors. The term MPC does not designate a specific control strategy, but a very ample range of control methods which make an explicit use of a model of the process to obtain the control signal by minimizing an objective function [14,15]. MPC Controller has been applied with satisfactory results in the hybridization of this type of microgrids in several papers, such as that carried out by Vahidi and Greenwell et al [16].…”

“…The start-up sequences of the electrolyzers are also considered and controlled with the use of logical variables. Combination of the high-level control and the low-level control published in [3] and [15] respectively is the main contribution of the article. The paper is organized as follows: Section II describes the microgrid with an explanation of the components, models and variables.…”