Nextronex has developed a new distributed solar inverter and wiring system that improves on traditional centralized designs. Their system uses low profile inverters placed throughout the solar array, connected by an integrated DC bus and zone boxes, to minimize voltage drops and copper use. This distributed architecture provides improved efficiency, fault tolerance, monitoring and maintenance capabilities compared to conventional large central inverters. Nextronex has also developed smart switching and control algorithms to optimize inverter-level efficiencies and response to changing conditions.

1. A New Utility Scale Solar Inverter and Wiring Topology
May 18, 2010
Peter Gerhardinger Roger King, Ph.D.
Chief Technology Officer Professor, Electrical Engineering
Nextronex Energy Systems University of Toledo M.S. 308
4400 Moline Martin Rd 2801 W. Bancroft St.
Millbury Ohio 43447 Toledo Ohio 43606
peterg@nextronex.com rking@eng.utoledo.edu

2. A New Utility Scale Solar Inverter and Wiring Topology
• Nextronex Energy Systems, LLC
• Formed June 2008
• Initial Offering Closed November 2009
• 2nd Round currently Open
• Over $ 2 MM invested to date
• Inverter System received UL 1741 Certification June 2010
• First Installation May – July 2010 (399 kW, OANG Site)
• Two utility patents (and related foreign filings) pending
• Over 6 MW sold to date

3. Solar Inverters – Technical Approaches
• (Insert Inverter Matrix Slide here)

4. Nextronex Field
• (Photo of Nextronex Field Here)

5. A New Utility Scale Solar Inverter and Wiring Topology
• Nextronex has developed a unique kit of parts
containing everything needed from the string
wiring to the utility connection
• Low Profile 150 kW inverters
• Smart Controller
• Zone Boxes with Telemetry
• Power Strip(s)
• Load Center(s)
• All components UL listed for operation up to
1000 V dc
• Best-in-class 98 % + peak efficiency
• Distributed Architecture (M/S Switching)

6. PV Plant Loss Factors (exclusive of panels)
% Improvement % Improvement
from Model from Actual Installations
1. DC Wiring Losses, 2 % nominal Could be as high
Defects as 15 %
2. Equipment Efficiency 2 % nominal 2 % nominal
and Reliability
3. Low Light Level 1 % - 3 % depending 1 % - 3 % depending
Energy Harvesting on climate on climate
4. Operation and – –
Maintenance Issues
% Improvement 5%-8% Up to 20 %

7. The DC Wiring Problem
• The DC collection system
represents a significant investment
in wire, connectors, and labor
• Problems are difficult to diagnose,
especially after commissioning
• Large variability if rows are long,
with many home runs (DC loss
increases with wire length)
• Commonly accepted 2% drop is
excessive for solar applications

8. The DC Wiring Problem
This is what you want to avoid

9. The DC Wiring Problem
• Installed Cost is proportional to Cu weight
• Operating Cost is proportional to CU loss
• Three Approaches:
Constant Area (CA) Proportional Area (PA) Constant V drop (CVD)
- Constant area (CA) and constant V drop (CVD) have identical
power less, while proportional area has 25 % less loss.
- Proportional Area (PA) has the lowest power drop but the largest
variation in voltage drop.

10. The DC Wiring Problem
• Conclusions:
• Volume of Cu needed is proportional to the square of the total current,
and the square of the linear dimensions -
• For all cases, total power loss and voltage drop are inversely
proportional to the conductor volume
-
• Tapping the collection bus in the center results in 4x less copper volume
than tapping at and end point
Constant Area (CA) Proportional Area (PA) Constant V drop (CVD)

11. A New Utility Scale Solar Inverter and Wiring Topology
Voltage Drop with Center Inverter Cluster

12. A New Utility Scale Solar Inverter and Wiring Topology
Voltage Drop with Perimeter Inverter

13. A New Utility Scale Solar Inverter and Wiring Topology
Voltage Drop with Center Inverter Cluster Voltage Drop with Perimeter Inverter

14. The Nextronex Solution
• Distributed Architecture
• 1000 V DC System (minimize IR Drop
and use 40 % fewer home runs)
• Low Profile Components for central
array placement
• DC Bus (Power Strip) with Integral
Zone boxes for very low loss, easy to
install and service DC collection
system Single Line System
• Ungrounded DC operation for best
safety (with differential GFD)

15. Inverter Switching / Sequencing
• Before sunrise, the controller
chooses the lead inverter for the
day (rotated, based on run time)
• The lead inverter manages the
MPPT for that day, and the
remaining inverters are brought on-
line in slave mode as needed
• Ramp rate, step size, timing have
been worked out to insure accurate
MPPT, and to quickly respond to
cloud transients

16. Inverter & System Efficiency
• The Ray-Max Inverter has a peak
efficiency of 98 %
• Using the Nextronex Switching
Algorithm, a 1 MW system with 6
inverters reaches peak efficiency at
3% (30 kW) output, and will begin to
export power at 650 W
• The companion Load Center has a
peak efficiency greater than 98 %,
giving a system efficiency of 96 %

17. MPPT Performance
Clear day performance Cloudy day performance

18. The Importance of Information
• Without data, it is impossible to keep a
solar array in top condition
• Overall Power and Energy Output can
be assessed against weather data
• String level monitoring to quickly
address faults and keep your panel
mfgr honest
• Inverter and Transformer data for
predictive maintenance
• Advanced telemetry for timely updates
and remote monitoring

19. Operation and Maintenance
• Distributed Architecture for Fault Tolerance
and Reliability
• Modular Inverter Design – Replace Core
Inverter in 30 Minutes without shutting
system down
• Smart Controller provides the centralized
control, data, and telemetry point to monitor
system performance and respond to faults
and alarms
• Zone level monitoring and switching to
isolate problem strings for servicing without
shutting system down

20. The Smart Grid
• Utilities will need to control the output parameters of a solar
array if the promise of the “smart grid” is to be realized
• Curtailment to protect distribution and transmission lines
• VAR and Power Factor Correction
• Phase imbalance and brownout correction
• Shut-down verification for safety of line personnel
• The Nextronex Smart Controller provides the communication
point and our inverters are programmed to respond to
external commands

21. A New Utility Scale Solar Inverter and Wiring Topology
Questions?

22. A New Utility Scale Solar Inverter and Wiring Topology
Thank you