A Reactive Power Compensation Scheme Using Distribution STATCOMs to Manage Voltage in Rural Distribution Systems

Flexible ac transmission system (FACTS) devices are often a recommended option for improving power quality. The most common shunt-connected FACTS device, namely the STATCOM, has become a viable option for distribution systems and has been employed for mitigating instances of voltage fluctuation, voltage unbalance, and in some cases harmonic distortion. As a distribution application, it has been termed D-STATCOM. D-STATCOMs also aid reducing the amount of reactive power drawn from the distribution system, reducing overall ampacity and aiding voltage management. However, it is well known that the degree of compensation provided by a D-STATCOM is a direct relationship with the system X/R ratio. For typical distribution systems, this results in large reactive power rating to perform appropriately. Unless an optimized reactive power scheme is developed, this will translate into large equipment rating near its installation site. This paper proposes a distributed reactive power management scheme, where reactive power is provided by one or more D-STATCOMs. The scheme is intended to boost low steady-state voltages and its output prescribes the instantaneous reactive power output of each participating D-STATCOM. For system boundary conditions, it also dictates the device rating. The proposed method is supported by an analytical development that estimates the amount of outputted reactive power to manage the voltage with a planning-specified voltage rise. Case studies representing real rural distribution systems applications are presented to demonstrate the proposed scheme.