Study on speed and torque control of a novel hydromechanical hybrid transmission system in wind turbine

Abstract

A wind turbine is the most typical machine used to capture energy from the wind. The system design goal of a wind turbine is to obtain as much energy as possible from the wind while transmitting as much of that energy to the grid as possible, all under the highest possible level of stability. Currently, many inherent weaknesses result in a high failure rate in common commercial wind turbines with gear drive systems. To improve the performance, in this study, a typical 1.5 MW gear transmission was redesigned into a novel hydromechanical transmission system (HMTS). Parameters related to the HMTS efficiency were analysed to ensure that the efficiency was relatively high. The variable speed ratio (VSR) and torque triple absorption (TTA) principle were thoroughly deduced. Moreover, a MATLAB/Simulink- AMESim cosimulation model was proposed, and a 30 kW proportional prototype was established. Both simulation and experimental results show that the structural design and proposed control strategies meet the design goals, including a relatively high transmission efficiency around the rated wind speed, speed control below the rated wind speed, and torque control above the rated wind speed. These achievements should guarantee the future application of the novel transmission system in wind turbines.