Commercial Technology & SmartGrid Leadership

PV Powered Team Completes SEGIS Stage 2 Work

In the third quarter of last year, PV Powered was selected to receive a Stage 2 award under the U.S. Department of Energy’s (DOE) Solar Energy Grid Integration System (SEGIS) program. The program is designed to develop innovations that increase energy harvest, reduce the cost of PV systems, and remove barriers to high levels of PV penetration onto the grid. In this stage, just completed, the company led a team of recognized distributed energy and smart grid partners including Schweitzer Engineering Laboratories, Sensus, Northern Plains Power technologies, and Portland General Electric to produce results in two key areas:

1.) Improve on methods of power island detection in order to enable solar power systems to distinguish between situations where the solar power system should be isolated from the grid versus situations where the solar power system should stay connected to help the grid deal with disturbances, and

2.) Develop improved methodologies for Maximum Power Point Tracking (MPPT), that enable the inverter to maximize the power output for different types of solar arrays under different conditions.

In the first area of development, the PV Powered team demonstrated, using the Oregon Department of Transportation’s “solar highway” system in Tualatin, Oregon how synchrophasors (devices that make simultaneous comparisons of the power at different locations on the grid) can be used successfully to detect islanding conditions.

In the second area described above, the PV Powered team was able to show increases in energy harvest across the board for differing module type families using selectable tuned MPPT algorithms.

The work also demonstrated how distributed solar power generating sources can communicate with the utility’s control system software.

The technologies developed as part of the SEGIS program will contribute directly to lowering the levelized cost of energy (LCOE) and increasing the energy harvest for our inverter customers.

Now, it’s on to Stage 3!
 

Phase 2 SEGIS Contract

Now, with our recent award of the largest of the five Phase 2 SEGIS contracts from the U.S. Department of Energy, we are working with recognized utility industry leaders Portland General Electric, Sensus, and Schweitzer Engineering Laboratories to develop innovations that increase energy harvest, reduce the cost of PV systems and address the fundamental challenges, facing the utility industry, of significant PV deployment on the grid.

We believe the inverter is the logical and most cost effective component of a distributed PV system architecture and provides the optimum platform for:  

   Dynamic two-way grid communications 
   Low voltage ride through and ancillary services 
   Advanced smart BOS solutions for reduced installed cost and maintenance 
   High resolution PV resource forecasting 
   Mitigation of fast transients due to clouds
 

PV Powered SEGIS Program
Funded by the Solar America Initiative and under the supervision of Sandia National Laboratories, PV Powered has assembled a multi-disciplinary team of industry experts to solve core systems problems that are emerging as barriers to enabling high penetration of PV on the utility grid. The team has chosen to focus on two key areas:

1. Solving utility systems integration problems
2. Improving the energy economics of PV systems

PV Powered’s SEGIS Team:
Below is a brief overview of the industry experts who are actively involved in the SEGIS Program.
 

Northern Plains Power Technologies


PV industry veteran Dr. Michael Ropp of Northern Plains Power Technologies brings a wealth of industry experience with primary expertise in island detection and maximum power point tracking methods. http://www.northernplainspower.com/
 

Schweitzer Engineering Laboratories


Schweizer Engineering Laboratories is a known innovator and leader in the utility industry providing protection, monitoring, control, automation, and metering for electric power systems. http://www.selinc.com

Portland General Electric

Portland General Electric is a progressive utility in the Northwest who has developed innovative methods and programs for managing and controlling distributed energy resources including solar.  Click here to download the PGE case study, Putting the Smart Inverter to Work at Portland General Electric
http://www.portlandgeneral.com


Sensus

Sensus provides real world, proven solutions of high-value metering, Automatic Meter Reading (AMR) and Advanced Metering Infrastructure (AMI) system solutions for water, gas, electric and heat utilities. http://www.sensus.com

Program Overview
Product reliability is core to the approach of the PV Powered SEGIS Team. High reliability is a fundamental requirement for PV systems that are expected to provide a return on investment. PV Powered has developed a product development process that focuses on designing reliability into the product from the point of conception to market introduction. PV Powered products are the first to enable greater than 20 years of reliable operation in harsh PV operating conditions. Having successfully introduced an industry leading, reliability focused product line to the market, the team has now shifted focus towards innovating next generation architecture at the solar inverter system level. As solar power plants become more widespread, focus is required in the areas of utility interaction. Solar power plants of tomorrow must be considered by utilities as part of their overall generation asset base. The PV Powered team envisions a solar power plant that operates efficiently and seamlessly with utilities and building energy management systems providers. Additionally, the team plans to work on achieving gains associated with efficient, reliable operation of the entire solar power plant to achieve better energy economics – more kilowatt-hours (kWh) generated per dollar spent on the solar power plant. Below is some additional detail on the two core focus areas of the industry team led by PV Powered.

Primary Focus Areas
Utility Systems Integration
As PV penetration on the utility grids of America continues to rise, new problems begin to emerge. These problems are generally associated with two key areas:

1. Intermittent nature of the distributed PV resource
2. Conflict between utility needs and existing grid interconnect standards governing distributed resource connection to the utility grid.

Both of the above problem areas are complex and cannot be solved by one entity alone and will not likely be completely solved during the duration of the SEGIS Program. SEGIS funding has enabled PV Powered to assemble a team to lay the foundational groundwork to solve these problems. The final solution will only be realized when interconnection standards have been changed to embrace PV as a key utility energy generation asset. Additionally, smart grid communications infrastructure will likely be required to fully solve all of these problems at a level that addresses high penetration of PV in the case of residential solar distributed generation. To address the aforementioned problems, the team has focused on development in the areas described below.

