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Active noise cancellation frequency‑locked loop with a notch filter
Lei Pan,Dongxing Xu,Jingmei Zhang,Chang Yin,Zifeng Wu,Yingjun Guo 전력전자학회 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.12
To improve the performance of frequency-locked loops (FLLs) under distorted grid conditions, a series of pre-filtering techniques have been added to remove harmonics. One of them is the FLL-based comb filter (COMB-FLL), which offers a high disturbance rejection capability. However, it has some disadvantages, such as approximating a fractional delay and compensating an accumulated round-off error in the digital implementation of COMB-FLL. To alleviate these problems, this study proposes an active noise cancellation (ANC) FLL with a notch filter (NF), which incorporates an NF and an ANC to improve the frequency-locking ability. In this research, the structure of a comb filter is simplified into an NF, and an ANC is creatively introduced to eliminate harmonics from the frequency signal obtained by FLL. Furthermore, ANC has been improved to make it suitable for electricity-related applications. The proposed FLL features a unique cascade structure, which has excellent frequency-locking ability and dynamic characteristics under normal, abnormal, and harmonically distorted grid conditions. The simulations and experimental results verify the validity and reliability of the proposed FLL.
Pang, Yi,Zhang, Jingmei,Xu, Dongxing,Yin, Chang,Wu, Zifeng,Sun, Hexu,Pan, Lei The Korean Institute of Power Electronics 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.1
This paper proposes a model predictive control (MPC) algorithm designed for nine-switch converter with output filter (NSCOF) to control two three-phase AC loads independently. A state function of each leg of nine-switch converter (NSC) is established to characterize the internal conditions of the NSC because the traditional model of the NSCOF does not involve the interior model of the NSC. Based on the NSCOF model with the state function of each leg, a prediction model of NSCOF is constructed. The two AC terminals of NSCOF are treated as one module when the MPC is designed. The proposed MPC achieves controlling two three-phase AC loads working under different frequency modes. Furthermore, this algorithm is independent of the modulation method for reducing the difficulty of the controller design and its limits. The simulation and experimental results reveal that the steady-state and dynamic response performance of NSCOF are substantially improved using MPC.