Comparative Analysis of Two Wind Turbines with Planetary Speed Increaser in Steady-State

Abstract

Planetary transmissions used as speed amplifiers in wind/hydro conversion systems typically rely on the conventional concept of mechanism with one input and one output. This concept is found in the most of the high power wind turbines; however, the need to implement in the built environment smaller wind turbines with speed amplifiers led to new turbine concepts such as counter-rotating rotors and classical generator. The paper presents a comparative analysis of two wind turbines with one rotor and respectively two counter-rotating rotors, which contain identical electrical generators and the same type of mechanical amplifier used as a 1 DOF mechanism and differential one respectively. With the assumption of maintaining the same electrical generator running point for both wind turbines, the steady-state behaviour of the considered turbines is identified and a comparative kinematic and static performance analysis is performed, aiming at highlighting the impact on efficiency and on constructive design and development of the two turbines.

Conceptual Synthesis of Speed Increasers for Wind Turbine Conversion Systems

“…The analysis of the eight representative conversion systems is performed using the schemes from The relationship between the multiplication ratio (i a ), the speed increaser efficiency (η) and the generator input power (P g ) for both cases of electric generator (fixed/mobile stator) are also presented in Figures 7-10 [23][24][25][26][27][28][29][30] for each representative solving variant, where T is the shaft torque, i 0 -interior static ratio, i a_R−GR/GS -multiplication ratio considering the GR/GS as output, i 0I / II -interior kinematic ratio of the planetary gearbox I/II, η 0I / II -interior efficiency of the planetary gearbox I/II, k t = T R2 /T R1 -ratio of the input torques, z i -teeth number of the gear i.…”

“…The advantages of each transmission are further highlighted, in order to facilitate the selection of the optimal solution under additional criteria (with respect to those already specified) that are specific to the application and the WT implementation site. The solution in Figure 8 can function in four cases depending on the value of the ratio between the R2 torque and the torque on the generator stator [28]; the case with the highest efficiency is further analyzed: the torque generated by the second rotor is bigger than the torque required for the mobile stator functioning (i.e., a part of the torque T R2 is distributed to the generator stator and the other part, along with the torque T R1 , is directed to the generator rotor through the gearbox); the solution illustrated in Figure 9 is similarly analyzed for the case when R1 speed (considered the main rotor) is bigger than or equal to that of R2.…”

“…In regard to the gearbox for WT conversion systems, several types of speed increasers are presented in the literature: spur or bevel gear trains [6,20,21], planetary gear train or combined solutions [16,[22][23][24][25][26][27][28][29][30][31][32][33], variable-ratio gearboxes [34] and a hybrid transmission including a planetary gear train and a control system, designed for a variable-speed WT [35]. The dynamic behavior of a combined planetary and spur gear type speed increaser under different internal and external excitations, based on a four degrees of freedom (DOF) dynamic model, is presented in [36].…”

“…(a) R is connected to a one DOF speed increaser, A, with two outputs: one for the GR, and the other for the GS (Figure 5c) [25,52]. (b) R1 and R2 are connected through a one DOF or two DOF speed increaser, A, with two outputs to the GR and GS ( Figure 5d) [24,[26][27][28]53,54]. (c) R1 is connected to the GR through a speed increaser, A1, and R2 is connected to the GS through another speed increaser, A2 ( Figure 5e) [33].…”

A Comparative Performance Analysis of Counter-Rotating Dual-Rotor Wind Turbines with Speed-Adding Increasers

“…The planetary speed increaser type is mainly used in high-power conventional wind systems and in counter-rotating turbines, due to their advantages: high amplification ratios, reduced radial sizes and better efficiency [1,3,16,17,[23][24][25][26][27][28][29][30][31][32]. With dual-rotor systems, the speed increaser, operating as a 2-DOF transmission, sums up the rotors' input speeds [26,30], while operating as a 1-DOF planetary transmission, it sums up the rotors' input torques [31][32][33].…”