A Precise Stability Criterion for Power Hardware-in-the-Loop Simulation System

Power hardware in the loop (PHIL) simulation is an attractive option for power system testing, as it combines the benefits of real-time digital simulation and physical experiments. In view of the fact that only systems with pure resistance have been considered in previous literatures, this paper presents a systematic and comprehensive approach to evaluating stability of different types of impedance. A rigorous stability criterion of a PHIL system based on the ideal transformer interface model which utilizes Nyquist stability criterion is introduced in this paper. Phase lag caused by delay time in the PHIL system is considered to be the essential cause of instability and in terms of Nyquist criterion, relative positions of the starting and ending points of the Nyquist curve completely determine stability conditions. Effectiveness of the proposed stability criterion is verified by experimental results conducted by RT-LAB.