Current source inverter for a 400 kW ocean waves induction generator

Abstract

Electrical energy generated from the ocean waves is a renewable energy being developed. One formof retrieving this energy is using the Oscillating Water Column (OWC) principle.In order to optimise this energetic resource, the electric generator must work at variable speeddepending on the input power. For the energy to be delivered to mains, the voltage magnitude andfrequency must be constant.This paper describes a system that uses a generator based on a wound induction machine with slipenergy recovery, which allows operation with variable speed and direct connection to the mains.The Slip Energy Recovery System (SERS) is based on a wound induction machine being controlledthrough the amount of rotor energy delivered to the mains by means of a static converter.The AC variable rotor voltage is converted to DC voltage with a rectifier groupment and thenconverted again to AC in order to be injected into mains.The use of an IGBT Current Source Inverter (CSI) as DC-AC converter minimises current harmonicsand allows smooth interaction between the random and variable input power and the mains.The main advantage of this system is the ability to generate 400 kW using a 200 kW machine and a200 kW CSI.The prototype appears as an important development due to work with a large renewable energysource at a significant power level. The good performance carried out by the equipment based on aninduction generator is reached through a well-controlled IGBT based current inverter that is presentedwithin this paper.