Fundamentals of Distribution System Voltage Control

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Course Overview

This course will start with the basics of distribution system voltage control. We'll look at examples of feeder configurations, voltage profiles, and planning calculations. You'll learn how tap changers, regulators, and capacitors interact with constantly varying loads to provide reliable and consistent voltage—from the substation to the customer meter. Next, we’ll explore the changing voltage profile of distribution feeders as a result of increasing levels of DER, including solar PV inverters. Finally, you’ll learn about emerging control methods, devices, and systems that will help you understand, analyze, manage, and mitigate “excursions” from acceptable voltages.

Course Outline


  • ANSI C84.1 Voltage Requirements
  • Overview of Voltage Drop Calcs
  • Overview of Power Flow

 Substation LTC Transformer Application

 Voltage Regulator Application

  • Line drop compensation
  • Load center compensation

 Capacitor Application

  • Sizing and placement

 Feeder Load Profiles and Voltage Profiles

  • Reactive power, voltage drop/imbalance
  • Radial and looped circuit

 Voltage and Loading Improvement Techniques

  • Phase balancing
  • Replacements of limiting equipment (wires and transformers)
  • Optimal placement of reactive power and voltage regulating assets
  • CVR (conservation voltage reduction)

 Application Examples – Reliability Improvement Methods and Technologies

  • Wire additions / replacements
  • Circuit reconfiguration / automation
  • Substation addition

Intro to DSSE (Distribution System State Estimation)

  • What is it? Why is it needed?
  • Input / output / algorithms
  • Transmission system state estimation vs. distribution system state estimation
  • Merging measurements, network models, and/or AMI for better state estimation

   Overview of ADMS Applications that Rely on DSSE

  • Basic and advanced applications
  • Volt-Var Optimization & (CVR)

   DSSE Applications, Examples, & Experiences

  • Challenges
  • Improvements

   Voltage Impacts of High DER Penetration

  • PV inverter operation overview
  • Output variability, controllability
  • Smart inverter capabilities
  • Smart inverter control strategies
    • Autonomous vs centralized
    • Autonomous volt-var control and characteristics curve

   Autonomous Inverter Volt-Var Control Challenges

  • Effectiveness
  • Unwanted oscillations
  • Var ramp-rate limit

   Overview – Var Compensation-based “Grid-Edge” Smart Devices

  • Ratings and types
  • Conventional vs new technologies for high DER penetration
  • Advantages of var-compensators

   Application and Operation of each type of Var-compensator

  • Secondary, Type 1
  • Secondary, Type 2
  • Primary


Muhammad Humayun

Muhammad Humayun is a Senior Consultant at EnerNex. He has over tenyears of project experience involving a broad range of power engineering topics. Muhammad’s expertise includesdistribution system planning, operation, and control; renewable integration, smart devices, smart inverter; protective relaying; distribution system state estimation; and reliability studies, load flow calculation methods, and contingency analysis. 

Muhammad conducts power systems studies using Synergi Electric, CYME, OpenDSS, MatLab, IEEE Flash, Visual Basic, Python, and other simulation tools. He has authorized or co-authored over 30 peer-reviewed articles.

Muhammad received a B.Sc. Degree in Electrical Engineering from the University of Engineering and Technology, Lahore, Pakistan, and his M.Sc. and Ph.D. Degrees in Electrical Engineering from Aalto University, Espoo, Finland, with majors in power systems.

David Mueller

David Mueller is the Director of Power System Studies with EnerNex. Since 1990 he has worked on a wide variety of projects to solve electric power problems. Dave has worked with companies such as Georgia Power, Dominion Resources, PSE&G, Duke Energy, Public Service of New Mexico, Delmarva Power, Wisconsin Electric Power Company, Con Edison of New York, Intel, Google, Apple, General Motors, East Midlands Electricity (UK), and the Electricity Supply Board (Ireland) to solve power quality problems.

Dave has also written many technical papers and articles on electric power quality,and has given over 100 presentations on these topics. He has presented these subjects in over 50 different cities,and has done work in over 25 different states in the U.S. Overseas, hehas presented power quality in around 13 countries.

Dave received a B.S.E.E. from University of Cincinnati, and a Master of Engineering from the Electric Power Engineering Department at Rensselaer Polytechnic Institute.

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Program Director

Kevin Rogers

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