Abstract
A centralized airflow control scheme for a complex ocean energy network (OEN) is proposed in this paper to reduce the output power variation (OPV). The OEN is an integrated network of multiple oscillating water columns (OWCs) that are located at different geographical sites connected to a common electrical grid. The complexity of the OWC-OEN increases manifolds due to the integration of several OWCs and design of controllers become very challenging task. So, the centralized airflow control scheme is designed in two stages. In control stage-1, a proportional-integral- (PI-) type controller is designed to provide a common reference command to control stage-2. In control stage-2, the antiwindup PID controllers are implemented for the airflow control of all the OWCs simultaneously. In order to tune the large number of control parameters of this complex system, a fitness function based on integral squared error (ISE) is minimized using the widely adopted particle swarm optimization (PSO) technique. Next, the simulation results were obtained with random wave profiles created using the Joint North Sea Wave Project (JONSWAP) irregular wave model. The OPV of the proposed OWC-OEN was reduced significantly as compared to the individual OWC. It was further observed that the OPV of the proposed scheme was lower than that achieved with uncontrolled and MPPT controlled OWC-OEN. The effect of communication delay on the OPV of the proposed OWC-OEN scheme was also investigated with the proposed controller, which was found to be robust for a delay up to 100 ms.
Highlights
Many countries around the world with a long coastal zone have been actively exploring ocean waves as an alternate energy source over the past five decades [1,2,3,4,5,6,7,8,9]
Due to high output power variation (OPV), hurdles remain in its grid integration. e OPV is defined as the difference between the maximum and minimum power generated from the oscillating water columns (OWCs) plant
Concluding Remarks and Future Challenges is paper presented a novel concept of OWC-ocean energy network (OEN) and its centralized airflow control to mitigate the OPV issue of ocean energy systems. e centralized airflow controller consisting of two control stages was designed using particle swarm optimization (PSO) due to complexity of tuning parameters. e PSO helped in choosing large number of control parameters of a very complex OWC-OEN by minimizing an integral squared error (ISE)-type fitness function
Summary
Many countries around the world with a long coastal zone have been actively exploring ocean waves as an alternate energy source over the past five decades [1,2,3,4,5,6,7,8,9]. E PID-based control approaches for OWC plants were developed in [23] for airflow and rotor speed control. Many advanced control techniques for OWC airflow as well as turbine rotor speed control techniques have been developed. E flow controller was designed in [35] for Wells turbines for harnessing maximum wave power using OWC. E OPV can be reduced further by suitably designing a centralized airflow controller for regulating the airflow of OWC chambers situated at different geographical sites. Two control schemes would be designed for OWC-OEN: (i) localized MPPT control and (ii) centralized airflow control for reducing OPV. E performance of an arbitrarily selected OWC site has been analyzed for relevant OWC parameters such as rotor speed, control signal, Wells turbine flow coefficient, and DFIG output power of controlled/uncontrolled OWC.
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