This review paper discusses power quality considerations for direct current (DC) electric power distribution systems, particularly DC microgrids. First, four selected sample DC architectures are discussed to provide motivation for the consideration of power quality in DC systems. Second, a brief overview of power quality challenges in conventional alternating current (AC) distribution systems is given to establish the field of power quality. Finally, a survey of literature addressing power quality issues in DC systems is presented, and necessary power quality considerations in DC distribution system design and operation are discussed.

Power electronics dominated systems, in particular systems including cascaded regulated converters, include converters that feed instantaneous constant power loads. To provide stable operation of buck converters with constant power loading, appropriate control of converter switching is required. In this work, the application of boundary control to buck converters with constant power loading is reviewed with a renewed focus on the synchronous topology, and the analysis and design of PD control for the same application is considered using geometrical insights from boundary control. The region of stable operation for the converter is verified using numerical simulation with ideal mathematical and switching models.