Dynamic Reactive Compensation

Case ID: 01096



Dynamic Reactive Compensation



The voltage profile of distribution feeders in the traditional power system is illustrated in Figure 1 where the red series represents the primary feeder voltage and the red points as the customer service voltage.  The voltage starts out high at the beginning of the feeder (substation transformer) and drops as power flows through cables, distribution transformers, and service wires before reaching its customers.  With the advances in distributed generation e.g. solar rooftop photo-voltaic (PV), the customer service voltage can be higher than the feeder level voltage as shown in the second red point.  By utilizing the HNEI-CVR algorithm, the voltage drop across the distribution transformer is eliminated resulting in a leveled feeder voltage profile illustrated in the solid back line.  This provides the substation LTC to shift the entire feeder voltage feeder down (black dashed series) to maximize conservation voltage reduction.



Case ID:





Conservation voltage reduction (CVR) and Volt-Var Optimization (VVO) are methods used by utilities to improve the efficiency of the electric power grid and manage the quality of electric power service to customers by controlling and optimizing voltage on distribution feeders that run from distribution substations to end-use customers.  By controlling and essentially lowering the service voltage across a distribution feeder and at the service point of interconnected customers (while maintaining the service voltage within industry accepted operating standards), customers may experience direct energy reduction savings and utilities may achieve a reduction in energy distribution losses and improved utilization of distribution capital assets.


Technology Overview

Researchers at Grid System Technologies Advanced Research Team (GridSTART) of the Hawaii Natural Energy Institute (HNEI) within the University of Hawaii have invented a novel methodology and new algorithms that will operate autonomously to first determine the appropriate amount and then dispatch (produce or absorb) reactive power to control the service voltage on a distribution feeder by minimizing the voltage difference across a distribution service transformer (single phase, three phase, and the like) to improve upon the limited effectiveness of traditional CVR and VVO methods while balancing the cost of capital investment needed to achieve the desired goal.  The algorithms can either be installed in a stand-alone controller or may be integrated into existing field deployed controllers. The effect of this control is a significantly more even (flattened) and stabilized voltage profile across the length of a distribution feeder.  This flattening and stabilization of the feeder voltage profile from end to end will maximize the CVR benefits for the utility and its customers.  This method of voltage control is dynamic, automated, and is independent of circuit topology, location, and circuit reconfiguration and operational switching.

The current HNEI-CVR algorithm computes the amount of reactive power required to minimize the voltage difference across the distribution service transformer, thereby raising or lowering the service voltage bringing it closer to a uniform voltage throughout the feeder.  The reactive power required by the loads on the transformer can be provided using the HNEI-CVR device and other distributed Volt-ampere reactive (VAR) resources thereby eliminating the need for it to come from the electric utility, which reduces system losses.  The HNEI-CVR device is a fast acting device that can shift reactive power in the 1-2 second time interval.

The idealized solution to maximize CVR potential savings is to maintain a constant voltage along the entire feeder path, thereby allowing the maximum level of voltage reduction and consequent cost savings across the entire distribution feeder.  The current HNEI-CVR solution addresses the voltage difference across distribution service transformers which can greatly enhance overall feeder voltage management and CVR value realization. 

The HNEI-CVR solution currently looks at dispatching reactive power to manage voltage.  As the power grid evolves and communication to various distributed resources becomes available, controlling both the real and reactive power can be implemented at a lower cost, thereby creating a better cost-benefit ratio.



Utility customers may experience direct energy reduction savings

Utilities may achieve a reduction in energy distribution losses and improved utilization of distribution capital assets

Minimize voltage fluctuation on distribution feeders to support increasing levels of renewable penetration



A patent will soon issue on US Patent Application No. 15/644,262



Development partner

Commercial partner


University spin out



Key Words

Boost voltage

Buck voltage

Conservation voltage reduction (CVR)

Distribution Feeder

Distribution Transformer



Energy Conservation

Energy Efficiency

Peak Shaving

Power Factor Correction

Power Flow

Power Supply

Secondary Voltage

Service Point

Service Transformer



Voltage Management System

Voltage reduction Voltage regulation

Voltage regulator

Volt-Var Optimization (VVO)

Patent Information:
Leon Roose
Staci Sadoyama
Hsun Jou
Marc Matsuura

For information, contact:
Rafael Gacel-Sinclair
Technology Licensing Associate
University of Hawaii
Energy:Conservation Voltage Reduction
Energy:Voltage Optimization
Engineering:Voltage Regulation

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