In the control of a high-speed BLDC motor, the commutation-point error and current ripple increase due to the phase delay component and the commutation method synchronized with the PWM switching cycle. To solve this problem, this paper proposes an optimal commutation sensorless control method based on the αβ-axis voltage of a stationary reference frame using a separate high-speed timer. The proposed commutation method sets the interrupter-point of a separate high-speed timer as the commutation-point, and determines the commutation-point by varying the interrupter period of the high-speed timer using the error between the estimated rotor angle and the commutation angle in the control period where the 6-step signal is changed. In the proposed 2-phase excitation sensorless control, the 6-step signal is determined through the commutation-point detection method based on the αβ-axis voltage of the stationary reference frame using LPF. The αβ-axis voltage of the stationary reference frame is calculated from the detected pole-voltage of each phase, and a digital LPF is applied to filter harmonic voltage components. The continuous rotor angle is calculated through the filtered αβ-axis voltage, and the final rotor angle is estimated by compensating the phase delay component by the LPF and ADC method. Using the estimated rotor angle, a 6-step signal is determined and the rotor speed is estimated based on the T-method. In addition, in the proposed 2-phase excitation sensorless control, H-PWM & L-PWM method was applied to reduce current ripple due to PWM switching.
The 2-phase excitation sensorless control with the proposed commutation method verified that the commutation-point error and current ripple were reduced through simulation and experiment.