Research On Self-sensing Technology Of AC Motor Under Full Operating Condition

The motor drive system can not only realize the energy conversion between electrical device and machine,but also get operating information as the sensor.Through considering all operating condition on AC motor control system,this thesis studies the self-sensing estimation method for input power and electromagnetic torque under the full operating condition of AC motor.Firstly,based on the rotor flux-oriented vector control system,through analyzing the voltage and current constraints of AC motors under full operating condition,this thesis introduces the current allocation method and the structure of current regulator to achieve the maximum torque output.An unified control scheme for induction motor(IM)and permanent magnet synchronous motor(PMSM)is designed.The simulation results verified the validity of the scheme,which provides the general basis for the self-sensing research of the AC motor control system for all operating condition..Secondly,in order to obtain the input power accurately under the full operating condition of AC motors,several special factors need to be analyzed.A compensation scheme is designed by considering the influence of the nonlinear of the inverter.A filter group is proposed in the synchronous rotating coordinate system to suppress noise on the voltage and current signal.Aiming at the problem that the reconstructed voltage signal is not synchronized with the current sampling signal,the phase regulating solution is added on the signal conditioning.The accuracy and feasibility of the input power self-sensing scheme is verified by simulation.Thirdly,the problems in the estimation of electromagnetic torque under the full operating condition of AC motors are also considered.Through comparing two methods for obtaining electromagnetic torque,the scheme based on stator flux is applied.In the observation of the stator flux in the induction motor,a corresponding solution is proposed to cope with the problems of pure integration calculation.The magnitude and phase error introduced by low-pass filter(LPF)are compensated before calculate the stator flux.As the back-emf is equal to zero at the standstill,the voltage model cannot be used to estimate the stator flux at the zero speed.This thesis utilizes the current model to estimate the stator flux at the standstill and lower frequency.And the feasibility of the solution is verified by simulation.When estimating the stator flux in the permanent magnet synchronous motor,a low-pass filter with a variable cut-off frequency is used,the estimated stator flux compensated magnitude and phase is consistent with the theoretical values.The feasibility of the electromagnetic torque selfsensing strategy based on stator flux is verified by simulation.Finally,the input power and electromagnetic torque self-sensing scheme under full operating condition of AC motor is tested valid on the experiment platform.