Wind Torque Research Articles

Combined Feedback–Feedforward Control of Wind Turbines Using State-Constrained Model Predictive Control

An application of model predictive control (MPC) to the wind turbine collective pitch and torque control problem in full-load operation is presented. The applied controller is able to include upstream wind speed information, e.g., from light detection and ranging measurements. Furthermore, a method is presented to include constraints on the turbine states in the problem formulation, such as on rotor speed, even in the presence of unmeasured disturbances. In a simulation study, the effects of both preview control and state constraints are evaluated for three different scenarios: normal operation, gusts, and grid-loss load cases. It is found that preview control provides significant benefits in normal operation and under gust conditions. It is further found that including state constraints in the MPC formulation can be used to avoid unnecessary shutdowns due to the violation of the overspeed limit or to control the turbine effectively when the turbine needs to run at a reduced level of generator torque.

MHD simulations of accretion onto a dipolar magnetosphere

This paper examines the outflows associated with the interaction of a stellar magnetosphere with an accretion disk. In particular, we investigate the magnetospheric ejections (MEs) due to the expansion and reconnection of the field lines connecting the star with the disk. Our aim is to study the dynamical properties of the outflows and evaluate their impact on the angular momentum evolution of young protostars. Our models are based on axisymmetric time-dependent magneto-hydrodynamic simulations of the interaction of the dipolar magnetosphere of a rotating protostar with a viscous and resistive disk, using alpha prescriptions for the transport coefficients. Our simulations are designed in order to model: the accretion process and the formation of accretion funnels; the periodic inflation/reconnection of the magnetosphere and the associated MEs; the stellar wind. Similarly to a magnetic slingshot, MEs can be powered by the rotation of both the disk and the star so that they can efficiently remove angular momentum from both. Depending on the accretion rate, MEs can extract a relevant fraction of the accretion torque and, together with a weak but non-negligible stellar wind torque, can balance the spin-up due to accretion. When the disk truncation approaches the corotation radius, the system enters a "propeller" regime, where the torques exerted by the disk and the MEs can even balance the spin-up due to the stellar contraction. The MEs spin-down efficiency can be compared to other scenarios, such as the Ghosh & Lamb, X-wind or stellar wind models. Nevertheless, for all scenarios, an efficient spin-down torque requires a rather strong dipolar component, which has been seldom observed in classical T Tauri stars. A better analysis of the torques acting on the protostar must take into account non-axisymmetric and multipolar magnetic components consistent with observations.

Analysis of the control structure of wind energy generation systems based on a permanent magnet synchronous generator

This paper presents the analysis of the two usual control structures for variable speed and fixed pitch wind energy generation systems, namely speed and torque control, to determine the most appropriate structure to improve both robustness and reliability of this kind of distributed generators. The study considers all the elements of a typical wind power generation system and it has been carried out in a general way, so that conclusions are independent of the kind of the AC/DC converter that it is used to process the energy at the output of the generator. Particular emphasis was placed on developing a model of the turbine where the mechanical torque is considered as a system variable and not an exogenous disturbance for the system, as in other previous studies. After showing that speed control presents several advantages in terms of stability and reliability, an experimental study of this technique was carried out by using a grid connected wind generation system, which is composed by a three-phase boost rectifier feeding the grid connected inverter. Other practical issues for the design of high efficient wind generation systems, like the use of a Kalman speed estimator to avoid the need of mechanical sensors, are also implemented in the prototype and discussed in the paper.

Analysis of inductance characteristics for a bearingless permanent magnet synchronous motor

In this paper, the inductance characteristics of a 2-pole surface-mounted bearingless permanent magnet synchronous motor (BPMSM) with 4-pole suspension force windings are investigated based on theoretical analysis and experimental investigation. Firstly, the winding configuration and operation principle of the BPMSM are presented. Secondly, the static and incremental inductances are defined. Then, based on the finite element (FE) analysis method, the static inductances of torque windings and suspension force windings in stator static coordinate reference are researched. In addition, the d- and q-axes static inductances in rotor revolving coordinate reference are obtained by 3/2 Transformation. Furthermore, taking the torque windings as an example, the incremental inductance of torque windings is studied, and the validity of the theory is confirmed by comparing the static and incremental inductances. Finally, the experimental study is carried out to verify the discussed numerical analysis. The results are helpful to measure parameters and build the mathematic model of BPMSMs, and lay a foundation for the further research on BPMSMs.

