Specific Features of a Counter-Rotating Transmission for Renewable Energy Systems

Abstract

A specific topical issue both for small hydropower plants and wind turbines refers to the discrepancy between the relatively low speed of the water turbine/wind rotor and relatively high speed of the electric generator: the turbine/rotor has higher performances at lower speeds, while the generator performances are increasing with the speed. Usually, this problem can be solved connecting a proper speed increaser between the turbine (increaser input) and generator (increaser output). Besides, the gearboxes used in the renewable energy systems (R.E.S.) allow generating the necessary electric energy while functioning at lower values of wind speeds or water flows. The paper presents and analyzes cinematically and dynamically a counter-rotating system that contains two coaxial turbines and a generator, connected through a bevel-planetary gear with two inputs (the two turbines) and one output (the generator). The system works relatively different from other drive trains used in the renewable energy systems, while having a much improved efficiency. Firstly, the kinematical and dynamic parameters of the planetary transmission are established in the paper. Then, a case study of a small hydropower plant equipped with a counter-rotating transmission that multiplies 5 times the input speed is analyzed. The numerical simulation results are analyzed in comparison with the classical solutions and recommendations concerning the use of counter-rotating systems are settled up.

Synergetic-PI controller based on genetic algorithm for DPC-PWM strategy of a multi-rotor wind power system

“…In addition to the simplicity and ease of implementation, synergetic control is considered one of the robust methods that give satisfactory results in terms of improving dynamic response and reducing electric current ripples of the electric machine [37]. This strategy can be expressed by equation (12). 266 267 where,T presents convergence speed, where the T> 0.…”

“…Whereas the multi-rotor WE is a development of the single-rotor WE in order to increase the value of torque and mechanical energy required to rotate the generator [11]. In addition, the use of multi-rotor WEs leads to a reduction in the area of wind farms and overcomes the winds generated by turbines in wind farms [12].…”

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

“…• the development of innovative concepts of wind turbines (with horizontal axis and counter-rotating rotors [1][2][3][4], or with multiple and smaller rotors in a spatial arrangement [5]). An example of comprehensive, but not exhaustive overview of research achievements in counter-rotating wind turbine systems development, characterization and use can be found in [4]; • the influence of rotor pitch on the output power of a conventional wind turbine [6] and of a counter-rotating wind turbine [7]; • the effect of the number of blades of counter-rotating wind turbines on the system performance [8]; • the performance of new types of counter-rotating wind turbine with vertical axis [9,10], etc.…”

“…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].…”

Comparative Analysis of a New Planetary Transmission With Deformable Element Usable in RES

“…2) is further presented in order to compare the properties of the two running cases. Taking into account this transmission ratio, the internal kinematical ratio can be determined using Willis's relations [2,9]: …”