Simulation of a power electronic conversion system with short-term energy storage for actively controlled wave energy converters

A simulation study is conducted to assess the feasibility of a Wave Energy Converter Power Electronic Converter architecture to achieve a four quadrant torque demand resulting from an active control strategy. The system consists of four induction generators controlled by three phase inverters, a DC bus with short term energy storage provided by supercapacitors and batteries, and an active rectifier to control the DC bus voltage and provide AC power to the grid. The components are realistically modelled and it is shown that the torque and speed requirements of the active control strategy can be achieved and that the electrical energy storage can provide required reactive power on a wave-by-wave time scale and longer term energy supply during a lull in wave excitation. The WaveSub WEC is used as a target device in order to make a meaningful study with realistic inputs. However the architecture of the PEC system is applicable to any device with a bi-directional rotary PTO requiring four-quadrant active control at the generators. Furthermore the PEC architecture and simulation model are readily expandable to arrays of wave energy converters.