A Practical Two-level Automatic Voltage Control System: Design and Field Experience

A practical two-level system-wide automatic voltage control (AVC) system has been developed, implemented and installed in a close-loop manner at several power systems. The architecture of this two-level system-wide AVC system is different from the traditional three-level hierarchical structure in that it is implemented centralized. Compared to three-level hierarchical structure, one distinguished feature of the two-level AVC system is that it does not require the need of performing zone division and it adapts to structural changes in network topologies. Another feature of the two-level AVC system is that it works even when the state estimation (SE) function at the underlying control center fails. To achieve a close-loop automatic voltage control, the two-level AVC system is equipped with two high-performance optimization-based voltage control modules: a reactive optimal power flow (ROPF) module and a corrective voltage control (CVC) module. In designing the AVC system, some domain knowledge and engineering judgments were developed and integrated in the overall solution method. At present, the two-level AVC system has been commissioned and put into a close-loop mode at three provincial power grids in China. The performance of the two-level system-wide AVC system has been very encouraging. This paper also describes some field performance of the AVC system.