Time Delay Identification Method Of Wind Turbine Simulator Based On Instability Characteristics Observation

The original intention of developing the wind turbine simulator is to replace the field test of the actual wind turbine with flexible,safe and low-cost ground experiments as much as possible.One of the core requirements of the wind turbine simulator is to accurately simulate the electromechanical dynamic process of the actual wind turbine,which can replace the actual wind turbine to carry out various studies and tests.The actual wind turbine has slow electromechanical dynamic characteristics due to its huge rotational inertia.The wind turbine simulator platform with small inertia needs to compensate the inertia gap between the actual wind turbine and the actual wind turbine through the inertia compensation strategy to achieve accurate simulation of slow dynamic.For the wind turbine simulator,the application of the moment of inertia compensation strategy can be attributed to the time-delay stability control problem of the closed-loop system.The existing research solves this problem by adding a digital filter to the compensation feedback loop to improve the stability of the system.The reasonable setting of the filter parameters is highly dependent on the accurate identification of the delay of the inertia compensation loop,and the identification accuracy needs to reach millisecond level to match the dynamic response time scale and the control time scale of the wind turbine.However,for the inertia compensation torque loop involving the three subsystems of controller,actuator and sampler,it is difficult to accurately measure the delay of the loop at millisecond level with low cost and noninvasiveness.The existing method of measuring the time delay obtained by observing the time difference between the control instruction and the actual response is not consistent,which leads to poor accuracy of the time delay measured by this method,and then involves the reasonable setting of the filter parameters after setting the filter parameters.The wind turbine simulator system is easy to exceed the stability margin in the operation process,leading to the instability of the experimental platform.Therefore,in order to identify the time delay of the accurate inertia compensation loop and provide accurate and effective reference for the reasonable setting of the filter parameters of the time delay stability control,the following research work is carried out based on the wind turbine simulator platform :1)Based on the simulation,the instability problem of the wind turbine simulator is reproduced.The application effect of the existing time delay identification method shows that the time delay plays a key reference role in the stability control algorithm.Then the instability characteristics of the wind turbine simulator are analyzed and studied by simulation,and it is found that the critical oscillation period of inertia compensation loop delay and compensation torque has a certain numerical relationship.2)From the perspective of time domain,according to the time domain response of the compensation torque,the deterministic numerical relationship between the instability oscillation period of the compensation torque and the time delay is further demonstrated.According to this relationship,the time delay identification method of the compensation circuit based on the observation of the instability characteristics of the simulator is proposed,and some improvement measures are taken to reduce the risk of the identification experiment.On this basis,the accuracy of the simulator model is further improved through the extended z transform,and the stability of the fractional model is analyzed from the perspective of frequency domain.Then,the time delay is identified by observing the instability boundary of the system,which effectively improves the identification accuracy.3)The time-delay identification method is applied to the 15 k W wind turbine simulator experimental platform,and the filter parameters of the time-delay stability control method are set according to the time-delay identification results.The dynamic characteristic simulation experiment of the wind turbine running in the maximum power point tracking control mode is successfully and stably carried out.The stable experimental results show the accuracy and effectiveness of the proposed time delay identification method for wind turbine simulator based on the observation of instability characteristics.