Two-way Utility Communications and Control
In Stage 2, PV Powered worked 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 enables 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.
Figure 1 GenOnSys Solar Dispatch Center
Smart Power Islanding Detection
One of the focal points of the distributed resource interconnection standard IEEE 1547 is to ensure an un-intentional power island does not occur as a result of the connected distributed generation. This function is typically performed by a sophisticated set of algorithms within the distributed generation (inverter) that provide active control and passive monitoring to determine if an un-intentional island exists. These control and monitoring algorithms are typically self-contained within the inverter. A weakness to this approach is that the inverter may not be able to differentiate between the cases of an un-intentional island and a grid disturbance in which support from the PV system could assist in utility stability. Current methods (and established standards) 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 has developed a new synchrophasor based method for island detection leveraging wide area network information between the solar power plant and a utility reference. This enables the inverter to differentiate between a true un-intentional island and a case where grid support from the PV plant could assist in reliable power delivery to customer loads. This technology enables a wide variety of smart grid functions.
In Stage 3 the team is focused on advancing three key areas relating to the use of synchrophasors with distributed generation:
- Working with Schweizer Engineering Laboratories to develop an early stage commercial product offering of a synchrophasor measurement and protection device for distributed generation.
- Lowering barriers to deployment of widespread PV through active participation on standards committees, including IEEE 1547.8.
- Working with SEL, NPPT, and PGE to identify and quantify additional tangible benefits to the use of wide area information on the distribution network.
Smart Power Islanding Detection
In Stage 2, the team 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.
Figure 2 Utility Integration Demonstration Site
The team demonstrated two-way communications and control, as well as the “Smart Power Islanding Detection” technique utilizing synchrophasors. Multiple abnormal grid operating conditions were demonstrated, including island events at quality factors of one and three respectively. Further, remote command and control of disconnect, curtailment, and active power factor control were demonstrated on the utility connected site.
In Stage 3, a new demonstration site has been identified on PGE’s network. The identified site is on a feeder that has up to 37% penetration of and will serve as an excellent site for fielding of early stage production inverters with SEGIS driven functionality.
Energy Economics
In Stage 2 PV Powered developed 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 acquired samples for the majority of these types of solar modules in Stage 2 and constructed a solar research field comprised of multiple configurable solar arrays to be used to develop and demonstrate the improved energy harvest algorithm.
Energy Harvest
In Stage 3, the new algorithm will be evaluated and tuned under sun on the configurable solar arrays. A photo of the solar research field constructed in Stage 2 is shown below. The configurable solar arrays are designed as test beds, making it easy to change module technologies, test varying tilt angles, and stringing combinations. Depending on the solar module technology installed, each test array provides between 500 and 4800 Watts of available DC power under full sun. Two identical arrays of each solar technology were developed to enable rapid validation of algorithm improvements, while maintaining a “placebo” array to validate the results. Once tuning is complete, the algorithm will be commercialized.
Figure 4 Solar Research Field
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 an energy producing device that must connect and participate in the overall energy management equation. In Stage 2 PV Powered worked 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 developed communications protocols and demonstrated the ability to easily connect inverters to energy management systems. No additional work is planned for Stage 3 in this area. The communication protocol development and feasibility work done in Stage 2 will benefit the industry as more energy management systems get paired with solar power plants.
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. In Stage 2, the team 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.
Top
of page |
