Power Conditioning Systems for Renewables, Storage, and Microgrids

Summary

This project develops the measurement science necessary to support the widespread use of advanced power electronics to provide new functionality in the smart grid supporting integration of new and variable resources. The introduction of variable renewables, responsive loads, storage and localized control into today’s electrical grid requires conversion of electric power from one form to another (AC to/from DC and/or conversion between different voltage levels), and requires conditioning the power quality needed by the subsystems being integrated. These functions are performed by Power Conditioning Systems (PCSs) that are a key enabler of large scale grid modernization.  This project researches tests and measurement methods for PCSs, and supports associated performance standards development to provide smart grid integration for these devices. PCS systems interface with the smart grid to support applications such as  renewable energy, demand response, and  plug in vehicles. A key goal of this project is to research interoperability of these devices in laboratory emulated microgrid scenarios as a precursor to deployment in selected building and campus scale microgrid demonstrations at NIST.

Description

Objective:  To establish standards and measurement methods, and test for smart grid and microgrid Power Conditioning Systems needed to transition from today’s low penetration of nondispatchable intermittent renewable energy sources to flexible grid operations that can actively adjust to varying grid conditions.

What is the new technical idea?  
The term Power Conditioning System (PCS) refers to the general class of devices that use power electronics technologies to convert electric power from one form to another; for example, converting between direct current (DC) and alternating current (AC), and/or providing specific operational interface functionalities required by the subsystems being interfaced by the PCS. Many “loads” on the power grid today are already interfaced through PCSs that provide the type of electricity needed by the load and also provide valuable grid interface characteristics.  A growing fraction of the power generation on the grid today is PCS based and the rate of penetration levels of PCS-based generation and storage is increasing very rapidly due to the addition of renewable/clean energy sources that produce DC (e.g., photovoltaic and fuel cell) or variable AC (e.g., wind turbines). 
 
Early standards and implementations for grid integration of distributed generation and storage (Distributed Energy Resources – DER) were intended for low penetration levels and are unable to ensure grid stability and safety for high penetration levels. The approach of this project is to use the PCS to provide an operational interface for DER that better meets these needs, enabling higher penetration levels and increased value proposition of the DER devices.  This NIST project participates in the international effort to coordinate standards and testing for PCS-based utility interactive grid support functions provided by DER (“Smart Inverters”). The project is also participating in the advancement of standards and test for future PCS-based grid architectures using microgrids to enable very high penetration level of DER, better grid resiliency, and more rapid grid restoration and recovery.

What is the research plan?
This NIST project addresses the critical standards and metrology gaps needed to support the transformation to high penetration levels of PCS-based distributed generators, storage and microgrids.  The project is enabling DER to be used as multifunctional operational assets to manage local and regional grid operations including the ability to island portions of the grid into resilient self-sustainable microgrids. Microgrids manage their own local resources and operations in both grid connected and islanded mode, and appear as a single controllable entity to the larger grid. Microgrids are an architectural construct that enable multi­level distributed control of the rapidly increasing numbers of DERs, controllable loads and other intelligent electric devices that are being connected to the grid.
 
The project plan has two tasks that address: 1) standards for advanced interface functionalities of PCS-based generators, storage, and microgrids, and 2) research application integration, interoperability, and measurement science associated with power conditioning systems. The first Task is accomplished by coordinating with industry and technical experts on development of interoperable standards for DER and microgrids, including through IEEE standards working groups and IEC technical committees, among others.  . To accomplish the second task, the project will complete construction, commissioning, and development of an integrated system control and data acquisition system for the microgrid research facility within the NIST Smart Grid Testbed.
 
The Smart Grid Testbed microgrid facility enables research on interoperability of PCS­based devices and controllers in microgrid scenarios. The lab also includes electrical interconnection and information exchange with devices and systems from other Smart Grid Projects located in adjacent labs within the overall Smart Grid Testbed.  

Major Accomplishments

Technology Transfer Outcomes: :  


 

• Several standards in the IEEE 1547 family and UL1741 have been developed and published, forming a technical foundation to support increased utilization of smart grid-interactive distributed energy resources (DER), and increased use of these standards is anticipated. Public rulemaking proceedings are also being conducted by FERC, the California Public Utility Commission and others referencing the need for the new functionalities of these standards. 
  • IEEE 1547.4 for grid islanding applications and IEEE 1547.6 for secondary networking were published. (FY11) 
  • UL 1741 Certification Requirements Document (CRD) "Special Purpose Utility Interactive Product Requirements" was published. (FY13) 
  • IEEE P1547.8 for advanced grid-interactive DER functionalities is on track for publication this year. (FY13) 
  • IEEE 1547a (Amendment 1 to IEEE 1547) is on track for publication this year, with modifications to address voltage regulation and frequency ride-through based on new functionalities needed to support interconnection of distributed energy resources. (FY13) 
  • IEC 61850-7-420 new edition is on track for publication in FY13 including the multifunctional electric storage, distributed energy resources operational interface of IEC 61850-90-7 (published this year) and harmonization and mapping with other standards. (FY13)