Kara Clark

Frequency responsive wind plant controls: Impacts on grid performance

Grid integration of wind power plants is complicated by a number of issues, primarily related to wind variability and the electrical characteristics of wind generators. Frequency control is a particularly significant issue with high levels of wind and solar penetration. A typical wind plant appears to the grid as a substantially different generation source than a conventional power plant. A significant difference is that the wind energy source is inherently uncontrollable. In addition, the electrical characteristics of wind generators result in a disturbance response that is naturally different from that of conventional synchronous generators. Without special controls, a wind plant does not inherently participate in the regulation of grid frequency as do synchronous machines. And, when wind generation displaces conventional synchronous generation, the burden of frequency regulation placed upon the remaining synchronous generators is increased. The paper summarizes results from a recent investigation of system frequency response in the Western US as it may be affected by large amounts of wind generation. Impacts and benefits of wind plant controls that provide frequency response are illustrated with quantitative examples. Both inertial and primary frequency response behaviors are examined.

Advanced controls enable wind plants to provide ancillary services

Grid integration of wind power plants is complicated by wind variability and the technical characteristics of wind generators. At high levels of wind power penetration, the need for several types of ancillary services increases while the traditional resources that provide those services may become less economic or available. This paper describes a suite of advanced wind plant controllers designed to improve system performance, reduce the need for additional ancillary services, and provide ancillary services instead of or in competition with conventional resources. Wind power plant controls can coordinate the real and reactive power response of multiple wind turbines and thereby make the plant function as a single “grid friendly” power generation source. The real power controls include active power regulation, frequency or governor response, power ramp rate limiter, start up/shut down sequencer, and inertial control. The reactive power controls include voltage regulation with or without active power production, reactive power or power factor control, and various fault ride-through capabilities.

Impact of High Solar Penetration in the Western Interconnection

This paper presents an overview of the variable characteristics of solar power, as well as the accompanying grid dynamic performance and operational economics for a system with significant solar generation. The paper will show results of economic operational simulations of a very high solar generation future for the western half of the United States.

Solar photovoltaic (PV) plant models in PSLF

Photovoltaic (PV) electric power generation may be a significant grid resource in the future. As such, there is an industry need for appropriate models for transmission and/or distribution planning studies. This paper describes the latest positive sequence, fundamental frequency models of GE solar PV plants. The model is as detailed as is appropriate for bulk power system studies, where the analysis is mainly focused on how the solar plant reacts to grid disturbances, e.g. faults or voltage excursions on the transmission system.

Validation of GE wind plant models for system planning simulations

GE Energy has an ongoing effort dedicated to the development of models of GE wind turbine generators (WTG) suitable for representing wind plants in system impact studies. This paper documents the present recommendations for dynamic modeling of GE wind plants using either Doubly Fed Asynchronous Generators (DFAG) or Full Conversion (FC) technology. This includes GEs 1.5 and 1.6 MW, as well as 2.5 and 2.75 MW WTGs. The paper presents both the overall model structure and validation results for the non-generic GE equipment models. The assumptions, capabilities and limitations of the plant model will also be discussed.

Hybrid wind and advanced gas turbine farms: firm dispatchable power for weak grids

The variability of power generation from wind farms presents an operational challenge for power systems with significant penetration of wind generation. In weak or relatively small systems, control of system frequency and power exchange can impact the viability of wind farms. The emergence of highly maneuverable, high efficiency simple-cycle gas turbines allows for hybrid wind/gas turbine systems with superior dynamic performance.

Western Wind and Solar Integration Study Phase 3A: Low Levels of Synchronous Generation

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. NREL and GE also thank the members of the technical review committee for their insightful comments and assistance. Participation in the committee does not imply agreement with the project findings. The committee included: NREL regrets any inadvertent omission of any project participants and contributors. CSCR composite short-circuit ratio CSP concentrating solar thermal power plant DG distributed generation, embedded PV ERMVA effective renewable MVA GE General Electric GW gigawatt HVDC high-voltage direct current Hz Hertz LCC line commutated converter LVPL low-voltage power limit mHz millihertz min minute MVA megavolt ampere MW megawatt NERC North American Electric Reliability Corporation NREL National Renewable Energy Laboratory OEM original equipment manufacturer PV photovoltaic solar power, utility-scale photovoltaic power plant RAS remedial action scheme REMTF WECC Renewable Energy Modeling Task Force s second SCMVA short-circuit MVA SCR short-circuit ratio VSC voltage source converter WECC Western Electricity Coordinating Council WTG wind turbine generator WWSIS Western Wind and Solar Integration Study vi This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications. Executive Summary The stability of the North American electric power grids under conditions of high penetrations of wind and solar is a significant concern and possible impediment to reaching renewable energy goals. The 33% wind and solar annual energy penetration considered in this study results in substantial changes to the characteristics of the bulk power system. This includes different power flow patterns, different commitment and dispatch of existing synchronous generation, and different dynamic behavior from wind and solar generation. The Western Wind and Solar Integration Study (WWSIS), sponsored by the U.S. Department of Energy, is one of the …

Wind Generation Applications for the Cement Industry

Wind generation is the fastest growing power source over the past decade and this growth is forecasted to continue. The latest wind turbines have robust designs for reliable performance and increased energy capture, as well as sophisticated control systems that support electric system requirements and enable cost-effective operation. While the majority of wind plants are being connected to the utility transmission grid, applications are growing among industrial users. Within the industrial segment, cement is a leader in promoting emission reductions and generating power through cleaner technology. However, the integration of conventional wind plants into industrial systems presents challenges to both operation and security, including: (1) Tripping due to transmission system faults (2) Voltage fluctuation under varying wind conditions (3) Inability to control active power production (4) Lack of reactive power control and voltage regulation in the absence of wind New wind turbine generator and wind plant technologies have substantially improved system performance. This paper mainly focuses on the requirements of cement plants, and the ability of the latest wind turbine technology to meet those requirements. The paper illustrates the performance of a wind plant integrated with a cement plant. A short discussion of the economic trade-offs and decisions surrounding industrial self-generation with wind is provided as well.

Impact of Market Behavior, Fleet Composition, and Ancillary Services on Revenue Sufficiency

This presentation provides an overview of new and ongoing NREL research that aims to improve our understanding of reliability and revenue sufficiency challenges through modeling tools within a markets framework.

Transient Stability and Frequency Response of the Us Western Interconnection Under Conditions of High Wind and Solar Generation

The addition of large amounts of wind and solar generation to bulk power systems that are traditionally subject to operating constraints set by transient stability and frequency response limitations is the subject of considerable concern in the industry. The US Western Interconnection (WI) is expected to experience substantial additional growth in both wind and solar generation. These plants will, to some extent, displace large central station thermal generation, both coal and gas-fired, which have traditionally helped maintain stability. This paper reports the results of a study that investigated the transient stability and frequency response of the WI with high penetrations of wind and solar generation. The main goals of this work were to (1) create a realistic, baseline model of the WI, (2) test selected transient stability and frequency events, (3) investigate the impact of large amounts of wind and solar generation, and (4) examine means to improve performance.