A Method for Estimating the Current–Flux Curve of a Single‐Phase Transformer for Electromagnetic Transient Simulations of Inrush Currents

When a transformer is energized, inrush currents whose magnitudes may reach tens of its nominal current occur. Since the inrush currents lead to a voltage drop, this may cause stops and malfunctions of electrical appliances. In addition, the overcurrents may cause an unnecessary operation of an overcurrent relay and affect the power quality of the distribution system. Currently, distribution system operators use current‐versus‐time curves of transformer inrush currents for the studies of such phenomena. However, the studies based on the current‐versus‐time curve give approximate results, and studies based on the current‐versus‐flux curve is required so as to obtain accurate results. Considering this point, this report proposes a method to convert a given current‐versus‐time curve to a current‐versus‐flux one for the case of single‐phase transformers. Using the current‐versus‐flux curve obtained, detailed simulations can be performed using an electromagnetic transient analysis program such as XTAP. In this report, the proposed method is validated by experimental results using a single‐phase transformer.     

Voltage Control Using PV Power Factor,Static Capacitor,and Transformer Tap for Large PV Penetration

The Japanese government has set 53 GW as the target level of PV deployment by 2030. However, the large‐scale introduction of PV will cause several problems in power systems. One of these problems is the increase in voltage due to decreased load demands associated with large PV active power output. Another problem is voltage variations caused by fluctuations in PV system output. In this paper, we focus our attention on the voltage and reactive power control for large‐scale PV deployment and propose voltage control using the PF (PV power factor), SC (static capacitor), and TAP (transformer tap). In the proposed method, the SC and TAP controls consider voltage stability through the use of VMPI‐i and VMPI‐i sensitivity, and the PF control suppresses voltage variation and voltage spikes. Finally, we simulate these controls using the Ward–Hale system to verify the validity of the proposed method.