PV Solar System Fundamentals
Before a technician can troubleshoot a photovoltaic system, the technician must understand what equipment is installed, how that equipment is connected, and how electrical power is expected to move through the system.
Part I establishes that foundation. These six lessons introduce common PV system configurations, modules, strings, arrays, inverter technologies, system components, power flow, equipment ratings, expected production, and the effects of aging.
Understand the System Before Troubleshooting It
PV troubleshooting should not begin with random electrical measurements. The technician first needs to identify the system configuration, locate the major components, understand the AC and DC power paths, and determine what the equipment is designed to do.
The lessons in Part I provide the working knowledge needed for the inspection and electrical troubleshooting procedures developed later in the course.
Identify
Recognize the PV system configuration and the major equipment installed at the site.
Trace
Follow DC generation and AC power through modules, strings, inverters, distribution equipment, loads, and the utility connection.
Establish Expectations
Use equipment ratings, system configuration, and operating conditions to determine what normal operation should look like.
PV Solar System Fundamentals
Complete these lessons in order. Each lesson adds another layer to the technician’s understanding of an installed photovoltaic system.
Introduction to Photovoltaic Solar Systems
Begin with the basic purpose and operation of a photovoltaic system. Identify the major sections of a typical installation and establish the relationship between solar generation, DC electricity, power conversion, AC distribution, building loads, and the utility.
DC Generation
AC Power
System Overview
Grid-Tied, Battery-Backed, and Off-Grid PV Systems
Compare the major PV system configurations encountered in the field. Learn how connection to the utility, battery storage, backup capability, and independent operation change the equipment and electrical paths a technician should expect to find.
Battery-Backed
Off-Grid
System Configuration
PV Modules, Strings, and Arrays
Examine how individual photovoltaic modules are electrically combined into strings and arrays. Understand the series and parallel relationships that determine system voltage and current and why those relationships matter during troubleshooting.
Strings
Arrays
Series & Parallel
String Inverters, Microinverters, and Power Optimizers
Identify the principal inverter and module-level power-electronics arrangements used in PV installations. Compare centralized string conversion with microinverter and optimizer systems and understand how each configuration changes the troubleshooting path.
Microinverters
Optimizers
Power Conversion
PV System Components and Power Flow
Bring the individual components together into a complete system. Trace electrical power from the array through disconnects, combiner equipment, inverter equipment, AC distribution, building loads, and the utility connection.
DC Power Path
AC Power Path
Disconnects
PV System Ratings, Production, and Aging
Learn how module and equipment ratings relate to actual field performance. Consider sunlight, temperature, system conditions, normal production variation, degradation, and aging before deciding that reduced output indicates an electrical failure.
Production
Temperature
Aging
Expected Output
Questions to Answer Before Beginning Diagnosis
When arriving at an unfamiliar PV installation, the first task is not to decide which component has failed. The first task is to understand the system well enough to know what should be happening.
What Type of System Is This?
Determine whether the installation is grid-tied, battery-backed, off-grid, or another configuration and identify all available energy sources.
How Is the Array Configured?
Identify modules, strings, arrays, combiner equipment, and the series and parallel relationships that determine DC voltage and current.
How Is Power Converted?
Determine whether the installation uses a string inverter, microinverters, power optimizers, hybrid equipment, or a combination of technologies.
Where Does the Power Go?
Trace the expected electrical path from the PV array through the conversion equipment and into the building electrical system or utility connection.
Ratings Are a Starting Point, Not a Guaranteed Field Reading
PV modules and other system components are rated under specified conditions. Actual field voltage, current, and power depend on system configuration and operating conditions including irradiance, module temperature, shading, orientation, equipment efficiency, and system age.
A technician should therefore establish a reasonable expected condition before interpreting a measurement as normal or abnormal. Later lessons build on this principle by comparing measurements between strings, modules, test locations, and expected system operation.
Build the System One Layer at a Time
Understand Basic PV Operation
Learn how photovoltaic modules generate DC electricity and how that energy becomes usable AC power in a typical installation.
Recognize System Configurations
Distinguish grid-tied, battery-backed, and off-grid systems so the available power sources and expected operating modes are understood.
Understand Modules, Strings, and Arrays
Establish how PV modules are interconnected and how series and parallel circuits affect the electrical characteristics of the array.
Identify the Conversion Technology
Determine whether DC-to-AC conversion occurs at a central inverter, at individual modules, or through a system using power optimizers.
Trace the Complete Power Path
Locate the major system components and follow the electrical path from solar generation through the building electrical system.
Establish Normal Expectations
Use ratings, environmental conditions, system configuration, production information, and equipment age to establish reasonable expectations before troubleshooting.
PV Circuits Can Remain Energized
Photovoltaic modules can produce electrical power whenever sufficient light reaches them. Opening a disconnect or shutting down an inverter does not automatically mean every conductor in the installation is de-energized.
Before inspecting or testing an installed system, technicians must identify possible energy sources, disconnecting means, equipment ratings, and circuits that may remain energized. Follow manufacturer instructions and applicable electrical and workplace-safety requirements.
Continue to Visual Inspection and Assessment
Once the system configuration, components, electrical paths, and expected operation are understood, the next step is to inspect the installation systematically before beginning electrical testing.
Part II covers inspection planning, modules and mounting systems, wiring and connectors, disconnects and equipment, and the appropriate use of thermal imaging as a diagnostic aid.
Return to the Complete Course
Return to the PV Solar Systems course landing page to access all five parts, from system fundamentals through battery energy storage systems.