考虑参数误差的无速度传感器异步电机低速发电工况稳定性提升策略

Enhanced Stability for Speed-Sensorless Induction Motor Drives in Low-Speed Regenerating Region Considering Parameter Uncertainties

对于无速度传感器异步电机控制系统,反馈矩阵理论上可以减小系统发电运行不稳定区域,改善低速发电工况下的转速观测性能。然而,由于电机参数误差,现有控制策略无法在低定子电流频率下实现理想的稳定性目标。针对这个问题,该文提出一种基于多误差项协同的反馈矩阵设计方法,提高系统对电机参数误差的鲁棒性,并提升转速观测的稳定性。首先,该文提出一种基于多误差项解耦的磁链误差在线观测方法,分析并设计了磁链误差权重系数。其次,在观测器反馈矩阵设计中引入电流误差项,实现电流误差项与磁链误差项的协同设计。在此基础上,将误差矢量系数矩阵行列式重构为抛物线函数,通过引入常数项满足系统稳定的必要条件,解决传统反馈矩阵设计方法对电机参数变化敏感的缺陷,提高观测器对参数误差的鲁棒性。在低定子电流频率下,所提方法可以在低速发电区域实现稳定的转速观测。最后,在2.2 kW异步电机平台上验证了所提方法的有效性。

The speed-sensorless induction motor drives(SSIMD)technique possesses high reliability,easy maintenance,low cost,and is adopted broadly.High performance of the SSIMD system relies on the precise rotor speed information.Recently,several papers have been reported to realize speed estimation as accurate as possible.For the SSIMD control system,the feedback matrix of the adaptive full-order observer(AFO)can theoretically reduce the unstable regenerating region,and improve the speed estimation performance in low-speed regenerating mode.However,the desired performance of existing methods deteriorates at low stator frequencies due to parameter uncertainties.The boundaries of the unstable region cannot coincidence with the inevitable parameter uncertainties.Actually,most of existing methods ignore the flux error,which is unable to be observed directly by instruments.Then the necessary conditions of the SSIMD control system cannot be satisfied at the low-speed regenerating mode.To solve the problem above,this paper proposes a feedback matrix design method.To design and select the robust feedback in SectionⅢ,a flux error online estimate method is introduced in SectionⅡbased on decoupling error terms.Existing literature points out that both the stator current error and the rotor flux error are composed of stator resistance error,rotor resistance error,and rotor speed error.Hence,the expression of the flux error can be obtained by the decoupling analysis.To determine the weight coefficients,variations of ratios N1 and N3 against different synchronous speeds and torque currents are presented.Then the weight coefficients can be selected appropriately.Introducing the flux error into the feedback matrix design,the mathematical model and the block diagram of the control system with the proposed feedback matrix design are given in SectionⅢ.To realize the necessary conditions of the SSIMD,the stability function of the AFO is reconstructed as a parabola.The function maximums and the robustness improvement design are discussed based on the vertex movement.With a constant term from the flux error,the stability of the SSIMD in the low-speed regenerating region can be guaranteed even if there are parameter uncertainties.The proposed method overcomes the sensitivity against parameter variation and enhances the robustness of AFO.Finally,the effectiveness of the proposed method is verified on a 2.2 kW IM experimental setup.Two identical machines are set to provide desired load torque and test the proposed method,respectively.In the load step experiment,the SSIMD control system operates stably with the proposed feedback design,when the stator frequency is 0.4 Hz.The conventional method fails to provide stable speed estimation at 0.6 Hz.The comparison experiments validate the superiority of the proposed method.To test the operation performance in the whole low-speed ranges,the speed reversal experiments are carried out.With the proposed feedback gains,the induction motor crosses the zero-stator-frequency line successfully with great speed observability.Furthermore,this paper shows the excellent speed tracking performance of the SSIMD control system using the loaded speed step experiments.The parameter robustness,as the core innovation in this paper,is validated by stator and rotor mismatches experiments.Although there are little observation errors,the control system works well.As conclusion,This paper has provided an alternative solution to enhance the stability of AFO,and also to realize the robustness of feedback gains against parameter uncertainties.The flux error has been estimated with the weight values derived according to IM operating conditions.On this basis,the current and the flux error are adopted as state variables of feedback gains term to design the multiple error-based feedback gains.The effectiveness has been confirmed by experiments in low-speed regenerating region.The stable operations have been realized against parameter uncertainties.