Abstract
A predictive current control strategy can realize flexible regulation of three-phase grid-tied converters based on system behaviour prediction and cost function minimization. However, when the predictive current control strategy with conventional switching patterns is adopted, the predicted duration time for voltage vectors turns out to be negative in some cases, especially under the conditions of bidirectional power flows and transient situations, leading to system performance deteriorations. This paper aims to clarify the real reason for this phenomenon under bidirectional power flows, i.e., rectifier mode and inverter mode, and, furthermore, seeks to propose effective solutions. A detailed analysis of instantaneous current variations under different conditions was conducted. An enhanced predictive current control strategy with improved switching patterns was then proposed. An experimental platform was built based on a commercial converter produced by Danfoss, and moreover, relative experiments were carried out, confirming the superiority of the proposed scheme.
Highlights
During the past few decades, a large variety of active systems have been connected to the electric power system, including geothermal generators, photovoltaic systems, wind turbines, and so on
Various types of model predictive controllers have emerged as effective strategies and promising alternatives for the control of power converters and electrical machines [2,3,4,5,6,7,8,9,10,11,12]
One feasible solution for the application of MPC is known as continuous set model predictive control [13,14]
Summary
During the past few decades, a large variety of active systems have been connected to the electric power system, including geothermal generators, photovoltaic systems, wind turbines, and so on. Most of these installations are connected to the grid with the assistance of grid-tied converters. With continuous set model predictive strategies adopted, control actions are considered to be continuous. By contrast, another approach called finite set model predictive control regards these discrete switching actions as the constraints of the system inputs [15,16]. The control actions are constrained to the limited available switching states, instead
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