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The paper proposes maglev wind yaw system (MWYS) for wind turbine to yaw for wind. Two degree-of-freedom (2-DOF) suspension model is constructed with the suspension current dynamics. A dual-loop cooperative suspension control including inverse system compensation, pseudo suspension control and hybrid decoupling control is proposed to ensure nacelle stable suspension without pitching. The inverse system compensation gives the nominal current reference; and then the pseudo suspension control is designed from sliding mode controller with the non-linear function to acquire two pseudo control input, and then 2 DOF disturbance observers based on two sliding mode surfaces and their sign function are proposed to get high frequency interference, and cooperate with the linear relationship to decouple and give two sides current reference. The closed-loop stability of nacelle suspension has proved by the Lyapunov function, air gap asymptotic tracking can be reached in finite time. The state feedback controller with adaptive compensation is designed to enhance the current dynamic response. Finally, the simulation and experimental results show that the proposed strategy has faster suspension dynamic response, smaller steady-state error and synchronization error.

A novel maglev wind yaw system (MWYS) based on the maglev technique and direct-drive structure was proposed to reduce the yaw power and failure rate. We firstly introduced the attraction force fluctuation and dynamic response time into the optimized design of axial flux motor, and constraints considering suspension start-up, DC input voltage of suspension converter, and safe pitch limitation are given. Using multi-objective sequential quadratic programming (SQP) technique, an optimization process is performed for minimising the suspension losses, attraction force fluctuation, and the fastest attraction force dynamic response, considering the practical constraints. Ultra-low speed requirement makes the yaw motion easily vibrate with torque pulsation, we adopt the stator fractional slot structure, and build stator slot permeance function and some constraints to perform the optimization of the stator construct parameters for minimising cogging torque by the Lagrange function method. Finally, the design example is given and a prototype is manufactured. The experimental results show that the presented design method, structure and the MWYS are feasible.

The maglev yaw system of wind turbines adopts maglev-driving technology instead of traditional gear-driving technology. It has many advantages, such as no lubrication, simple structure, and high reliability. However, the stable suspension control of maglev yaw system is difficult to achieve due to the unknown disturbance caused by crosswind in a practical environment. In this article, an adaptive sliding mode cascade controller based on radial basis function neural network is proposed for the stable suspension control of maglev yaw system. First, the dynamic mathematical model of maglev yaw system is established. Second, an adaptive sliding mode robust controller using radial basis function neural network is designed as the outer loop air gap tracking controller for precise position control, where radial basis function neural network is employed to estimate the unknown parameter containing disturbance. To eliminate the limitation of the traditional exponential approach law based on sign function in the sliding mode control, an exponential reaching law based on hyperbolic tangent function is introduced to guarantee the smooth suspension control of maglev yaw system. Third, an adaptive controller as the inner loop current tracking controller is designed. Finally, the corresponding simulations and analysis are carried out. The simulation results show that the proposed controller can guarantee the suspension stability of maglev yaw system and suppress the disturbance effectively. Compared with the cascade proportional–integral–derivative controller and improved double power reaching law integral sliding mode controller, the proposed controller has a faster dynamic response and stronger robustness in the presence of unknown external disturbance.

A magnetic-levitation (maglev) Wind Yaw System is proposed to make the nacelle yaw for wind direction without friction. Due to the multi-point suspension nonlinear coupling and higher suspension weight, a double closed-loop control strategy for single-point suspension control is proposed including suspension air gap loop and the current tracking loop. A MDOF dynamic model based on the mechanical geometry and motion dynamics is developed and then transformed into the mult-point suspension model. Then we unify the cross coupling terms and pitching disturbance into synchronous disturbance, and then proposed a composite control strategy to set suspension current reference for current tracking loop, including main tracking controller, adaptive synchronization controller and adaptive disturbance controller. The multi-point suspension simulation platform of maglev wind yawing system is built to carry out the dynamic suspension tracking and pitching disturbance experiment, and the poposed strategy has good dynamic tracking ability, the steady-state air gap error is only 0.003mm, and the reference switching recovery time is 0.445s . As pitching torque of 220Nm is subjected to the nacelle, the maximum air gap fluctuation is only 0.38mm, and the maximum synchronization error is 0.19mm, but these of the PID controller can reach to 2.82mm and 10mm respectively, which validate the proposed composite control and the rationality of four point nacelle suspension.

In this paper, the magnetic field characteristics of the magnetic force line of the electrified suspension winding are deeply analyzed, and a magnetic levitation ball motion model with axial and horizontal two degrees of freedom is constructed. At the same time, considering the matching and mismatching interference in the system, the model is transformed into a model with only matching interference; Secondly, in order to solve the problem that it is difficult to obtain the velocity and acceleration of the air gap and the realtime observation of the disturbance, in this paper, a sliding mode air gap velocity and acceleration observer with disturbance reconstruction is proposed. Based on this observer, a sliding mode tracking controller is designed. Finally, a sliding mode state observation and tracking cooperative control simulation platform with disturbance reconstruction is built to verify the optimization of the proposed control strategy in dynamic response speed, tracking error and anti-interference performance compared with the traditional PID control.

The yaw system is one of the important parts of the horizontal axis wind turbines. In this paper, a control method combined model predictive control (MPC) with PID based on model mismatch compensator is proposed to improve the dynamic suspension stability of maglev yaw system (MYS) at the equilibrium point. First, the dynamic mathematical models of the MYS are built and analyzed. Second, the MPC-PID suspension controller is designed, and the stability analysis of the designed maglev control system is carried out by using the Routh stability criterion. Third, the model mismatch compensator is designed to eliminate the influence on the system resulting from the inaccuracy of linearization model and uncertain external disturbance. Finally, the simulation experiments are carried out for different control schemes based on the parameters of the experimental prototype, and the simulation results show that the proposed MPC-PID controller based on the model mismatch compensator has higher control accuracy, and the MYS can reach the stable state with in shorter time, therefore the controller is substantiated to be feasible and superior.

Among all the faults that lead to a wind power system shut down, yaw gear drive faults accounted for a considerable proportion. In this paper, a novel single-sided disc motor with independent controllable excitation magnetic poles, which is a candidate direct-drive solution, is proposed for the yaw system. In the design process, the influence of the structural parameter on the decoupling control performance of the tangential force and the axial force is considered. Moreover, the trends of the electromagnetic torque and the axial force are calculated by 3D finite-element analysis (FEA) when armature current and excitation current change. Finally, both the finite-element analysis and the test measurement verify that the design is correct and effective.

Reliable and accurate models are urgently needed for research on the control strategies to promote the energy conversion efficiency in compress air energy storage (CAES) system. This paper mainly studies expansion and power generation, which is called the scroll expander generator system with the permanent magnet synchronous generator (PMSG) using the rectifier and buck circuit. Considering influence of air leakage, the scroll expander model is established based on the change of chambers volume, air mass and pressure. A steady model of generator is described with the duty ratio of buck chopper and speed. The control strategies including valve and Buck chopper controller are adopted to quickly track the optimized speed and keep the load voltage constant. The experiment and simulation study validated the model and proved that the proposed control strategies can operate effectively on the variable working conditions. Experiment results point out that the optimized working speed is corresponding with the minimum air consumed power, instead of the maximum efficiency of scroll expander.