Power Conditioning Systems for Renewables, Storage, and Microgrids

This project develops measurement methods for Power Conditioning Systems (PCS) and associated High-Megawatt (HMW) power electronics technologies needed to provide dispatchable smart grid-enhanced interfaces for Distributed Energy Resources (DER) including Energy Storage. The PCS grid applications supported include smart grid interfaces for individual renewable/clean energy and storage systems including plug-in vehicles used as storage, as well as microgrids, and DC circuits.

Objective:  Establish by FY15 standards and measurement methods for grid PCSs and associated component technology needed to transition from today’s low penetration of non-dispatchable intermittent renewable energy sources to the future smart grid-enabled high-penetration of dispatchable distributed generators, storage, and microgrid architectures.  

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 electrical energy from one form to another; for example, converting between direct current (DC) and alternating current (AC), and/or converting between different voltage levels, and/or providing specific power qualities required by the subsystems being interfaced by the PCS.  Power electronics technologies and PCS applications have continuously progressed since the invention of the power transistor (the key enabling technology) and are transforming the way electricity is generated, stored, delivered, and used, as well as the way mechanical systems are actuated.

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 such as unity power factor (phase of AC current draw is aligned with AC voltage) and reduced waveform harmonics (reduced sinusoidal distortion of load current). The transition to PCS-based loads occurred over the last three decades, starting with low power loads and evolving toward high power loads such as today’s large variable speed electric motor drives (up to 100 MW).  The grid “power delivery system” itself has also begun to use PCSs such as Flexible AC Transmission System (FACTS) devices that inject corrective power waveforms into the grid, and High Voltage DC Transmission (HVDC) stations that convert between AC and DC for long distance transmission (at 1000 kV, 1000 MW levels).

On the other hand, only a fraction of power generators on the grid today are PCS-based (<<1% overall) and we are on the verge of a transformation to much higher penetration levels of PCS-based generators (>10%) that will occur over only a few years. The transformation is partially due to the addition of renewable/clean energy sources that produce DC (photovoltaic and fuel cell) or variable AC (wind turbines) and thus require a PCS to convert to regulated AC for the grid.  The distributed nature of solar energy also poses unique challenges in simultaneously meeting the requirements to provide grid stability by remaining connected during abnormal grid conditions, while also ensuring safety by deenergizing or separating into a microgrid island when the distribution grid goes down. Microgrids provide resiliency and power quality advantages to consumers and contribute to overall stability of the grid. Advanced, smart-grid-enabled PCS-based generator and microgrid functions developed as a result of this project are providing solutions to these and many other issues and will enable distributed generators to provide valuable grid supportive functions.

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, and distributed generators.  The project will enable DER to be used by utilities as multi-functional operational assets to manage local and regional grid operations including the ability to island into resilient self-sustainable microgrids.

The project plan has three tasks that address 1) metrology and standards for interface functionalities of PCS-based generators and microgrids, 2) advanced PCS technologies needed to support these applications, and 3) the transition through conformity and interoperability testing and application integration:

Task 1 – Grid PCS Performance Specifications and Test Methods:

• Establish sustainable process for advancement of PCS functionalities, international standards, regulatory and business models, conformity testing, and microgrid architectures to facilitate high penetrations of DER and enable a more resilient grid (FY12-13).
• Establish laboratory to address critical metrology challenges in conformity and interoperability testing of smart grid enabled PCS functions for grid interconnection of DER and microgrids (FY13-14).
• Develop and evaluate measurement methods and procedures to support industry conformity and interoperability testing of smart grid-enabled PCS functions (FY14)

 
Task 2 – Support Supply Chain for Grid PCS Enabling Technologies:

• Coordinate multi-agency programs to develop advanced PCS component technologies and system demonstrations and provide data and analysis enabling advancement (FY12-FY14).
• Develop measurement systems and methods to characterize performance of advanced PCS component technologies (FY13-14).
• Establish theoretical foundation, compact simulation models, virtual prototypes, and model parameter extraction and validation procedures for advanced HMW PCS technologies (FY14-15).
• Lead Interagency Advanced Power Group (IAPG), Electrical Systems Working Group (ESWG) and establish its multiagency microgrid effort, and facilitate the development of the High-Megawatt PCS Industry R&D Roadmap to identify power electronics technologies necessary to meet cost and performance goals for high penetration of DER and microgrids (FY12-FY14).

