Variable Active and Reactive Power Control Using OLTC in The Power Network

Renewable energy integration has introduced different challenges in the different stages in the power network, namely transmission and distribution. On the one hand, there is the voltage control through reactive power compensation and on the other hand, the need to avoid congestion as well as optimizing the utilization of the existing infrastructures due to large inflow of generated power. Therefore, it revolves around the balance of power control - be it reactive and active. With the variability in generation, variability in the control of active and reactive power is also required. This paper focusses on the Variable Shunt Reactor (VSR) and the Phase Shifting Transformer (PST) where the variability achieved by the use of On-Load Tap-Changers (OLTC).

The focus is on the extended regulation range offered by OLTC for variable shunt reactor along with the design challenges of the reactor. For the phase shifting transformer, the basic principle of phase angle regulation, the design and its applications will be discussed. As the OLTC plays an important role in PST, its selection depends on many factors, which will be detailed in the subsequent sections. To summarize, the advantages to the utilities through the use of OLTC's in these equipment, are discussed.