Improved model predictive control scheme for AC/DC matrix converters by considering input filter power ripple under imba
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ORIGINAL ARTICLE
Improved model predictive control scheme for AC/DC matrix converters by considering input filter power ripple under imbalanced grid voltage conditions Thanh‑Luan Nguyen1 · Hong‑Hee Lee1 Received: 25 May 2020 / Revised: 10 August 2020 / Accepted: 23 August 2020 / Published online: 7 September 2020 © The Korean Institute of Power Electronics 2020
Abstract The power ripple in the input filter is normally ignored in the conventional model predictive control scheme (MPC) of an AC/DC matrix converter under imbalanced grid voltage conditions. Unfortunately, this power ripple causes output power and current ripples. Some methods compensate this power ripple to obtain a ripple-free output current. However, these methods are generally complicated due to the increased computational and control burden or the use of a digital filter to estimate the power ripple. Moreover, the compensation of power ripple results in current distortion on the grid side, which has yet to be fully addressed. This paper presents an improved MPC scheme to simultaneously compensate input filter power ripple and reduce grid current distortion under imbalanced grid voltage conditions. The power ripple is calculated based on the grid voltage and its 90 electrical degrees delay signal, which makes the implementation simple without grid voltage components extraction or digital filter design. Furthermore, a closed-loop current controller is proposed to reduce the harmonic distortion of the grid current. The feasibility of the proposed MPC scheme is confirmed by both simulation and experimental results. Keywords AC/DC matrix converter · Model predictive control · Imbalanced grid voltage · Output current ripple
1 Introduction The AC/DC matrix converter (MC) has recently received a great deal of interest in research for AC/DC power conversion due to its significant advantages such as bidirectional power flow, sinusoidal AC current, and controllable input power factor [1–3]. AC/DC MCs provide single-stage AC-DC buck conversion and DC-AC boost conversion without an intermediate DC-link capacitor. In addition, they can achieve high conversion efficiency, high power density, and long life. All of these advantages make AC/DC MCs promising for industrial applications such as energy storage systems [4, 5], AC/DC microgrids [6], and vehicle-to-grid (V2G) systems [7, 8]. Model predictive control (MPC) has emerged as a competitive method to control power converters due to its advantages of simplicity, fast dynamic response, and flexibility in * Hong‑Hee Lee [email protected] 1
School of Electrical Engineering, University of Ulsan, Ulsan, South Korea
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terms of its ability to control different variables and constraints. Several advanced MPC schemes have been presented to effectively drive AC/DC MCs [9–11]. In [9], a proportional–integral (PI) controller was applied for an output current reference to improve the dynamic performance of the grid current. The quality of the grid and output currents of an AC/DC MC have been e
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