Research On Control Strategy For Speed Tracking Of Permanent Magnet Synchronous Generator Wind Turbine With Disturbances

As a new wind energy conversion system (WECS), the direct driven permanent magnet synchronous generator is widely used in modern wind power industry, which is featured with simple structure, high efficiency. However, the wind energy conversion system is a nonlinear, strong-coupling, multivariable complex system, and the wind speed has characteristics of randomness, time variant and uncontrollability. It is difficult to obtain the accurate plant model and to measure the disturbances in many practical systems, which will pose a huge challenge to the initial design. Therefore, it is of great significant to design an advanced control algorithm with a simple algorithm, strong anti-disturbance ability as well as being independent of the system mathematical model for WECS.To extract the optimal power from the wind turbine by tracking the speed, the active disturbance rejection control (ADRC) scheme is introduced to the control of WECS, with arm of improving the resistance to disturbances. Based on the analysis of the direct driven permanent magnet synchronous generator system, the main works of this paper are organized as follows:(1) Considering the unique characteristics of this system, this paper proposed an effective strategy based on ADRC. First, The ESO can treat the lumped disturbances including internal disturbances, i.e., parameters variations, control couplings, unmodeled and nonlinear dynamics of the plant and external disturbances as an extended state of the original system and dynamically compensate for them through the feedback controller in real time. Simulation results show that the proposed control strategy has strong robustness against uncertain dynamics and resistance to disturbances.(2) The WECS is a complex dynamic system with many disturbances, when the system inertia and drive torque and other parameters change in a large scale with the variation of the disturbances and wind speed, ESO may not be able to estimate the lumped disturbances accurately and, as a result, the control performance of ADRC may be degraded. To deal this problem, a Model-compensation ADRC is proposed in this paper. Such challenge can be mitigated by making full use of the model information, obtained by torque observation and inertia identification, in the design of ADRC, thereby relieving the load of ESO and improving the control performance of the whole system. The effectiveness of the proposed control strategy is verified in simulation studies with promising results.(3)The time delay is inevitable in the WECS, the presence of system time delay introduces extra phase lag, which reduces the closed-loop stability. Since the Smith Predictor is specifically designed for delayed-systems, we employs it to the design of ADRC in this paper. The idea of incorporating the Smith Predictor technique is to have the controller act on the undelayed part of the system so it can provide a faster reaction to the changes in the system to improve the tracking performance. Simulation results show that the proposed control strategy has strong resistance to time delay and as a result, improve the control performance.