Toshiyuki Ajima

A torque ripple reduction method by current sensor offset error compensation

This paper presents a reduction method for a torque ripple resulting from a motor phase current sensor offset error for motor drive applications such as a hybrid electric vehicle (HEV). The proposed method compensates for the detected motor phase current offset error by subtracting the detected motor phase current offset error value indirectly estimated using the inverter offset voltage reference value from the detected motor phase current value after the offset component of the inverter output voltage reference is calculated by a discrete Fourier transform and a digital low pass filter. The main feature of the proposed method is its ability to compensate for the detected motor phase current offset error that varies during inverter-motor drive. In this paper, the effectiveness of the proposed method with the motor torque analysis is discussed in detail. In the condition of the torque reference from 10[Nm] to 100[Nm] and the motor rotation speed of 1000[rpm], the average value of the torque ripple with the proposed method is 10[Nm] and is reduced by one-second (1/2) compared with the average value of the torque ripple without the proposed method.

A compensation method for a motor phase current sensor offset error using a voltage-source-inverter output voltage reference value

This paper presents a method for reducing a motor torque ripple resulting from a motor phase current sensor offset error for motor drive applications such as a hybrid electric vehicle. The proposed method estimates the motor phase current sensor offset error on the basis of the direct voltage value included in the voltage source inverter output voltage reference value calculated by a discrete Fourier transform. It then compensates for the motor phase current sensor offset error by subtracting the estimated motor phase current sensor offset error value from the detected motor phase current value. Its main feature is its ability to compensate for the motor phase current sensor offset error that varies due to temperature change while a voltage source inverter and a motor are driven. The effectiveness of the proposed method for reducing the motor torque ripple with reference to simulation results is discussed in detail. These simulation results reveal that the proposed method can compensate for the motor phase current sensor offset error with less than or equal to +-1[A] difference and reduce the average value of the motor torque ripple to half (1/2) of that without the proposed method in steady state in which the motor torque reference is from 10[Nm] to 80[Nm] and the motor rotation speed is 1000[rpm]. Also, in the transient conditions in which the motor rotation speed and the motor torque reference vary, the motor phase current sensor offset error can be compensated for normally, and the stable motor torque without a motor torque ripple of a fundamental frequency component can be obtained.

A novel compensation method for a motor phase current sensor offset error varied during a VSI-motor drive

This paper presents a method for reducing a torque ripple resulting from a motor phase current sensor offset error for motor drive applications such as a hybrid electric vehicle. The proposed method compensates for the motor phase current sensor offset error by subtracting a motor phase current sensor offset error value estimated by using a discrete Fourier transform from a detected motor phase current value. Its main feature is its ability to compensate for the motor phase current sensor offset error that varies due to temperature change during the inverter-motor drive. Simulation results reveal that the proposed method can estimate the motor phase current sensor offset error with less than or equal to +-2[A] difference and reduce the average value of the motor torque ripple to half (1/2) of that without the proposed method in a steady state.

Optimal pulse pattern determination based on Pulse Harmonic Modulation

The design of optimized modulation schemes at low pulse ratios, e.g. Selective Harmonic Elimination (SHE), has been widely studied. However, most previous work has focused on half-wave symmetry pulse patterns. For variable speed and variable torque applications, non-half-wave symmetry SHE modulators depending on the power factor angle still achieve highly efficient inverters in many power factors. Unfortunately, few papers have studied inverter loss on non-half-wave symmetry SHE modulators. Thus, this paper proposes our original SHE method: Pulse Harmonic Modulation (PHM). Its mechanisms are explained in detail. Additionally, different pulse patterns of PHM are quantitatively compared. On the basis of this comparison, several design criteria are proposed for modulators at low pulse ratios.

Analysis of vibration of permanent magnet synchronous motor with distributed winding for the PWM method of voltage source inverters

This paper presents an evaluation of noise and vibration in a distributed winding permanent magnet synchronous motor driven by voltage source pulse width modulation (PWM) inverters. The permanent magnet synchronous motor (PMSM) is widely used as an important driving source in a variety of fields. However, it generates electromagnetic noise and vibration because of PWM inverters. This paper describes the frequency of the electromagnetic noise caused by a distributed winding PMSM. We investigated the electromagnetic force generating the noise by using a couple of analyses between a circuit simulator and a two-dimensional finite element analysis (2-D FEM). It is found that the electromagnetic noise and vibration results from an electromagnetic force spaced at the 0th order of space harmonics. In addition, the electromagnetic noise and vibration mode of this element are demonstrated in the experiment.