Kazuaki Tobari

A stable field-weakening control using voltage phase operations in the high-power region

A field-weakening control is required in order to achieve high power output and stable control in the voltage saturation region. In this paper, a voltage phase-operated field-weakening control and a frequency-compensation control are presented. The voltage phase operation control adjusts the voltage phase command with the voltage maintained at the maximum value. Therefore the proposed control can provide higher output power. The frequency compensation control decreases motor speed command in the motor torque limit region, and the motor speed overshoot is thus suppressed. Experimental results show that the proposed controls are effective in suppressing motor speed overshoot and allowing high power output.

Position sensorless control method at zero speed region for permanent magnet synchronous motors based on block commutation drive

A new position sensor-less method has been developed for permanent magnet synchronous motor (PMSM) drives in zero speed regions. This method utilizes the induced voltage caused by magnetic saturation (IVMS) of PMSM. The rotor position can be detected by IVMS. Furthermore, we introduce a bi-polar pulse modulation to the zero-speed region. By this modulation, both the normal and reversal direction IVMS can be detected and the bi-direction drive achieved. The principle of the proposed method and the experimental results are discussed in this paper.

A simplified sensorless vector control based on the average of the DC bus current

This paper describes a simplified sensorless vector control for permanent magnet synchronous motors (PMSM) using the average of the DC bus current. This method sets up the drive control system at relatively inexpensive because the micro controller does not need to have a precise timer and the calculation load is slight. The proposed method effectively changes two different current estimation methods in accordance with the operation mode. First, the controller estimates d-axis current and identifies back-EMF parameter in synchronous operation mode at the low speed region. The identification error of back-EMF parameter affects efficiency of the proposed system, so it needs to be zero. Second, the controller estimates q-axis current in vector control mode. The identified parameter and q-axis current define voltage reference to realize high efficiency drive. Experimental results confirm the effectiveness of proposed method.

A novel PWM pulse modifying method for reconstructing three-phase AC currents from DC bus currents of inverter

A novel PWM pulse modifying method for DC bus current detection has been developed to reduce acoustic noise and distortion. DC bus current detection needs wide pulse durations to reconstruct three AC currents. PWM pulse modifying methods have been proposed to expand short pulse durations at low modulation. However, harmonic currents caused by modification signals distort reconstructed currents and create a specific frequency. In this paper, several PWM modifying methods are examined. Moreover a method for modifying signals is proposed that prevents harmonic currents from distorting reconstructed currents and creating a low frequency. Simulated and experimental results show good performances of total harmonic distortion and a high frequency.