An assessment of reactive power/voltage control devices in distribution networks

This paper provides an assessment of candidate voltage/reactive power control devices for distribution systems. The recent trend toward distributed energy resources (DERs), and distributed generation (DG), in particular, is often based on the rationale to support voltage and compensate for reactive power closer to the end users. This situation calls for a systematic approach to assessing alternatives for voltage control, both old and new. In this paper we illustrate on a simplified distribution network various voltage control devices, such as DERs, DGs, under-load-tap-changing transformers (ULTCs), static var compensators (SVCs), and supervar controllers. We illustrate how their dynamic characteristics differ. Moreover, we show that enhancing control logic of the existing controllers is often as good as adding the latest hardware. In order for such enhanced performance to be achieved a more involved system-wide coordination is often necessary. The ultimate decision is based on several criteria and it reflects trade-offs between the complexity of devices, their cost and communications requirements