Scholarly record

PARTICULARITIES OF HYDRAULIC DRIVE SYSTEMS FOR LIFTING AND LOWERING OF MEDIUM-POWER WIND TURBINES

Teodor Popescu

Abstract

All wind turbines have their main components (the rotor, mechanical transmission, generator) housed in a nacelle, supported by a pillar (large-sized) or a prop (small or medium-sized). Such a prop can be a guyed, a free standing, or a hydraulic one. While the former types of props require a lifting device for turbine installation and maintenance, the third type is provided with its own hydraulic system, which performs these operations. The hydraulic prop, which may have a height of 12...30 m and support wind turbines of 3...50 kW, includes two segments: one at the base, short, embedded in a reinforced concrete foundation, and the other, mobile (the prop itself), which is fastened to the first one through a "hinge" and can be lifted or lowered. The purpose of this research is to establish the schematic diagram of the hydraulic drive system, able to ensure: complete safety of load (prop and nacelle) movement; load holding at any desired position or if the hoses are broken; control of the load lifting and lowering speed, regardless of the positioning of its center of gravity towards the hinge geometric center. The following techniques have been used for this goal: an analysis of hydraulic lifting equipment, which swings the load around a joint; developing a schematic diagram of the hydraulic drive system, including a dual overcenter valve for a wind turbine prop; customization of the diagram to a specific case, by practically implementing a hydraulic drive system, with standardized components; demonstration of system functionality by using it to lift and lower a medium-power wind turbine. Tests under real operating conditions have validated experimentally the schematic diagram of the hydraulic drive system, namely: safe load movement; speed control of the load movement for both directions; safe load holding at any desired height, between the hinge elevation relative to the ground and the maximum prop elevation. Experimental validation of the hydraulic drive system developed should produce a change in the use of wind turbine props, in the direction of a large use of hydraulic props and less use of guyed or free standing props.

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