A Simple Method to Reduce Torque Ripple in Direct Torque-Controlled Permanent-Magnet Synchronous Motor by Using Vectors With Variable Amplitude and Angle

Abstract

Abstract-In this paper, a modified direct torque control (DTC) for permanent magnet synchronous machine is proposed, which enables important torque and flux ripple reduction by using voltage vectors with variable amplitude and angle. Conventional DTC presents some drawbacks, including large torque ripple, variable switching frequency and acoustic noise. The reason lies in that t h e switching table is composed of a limited number of discrete voltage vectors with fixed amplitude and position. Moreover, the selected vector will work during the whole sampling period, a n d hence their effects on torque and flux may usually be too large or too small. In the proposed DTC, the amplitudes of torque and flux errors are differentiated and they are employed to regulate the amplitude and position of the output voltage vectors on-line, which would finally be synthesized by space vector modulation (SVM). Two simple formulas are developed to derive the amplitude and position of the commanding voltage vectors from the errors of torque and flux. Conventional switching table and hysteresis controllers are eliminated and fixed switching frequency is obtained with the help of SVM. Stator flux is estimated from an improved voltage model, which is based on a low-pass filter with compensations of the amplitude and phase. The proposed DTC exhibits excellent dynamic performance and significant torque ripple reduction at steady state, which are validated by the presented simulation and experimental results.

Direct Stator Flux Vector Control Strategy for IPMSM using a Full-order State Observer

“…Although lower torque ripple output is exhibited, the algorithm is more complex when applied to the IPMSM. Two weight factors are employed in [28] to determine the amplitude and angle of the desired voltage vector. It is a time-consumption job to find the proper weight factors.…”

“…The pure integrator used in the traditional voltage-based model deteriorates the performance of the estimator due to the DC drift and initial value [29]. A low-pass-filter estimator with compensation of amplitude and phase angle is utilized in [28] to remedy the problems. To reduce the parameter sensitivity, many closed-loop adaptive observers based on advance models have been developed, such as an adaptive sliding observer [30,31], an observer based on extended Kalman filter (EKF) [32], a hybrid current-voltage model estimator [33][34][35], and so forth.…”

Design of the Modified PID Speed Controller to Reduce the Speed Ripple

“…PMSM(Permanent Magnet Synchronous Motor)은 고 효율 특성과 높은 토크 및 우수한 제어성으로 인하여 산업용, 가정용 및 로봇 응용 분야에 널리 적용되고 있 다 [1][2][3][4][5][6][7][8] . 특히, 최근에는 로봇 및 전기 자동차의 구동 장 치로 그 활용도가 점점 확대되고 있다 [1][2][3][4][5][6][7][8][9][10] .…”

“…특히, 최근에는 로봇 및 전기 자동차의 구동 장 치로 그 활용도가 점점 확대되고 있다 [1][2][3][4][5][6][7][8][9][10] . PMSM은 전 동기의 설계 특성상 영구자석이 고정자의 슬롯을 지나 는 부분에서 코깅(cogging) 현상에 의한 토크 리플이 존 재하게 되며, 이러한 코깅 토크는 속도 리플을 발생하게 된다.…”

“…하지만, 코깅 토크에 의한 토크 리플은 전기적 주 파수가 빠르고, 관측기에 의해 추정토크를 연산하는 경 우 연산의 지연과 주기적인 리플로 인하여 그 오차를 보상하기가 매우 어렵다. 코깅 토크와 같은 주기적인 리 플에 의한 속도오차를 보상하기 위해서 전동기의 토크 전류에 주기적인 코깅 토크를 보상하는 토크 성분을 추 가하여 보상할 수 있으나, 이는 전동기의 파라미터를 정 밀하게 추정해야하고, 회전자 위치에 따른 코깅 토크의 분석을 필요로 한다 [2][3][4] .…”