Passivity-Based Multisampled Converter-Side Current Control of LCL-Filtered VSCs

Abstract

With the gradually decreasing cost of high-performance digital processors, multisampling current control is a potential method to reduce the control delay and improve the stability in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> -filtered grid-connected converters. In the practical implementation, an antialiasing filter is required to remove the sampled switching harmonics and suppress the low-order aliasing. However, due to the phase lag from the antialiasing filter, the dissipative region of converter output admittance still cannot be lifted to switching frequency, which leads to a risk of system instability under wide grid admittance variation. In order to tackle this challenge, a filter capacitor voltage feedforward scheme using multisampling is proposed in this article. Consequently, the dissipation below the switching frequency is harvested for a three-phase converter. Furthermore, by doubling the multisampling rate, the proposed method can extend the dissipative region to the apparent switching frequency for a single-phase converter using unipolar modulation. The experimental results validate the effectiveness of the proposed method on a down-scaled single/three-phase converter.