基于单相无刷直流电机的高效全速域无位置控制策略

High-Efficiency Full-Speed Domain Sensorless Control Strategy Based on Single-Phase Brushless DC Motor

以单相无刷直流电机(SPBLDC)控制系统为研究对象,针对小型风机位置传感器安装受限等问题,提出基于单相无刷直流电机的高效全速域无位置控制策略,该策略通过单相I/f电流幅值与功率因数补偿相结合的控制方法实现。通过构建SPBLDC的小信号模型,根据小信号根轨迹分析法,分别对单相I/f电流幅值控制以及单相I/f电流幅值与功率因数补偿相结合控制方法下系统全速域稳态及动态调速过程进行稳定性分析,选取了合适的升速斜率,理论分析了该控制策略能够提高电机运行效率,同时保证系统全速域均具备良好的稳定性能。在Matlab/Simulink环境中仿真验证该控制策略下系统全速域均高效运行于最大转矩/电流比状态,电机转速、电流收敛性能及稳定性均有提升。最后,实验验证了该控制策略的有效性及工程应用的可行性。

This study focuses on the single-phase brushless DC motor(SPBLDC).The small DC fan has some problems,such as the complex installation of position sensors,low reliability under high&low temperatures,and low operating efficiency.Therefore,this paper proposes a control strategy based on power factor compensation based on the traditional I/f current amplitude control.By controlling the back electromotive force(EMF)and the current vector of SPBLDC in the same direction,the SPBLDC can operate at the optimal power factor state,thereby improving the operating efficiency and stability of the system.The methods of this paper are as follows.In the single-phase motor H-bridge inverter topology,the voltage and current of the single-phase winding under vector control are approximately sinusoidal functions.The back EMF of the single-phase motor is a rotating space vector.In order to reflect and analyze the phase and amplitude relationship of single-phase winding voltage,current and back EMF in the rotating coordinate system more intuitively and realize the high-precision and high-performance vector control.The space rotation coordinate system of the single-phase motor is then constructed.The single-phase winding voltage and current are equivalent to the space vector.According to the three different phase relations between the current and the back EMF,a power factor compensation control strategy is proposed based on the traditional I/f current amplitude control.Assume that the voltage amplitude of the inverter when the motor operates at the optimal power factor is the ideal voltage amplitude.To make the back electromotive force and current converge in the same direction,the ideal voltage amplitude is subtracted from the instantaneous output voltage of the inverter.Afterward,the given current amplitude is adjusted through a PI controller to reduce the current amplitude and allow the motor to operate at the maximum torque/current ratio.Based on the spatial rotation coordinate system,the small signal model of SPBLDC is constructed.According to the small-signal root locus analysis method,the full-speed stability analysis of single-phase I/f current amplitude control and power factor compensation control methods is carried out.The closed-loop pole positions of the system before and after the power factor compensation control are compared.After adding the power factor compensation control,the closed-loop poles in the middle and high-speed sections shift significantly to the left.The real part expands about 9 times,while the imaginary part is almost unchanged.The system has a greater damping ratio and stability margin.The stability of the system under different ramp rates is analyzed,and the appropriate ramp rates in practical engineering applications are selected.The experimental results show that the phase voltage amplitude decreases by 36%,the phase current amplitude decreases by 49%,and the phase difference between voltage and current decreases from 30°to 5°at the steady speed of 3000 r/min with power factor compensation.According to the motor space vector diagram,the back EMF vector and the current vector are almost in phase,with an angle close to zero degree.The current reactive component and the phase current amplitude are reduced,indicating that the power factor compensation control can make the motor close to the maximum torque/current ratio state.Accordingly,the motor operation efficiency is improved.The pulsation and oscillation of DC bus current and phase current amplitude are significantly reduced under the power factor compensation control when the speed is increased to 3542r/min at the theoretically designed ramp.This reduction in pulsation and oscillation indicates that the damping of the system is increased,and the stability is improved.Theoretical analysis and experimental results show that the system can achieve low current oscillation and low-speed pulsation under steady state and dynamic speed regulation process using the sensorless control strategy of single-phase I/f control combined with power factor compensation.The motor operates efficiently at the optimal power factor state in the full speed range and has good dynamic and steady performance,making it highly valuable for engineering applications.