Post on 15-Jan-2017
Design and Development of an Open-Source Simulation Tool for Grid-Connected PV SystemsDidier Thevenard, PhD, P.Eng. & Abhijeet PaiCanadian Solar O&M, Guelph, ON (Canada)
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Agenda
1 Motivation & the O&M perspective
2 Design objectives
3 Implementation
4 User Interface and “Demo”
5 Under the hood: models and algorithms
6 Validation
7 Future work and goals
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Motivation: O&M Perspective
First motivation: Monthly reporting
Second motivation: Operational help
Provide customers
with expected performance
from their system
Estimate lost production
during system or component
downtime
Determine if severe
deviations occur during
system operations on a daily basis
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Design Goals / CASSYS
“COMPATIBLE” WITH PVsyst
ABLE TO USE ANY TIME STEP
FAST
MODELING THE SYSTEM
AS IT IS
EASY TO USE
AUTOMATABLE
OPEN SOURCE AND
FREE
CAnadian Solar SYstem Simulator
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Design goals: “Compatibility” with PVsyst
PVsyst is the most recognized and accepted PV simulation tool - this is the tool we use when we sell solar farms
CASSYS has no intention of competing with PVsyst
Goals are different: design vs. operations
PVsyst does much more than grid-connected systems
PVsyst is “bankable”
“Compatiblity” should be understood in terms of
Similarity of models
Similarity of inputs
Similarity of results
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CASSYS: Architecture
Interface: Microsoft Excel
Interface: Microsoft Excel Excel is widely used in engineering
circles Offers many features for edition, data
validation, and graphics Also used to retrieve data: data
connections, pivot tables
Simulation Engine: C#
Free and excellent development environment
Object-oriented language – promotes modularity and extensibility
Fast Enabled us to reuse existing code
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CASSYS: Architecture (cont’d)
CLIMATIC DATA
PV ARRAY LOSSES
XML
SYSTEM DEFINITION
B.O.S LOSSESSITE LOCATION
OUTPUT FILE
EXCEL INTERFACE
C#SIMULATION
ENGINE
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CASSYS Interface
“DEMO”
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CASSYS Interface
END OF “DEMO”
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Under the hood: models and algorithms
Physical models are similar to those used by PVsyst
Irradiance and array-sun geometry Perez/Hay transposition models Row-to-row shading with electrical effect Tracking systems with back-tracking
PV array model Incidence angle modifier Soiling Single-diode PV model
Inverters Defined by efficiency curve Start/Stop voltages defined by user
Transformer Constant iron loss and quadratic resistive loss
Full description of algorithms available on CASSYS web site
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Validation: against PVsyst
Detailed document comparing CASSYS against PVsyst 5.64 is available on GitHub
Example of comparison when POA irradiance and panel temperature are used as inputs:
Output Variable Difference Global Horizontal Irradiance -0.26% Horizontal Diffuse Irradiance 0.22%
Beam POA Irradiance -0.37% Diffuse POA Irradiance 0.50%
Ground Reflect POA Irradiance -0.26% Global POA Irradiance 0.00%
Effective POA Irradiance corrected for Shading and IAM -0.36% Soiling Loss -5.76%
Module Quality Loss -6.22% Mismatch Loss -6.22%
Ohmic Losses DC -0.89% Effective Power at the Output of the Array -0.34%
Available Power at Inverter Output -0.34% Ohmic Losses AC -0.97%
Energy delivered to the grid -0.35%
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Validation: against PVsyst (cont’d)
Example of comparison when POA irradiance and panel temperature are used as inputs (cont’d)
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Validation: against measured data – sunny day
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Comparing CASSYS Simulated Performance & Measured Performance
Measured Power (kW)
Simulated Power (kW)
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Validation: against measured data – overcast day
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Pow
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Comparing CASSYS Simulated Performance & Measured Performance
Measured Power (kW)
Simulated Power (kW)
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Daily Diffuse Fraction
Daily Error (Measured - Simulated Production) v. Diffuse Fraction
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Future developments
New models
Non c-Si technologies
Far shading
Sub-arrays with multiple orientations
3D shading
Modification of existing models
Single-diode model improvements (spectral effects)
Temperature-dependent transformer efficiency
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Conclusions
CASSYS is an open-source software for the simulation of grid-connected PV systems
Focus is to provide a transparent, flexible and automatable tool that can be used in operational settings
Program can be used to help identify and quantify production downtime and under performance issues
Setup file, source code, physical models and testing results are available at:
canadiansolar.github.io/CASSYS/
Thank You!