# PV_LIB Toolbox: Getting Started

The purpose of the PV Performance Modeling Library (PV_LIB) Toolbox for Matlab is to provide a component based library of open source functions for PV modelers to use to learn about and construct custom models of PV performance. The initial release of the toolbox includes a complete set of functions that allow a user to convert typical weather (e.g., irradiance, temperature, wind speed, and air pressure) data along with a basic PV system design and simulate the AC power output from a PV system.

## Contents

- Standard PV Modeling Steps
- What Data is Available?

## Standard PV Modeling Steps

Sandia National Laboratories has defined nine general modeling steps that are usually involved in modeling a PV system’s performance. These steps assume that the PV system has been defined. The steps are listed below:

1. Irradiance and Weather – Collection of irradiance and weather measurements at standard orientations.
2. Incident Irradiance – Transposition and translation of irradiance components to the plane-of-array
3. Shading and Soiling - Reduction in irradiance reaching the module and array
4. Cell Temperature – Calculation of cell temperature from irradiance, air temperature, and wind speed.
5. Module Output – Determination of the IV curve for the module in the array environment
6. DC and Mismatch Losses – Accounting for the effects of mismatch in series connected strings and DC wiring losses.
7. DC to DC Max Power Point Tracking - Calculation of the DC voltage required to maximize power.
8. DC to AC Conversion – Conversion of the DC power to AC power, including variable efficiency and parasitic losses.
9. AC Losses – Accounting for AC losses before the utility meter.

## What Data is Available?

The process of modeling the performance of a PV system depends on what kind of weather data is available. Some typical starting points are listed below. Example scripts using PV_LIB functions have been developed for these various scenarios.

- Standard Weather Data - (e.g., Typical Meteorological Year)

1. Direct Normal Irradiance (DNI)
2. Global Horizontal Irradiance (GHI)
3. Diffuse Horizontal Irradiance (DHI)

PVL_TestScript1 provides a complete example of how to model a PV system using standard weather inputs from a TMY3 file.

- Global Horizontal Irradiance only

PVL_TestScript2 provides an example of how to estimate plane of array beam and diffuse irradiance starting with only global horizontal irradiance data.

Copyright 2015 Sandia National Laboratories