Voltage Regulation: Tapping Distributed Energy Resources

Voltage Regulation

Reactive power is the key to an efficient and reliable grid.

Traditionally, the role of the distribution system is to provide the interconnection between the generation and transmission system and industrial, commercial, and residential load centers. The distribution systems generally can be considered to be passive networks- that is, they do little to dynamically regulate voltage. In contrast, the transmission system operator must deal with voltage problems that arise from a number of power-system events such as lost load, line or cable outages, dropped generation, capacitor bank outages, heavy power transfers, parallel flows, or unusually high or low load demands. The primary voltage control methods available to the operator include increasing or decreasing generation and adding or adjusting sinks or sources of reactive power in the system. In the future, real-time regulation of voltage at the customer's own buses may be best performed using local sources of active and reactive power, or distributed energy resources (DER). Local regulation is much more efficient with local sources, and the DER can supply precisely the level of regulation needed. In some areas it may be most economical for the distribution utility to supply only a nominal level of reliability, and the reliability would be elevated to the customer's requirements with DER.1 Within the customer's distribution system, some buses may be designated for critical or sensitive loads, and some may be for loads that could be reduced or shed if needed to maintain correct voltage at the critical loads. This concept already is occurring in some parts of the country.