A Synchronous Modulation Method Transitioning from Asynchronous Modulation to Phase Synchronization

Abstract

The invention discloses a synchronous modulation method for transitioning from asynchronous modulation to phase synchronous modulation. The specific implementation steps are as follows: determine the carrier ratio N of synchronous modulation, and simultaneously determine the phase angles 0, 2π*1 / N, and 2π*2 / N of phase synchronization ...2π*(N‑1) / N; when the motor is at low speed, the asynchronous modulation method is adopted, the motor speed rises but the carrier frequency is fixed, when the motor operating frequency exceeds the carrier frequency divided by the set synchronous modulation ratio, it enters the synchronous modulation stage; enters After the synchronous modulation stage, the synchronous modulation of the phase synchronization is realized, and it is judged whether the vector angle is close to any one of the N phase synchronizations. The above steps realize the transition from the asynchronous modulation to the synchronous modulation of the phase synchronization. The invention ensures the smoothness of the transition, and finally enters the stage of synchronous modulation of phase synchronization, the modulated voltage frequency realizes a fixed carrier ratio according to the change of the carrier frequency, and ensures the absolute synchronization of the phase angle.

Description

Technical field [0001] The present invention belongs to the field of inverter control motor speed regulation, specifically relates to an asynchronous modulation transition to phase synchronization synchronous modulation method. Background [0002] In the field of inverter control motor speed regulation, as the motor speed increases, limited by the processing speed of the main control chip or the large switching loss of the power device, the carrier frequency cannot be further increased, at this time, the low-speed asynchronous modulation transition to high-speed synchronous modulation, that is, the carrier frequency is fixed as an integer multiple of the operating frequency (that is, the carrier ratio is fixed), which can ensure that the harmonics are minimized at a relatively low carrier frequency, and in order to further obtain a good symmetrical effect, the synchronous modulation method of phase synchronization is adopted. That is, a vector with a fixed angle in one operating ...

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Problems solved by technology

[0003] In the traditional synchronous modulation method, the calculation of the SVPWM vector angle is based on the current operating frequency and carrier frequency (equation 8 below). The vector angle in the modulation stage changes randomly. In addition, it is limited by the carrier adjustment accuracy of the main control chip such as DSP and the truncation error of angle calculation, which will lead to a certain deviation in the phase angle of each fundamental wave cycle, and this deviation The continuous accumulation of will lead to continuous changes in the phase angle, resulting in the inability to achieve angular synchronization

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