Research On The Influence Of Multi-pump Switching On The Operating Characteristics Of Digital Hydraulic Wind Turbines

Hydraulic drive eliminates the power conversion device,has the advantages o f stepless speed regulation,high reliabilit y,simple structure and high power densit y,and gradually beco mes the hot spot of wind power generation technology research.The tradit ional hydraulic wind turbine uses a single quantitative hydraulic pump to drive a single variable hydraulic motor.When the wind turbine operates at low and mediu m wind speeds,the working condit ion of the hydraulic pump and hydraulic motor deviates from the rated working condition,which leads to low efficiency of the who le unit.At the same time,as wind turbines show a trend toward larger size,the single large displacement hydraulic pump current ly available in the market for hydraulic wind power generation cannot meet the power requirements of megawatt-class wind power generation.Therefore,this thesis co mbines the development trend of digital hydraulic techno logy at home and abroad,proposes a digital hydraulic wind turbine system,designs the maximum power tracking control and mult i-pump switching contro l method,studies the influence law of mult i-pump switching on the system characterist ics of digital hydraulic wind turbine u nder different working conditions,and proposes a mult i-pump staggered switching control strategy to reduce the hydraulic shock caused by mult i-pump switching.The research results provide a theoret ical basis and technical reference for the stable operatio n and efficient utilization of wind energy in digital hydraulic wind turbines.The main research w ork of the paper is as follows:First ly,this paper designs a 5MW digital hydraulic wind turbine scheme and establishes the mathemat ical model of the main co mponents of the digital hydraulic wind turbine based on the analysis of its working principle;in order to ensure the normal operation of the digital hydraulic wind turbine and improve the wind energy absorption efficiency o f the digital hydraulic wind turb ine,the maximum power tracking control method based on the opt imal blade tip speed ratio is proposed;the hydraulic pump displacement co mbinat ion coding method of the digital hydraulic wind turbine is determined,and the multi-pump switching control rules under different wind speeds are formulated.Secondly,according to the working principle of digital hydraulic wind turbine and the maximum power tracking contro l method,the system working characterist ics test scheme of 5MW digital hydraulic wind turbine is designed,and AMESim simulation model of digital hydraulic wind turbine is established to study the influence law o f three working conditions on the working characterist ics of digital hydraulic wind turbine,such as wind speed change,mult i-pump switching at constant wind speed and different switching methods of mult i-pump.At the same time,according to the pheno menon of large flow shock when switching hydraulic pumps,a multi-pump staggered switching contro l strategy is proposed to determine the optima l switching time of the switching valve to reduce the flow shock when switching multiple pumps in the digital hydraulic wind turbine,and the simulat ion results show that the flow shock of the system is reduced by 50% after using the mult i-pump staggered switching contro l strategy.Finally,a digital hydraulic wind turbine semi-physical simulat ion test bench was built to experimentally study the operating characteristics of the digital hydraulic wind turbine under three operat ing condit ions: wind speed variation,mult i-pump switching at constant wind speed,and mult i-pump staggered switching contro l,respectively,and the experimental results were consistent with the trend o f the simulation results,which verified the accuracy o f the simulat ion model and the feasibilit y o f the mult i-pump staggered switching contro l strategy.