Transitioning from Heterogeneous VSC to Homogeneous VSC Based Power Systems: Leveraging Dual-Port Grid-Forming VSCs

Abstract

Grid-tie voltage source converters (VSCs) can operate in three distinct modes: AC-dominant, DC-dominant, and balanced, depending on the placement of the stiff voltage sources, as shown in Figure 1. The distinct operation modes of VSCs typically require different synchronization control techniques. For instance, the grid-following (GFL) control, which utilizes a phase-locked loop to track the AC grid phase and frequency, can be employed for VSCs operating in the AC-dominant mode and the balanced mode. On the other hand, the grid-forming (GFM) control is utilized for VSCs operating in the DC-dominant mode and the balanced mode. Therefore, neither GFM control nor GFL control can serve as a universal synchronization control technique for VSCs to operate in all of the three modes. While the combination of the GFL VSCs and the GFM VSCs can handle applications that require the VSCs to operate in all of the three modes, effectively accommodating and coordinating the heterogeneous GFL and GFM VSCs remains challenging for power systems.