Interoperability Standards and Open Testing Framework to Support High-Penetration Distributed Photovoltaics and Storage
High penetration of legacy inverters on the California grid can exacerbate problems associated with grid stability. While power technology to address grid operating variability exists in inverters—for example, voltage and frequency excursions, power surges or sags—a standard and cost-effective communication interface, to monitor and control inverter functions, has not been broadly deployed. Without this interface, it is expensive and risky for grid operators to monitor and control diverse DER assets, participation in ancillary services markets is beyond reach, and the market for PV systems could be severely constrained.
With increased PV penetration, and lacking an effective solution, California could face a crisis within the next few years that will be costly to address and that could stifle the market. While the international standards community acknowledges this technology gap, development of international standards is slow. Experts have stated that appropriate international communication standards may take a full decade to be realized. To fill the gap, the SunSpec Alliance, including the majority of leading inverter manufacturers and fleet operators, has developed a de facto communication standard that is harmonized with the future international standard (IEC 61850-90-7). What is missing is the availability of a test framework to prove interoperability, empirical data to validate the effects of smart inverters on the grid, and market data to evaluate the economic impact that smart inverters bring.
This project will deliver a turn-key, smart inverter standardization and go-to-market solution to enable high PV penetration beyond the 15% IEEE guideline. The core of the solution is a collection of smart inverter brands (seven manufacturers), all supporting the CA Rule 21 smart inverter functions and the open SunSpec communication interface. This interface is compatible IEEE 1547, low-cost, scalable from residential to large-scale commercial systems, and results in plug and play compatible solutions. This new capability fills a critical technology gap, enables grid operators to monitor and control DER assets cost effectively, improves grid stability, and enables DER systems to participate in ancillary services markets.
The CA Rule 21 smart inverters are complemented by a smart inverter test framework and open source software software tools to enable rapid product development and safety testing. To estimate grid impacts, power flow models to emulate target feeder conditions will be created. To validate the power flow models, and to prove interoperability with wholesale electricity markets, a 50 unit pilot test will be deployed and circuit data will be collected. Finally, the project team will assimilate and analyze the data collected during the lab tests and field pilot to demonstrate the validity of the predicted benefits specified in the project goals.
Anticipated Benefits for California
This project will provide significant public benefits to California IOU electricity ratepayers by meeting EPIC goals including lower costs for electricity, more reliable electricity supply, and reduced emissions.
IOU Cost avoidance for circuit upgrades: Studies suggest that savings of $0.16 to $0.30 per installed watt are achievable. With smart, interoperable inverters, DER can perform many tasks that are now performed by specialized distribution grid equipment (e.g. volt/var control, curtailment, frequency regulation). Cost avoidance for grid upgrades can be achieved by adding smart DER capacity to circuits.
Reduced system installation and commissioning costs: At California labor rates, savings of $0.03 to $0.06 per watt for residential systems can be achieved. A standard communication interface like the one proposed in this project will result in a reduction of approximately three- to six hours of labor per installation.
Reduced monitoring system maintenance costs: The lifetime cost benefits of a standard communication interface can result in a $0.02 per installed watt savings due to decreased need for specialized labor. Many fleet operators support three or more monitoring systems and need to employ specialized personnel as a result.
Reduced monitoring system switching costs: Savings from standardization can provide $0.05 per installed watt savings in avoided switching costs. Plug and play capability means that the sensor components and software interfaces can be preserved. Factory integration also provides savings.
Improved power delivery reliability: The testing of smart inverters will demonstrate that higher levels of PV penetration can be achieved, with fewer conventional generating sources, while providing enhanced reliability by delivering services that were previously provided by conventional generating sources.
Improved capacity optimization and flexibility: Integration of energy storage with renewables provides greater flexibility to local capacity and increases reliability through improved capacity optimization. Energy storage can also help reduce loads and provide services like ramping and voltage support to maintain reliability.
Decreased GHG emissions: As a byproduct of comparing the pre-installation and post-installation load profiles of the facilities participating in the field demonstration, the project team will estimate the resulting GHG emissions reductions.
California Energy Commission contract number: EPC-14-036
Prime Contractor: SunSpec Alliance
Partners: Kitu Systems, University of California at San Diego, CAISO, and others
In-Kind Contributions: $2,066,875 from major and minor project partners
Term: July 2015 to March 2019