A New Utility Scale Solar Inverter & DC Collection System September 15, 2011
Jun 20, 2015
A New Utility Scale Solar Inverter & DC Collection System
September 15, 2011
• Nextronex Inc.• 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
• First Solar compatibility approval March 29, 2011
A New Utility Scale Solar Inverter & DC Collection System
• 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)
• Smart Grid Capability
A New Utility Scale Solar Inverter & DC Collection System
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
• Ungrounded DC operation for best safety (with differential GFD)
Single Line System
PV Plant Loss Factors (exclusive of panels)
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 % dependingEnergy Harvesting on climate on climate
4. Operation and – – Maintenance Issues
% Improvement 5 % - 8 % Up to 20 %
% Improvement from Model
% Improvement from Actual Installations
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
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 %
MPPT Performance
Clear day performance Cloudy day performance
Nextronex Linear Design
• (Photo of Nextronex Field Here)
Nextronex Cluster Design
• (Photo of Nextronex Field Here)
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
The DC Wiring Problem
• Installed Cost is proportional to Cu weight
• Operating Cost is proportional to CU loss
• Three Approaches:
- 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.
Constant Area (CA) Proportional Area (PA) Constant V drop (CVD)
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)
A New Utility Scale Solar Inverter and Wiring Topology
Voltage Drop with Perimeter InverterVoltage Drop with Center Inverter Cluster
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
• Inverter and Transformer data for predictive maintenance
• Advanced telemetry for timely updates and remote monitoring
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
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
A New Utility Scale Solar Inverter & DC Collection System
Questions?
Contact Brandon Lohmeyer, Account Manager
Office: (567)225-3341
Email: [email protected]