A Control Scheme for Manipulation of Steady State Voltage Stability of Integrated Transmission and Distribution Networks

This paper furthers the concept of static stability limit breakdown margin for circuit elements and steady state voltage stability of unbalanced, multiphase integrated Transmission and Distribution (T&D) systems. For large multiphase system with multiple voltage levels, identification of weak links in the system and their reinforcement is demonstrated. As proposed previously, the reinforcement may come in the form of impedance modification, line addition or reactive compensation. Here, utilizing the impedance changing capability of distributed series reactors (DSRs), a control scheme is proposed for dynamic manipulation of voltage stability limits of system buses. This manipulation of stability margin enables flexible operation of the system, where the voltage stability limits of system buses can be changed to increase the net load capability of the buses in events of system contingencies and/or load/generation fluctuations. The proposed concepts are implemented using a robust power flow based on Graph Trace Analysis (GTA). Case studies demonstrate the effectiveness of the methods using an integrated T&D model formed from IEEE standard transmission and distribution models.