Abstract

In low-voltage applications using low-Q LC filters, alias-free capacitor voltage acquisition can be achieved, but synchronous capacitor voltage sampling under high-Q filters used in high-voltage applications in grid-forming converters causes some degree of distortion and results in degradation of the power supply quality. And the 1.5 beat delay inherent in this approach limits the control bandwidth, reduces the stability region, and results in an inadequate time domain response. Despite these shortcomings, this approach is widely accepted in practice. This paper concludes that sampling 2us before the synchronous instant results in almost the same distortion as synchronous sampling, however, it can improve the dynamic performance of the system. A distortion-acceptable univariate feedback voltage dual-loop active damping control topology with much reduced computational delay is proposed, which is based on an internal active damping loop using a discrete lead compensator and a proportional resonance controller in the external voltage loop.