Self-synchronous control of doubly-fed linear generators for ocean wave energy applications

A versatile doubly-fed linear generator was recently presented for application in the point absorber ocean wave energy converter (WEC). Although the machine may be operated as a classical synchronous machine, or as a singly- or doubly-fed induction machine, a self-synchronous approach to operating the machine is found to be attractive in low speed, high force applications. This is particularly beneficial for WECs since operating conditions alternate between positive and negative velocity at low speeds with high force. This characteristic lends itself to the proposed unique control approach. This paper develops the analytical concepts behind this controller as well as detailed simulation results.