Task 3 – Microgrid PCS Testing and Application Integration:

• Phase 1: Functionality Development and Testing (FY12-13)
• Phase 2: Interoperability Testing in NIST Smart Grid Test Facility (FY14)
• Phase 3: Transition Microgrid PCS devices to applications (possibly Net Zero House)

Recent Results:  

Output: In FY10, this project defined PCS technologies needed to reduce the cost of high-megawatt fuel cell power plant grid integration systems for the DOE Office of Fossil Energy, and also developed an Interagency Advance Power Group (IAPG) roadmap for high-voltage PCS technologies defining the device and material goals required to meet multiple agency and industry needs, resulting in:

• Outcome: In FY10, the NIST High Megawatt PCS work was highlighted as a foundational approach to reduce cost of solar power grid integration at the Dollar Per Watt Solar Grand Challenge Workshop held by the U.S. Secretary of Energy in formation of the Sunshot Initiative.
• Outcome: In FY11, NIST was invited to become a member of the IAPG and the NIST Director signed the agreement.
• Outcome: In FY11, the DOE Solar Energy Grid Integration Systems program initiated a new project to demonstrate application of high-voltage silicon-carbide devices for solar power plant grid integration (first described in this project’s fuel cell study).
• Outcome: In FY12, this project coauthored a publication describing the first 15,000 V Silicon-Carbide Insulated Gate Bipolar Transistor (IGBT) developed for a DOE ARPA-E program, and also coauthored a publication describing the first 4,500 kV Hybrid Silicon IGBT/Silicon-Carbide Schottky diode module for a Navy ship power program. These devices were demonstrated for the first time in the unique NIST high-voltage, high-frequency power semiconductor device characterization facility developed for DARPA.
• Outcome: In FY12, based on information in the IAPG high-voltage semiconductor roadmap developed by this project, the Office of the Secretary of Defense initiated a new Army/Navy High-Voltage Silicon-Carbide Power Device Mantech Program and the DOE Assistant Secretary, Office of Energy Efficiency and Renewable Energy held a workshop to initiate a new cross-cutting DOE program on Silicon-Carbide (and other wide band-gap semiconductor) power devices.

Output: In FY11, the NIST Smart Grid Interoperability Panel (SGIP) approved the formation of the new Distributed, Renewables, Generators and Storage (DRGS), Domain Expert Working Group (DEWG) based on the proposal and leadership from this project, resulting in:

• Outcome: In FY12, DOE initiated a new program on Plug and Play Solar Energy that seeks to reduce balance of system costs using power electronics and smart grid enabled self-commissioning, self-monitoring, and safety enhanced wiring system.
• Outcome: In FY12, this project completed the design of a new Microgrid PCS Test Lab within the NIST Smart Grid Interoperability Test Facility. The lab is being constructed and integrated with other smart grid test labs.

Standards and Codes:  

Output: In FY09, this project initiated and led the NIST/SGIP Priority Action Plan 07 on “Interconection and Object Models Standards for DER and Electric-Storage,” and in FY 10 requirement for smart grid interoperability were transferred to the SDOs, resulting in:

• Outcome: In FY11, IEEE published standard 1547.4 “Guide for Design, Operation, and Integration of Distributed Resource Island Systems [microgrids] with Electric Power Systems.”
• Outcome: In FY12, IEC published document 61850-90-7 “Object Models for Photovoltaic, Storage, and other DER inverters,” and a new edition of  the IEC Standard 61850-7-420 “Basic Communication Structure - Distributed Energy Resources Logical Nodes” based on this document is expected in FY13.
• Outcome: In FY12, IEEE completed a third draft of standard P1547.8 “Recommended Practice for Establishing Methods and Procedures that Provide Supplemental Support for Implementation Strategies for Expanded Use of IEEE Standard 1547,” and the standard is expected to be completed in FY14.
• Outcome: In FY 12, IEEE 1547 was published as an International IEC Publicly Available Specification (PAS).
• Outcome: In FY 12, IEEE initiated the process to amend the IEEE 1547 base standard “Interconnection of Distributed Resources with Electric Power Systems” (that is adopted by most US States in accordance with the Federal Energy Policy Act of 2005).