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Advanced Inverter Technologies Report

Advanced Inverter Technologies Report

Full Title: Advanced Inverter Technologies Report
Author(s): Elizaveta Malashenko, Stephen Appert and Wendy al-Mukdad
Publisher(s): Public Utilities Commission, State of California
Publication Date: January 1, 2013
Full Text: Download Resource
Description (excerpt):

This report examines the present and evolving capabilities of advanced inverter technologies for both primary and secondary distribution applications. Inverters are power electronics-based devices which convert direct current (DC) to alternating current (AC), a function which is fundamental to the integration of power from many sources into the distribution system. Inverters are widely used in conjunction with a range of Distributed Energy Resources (DER), particularly photovoltaic and wind turbine generators and energy storage resources. In these applications, inverters convert a generated or stored DC to a precisely modulated and grid- synchronized AC waveform. This waveform’s frequency is to be identical and to the grid frequency, enabling the supply of this electric power to an interconnected load or into the distribution system. Beyond this fundamental purpose and the requisite functionalities that this purpose entails, there exist a range of complementary, technologically viable, and demonstrated functions that an inverter may be designed to provide, including the following:

  1. Reactive Power Control. An advanced inverter has the ability to supply or absorb reactive power, measured in VARs, in the desired quantity. This provides for more efficient distribution and improved power quality.
  2. Voltage and Frequency Ride-Through Responses. In the presence of fluctuations in the distribution system’s voltage or frequency, this advanced inverter function seeks to correct the fluctuations by modulating reactive or active power, respectively. In the case of temporary and resolvable conditions, this can allow the DER to continue operation through a fault.

Advanced inverter functionalities represent a significant opportunity to improve the stability, reliability, and efficiency of the electric power distribution system, particularly as DER become incorporated onto the grid at higher penetration levels. Autonomous implementation of advanced functionalities could provide localized nodes of stability and control on a distribution feeder. When coupled through sophisticated communication, augmented protection, and intelligent control, interconnected advanced inverters could have significant beneficial impact upon the efficiency and reliability of the distribution system. Utility distribution automation or distribution management systems will be central to the integration of these functionalities, enabling necessary and sufficient communication, protection, and control measures.

Despite proof of concept by national electric power systems in Europe, implementation of these functionalities is not presently supported by the standards which govern inverters in the United States, preventing both widespread adoption of these functions and realization of the corresponding benefits to the distribution network. In addition, there is a lack of consistent U.S. interoperability and performance standards for inverters and inverter controllers to communicate with utility distribution management systems. This discrepancy will make full realization of the potential benefit of advanced inverter functionalities difficult, especially in the context of safely and reliably enabling higher penetrations of distributed energy resources.

All statements and/or propositions in discussion prompts are meant exclusively to stimulate discussion and do not represent the views of OurEnergyPolicy.org, its Partners, Topic Directors or Experts, nor of any individual or organization. Comments by and opinions of Expert participants are their own.

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