Sensorless control method of permanent magnet synchronous motor

A sensorless control system for a permanent magnet synchronous motor (PMSM), the system comprising:

• a power supply circuit configured to receive a direct current (DC) power and to supply energy to other components of the system;
• a sampling circuit coupled to the PMSM, the sampling circuit being configured to sample a voltage across a sampling resistor connected in series with a phase winding of the PMSM and to output a signal representative of a phase current of the PMSM;
• a main control circuit, comprising a microcontroller and a memory storing computer-executable instructions, the main control circuit being coupled to the sampling circuit to receive the signal representative of the phase current and being coupled to a drive circuit, the main control circuit being configured to:
• transform the sampled three-phase current into a two-phase current (Iα, Iβ) in a stationary coordinate system;
• design a Luenberger observer model in the stationary coordinate system based on a resistance (R) and an inductance (L) of the PMSM, and on the two-phase current and a two-phase voltage;
• calculate and select a feedback coefficient (K1, K2) for the Luenberger observer model based on a parameter selection method to obtain optimal feedback coefficients;
• obtain an estimated back electromotive force (back-EMF) via the Luenberger observer;
• calculate an estimated electrical angle (θ) from the estimated back-EMF using a phase-locked loop (PLL), and derive an estimated angular velocity (ω) from the estimated electrical angle;
• establish a speed closed-loop control using the estimated electrical angle and the estimated angular velocity;
• transform the two-phase current (Iα, Iβ) into a stator current (Id, Iq) in a rotational coordinate system;
• establish a current closed-loop control using the stator current (Id, Iq) to obtain a stator voltage (Ud, Uq) in the rotational coordinate system;
• modulate a space vector pulse width modulator (SVPWM) using the stator voltage (Ud, Uq) and the estimated rotor position (θ) to generate a pulse width modulation (PWM) signal;
• and
• wherein the drive circuit is configured to receive the PWM signal and drive the PMSM based on the PWM signal to generate a rotating magnetic field, thereby achieving sensorless field-oriented control (FOC) of the PMSM.