Power Flow Modelling in a Planetary Speed Increaser for Wind Turbines with Counter-rotating Electric Generator

Abstract

The paper presents the kinematic and static modelling of a planetary speed increaser with one input and two outputs and a closed power loop, which is required in establishing the power flow transmitted by the increaser from a wind rotor to a counter-rotating electric generator (with mobile rotor and mobile stator), during operation at constant input power. The modelling algorithm starts in the first stage by establishing the block scheme for the connection of the component gears, two bevel gear pairs and a spur planetary gear set, and the kinematic and static correlations specific to the component mechanisms, and the inner and outer links of the speed increaser. The planetary speed increaser transmission functions are set up analytically in stage II of the kinematic modelling, followed by the determination of the relations for the transmission efficiency and torques on each power branch (stage III). In the second part of the paper a relevant numerical case is presented, which highlights the influence of the kinematic ratios of the bevel gear pairs on the amplification ratios and efficiencies, as well as the power flow through the planetary transmission. The results are useful to wind turbine designers and developers in the process of functional and constructive optimization of wind system solutions with a counterrotating electric generator.