Abstract
Repetitive operation is extensively present in the inverter compressor refrigeration field. Research illustrates that an approximate periodic load disturbance deteriorates its self-sensing and efficiency in a low frequency range. According to an internal model theorem, a repetitive controller can realize periodic signal tracking or suppression; however, ideal repetitive control (IRC) can not be directly employed in practical application owing to its excessive sensitivity to period-time uncertainties or aperiodic component, etc. In addition, the ratio between period delay to sampling time can not always maintain an integer which causes the resonant frequencies to deviate from the interested. Even if the ratio is a fixed integer, the auxiliary function for stabilization in a conventional repetitive controller can result in the steady state tracking error. In this paper, a revised repetitive controller with a novel Savitzky–Golay (S–G) filter is proposed, the S–G filter cascaded with a traditional delay element can approximate the delay element with any ratio. Aiming at a different operating condition, a second order generalized integrator (SOGI) based observer is employed to extract disturbance fundamental component, and Steiglitz–McBride based adaptive notch filter (SM-ANF) is adopted for frequency estimation. The proposed scheme varies the S–G filter according to variable fundamental frequency and maintains its resonant frequencies corresponding with the fundamental and harmonic disturbance. In the end, simulations and experiments are implemented and results illustrate that speed fluctuation can be effectively suppressed by the proposed method.
Highlights
Owing to the characteristics of a simple structure, high power density, wide speed range and easy implementation, induction motor (IM) has been extensively replaced by a permanent magnetic synchronous motor (PMSM) in the inverter compressor refrigeration field
From the analyses mentioned above, it can be observed that both methods have some limitations which can be inappropriate for periodic disturbance suppression; the corresponding speed fluctuation ratio is still obvious in a low frequency range
The paper is organized as follows: the overall structure of inverter compressor control system is described in Section 2; in Section 3, the Savitzky–Golay (S–G) filter and the revised repetitive controller are introduced; in addition, the design method and implementation are presented; in Section 4, a disturbance observer based on a second order generalized integrator (SOGI) is proposed to extract a disturbance fundamental wave, and fundamental frequency is estimated by Steiglitz–McBride based adaptive notch filter (SM-adaptive notch filter (ANF)); in Section 5, simulation and experimental results are presented, which demonstrate validity and effectiveness of the proposed scheme
Summary
Owing to the characteristics of a simple structure, high power density, wide speed range and easy implementation, induction motor (IM) has been extensively replaced by a permanent magnetic synchronous motor (PMSM) in the inverter compressor refrigeration field. Aiming at specific frequency harmonic disturbance, phase compensation can be employed to broaden loop bandwidth, and an appropriate gain of RC can be determined to satisfy stability requirements [24] This method is sensitive to period-time variation or uncertainties, and it is unsuitable to suppress speed fluctuation for an inverter compressor driving in a variable operating condition. The paper is organized as follows: the overall structure of inverter compressor control system is described in Section 2; in Section 3, the Savitzky–Golay (S–G) filter and the revised repetitive controller are introduced; in addition, the design method and implementation are presented; in Section 4, a disturbance observer based on a second order generalized integrator (SOGI) is proposed to extract a disturbance fundamental wave, and fundamental frequency is estimated by SM-ANF; in Section 5, simulation and experimental results are presented, which demonstrate validity and effectiveness of the proposed scheme
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