Review of PREPA Technical Requirements for Interconnecting Wind and Solar Generation

The U.S. Department of Energy (DOE) and the National Renewable Energy Laboratory (NREL) have partnered with the Government of Puerto Rico to assist in addressing barriers to the deployment of energy efficiency and renewable energy in Puerto Rico. This document provides an overview of the minimum technical requirements (MTR) for interconnection of wind power and photovoltaic generation developed by the Puerto Rico Electric Power Authority (PREPA). Integrating a large amount of variable renewable generation such as wind and solar into an electrical grid presents several potential challenges for operating a power system, particularly with small island grids like the Puerto Rico electrical system. Establishing valid technical requirements for interconnection of variable renewable generation to the electric grid is an important step in overcoming such challenges. The interconnection requirements need to address several important aspects of renewable integration such as safety, impacts on power system reliability and performance, and costs. Being an isolated island system, PREPA does not fall under Federal Energy Regulatory Commission (FERC) jurisdiction, and therefore FERC interconnection standards are not required to be applied to generators in Puerto Rico. In this regard, PREPA has developed its own set of interconnection requirements with which all transmission-level wind and solar PV generators shall comply. In this report, NREL provides an impartial third-party review of PREPA’s MTRs, drawing comparisons with other similar requirements and best engineering practices. Over the course of the collaboration on the MTR review (2012-2013), PREPA revised the MTRs based on the draft review. As such, PREPA’s responses to the recommendations are also included in this report. The PREPA MTRs are anticipated to constantly evolve as the level of renewable penetration increases, modeling tools are improved, and experience with system performance increases. This review is intended to assist PREPA in this process. Acknowledgements The authors would like to acknowledge the substantial contributions to this report provided by staff at PREPA, the Governor’s Office, and the Puerto Rico Energy Affairs Administration (PREAA). NREL worked closely with staff from PREPA, PREAA, and the Governor’s Office throughout the technical review of PREPA’s MTRs to ensure accurate understanding of Puerto Rico’s electricity grid and the status of renewable energy integration. The authors would like to particularly thank Martin Perez, Luis Francis, Alvin Roman (PREPA) and Efrain O’Neill (Governor’s Energy Affairs Advisor) for their significant contributions and support of this effort, especially for reviewing the recommendations and providing a summary of PREPA’s responses. The authors would also like to thank Jennifer DeCesaro and Steve Lindenberg from DOE who sponsored this work, this effort could not have been completed without their support and involvement. This report is available at no cost from the National Renewable Energy Laboratory (NREL) iv at www.nrel.gov/publications. List of Abbreviations and Acronyms AGC automatic generation control DER distributed energy resources DFIG double-fed induction generator ERCOT Electric Reliability Council of Texas FESTIV Flexible Energy Scheduling Tool for Integration of Variable Generation FRT fault ride-through HECO Hawaiian Electric Company HVRT high-voltage ride-through Hz hertz IEC International Electrotechnical Commission IEEE Institute of Electrical Engineers & Electronics Engineers kV kilovolt LVRT low-voltage ride-through ms millisecond MTR minimum technical requirements MVA mega volt ampere MVAR mega volt ampere reactive MW megawatt NERC North American Electric Reliability Corporation PFR primary frequency response PSLF Positive Sequence Load Flow POI point of interconnection PQ power quality PPA power purchase agreement PRC protection and control PREPA Puerto Rico Electric Power Authority PSCAD power systems computer aided design PSS/E power system simulation for engineering PV photovoltaic RR ramp rate SCADA supervisory control and data acquisition SCR short circuit ratio STATCOM static synchronous compensator SVC static VAR compensator VAR volt ampere reactive VRS voltage regulation system WPP wind power plant WTG wind turbine generator ZVRT zero-voltage ride-through This report is available at no cost from the National Renewable Energy Laboratory (NREL) v at www.nrel.gov/publications. Table of