Abstract

The growing wave energy sector requires an efficient and flexible testing process for the development phase of wave energy systems. Real-time hybrid testing is a promising technique for the accelerated testing of wave energy conversion systems. This article presents an experimental study on developing a hybrid testing platform for wave energy systems at the Wallace Energy System and Renewables Facility (WESRF) at Oregon State University. The wave energy conversion system is broken down into numeric (i.e., virtual) and physical (i.e., hardware) components. The numeric component involves software components such as the control algorithm for Wave Energy Converter (WEC) and controller for the power electronic converters and numerical models for the WEC device hydrodynamics. The hardware involves an ocean wave emulator testbed, Power Take-Off (PTO) mechanism, power electronics, and instrumentation. The numeric components are implemented in a real-time target machine and are interfaced with the experimental system. A case study implementation of Nonlinear Model Predictive Control (NMPC) is presented for a single degree of freedom heaving nonlinear WEC model with a Permanent Magnet Synchronous Generator (PMSG) as a PTO system. A Field-Oriented Control (FOC) algorithm controls the PMSG-PTO generation using a three-phase Integrated Intelligent Power (IIP) module converter. A demonstration of the proposed hybrid testing setup is provided.

Highlights

  • The growing wave energy sector requires an efficient and flexible testing process for the development phase of wave energy systems

  • A step time of 0.1 sec is used for Nonlinear Model Predictive Control (NMPC) formulation, close to one-tenth of the peak wave period, while a faster sampling time of 0.001 sec is selected for the Power TakeOff (PTO) current control loop

  • NMPC optimization algorithm, considering the Wave Energy Converter (WEC) dynamics and PTO characteristics in (21), generates a PTO force that maximizes the power captured by the WEC

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Summary

INTRODUCTION1 optimization method that maximizes a cost index while

RENEWABLE energy technologies present a sustainable, low-carbon solution to growing global energy demands. Realtime hybrid testing is a promising technique for accelerated testing of WEC and PTO systems at their development phase It involves breaking down the system into numerical and physical components and running the integrated hardware-software set up in real-time to access and evaluate the overall system performance [22]. PTO generator winding resistance implementation compared to ideal PTO models in most of the literature above This experimental study involves breaking down a casestudy point absorber type WEC testing into numerical (i.e., virtual) models and physical (i.e., hardware) systems and running them in real-time to evaluate control techniques under numerous sea states. The hybrid testing experiments are performed, and results of the successful performance of the hybrid platform are presented

TIME DOMAIN MODEL OF A WAVE ENERGY CONVERTER
Heave Dynamics of WEC
Nonquadratic WEC-PTO Model
IMPLEMENTATION OF NMPC FOR WEC
Prediction Model for NMPC
PMSG Control Strategy
HYBRID TESTING SCHEME
EXPERIMENTAL RESULTS AND DISCUSSION
CONCLUSION

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