A Speed Sensorless Wide-speed Range Control Strategy For Permanent Magnet Synchronous Motors

Permanent Magnet Synchronous Motor(PMSM)has the advantages of simple rotor structure,small size,high efficiency,high energy density and good speed regulation performance.It is widely used in aviation,electric vehicles and household appliances.However,due to the presence of mechanical encoders,the connection lines and circuits of the control board will increase accordingly.In harsh environments,not only is the system susceptible to interference,but costs will also increase.This has prompted scholars at home and abroad to conduct in-depth research on the sensorless control of this type of motor.The study found that in the low-speed field,surface-mounted PMSMs with approximately equal d and q axis inductances usually use the pulse voltage injection method.However,the traditional pulse voltage injection method is modeled without considering the motor impedance and cross-coupling of the inductance,which will cause a large position error and affect the system’s steady-state performance.In the field of medium and high speeds,the sliding mode observer method has been widely studied,but the algorithm has switching functions and low-pass filters,which will cause high-frequency chattering and poor system stability.A single sensorless algorithm can only have its performance within a certain speed range,and it is not compatible with the high-performance operation of the motor at zero speed,low speed,medium and high speed.This paper takes a 1kW SPMSM as the research object,and classifies the zero-speed,low-speed and medium-high-speed domains of the motor.When the motor is at rest,the positive and negative alternating voltage vector injection method is used to counteract the influence of the motion torque on the motion state of the motor,so that the motor obtains the initial position of the rotor at rest.When the motor needs to run at low speed,theoretical analysis of the non-ideal conditions is carried out,and a position compensation strategy is proposed to improve the accuracy of the pulse voltage injection method algorithm in position detection.Simulation proves the feasibility of the scheme.When the motor needs to run at high speed,an improved adaptive sliding mode observer sensorless control strategy for SPMSM is proposed.Compared with the traditional sliding mode observer of the EMF method,this method uses the extended sliding mode observer and The combination of the speed observer can effectively suppress the high-frequency chattering component existing in the traditional sliding mode position detection method and improve the steady-state performance of the speed loop.The simulation verifies the effectiveness of the control strategy.Finally,a set of DSP-based 1kW surface-mounted permanent magnet synchronous motor speed sensorless drive control system experimental platform was built.In the zero-speed domain,the software operation of the voltage vector injection method is explored,and the position is estimated to be within the error range of ± 1 degree.In the low-speed domain,the position and speed waveforms of the pulse voltage injection method before and after the improvement are compared,the estimated value can track the actual value more smoothly,and the position error is reduced.In the high-speed domain,the sliding mode observer algorithm before and after the improvement is compared,and the high-frequency chattering components of the rotation speed and position are significantly reduced.In order to combine the above algorithms,this paper selects different algorithms based on the given speed judgment,which makes the control strategy with more outstanding performance and wider speed domain possible.