Abstract: A wind turbine power production system with a closed loop hydrostatic transmission system for the transfer of mechanical energy from a wind turbine rotor to an electric generator. The hydrostatic transmission system comprises a closed loop with a pump and a motor connected by tubes or pipes. The assembly of the wind turbine rotor and the pump is arranged for rotating about a vertical axis above a swivel arranged for transferring fluid to and from the motor, fluid reservoir and other components arranged below the swivel.

Abstract: A turbine (2) driven electric power production system (1),—said turbine (2) arranged for being driven by a fluid (3) having a fluid speed (v) varying in time,—said turbine (2) connected to a hydrostatic displacement pump (6) further connected to a hydrostatic displacement motor (8) as part of a closed loop hydrostatic transmission system (7),—said motor (8) arranged for driving an electrical generator (9) supplying AC power (10) at a frequency (fg) near a given desired frequency (fdes), characterized by a closed loop system arranged for controlling a volumetric displacement (13) of the hydrostatic motor (8), comprising—a fluid speed meter (11m) arranged for producing a speed signal (11s) representing a speed (v) of said fluid (3), and—a rotational speed meter (12m) arranged for providing a rotational speed signal (12s) representing a rotational speed measurement (?) of said turbine (2), —a motor displacement control system (15) for continuously receiving said speed signal (11s) and said rotational speed signa