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Volt/VAR Optimization

Battelle Number(s): 30640
Clearance Number: PNNL-SA-151356
Patent(s) Issued
Available for licensing in all fields


Volt/VAR optimization (VVO) saves time and money, decreasing the amount of energy needed to provide end-use customers with unchanged quality of service. It is a process for managing voltage levels and reactive power to achieve the most efficient grid operation possible by reducing end-use energy consumption, peak demand, and – to a lesser extent – system losses. During the process, voltage control devices at a substation and on the circuit – such as tap changers, voltage regulators, and shunt capacitators – can be used to reduce the voltage drop from the substation to the end of the line and reduce the service voltage to customers while maintaining the voltage within defined limits. Efficiency gains are primarily a result of reducing the system voltage. These efficiency gains result in less energy consumed by the end-use equipment served by the distribution system, while maintaining the same level of service to the customer. The most common efficiency improvements are the reduction of end-use energy and the regulation of power factor to a specified value. When properly implemented, VVO systems provide end-use customers with the same quality of service and reduce annual energy consumption.

A VVO system has two main functional components. The primary function is the coordination of tap changers – typically at the substation – and voltage regulators at the substation, circuit locations, or both. The second function is the coordination of capacitors with a weighted dual objective of voltage flattening and power factor correction.

This invention creates a more efficient method of evaluating the effectiveness of a VVO system in reducing energy consumption and peak demand. It does this by using the change in active power demand through a small number of transitions from a VVO on-state to a VVO off-state and collecting data at time intervals for a period before and after the system is transitioned from the on-state to the off-state. Instead of the traditional day-on/day-off approach, the changes in active power demand from normal voltage control device operations are used. This method provides the possibility for a continuous estimate of system performance.


  • Enables accurate and continuous evaluation and validation of a utility’s VVO systems for peak and energy reductions, saving time and money. If integrated into VVO tools, this method of evaluating an optimization system could continually show system performance – not just when commissioned. Regulatory authorities require the validation, which typically is an expensive, two- to three-month, day-on/day-off evaluation process.
  • Allows utilities to perform their own VVO evaluation, rather than hiring an outside contractor, thus reducing costs and time consumption.

  • The method of evaluating change in energy consumption due to VVO disclosed in this invention takes less time than currently common evaluation methods and systems.


The invention – a method of evaluating an optimization system – allows utilities to perform VVO evaluations in less time than existing evaluation processes. Generally, outside firms are hired by utilities to conduct the evaluations and execute the analysis. Performing this function in-house reduces costs. The ability to continually provide an estimate of system performance enhances operations and can provide a basis for rate recovery decisions with regulators.


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