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UT Power Engineering Laboratory - "Powering the Future "

Reactive Power Planning


Wenjuan (Wendy) Zhang
Dr. Fangxing Li
Dr. Leon M. Tolbert


Reactive power is critical to support voltage and regulate power factor in electric power systems. However, the reactive power in US power systems was not very well planned and managed, as evidenced by the Great 2003 Blackout that occurred in northeastern US and Canada in August 2003. Thus, the U.S. Department of Energy has funded a project at Oak Ridge National Lab to study Distributed Energy Resources for Reactive Power Compensation.

Reactive power planning, also referred to as VAR planning or optimal VAR source allocation, involves optimal location and sizing of the VAR source. It aims to identify the best tradeoff between the investment cost of new VAR source and the benefits in system operations derived from the presence of additional reactive compensators.

This research consists of four parts. First, a literature survey is made on static and dynamic reactive power planning. Second, a generalized assessment of the economic benefits from reactive power compensation is proposed. Third, the sensitivity analysis of the economic benefit of reactive power compensation is presented and modeled. Last, the generalized reactive power planning model considering voltage stability margin is summarized.


GAMS (General Algebraic Modeling System)
MINOS (NLP solver)
DICOPT++ ( MINLP solver)

fig 1. B1-B3 & Bt versus Var compensation at bus 3

In one word, continuously increasing Var is not necessarily better; the benefits may decrease at some point with the Var compensation increasing.

Related publications and presentations

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