Filter Design for Cable Overvoltage and Power Loss Minimization in a Tidal Energy System With Onshore Converters

Abstract

By moving the back-to-back ac-dc-ac converters in a tidal current conversion system (TCCS) onshore, maintenance requirements and cost are reduced significantly. This is because underwater components are not easily accessible and operate in a harsh environment. In addition to increased maintainability, the concept of long-distance controls offers maximum power capture from the tidal currents in the same way that a converter in the nacelle would offer. However, a number of challenges are associated with the concept of controlling electrical machines through long cables, which include electromagnetic traveling waves in the cables and system resonance. These phenomena can induce overvoltages at the generator terminals which can lead to system failure and high harmonics that can induce extra power losses. The major contribution of this paper is a new method of filter design for systems with long-distance controls and for minimization of system power loss. The proposed method is validated by developing a full resource-to-grid TCCS in MATLAB/Simulink. Simulation results show that using the proposed method, overvoltage mitigation can be achieved in the same way as literature-based filters, but at the same time, minimize the total system losses. The results from the analysis can be used to optimize tidal energy conversion systems with a similar electrical configuration.