Abstract
Wave energy emulators provide an option to extend studies of wave energy converters (WECs) in an electric power laboratory facility and to evaluate the performance of controllers in an experimental set-up. In addition, the integration of control strategies in different steps of the energy conversion process is an important step to improve the WEC overall behaviour that has not yet been widely discussed. This paper proposes a real-time emulator and a hierarchical control scheme for a hyperbaric WEC consisting of floating bodies, hydropneumatic storage system (HSS), hydraulic turbine, and doubly fed induction generator (DFIG). The proposed emulator is based on a typical electric power laboratory facility, where a numerical model reproduces the dynamics of the wet subsystem and a hardware is the WEC electrical subsystem. Thereby, a squirrel-cage induction motor (SCIM) is coupled shaft-to-shaft with the DFIG. The SCIM reproduces the characteristics of torque and speed that would be observed in the real system, and then, the DFIG is subjected to a primary drive with same dynamic characteristics of the real plant. The hierarchical control integrates the generator and HSS controllers considering the optimal operating pressure for local sea state conditions. Experimental results illustrate the performance of the emulator and controllers.
Highlights
Prior to the deployment of full-scale prototypes, wave energy converters (WECs) are commonly studied by numerical simulations and experimental tests by means of small-scale models at wave basin facilities
The hardware is the electrical subsystem of the WEC and a numerical model reproduces the dynamics of the wet subsystem
Wave energy emulators have been proposed for direct-drive WECs [14, 15], oscillating water column plants [16], a point absorber with electromechanical power take-off (PTO) system [17], and a flaptype WEC [18]
Summary
Prior to the deployment of full-scale prototypes, wave energy converters (WECs) are commonly studied by numerical simulations and experimental tests by means of small-scale models at wave basin facilities. A number of studies have investigated the design and implementation of control systems for WECs, in order to improve the energy absorption or other performance factors [1,2,3,4,5,6,7,8] Such studies are usually carried out with numerical models, but a few control schemes have been tested at wave tank scenarios [9,10,11,12,13]. The development of WEC emulation systems in typical electric power laboratory settings can represent a feasible option for carrying out experimental studies, where electrical subsystems are conveniently assembled. Wave energy emulators have been proposed for direct-drive WECs [14, 15], oscillating water column plants [16], a point absorber with electromechanical power take-off (PTO) system [17], and a flaptype WEC [18]
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