Uncontrollable phenomenon and digital control delay analysis for high-speed permanent magnet synchronous motor drive

This paper makes a detailed research about uncontrollable phenomenon and digital control delay for a high-speed permanent magnet synchronous motor(PMSM) drive. System stability and the influence of digital control delay are serious problems which have been concerned in the past few years. Traditional work about this point cares only about the stability margin of dynamic mathematical model. However, in this paper, it is pointed out from the analysis results that the drive system may be out of control even though the system has enough stability margin. It is induced by abnormal saturation of PI current regulator in d-axis, and this phenomenon may be deteriorated by digital control delay. This paper makes detailed analysis about this uncontrollable phenomenon and deduces an essential stability operating condition which is relative to motor parameters and digital control delay. To solve this problems, a compensation unit is required. In this paper, a simple compensation matrix is added to the control scheme of high-speed PMSM. At last, simulation results verify the correctness of the analysis results and compensation effectiveness in this paper.