Design of Suspension Control System for Bearingless Motor

Bearingless motor, which combines characteristics of alternating current motor and magnetic bearing, can operate without magnetism suspension bearing by making use of magnetism suspension bearing winding that produce magnetism suspending power in the motor stator. Through torque winding and suspending power winding decoupling control, it can make the motor rotor to produce torque and suspension simultaneously. The bearingless motor features high speed and little friction etc. It is one of current hot research areas. The design of bearingless motor suspension control system is the key of this research. The basic principle of the bearingless motor suspension control is introduced and the design of the suspension control system based on the directional magnetic field of torque winding rotor is provided in the paper.

8/10 베어링리스 SRM의 고속 직접전류제어

Novel 8/10 bearingless switched reluctance motor, which can control rotor radial positions with magnetic force, is proposed. The motor has combined characteristics of switched reluctance motor and magnetic bearing. This paper proposes a air-gap control system method of suspending force control in a bearingless switched reluctance motor (BLSRM). The proposed radial force control scheme is independent to the torque winding current. A PI direct current control (DCC) controller and look-up table are used to maintain a constant rotor air-gap. From the analysis and the experimental results, it is shown that the proposed strategy is effective in realizing a naturally decoupled radial force control of BLSRM.

Blasius Boundary Layer Perturbation for Optimal Wind Rotor

Flow on the lee side of wind turbines has been assumed to be helical, with swirl constrained by a pressure increase with radius. This would imply secondary flow into the axis in the blade boundary layer with the heavy swirl optimal at low speed ratios. But in the DTU wind tunnel, tufts on the BEM optimal torque wind stator did not show secondary flow. In fact the straight smoke trails observed behind the stator imply uniform pressure. For BEM optimal and practicable rotors, the interference increases with local speed ratio so the pressure on the lee side actually decreases with radius. In the limit of high speed ratio the pressure gradient again vanishes and the difference between Coriolis and curvilinear secondary forcing terms is a simple function of the apparent wind. Using this function for all speed ratios avoids any pressure gradient and secondary flow towards the axis. The universal profile of such approximated secondary flow and its effect on the chordwise boundary layer are studied as perturbations of the Blasius flat plate layer for Glauert's BEM optimal rotor.

Modeling of bearingless permanent magnet synchronous motor based on mechanical to electrical coordinates transformation

A bearingless permanent magnet synchronous motor (BPMSM) has two sets of stator windings, torque windings and suspension force windings. By analyzing the flux linkage intersection between the two sets of windings, a method of transforming mechanical coordinates to electrical coordinates is put forward. According to this method, flux linkage equations and voltage equations of the two stator windings are derived. The electromagnetic torque equation of the BPMSM is derived based on the analysis of the role of Lorentz force in the BPMSM. After analyzing the mathematical formula of various sort radial forces in the BPMSM, a complete function of radial suspension forces for the BPMSM is obtained. Finally, an experimental system control diagram and some test results are discussed. This mathematical model provides a theoretical foundation for BPMSM simulation study, experiment waveform analysis and structure design.

Modeling and Simulation of Control System for Power Magnetic Bearings

In the light of the strongly coupled and nonlinear characteristics of a power magnetic bearing, a new control algorithm, which can integrate the vector control of torque windings and the independent control of levitation windings, is proposed to solve the coupled relationship between torque windings and levitation windings effectively. Additionally, a good speed regulating performance and stable levitation capability can also be obtained by using the algorithm. Finally, a simulated model is built according to the essential method of the algorithm and MATLAB/Simulink is adopted to analyze the control system quantitatively and qualitatively.

IPM Traction Machine With Single Layer Non-Overlapping Concentrated Windings

In this paper, an interior permanent-magnet traction drive machine with single layer non-overlapping concentrated stator winding is analyzed. In the single layer winding design, the number of stator slots and a winding factor are specifically considered. Moreover, the effect of varying the coil pitch on the winding factor and torque pulsations is investigated. A new calculation method is proposed, whereby the constant torque and field-weakening speed characteristics of the machine drive can be predicted using torque and flux linkage functions. The measured and predicted field-weakening performance of a 150-kW direct traction drive machine is presented.

Bearingless motor’s radial suspension force control based on flux equivalent with virtual winding current analysis method

A bearingless motor has two sets of intercoupling stator windings, namely torque windings and suspension force windings. The decoupling control of the two sets is difficult and a key technology to stable operation for a bearingless motor. In this paper, a simple, reliable and accurate analysis method is put forward using the concept of flux equivalent with virtual winding currents. By this method, the suspension operation condition P B=P M±1 for bearingless motors is testified, and under the rotation condition of the motor, it is also proved that currents in suspension force windings must have the same phase sequence and frequency as torque windings to generate a stable single direction radial force in the rotor’s whole circumference. On this basis, the control strategy of realizing the suspension operation of the bearingless motor is presented, and a prototype of the bearingless surface-mounted permanent magnet synchronous motor is tested. The research results have indicated that the experimental results correspond with theoretical analysis adopting this method, a stable and reliable radial suspension force can be generated, and the validity and feasibility of this control strategy are confirmed.

