Online and Offline Stability Analysis Methods for the Power Electronic-Based Components in Design and Operational Stages

Power electronic-based components (PECs) are at the heart of the enabling technologies for the smart-grids. They improve the controllability of the power system and provide excellent features such as load regulation, high power factor, and transient performance. However, they can behave as negative impedance due to their capability to operate as constant power loads, and jeopardize the stability of the power systems. Therefore, stability analysis of the power electronic-based distribution systems is crucial for development of the future smart-grids. This paper provides two methods to analyze stability: real-time (online) and offline. In real-time approach, the system's small-signal stability is investigated based on d - q impedance measurement and unit circle criterion and by calculating source and load impedances simultaneously and in a range of frequencies. In offline approach, the system dynamics are identified from the bode plots and then based on the eigenvalue analysis, the stability of the system under different loading conditions is analyzed. Furthermore, small-signal stability of a solid state transformer (SST) as an advanced PEC with power factor correction is investigated via the proposed methods. In addition, hardware experiment is developed though power hardware-in-the-loop experiment to assess stability of an SST in load variation and validate the real-time capability of the proposed technique.