Modeling and Analysis of an Offshore Wind Turbine With Fluid Power Transmission for Centralized Electricity Generation

Abstract

This paper presents a mathematical model of an innovative offshore wind turbine with fluid power transmission. The proposed concept is a variable-speed, pitch controlled turbine which differs from conventional technology by using fluid power technology as a medium to transfer the energy from the wind. The final aim is to use several turbines to centralize electricity generation. Unlike conventional variable speed concepts, the proposed turbine comprises a passive-torque control method which allows the turbine to operate at optimal aerodynamic performance for different wind speeds. A numerical model of a single turbine is developed and time-domain simulations are used to analyze the dynamic response of the different operational parameters to a turbulent wind speed input. The results are compared with those of a reference offshore wind turbine with similar characteristics. It is shown that operation below rated wind speed with a passive control is possible for a single turbine with a better dynamic performance than the reference in terms of transmission torque. However, the efficiency of the energy transmission is reduced throughout the operational range. The addition and simulation of more turbines to the hydraulic network is necessary to determine to which extent the benefits of a centralized wind farm compensate for the relatively lower efficiency.

Power Generation Control of a Monopile Hydrostatic Wind Turbine Using an <inline-formula> <tex-math notation="LaTeX">$\mathcal{H}_{\infty}$ </tex-math> </inline-formula> Loop-Shaping Torque Controller and an LPV Pitch Controller

“…1. The simulation results demonstrate that our torque controller achieves very good tracking behaviours and our pitch controller obtains much better overall performances (in regulating the rotor speed & generator power and reducing the loads on the blade bearings & tower) than the gain-scheduled PI pitch controller developed in [5].…”

“…We employ the HST mathematical model (2.1)-(2.3) from Laguna [5], and the parameters therein which were tailored for a simplified NREL 5-MW HWT.…”

“…the utilisation of a synchronous generator without the need for power electronics to match the grid frequency [1]. The motor & generator of the HST drivetrain can be either configured in the nacelle [2], [3] or at the tower base [4], [5]. In the present paper, we consider the former configuration, which has less operation & maintenance costs [1].…”

“…Wang and Stelson proposed a model predictive torque control scheme whose tracking performance was not desirable either [3]. Several papers designed PI/I pitch controllers based on a linearised single degree-of-freedom (DOF) model describing the angular rotation of the rotor/pump shaft [2], [4], [5]. They did not consider the undesirable responses during the transition between Regions 1 and 2 (due to pitch saturation).…”

Simulation of an offshore wind farm using fluid power for centralized electricity generation

“…The results showed good dynamic behaviour for turbulent wind conditions where reduced fluctuations of the drive train torque and power are obtained despite the reduced energy capture. The integration of a single turbine with a Pelton runner using water hydraulics was introduced in Jarquin Laguna (2015), where a passive variable-speed strategy was proposed. However, the addition and simulation of more turbines to the hydraulic network was not included.…”