The stability of accretion discs with inflow driven purely by magnetic winds

A model is presented for an accretion disc in which the inflow is driven purely by the angular momentum removed in a centrifugally accelerated magnetic wind. Turbulent discs around compact stars are considered, with the required magnetic field being generated in the disc by a simple dynamo. The turbulent magnetic Prandtl number, Np, measures the ratio of turbulent viscosity to turbulent magnetic diffusivity. Formally, the hypothetical limit Np 0 corresponds to the magnetic wind torque dominating the viscous torque, but in practice the inflow is magnetically controlled for Np≲ 0.1. The suggestion by previous authors that purely magnetic wind-driven discs may be unstable is investigated. A detailed steady solution is found which allows perturbations to the thermal balance and vertical equilibrium to be calculated, and hence the effect of perturbations to the magnetic diffusivity, η, to be assessed. For a standard parametrized form of η, the wind-driven angular momentum balance is found to be linearly unstable. An increase in the inflow rate leads to increased bending of the poloidal magnetic field and an enhanced wind mass loss rate. This increases the angular momentum loss rate which drives further inflow. There is a resultant increase in η, due to the temperature perturbation, but this does not relieve field bending sufficiently to prevent the instability.

Accretion‐powered Stellar Winds. II. Numerical Solutions for Stellar Wind Torques

[Abridged] In order to explain the slow rotation observed in a large fraction of accreting pre-main-sequence stars (CTTSs), we explore the role of stellar winds in torquing down the stars. For this mechanism to be effective, the stellar winds need to have relatively high outflow rates, and thus would likely be powered by the accretion process itself. Here, we use numerical magnetohydrodynamical simulations to compute detailed 2-dimensional (axisymmetric) stellar wind solutions, in order to determine the spin down torque on the star. We explore a range of parameters relevant for CTTSs, including variations in the stellar mass, radius, spin rate, surface magnetic field strength, the mass loss rate, and wind acceleration rate. We also consider both dipole and quadrupole magnetic field geometries. Our simulations indicate that the stellar wind torque is of sufficient magnitude to be important for spinning down a ``typical'' CTTS, for a mass loss rate of $\sim 10^{-9} M_\odot$ yr$^{-1}$. The winds are wide-angle, self-collimated flows, as expected of magnetic rotator winds with moderately fast rotation. The cases with quadrupolar field produce a much weaker torque than for a dipole with the same surface field strength, demonstrating that magnetic geometry plays a fundamental role in determining the torque. Cases with varying wind acceleration rate show much smaller variations in the torque suggesting that the details of the wind driving are less important. We use our computed results to fit a semi-analytic formula for the effective Alfv\'en radius in the wind, as well as the torque. This allows for considerable predictive power, and is an improvement over existing approximations.

Accretion‐powered Stellar Winds. III. Spin‐Equilibrium Solutions

We compare the stellar wind torque calculated in a previous work (Paper II) to the spin-up and spin-down torques expected to arise from the magnetic interaction between a slowly rotating ($\sim 10$% of breakup) pre-main-sequence star and its accretion disk. This analysis demonstrates that stellar winds can carry off orders of magnitude more angular momentum than can be transferred to the disk, provided that the mass outflow rates are greater than the solar wind. Thus, the equilibrium spin state is simply characterized by a balance between the angular momentum deposited by accretion and that extracted by a stellar wind. We derive a semi-analytic formula for predicting the equilibrium spin rate as a function only of the ratio of $\dot M_{\rm w} / \dot M_{\rm a}$ and a dimensionless magnetization parameter, $\Psi \equiv B_*^2 R_*^2 (\dot M_{\rm a} v_{\rm esc})^{-1}$, where $\dot M_{\rm w}$ is the stellar wind mass outflow rate, $\dot M_{\rm a}$ the accretion rate, $B_*$ the stellar surface magnetic field strength, $R_*$ the stellar radius, and $v_{\rm esc}$ the surface escape speed. For parameters typical of accreting pre-main-sequence stars, this explains spin rates of $\sim 10$% of breakup speed for $\dot M_{\rm w} / \dot M_{\rm a} \sim 0.1$. Finally, the assumption that the stellar wind is driven by a fraction of the accretion power leads to an upper limit to the mass flow ratio of $\dot M_{\rm w} / \dot M_{\rm a} \la 0.6$.

