DC-link stress analysis for the grid connection of point absorber type wave energy converters

Highly random nature of input power from wave energy converters (WEC), especially from direct-driven point absorbers, demands customized power electronic converters for grid connection. In this paper, analysis and comparison of the DC-link stresses in the converter systems for two cases - a single and three collective units, of wave energy converters is given. The AC/DC/AC converter system includes a conventional uncontrolled three phase rectifier, a DC/DC converter to boost the DC-link voltage and an inverter with RL load. The system has been studied under two different controller actions for the DC/DC converter: with constant boost factor and with constant DC-link voltage. A Proportional Integral controller has been used to regulate the voltage in the latter case. Matlab/Simulink based system simulation has been done to compare the DC-link stress. The analysis shows the comparison in DC-link stresses and the requirements of the system for different cases, proving the advantages and the importance of having customized active power conversion methods for minimizing the DC-link stresses.