Optimal Power Management Strategy for Energy Storage with Stochastic Loads

Abstract

Abstract:In this paper, a power management strategy (PMS) has been developed for the control of energy storage in a system subjected to loads of random duration. The PMS minimises the costs associated with the energy consumption of specific systems powered by a primary energy source and equipped with energy storage, under the assumption that the statistical distribution of load durations is known. By including the variability of the load in the cost function, it was possible to define the optimality criteria for the power flow of the storage. Numerical calculations have been performed obtaining the control strategies associated with the global minimum in energy costs, for a wide range of initial conditions of the system. The results of the calculations have been tested on a MATLAB/Simulink model of a rubber tyre gantry (RTG) crane equipped with a flywheel energy storage system (FESS) and subjected to a test cycle, which corresponds to the real operation of a crane in the Port of Felixstowe. The results of the model show increased energy savings and reduced peak power demand with respect to existing control strategies, indicating considerable potential savings for port operators in terms of energy and maintenance costs.

Optimal Energy Management and MPC Strategies for Electrified RTG Cranes with Energy Storage Systems

“…An Energy Storage System (ESS) is a significant tool for a more energy efficient ecosystem and help to decrease environmental concerns [1,2]. In general, the objective of an ESS is to reduce the cost of electricity and avoid the need to upgrade the distribution network by shifting energy consumption from peak to valley periods [2].…”

“…ESS's are expected to be more frequently applied to a wide range of demand side applications. Recently, sea ports are moving towards replacing diesel RTG cranes [3,4], which move containers on a port platform and organise container storage in the yard area, with electric RTG cranes to reduce green gas emissions and improve energy efficiency [1][2][3]. In RTG crane system, most of electricity energy or fuel consumption comes from hoisting containers with different weights to several heights.…”

“…In order to increase the energy savings in electrified or diesel RTG crane systems, ESSs have been used for peak shaving during the lifting period by using recovered potential energy that has accrued during the lowering period and avoid dissipating energy through the dump resistors as heat [1,[6][7][8][9][10][11]. In the literature, ESS control algorithms on an RTG crane system, which can be either a diesel or electrified crane, mainly focus on using conventional control strategies that use a reference value (set-point control) of power [1,9], SoC [7] or voltage [3,11] to store recovered potential energy and regenerate it during the lifting phase which helps to increase energy savings and reduce gas emissions. Table 1 summarises the peak reduction algorithms used in an RTG crane model produced by different authors along with their achievements and limitations.…”

“…Pietrosanti et al [1] present an optimal management strategy for RTG cranes with flywheel energy storage located at the DC side of the crane. The control strategy aims to find the optimal operation conditions for ESSs by charging the storage during the lowering mode and discharging it during the lifting mode, under uncertainties of the duration of RTG crane stochastic power loads [1].…”

“…The control strategy aims to find the optimal operation conditions for ESSs by charging the storage during the lowering mode and discharging it during the lifting mode, under uncertainties of the duration of RTG crane stochastic power loads [1]. Baalbergen et al [12] developed diesel RTG crane systems equipped with battery storage.…”