3 4 thevenard-pai epri-sandia 2016-05 presentation

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)

2www.canadiansolar.com

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


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


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


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


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


CASSYS: Architecture (cont’d)

CLIMATIC DATA

PV ARRAY LOSSES

XML

SYSTEM DEFINITION

B.O.S LOSSESSITE LOCATION

OUTPUT FILE

EXCEL INTERFACE

C#SIMULATION

ENGINE


CASSYS Interface

“DEMO”


CASSYS Interface

END OF “DEMO”


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


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%


Validation: against PVsyst (cont’d)

Example of comparison when POA irradiance and panel temperature are used as inputs (cont’d)


Validation: against measured data – sunny day

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Comparing CASSYS Simulated Performance & Measured Performance

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Simulated Power (kW)


Validation: against measured data – overcast day

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Comparing CASSYS Simulated Performance & Measured Performance

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Daily Diffuse Fraction

Daily Error (Measured - Simulated Production) v. Diffuse Fraction


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


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!

3 4 thevenard-pai epri-sandia 2016-05 presentation

Technology

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