VAR flow control for grid capacity optimization

Increase or decrease in the reactive power (VAR) load requirements on any bus leads to voltage fluctuations at that bus. Therefore, VAR flow control is very crucial for the integrity of power systems as it may lead to voltage instability or severe circulating current. The circulating current in the power systems will cause system stresses and will reduce the generator´s capacity. Therefore, a quick automated control system is needed to continually regulate the VAR flow. This can be done through the VAR control system in either the generator or the transformer; however, a very sophisticated control system is needed for coordination between them. In this paper we will share our experience in deploying an advanced technique to coordinate between all VAR systems to stabilize the voltage and minimize the circuiting current. We utilized the existing Distributed Control System (DCS) infrastructure, in one of the local industrial plants, to automate the VAR regulation without adding any additional components. The new logic detects any voltage instability or any circulating current and selects the most appropriate VAR system, whether it is a generator VAR or a transformer VAR, to correct the VAR flow. At the end, the voltage will be fixed. In this paper we will describe how this package works, the system logics, and the system operations.