Research on an Integrated Hydrostatic-Driven Electric Generator with Controllable Load for Renewable Energy Applications

A hydrostatic transmission is a promising technology in renewable energy harvesting, such as wind energy and wave energy, where the hydrostatic-driven electric generator is a key energy conversion component. By using analytical and experimental methods, this paper investigates the performance of a novel hydrostatic-driven electric generator which integrates the functions of an axial piston hydrostatic motor and a permanent magnet electric generator together. The experimental platform consists of a prototype, an adjustable hydrostatic power source, a controllable electrical load, and various sensors. Energy conversions between hydrostatic and electrical forms are evaluated under different operating velocities and control signals. Power loss distributions are presented by combining measured data and analytical calculation. Thermal experiments are implemented under both of natural and oil-forced cooling conditions and it is found that the temperature rise is much lower when the machine is cooled by hydraulic oil. The experiments validate the energy conversion efficiency, steady controllability, and cooling capability of the integrated hydrostatic-driven electric generator. The results can provide references for further efficiency optimization, dynamic control, as well as practical application.