Development of power hardware-in-the-loop simulation test-bed to verify DC system stability

Abstract

This thesis proposes a test-bed utilizing Power Hardware-in-the-Loop Simulation (HILS) to validate the stability of DC system. Typically, DC systems have a structure where source systems and load systems share a DC Bus. This structural arrangement can lead to impedance interactions between systems, potentially compromising the overall system stability. The test-bed implementation is crucial for analyzing and validating these phenomena. In this thesis, a test-bed is proposed that employs Power HILS to validate the stability of DC system, incorporating Ideal Transformer Method (ITM) and Damping impedance Method (DIM) within Power HILS. A comprehensive analysis of stability and accuracy is conducted, systematically examining the impedance interactions in the DC system using the Extra Element Theorem (EET) and the concept of uncoupled converter. Based on these analyses, precise simulations of non-ideal modeling in Power HILS are achieved. Additionally, a new offline DIM design method is proposed, considering the characteristics of Constant Power Load (CPL) in the load system and the input filter. Finally, this research introduces the Opposing Argument Criterion (OAC) to discern the stability of DC systems, employing a real 500-W Dual-Active-Bridge (DAB) converter. The effectiveness of the proposed test-bed and the proposed offline DIM design method are than validated. This thesis explores deeply into stability issues arising in the DC system composed of multiple converters, addressing challenges such as EET and the low-frequency voltage on the shared DC Bus. It underscores the importance of practical converter system stability tests and provides a comprehensive analysis of the impact of non-ideal characteristics in Power HILS on accuracy and stability.