Research On Indirect Power Control And No-load Grid-connection Technology Of Brushless Doubly-fed Motor Based On Active Disturbance Rejection Control

With the development of modernization,traditional energy sources are becoming less and less able to meet the needs of the times.As a clean energy source,wind energy has gradually attracted people’s attention.Brushless Doubly-Fed Induction Generator(BDFIG)can achieve variable speed Constant frequency power generation does not require brushes and slip rings,which has attracted more and more attention in the field of wind power generation.In the past ten years,experts and scholars have conducted a lot of research on the ontology structure and control strategy of BDFIG,which has promoted the rapid development of BDFIG and brought it closer to commercial applications.Most of the current control systems use PID controllers.With the gradual complexity of the control system and the severe working environment,PID controllers begin to show deficiencies,and in many cases it is difficult to meet the requirements of the actual situation.1.A control method of BDFIG no-load grid-connected voltage phase based on controlling winding flux is proposed.Compared with PID control,Active Disturbance Rejection Control(ADRC)has more prominent advantages.Linear ADRC(LADRC)has similar control performance with ADRC and the controller parameters are greatly reduced,which is becoming more and more popular by researchers.This article has done the following research on the no-load grid connection and indirect power control of the brushless doubly-fed generator.1.Research on BDFIG no-load grid-connected control method(1)A BDFIG no-load grid-connected voltage phase control method based on the control winding flux was proposedBy analyzing the relationship between the BDFIG power winding voltage and the control winding flux,a power winding voltage phase control method based on the control winding flux was proposed,and the control system block diagram was constructed to realize the real-time control of the BDFIG voltage phase.On this basis Realized the real-time control of the voltage amplitude,phase and frequency of the BDFIG power winding,and can automatically completed the grid connection when the grid connection conditions were met,effectively reducing the inrush current when BDFIG is connected to the grid without load,and improving the stability of the control system.The method does not require coordinate transformation,the control structure and algorithm are simple,and the implementation is convenient.The simulation results verified the effectiveness of the control strategy.(2)Completed the BDFIG no-load grid-connected experiment based on the control winding flux.In order to verify the performance of BDFIG no-load grid-connected control,the hardware device required for BDFIG no-load grid-connected was added to the existing experimental platform.This device can realize the communication with the main control system and judge the amplitude of the BDFIG power winding voltage in real time.When the grid connection conditions are met,the main control system automatically sends instructions,and the hardware device controls the grid connection switch to close to realize the BDFIG grid connection.After being connected to the grid,the control system can automatically switch to the indirect power control strategy to realize the control of active power and reactive power.The BDFIG no-load grid-connected experiment based on the control winding flux was completed on the built experimental platform.The experimental results under supersynchronous and sub-synchronous operating states showed that the proposed BDFIG no-load grid-connected control strategy can adjust the BDFIG power winding voltage in real time and make it meet the grid-connected conditions.The inrush current was small during grid-connected,and flexible grid-connected was realized.(3)No-load grid-connected control of BDFIG based on LADRC controller was proposed.In the above-mentioned BDFIG no-load grid-connected control system,the PI controller will have a certain overshoot and a certain inrush current when grid-connected.To solve this problem,the LADRC controller was applied to the BDFIG no-load grid-connected control system,which reduces the overshoot of the BDFIG power winding voltage amplitude and phase during the adjustment process,as well as the current impact during grid-connected,and improves the system’s performance,at the same time,the anti-disturbance performance of the system is improved.A BDFIG no-load grid-connected simulation model based on LADRC controller and PI controller was built on the simulation platform.The simulation results showed that LADRC controller has greater application advantages compared with PI controller.2.Indirect power control of BDFIG based on LADRC controller was proposed.The research results show that there is a serious coupling between active power and reactive power in the BDFIG indirect power control system based on PI controller.In addition,the same set of PI controller parameters cannot meet the requirements under all operating states(the given power changes).Aiming at this problem,a BDFIG indirect power control based on LADRC controller was proposed.The simulation results showed that the use of LADRC controller in the control system can effectively reduce the coupling between active and reactive power,when the BDFIG operating state changes,the ADRC controller parameters do not need to be changed and the control performance can meet the requirements,which improves the stability of the control system.