Decoupling Control of High-Speed PMSM——Digital Delay by Low Carrier Ratio and Smith Predictive Control
When the permanent magnet synchronous motor(PMSM)runs at high speed,due to the limited switching frequency of the inverter,the carrier ratio is low,and the problem of digital delay will be aggrava-ted,which directly affects the control performance of the system and even causes the system instability.Ai-ming at the problem of digital delay under low carrier ratio condition,the digital delay was modeled accurate-ly in complex vector form.The influence of digital delay on the system performance was analyzed based on the root locus of speed and current loop bandwidth,closed-loop zero pole diagram and bode diagram,and the critical instability speed of the system was given.Combined with the complex vector decoupling strategy,an improved decoupling and delay compensation current control strategy based on Smith predictive control was proposed.This strategy can avoid the instability of the system at high speed and low carrier ratio,improve the stability of the current loop,and the system has better dynamic response and decoupling performance.Simulink simulation was used to verify the effectiveness of the proposed decoupling and delay compensation control strategies.
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