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In order to reduce the chattering and phase shift, this article proposes an enhanced sliding mode observer (SMO) for the sensorless control of permanent magnet synchronous motor (PMSM). In the conventional SMO, a low-pass filter (LPF) is commonly employed to extract the back electromotive forces (EMFs) from the sliding mode switching function, which brings the phase shift and degrades the precision of position and speed estimations. In this article, a frequency-adaptive complex-coefficient filter (FACCF) is adopted to replace the LPF. Since the FACCF has no phase shift and amplitude attenuation at the central frequency, it can be used to extract the EMFs without distortion while the chattering can also be suppressed. For an easy parameter design, the normalized phase-locked loop is used to obtain accurately the position and speed estimations. The experiments are carried out on a 3-kW PMSM drive, and the results verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper presents an active state-of-charge (SOC) balancing control strategy for modular super capacitor energy storage system (ESS). The strategy has a master–slave structure, including a common dc bus voltage loop and individual slave current loop for each submodule. The common voltage loop ensures the ability of the system to stabilize dc bus voltage cannot be affected by SOC balancing control, and provides a same original current reference for all submodules. SOC information is introduced into current loops to achieve SOC balancing control. The highest SOC is taken as a reference for low SOC modules, thus, the low SOC modules can regulate the submodule average operation current according to the SOC reference and their own SOC. In order to minimize system current deviation caused by the introduction of SOC, a current correction method is proposed to improve system current regulate performance. The proposed strategy can achieve SOC balancing control during ESS charging and discharging process dynamically, in addition, the modularity of the system is improved and the proposed strategy has favorable stability. A modular ESS prototype consisting of three half-bridge submodules is tested in the laboratory, and the experimental results verify the effectiveness of the proposed control strategy. [ABSTRACT FROM AUTHOR]