May 2004 NREL/SR-560-36243 Z. Ye, R. Walling, L. Garces, R. Zhou, L. Li, and T. Wang General Electric Global Research Center Niskayuna, New York Study and Development of Anti-Islanding Control for Grid-Connected Inverters National Renewable Energy Laboratory 1617 Cole Boulevard, Golden, Colorado 80401-3393 303-275-3000 www.nrel.gov Operated for the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy by Midwest Research Institute Battelle Contract No. DE-AC36-99-GO10337 May 2004 NREL/SR-560-36243 Study and Development of Anti-Islanding Control for Grid-Connected Inverters Z. Ye, R. Walling, L. Garces, R. Zhou, L. Li, and T. Wang General Electric Global Research Center Niskayuna, New York NREL Technical Monitor: B. Kroposki Prepared under Subcontract No. NAD-1-30605-01 National Renewable Energy Laboratory 1617 Cole Boulevard, Golden, Colorado 80401-3393 303-275-3000 www.nrel.gov Operated for the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy by Midwest Research Institute Battelle Contract No. DE-AC36-99-GO10337 NOTICE This report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof. Available electronically at http:/www.osti.gov/bridge Available for a processing fee to U.S. Department of Energy and its contractors, in paper, from: U.S. Department of Energy Office of Scientific and Technical Information P.O. Box 62 Oak Ridge, TN 37831-0062 phone: 865.576.8401 fax: 865.576.5728 email: mailto:reportsadonis.osti.gov Available for sale to the public, in paper, from: U.S. Department of Commerce National Technical Information Service 5285 Port Royal Road Springfield, VA 22161 phone: 800.553.6847 fax: 703.605.6900 email: ordersntis.fedworld.gov online ordering: http:/www.ntis.gov/ordering.htm Printed on paper containing at least 50% wastepaper, including 20% postconsumer waste iii List of Acronyms AC alternating current AI anti-islanding BPF band-pass filter DC direct current DG distributed generation, or distributed generator GE General Electric GEFS General Electric frequency scheme(s) IEEE Institute of Electrical and Electronic Engineers IGBT insulated gate bipolar transistor LVRT low-voltage-ride-through N/A not available, or not applicable NDZ non-detection zone(s) PV Photovoltaic(s) SFS Sandia frequency scheme(s) THD total harmonic distortion, or harmonics iv Acknowledgements The work has been contributed by the following team members: GE Global Research Center: Zhihong Ye, Lei Li, Luis Garces, Rui Zhou, Mark Dame, Peter Sanza, Ellen Liu, Richard Zhang, Timothy Wang, and Bill Premerlani. GE Power Systems Energy Consulting: Reigh Walling and Nick Miller. GE Industrial Systems: Jack DAtre. The authors would also like to thank Dr. Michael Ropp from South Dakota State University for his valuable comments. v Table of Contents List of Acronyms.iii Acknowledgementsiv List of Figures.vii 1 Executive Summary.1 2 Introduction .2 2.1 Background .2 2.2 Objectives7 2.3 Technical Approach 7 2.4 Report Outline.7 3 Grid-Connected Inverter Modeling8 3.1 Data for the Inverter Modeling8 3.2 Switching Model.9 3.3 Average Model9 3.4 Control Block Diagram.10 3.4.1 Constant Current Control.10 3.4.2 Constant Power Control.11 4 GE Anti-Islanding Concepts and Implementations.13 4.1 Basic Concepts13 4.1.1 Positive Feedback.13 4.1.2 DQ Implementation14 4.2 GE AI Implementations.16 4.2.1 Voltage Schemes16 4.2.2 Frequency Schemes17 4.2.3 Implementations for Single-Phase Inverter18 5 Design Guidelines Based on Frequency-Domain Analysis20 5.1 Stability Theory Based on Loop Gain.20 5.2 GE AI Design Guidelines22 5.2.1 Gain22 5.2.2 Band-Pass Filter .24 5.2.3 Limiter24 5.2.4 Quality Factor.24 5.2.5 Power Level25 6 Performance Evaluation with Time-Domain Simulation27 6.1 Performance Evaluation for Voltage Scheme .27 6.1.1 Baseline Case without AI.27 6.1.2 Voltage Scheme with P = 100 kW, Qf = 1.827 6.1.3 Voltage Scheme with P = 33 kW, Qf = 1.830 6.1.4 Voltage Scheme with P = 100 kW, Qf = 5.30 6.1.5 Voltage Scheme with P = 100 kW, Qf = 1.8, and Reduced Gain 30 6.2 Performance Evaluation for Frequency Scheme.34 6.2.1 Frequency Scheme with P = 100 kW, Qf = 1.834 6.2.