Lateral wind force and torque estimation for a driving assistance

Main topics of driving assistances with respect to degraded driving situations, are low friction or low visibility. Thus, wind related problems are often less considered. However on high bridges or near sea shores, wind can generate car accident. In fact, wind shall have a huge impact on vehicle dynamic. For light vehicle, it could surprise the driver, resulting in a lateral movement. Looking at heavy truck, wind can be an additional factor that initiate a rollover. In this paper, an observer based method for the estimation of wind impact on vehicle dynamic is proposed. It develops the problem of numerical observability of the wind impact and propose an architecture to measure it. Next, it uses this knowledge in order to build a safe speed profile.

Analysis of a new 5-phase bearingless induction motor

This paper addresses the bearingless motor with a single set of multiphase windings. The interaction between M and M±1 pole-pair magnetic fields produces radial force. Based on this principle, a bearingless machine is obtained. Conventional bearingless machine has dual windings, levitation windings and torque windings, which produce the two magnetic fields. In the proposed bearingless motor, the two needed magnetic fields are produced by feeding two groups of currents to a single set of multiphase windings. Taking a 5-phase induction motor as example, the inductance matrices, considering air gap eccentricity, are calculated with the modified winding function method. The radial force analytical model is deduced by virtual displacement, and its results are validated by FEA. The mathematical model of the new bearingless machine is set up, and the simulation results verified the feasibility of this novel bearingless motor.

Optimization of Stator Design in a Consequent-Pole Type Bearingless Motor Considering Magnetic Suspension Characteristics

In this paper, a design optimization method for a consequent-pole bearingless motor is presented. This produces stable magnetic suspension under motor torque generation. The suspension force reduction and direction error, which can be caused by torque generation, are limited in the proposed designs. In the optimization routine, the number of suspension and torque winding turns and air-gap length are carefully assessed. Three stators are constructed for experimental verification. The amplitude and direction errors for the suspension force are found to be within acceptable ranges and the operation of the magnetic suspension is acceptable

2519 小規模低風速型風車の開発に関する基礎研究 : 風速とトルクの特性(S47-3 自然の流体エネルギー利用技術(風車1),S47 自然の流体エネルギー利用技術)

2519 小規模低風速型風車の開発に関する基礎研究 : 風速とトルクの特性(S47-3 自然の流体エネルギー利用技術(風車1),S47 自然の流体エネルギー利用技術)

Antenna mean wind torques: a comparison of field and wind-tunnel data

Accurate information about the action of wind on antennas is required for the sizing of antenna motors and for reliable prediction of antenna pointing errors in windy weather. For these purposes, wind-tunnel data were obtained 40 years ago, using a scaled antenna model. However, their accuracy has been challenged, since they have not yet been verified in a field environment (i.e., for a full-sized antenna, with real wind instead of a steady air flow, and with the influences of the actual terrain, etc.). The purpose of this investigation was to obtain appropriate field measurements, compare them with the available wind-tunnel data, and verify the usefulness of the wind-tunnel data. For this purpose, we measured the steady-state (mean) wind torques of the NASA Deep Space Network 34-meter antenna, calculated the dimensionless wind torques for a variety of wind yaw angles and antenna elevation angles, and compared them with the wind-tunnel data. The results showed that the differences between the wind-tunnel torques and the field torques were less than 10%.

Orientations of Spin and Magnetic Dipole Axes of Pulsars in the J0737-3039 Binary Based on Polarimetry Observations at the Green Bank Telescope

We report here the first polarimetric measurements of the pulsars in the J0737-3039 binary neutron star system using the Green Bank Telescope. The data suggest that the primary star (pulsar A) has a wide hollow cone of emission, which is an expected characteristic of the relatively open magnetosphere given its short spin period, and that pulsar A has a small angle between its spin and magnetic dipole axes, 4° ± 3°. This geometry suggests that pulsar A's wind pressure on pulsar B's magnetosphere will depend on orbital phase. This variable pressure is one mechanism for the variation of flux and profile shape of pulsar B with respect to the orbital phase that has been reported. The response of pulsar B to the pulsar A wind pressure will also depend on the particular side of its magnetosphere facing the wind at the spin phase when pulsar B is visible. This is a second possible mechanism for variability. We suggest that pulsar B may have its spin axis aligned with the orbital angular momentum owing to pulsar A's wind torque that contributes to its spin-down. Monitoring the pulsars while geodetic precession changes spin orientations will provide essential evidence to test detailed theoretical models. We determine the rotation measures of the two stars to be -112.3 ± 1.5 and -118 ± 12 rad m-2.