SANDIA REPORT
SAND2016-4856
Unlimited Release
Printed May 2016
Analysis of PV Advanced Inverter
Functions and Setpoints under Time
Series Simulation
John Seuss, Matthew J. Reno, Robert J. Broderick, Santiago Grijalva
Prepared by
Sandia National Laboratories
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SAND2016-4856
Unlimited Release
Printed May 2016
Analysis of PV Advanced Inverter
Functions and Setpoints under Time
Series Simulation
Matthew J. Reno, Robert J. Broderick
Photovoltaics and Distributed Systems Integration
Sandia National Laboratories
P.O. Box 5800
Albuquerque, New Mexico 87185-1033
John Seuss, Santiago Grijalva
School of Electrical and Computer Engineering
Georgia Institute of Technology
777 Atlantic Drive NW
Atlanta, GA 30332-0250
Abstract
Utilities are increasingly concerned about the potential negative impacts distributed PV may
have on the operational integrity of their distribution feeders. Some have proposed novel
methods for controlling a PV system’s grid-tie inverter to mitigate potential PV-induced
problems. This report investigates the effectiveness of several of these PV advanced inverter
controls on improving distribution feeder operational metrics. The controls are simulated on a
large PV system interconnected at several locations within two realistic distribution feeder
models. Due to the time-domain nature of the advanced inverter controls, quasi-static time series
simulations are performed under one week of representative variable irradiance and load data for
each feeder. A parametric study is performed on each control type to determine how well certain
measurable network metrics improve as a function of the control parameters. This methodology
is used to determine appropriate advanced inverter settings for each location on the feeder and
overall for any interconnection location on the feeder.
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CONTENTS
1. INTRODUCTION.................................................................................................................. 11
2. MODELING ADVANCED INVERTER FUNCTIONS .................................................... 13
2.1. Advanced Inverter Functions Considered ........................................................................ 13
2.1.1. Ramp-Rate Control............................................................................................. 13
2.1.2. Fixed Power Factor Control ............................................................................... 13
2.1.3. Volt/Watt Control ............................................................................................... 13
2.1.4. Watt-Triggered Power Factor Control ............................................................... 14
2.1.5. Watt-Priority Volt/Var Control .......................................................................... 14
2.1.6. Var-Priority Volt/Var Control ............................................................................ 14
2.2. Example Simulations Demonstrating Advanced Inverter Functions ............................... 15
2.2.1. Weekly Irradiance, Load Selection, and Basecase Simulation .......................... 15
2.2.2. Ramp-Rate Control Example ............................................................................. 17
2.2.3. Volt/Var Control Examples ................................................................................ 18
2.2.4. Power Factor Control Examples......................................................................... 19
2.2.5. Volt/Watt Control Examples .............................................................................. 19
3. ANALYSIS METHODOLOGY ........................................................................................... 21
3.1. Study Feeders ................................................................................................................... 21
3.1.1. Feeder CO1......................................................................................................... 21
3.1.2. Feeder CS1 ......................................................................................................... 21
3.2. Measured Impact of Inverter Controls on Network ......................................................... 23
3.2.1. Network Metrics Considered.............................................................................. 23
3.2.2. Performance of Controls with Generic Parameters ............................................ 23
3.3. Scoring Positive or Negative Controller Impacts ............................................................ 29
3.4. Approximations Made to Reduce Computation Time ..................................................... 29
3.5. Search Algorithm to Find Optimum Settings per PV Location ....................................... 31
4. ADVANCED INVERTER CONTROL TYPE PERFORMANCE ................................... 35
4.1. Inverter Ramp-Rate Limiting ........................................................................................... 35
4.2. Constant Power Factor Control ........................................................................................ 37
4.3. Volt/Watt Control ............................................................................................................ 39
4.4. Watt-Triggered Power Factor Control ............................................................................. 44
4.5. Watt-Priority Volt/Var Control ........................................................................................ 49
4.6. Var-Priority Volt/Var Control.......................................................................................... 52
5. GENRALIZED CONTROL SETTINGS FOR EXAMPLE FEEDERS .......................... 53
6. CONCLUSIONS AND FUTURE RESEARCH .................................................................. 55
7. REFERENCES ....................................................................................................................... 57
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FIGURES
Figure 1. Example Volt/Var droop curve with a slope of 25∆𝑸/∆𝑽 and a deadband of width
0.02V. ........................................................................................................................... 15
Figure 2. Weekly load selected for QSTS simulation’s LDC selected as the least-square-error of
the yearly data’s LDC. ................................................................................................. 16
Figure 3. Weekly 1-minute resolution load and irradiance data selected for QSTS simulat