Two-way Utility Communications and Control
PV Powered is working with Portland General Electric to integrate two way communications between the solar power plant and their GenOnSys distributed resource command and control (SCADA) system. This will enable the utility to disconnect their fleet of distributed resources remotely if needed, and receive status and assert control commands as necessary. Below is a screen capture of PGE’s GenOnSys Solar Dispatch Control application.

Smart Power Islanding Detection
One of the key focus points of distributed resource interconnection standard IEEE 1547 is to ensure an un-intentional power island never occurs for more than a very short period of time (less than two seconds) on a normal utility connected distributed resource (PV system). This function is typically performed by a sophisticated set of algorithms within the inverter that provide active control and passive monitoring to determine if an un-intentional island exists. These control and monitoring algorithms typically are self-contained within the inverter. A weakness to this approach is that the inverter cannot differentiate between the cases of an un-intentional island and a grid disturbance in which grid support from the PV system could assist in utility stability. Current methods lead the inverter to disconnect from the grid under circumstances when the additional generation is needed most. This problem will become increasingly severe as PV power plant grid penetration continues to increase.
The team is focused on demonstrating a new method for island detection leveraging synchrophasor measurements between the solar power plant and a utility reference synchrophasor measurement. This will enable the inverter to differentiate between a true un-intentional island case and a case where grid support from the PV plant is required. With this foundational block, the industry will have one of the key technology components in place to embrace increasing PV penetration.

Site Demonstration
The team has selected a solar demonstration site in Portland, Oregon serviced by Portland General Electric to demonstrate the utility integration technologies developed under the SEGIS program. Below is a photo of the site.

 

The team will demonstrate two-way communications and control, as well as the “Smart Power Islanding Detection” technique utilizing synchrophasors. Multiple abnormal grid operating conditions will be demonstrated. Portland General Electric, Schweizer Engineering Laboratories, NPPT and Sensus continue to be instrumental in developing the technologies for the site demonstration.

Energy Economics
The second major focus area for the team is energy economics. To achieve widespread adoption of PV, solar power plants large and small must be reliable, economical, installable, and serviceable. Funding from the SEGIS program is enabling PV Powered to lead development of new technologies and standards that will open the door for widespread PV adoption. One key area funded by the SEGIS program is bundled under the umbrella of “Energy Economics”. This includes three areas of development detailed below.

Energy Harvest
PV Powered is in the process of developing a new MPPT algorithm that provides highly accurate tracking efficiency over static and dynamic irradiance conditions for a wide range of PV technologies from high fill-factor technology like concentrated solar or mono-crystalline silicon to low fill-factor thin film technologies like copper indium gallium arsenide (CIGS) and cadmium telluride (CdTe). The team has acquired samples for each of these types of solar module and constructed “Mobile Solar Carts” to be used to develop and demonstrate improved energy harvest algorithms. These new algorithms will be evaluated and tuned under sun on the “Mobile Solar Carts”. A photo of a sample “Mobile Solar Cart” is shown below. The carts are designed as a test bed, making it easy to change module technologies, test varying tilt angles, and stringing combinations. Depending on the solar module technology installed, each cart will provide between 500 and 2500 Watts of available DC power under full sun. Two identical carts of each solar technology are being developed to enable rapid validation of algorithm improvements, while maintaining a “placebo” array to validate the results.

 

Additionally, the team is working to develop a proposed standard dynamic test plan for quantifying MPPT efficiency. MPPT is a key function of solar inverters and can affect overall solar power plant efficiency by a substantial amount, especially under dynamically changing irradiance conditions. As power conversion efficiency nears theoretical maximum, energy harvest and lifetime operating cost become key components of maximizing return on investment for solar power plant owners.

Energy Management Systems Integration
As building energy management systems become more ubiquitous and sophisticated there is an increasing demand to incorporate PV systems into the overall building energy management system. Energy management system controllers are designed to allow system owners to operate their facility in the most efficient and reliable way possible. The solar power plant is a key energy producing device that must connect and participate in the overall energy management equation. PV Powered is working with leading energy management system providers such as Tridium, Johnson Controls and Echelon to ensure that inverters can easily connect and add value to the facility energy management system. The team is developing communications protocols and demonstrating the ability to easily connect inverters to energy management systems. Once this is complete, the team will work with energy management providers to develop additional value associated with the combination of solar energy systems coupled to sophisticated energy management systems.

Improved Power Plant Balance of System Components
PV Powered has released a new smart string combiner product line called the IntelliString™. This smart combiner provides string level current monitoring, and also can provide monitoring for groups of strings in the case of thin film module technologies where string count is high and string current is low. SEGIS funding is enabling PV Powered to direct resources towards developing more tightly integrated balance of systems (BoS) components that can enable better system management and increase overall energy production at an acceptable cost. The IntelliString™ represents the first step. The team is now focused on tighter inverter integrated BoS monitoring and control components that will provide additional value to solar system integrators, owners, and operators. These advances will lead to less downtime and more predictable operation, improving the overall economic equation for solar power plants.

Summary
The SEGIS program is enabling technology and standards development that will enable the PV industry to work with established energy stakeholders including system owners and integrators, building energy management systems, and utilities. 

Click here to download our white paper, Laying the Foundation for the Grid-Tied Smart Inverter of the Future

To learn more about the SEGIS program, visit the Sandia National Laboratories website