WEETICS: Wave Energy Enhancement Through Innovative Control System

Overview

Despite the significant achievements in the last decades, wave energy devices are at an earlier stage of development than other offshore renewable energy technologies.

Unfortunately, an issue normally relegated to the last phases of development is the design of global control architectures and supervisory systems. This is a common mistake that can cause serious consequences when the Wave Energy Converter (WEC) is deployed, such as instability, poor efficiency and low availability. Hence, integrating the development of the control system in early development phases is a key element of project success as it can bring coherence between all WEC components and take care for its safe operation.

The main aim of WEETICS‐Stage 1 is to assess the feasibility of a novel control system methodology, and its applicability to different WECs and Power Take‐Off (PTO) typologies. The proposed control system considers the device as a whole system and is structured in three layers, each one with a clearly defined goal. This solution is inspired by the last developments and experience gained after WEC sea trials, and foresees technology transfer from other mature sectors such as the wind industry, robotics and aeronautics.

The control system consists of a 3-layer global solution, each one having its clearly defined goal. The 1st layer is the main program implemented in the WEC Programmable Logic Controller (PLC) in charge of ensuring the safe device operation. It includes several control levels and centralises all necessary monitored data from all the sub-systems. The 2nd layer is implemented in the PLC and enabled by the 1st layer. It is the real time core controller where the control strategy is applied to optimise power production and the overall WEC performance. It includes 3 control strategies: a basic sea-state control, a non-linear MPC and fault tolerant control. The 3rd layer is an external one which processes the database fed by layer 1 through data fusion between various data sources (real data streams from the WEC and its environment and fast access to historical data in the database) and uses machine learning to advise the 2nd layer in charge of maximising the power production and the 1st layer to tackle availability issues.

The control methodology as developed here is generic and applicable to any WEC type. It is meant to set a new approach in terms of WEC control design, encapsulating WEC technology specificities in layer 2 and placing it in a broader framework.

Tecnalia also presented a poster on their Stage 1 Control Systems project at the 2017 WES Annual Conference.