An Adaptive Fixed-Time Cascaded Distributed Control for Bipolar-Type DC Microgrids Considering Time Delays

In this article, an adaptive fixed-time cascaded distributed control is proposed for bipolar DC microgrid (MG) to achieve current sharing and voltage regulation at fixed time while eliminating the accuracy deviation effect of time delay. Compared with parallel distributed control based on double information exchange, the proposed cascade controller releases space through local voltage compensation, simplifies the controller structure, and saves computational resources. In order to enhance the time delay resilience and regulation sensitivity of the cascade control, an additional intermediate variable information exchange and proportional control are introduced. Based on this, the fixed-time algorithm is introduced into the cascade control to realize the objective fixed-time convergence and an adaptive rule based on local information is designed to select the control gain to enhance practicality. In addition, the stability of the system is ensured by rigorous small-signal and Lyapunov stability analyses, the effects of various parameters on the dynamic performance are investigated, while convergence time bounds and time delay margins are obtained. Finally, the experimental validation of the bipolar DC MG shows that the proposed strategy achieves control objectives with the advantages of fast convergence and resistance to time delay.

I. Introduction

In Recent years, the DC microgrids (MGs) have received increasing attention as highly autonomous power systems with flexible integration of various distributed generators (DGs) [1]. Compared to conventional AC MGs, the majority of DGs and loads in DC MGs have DC nature that reduce the conversion link and make their structure simpler. Moreover, power quality, frequency regulation, and reactive power are avoided. Hence, DC MGs have high efficiency, reliability, and scalability [2] and [3].