부산대학교 도서관

Unified Virtual Oscillator Control (uVOC) is a time-domain control law that combines grid-following control (GFL) and grid-forming control (GFM). Despite extensive stability analysis of uVOC and similar control schemes, the impact of digital control delay remains unexplored. This delay, stemming from the digital control period to avoid algebraic loops, introduces a significant steady-state power error in reactive power tracking, posing challenges in determining an appropriate droop coefficient for reactive power and voltage magnitude. Moreover, the delay induces oscillations at twice the fundamental frequency in active and reactive power, resulting in elevated power losses. This paper presents a comprehensive quantitative analysis establishing the correlation between steady-state power errors and digital control delay. Furthermore, it conducts a qualitative analysis to investigate the underlying causes of these oscillations. To mitigate the effects of the time lag, a lead function is proposed as a countermeasure. The effectiveness of this lead function is validated through simulation studies, encompassing the elimination of steady-state power errors, attenuation of power oscillations, and influence on the system's dynamic response.