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PV Inverter: Understanding Photovoltaic Inverters

Discover all the features of photovoltaic inverters and use this guide to choose the best one for your project.

In the vast landscape of solar energy,  PV inverters play a crucial role, acting as the pulsating heart in photovoltaic systems. In this article, we will delve into the fundamental role of inverters in the solar energy generation process and their necessity in converting direct current (DC) into usable alternating current (AC).

At the end of this article, you can also watch two short videos showing you how to operate with a tool for the design of photovoltaic systems and, consequently, how to choose and configure an inverter.

Photovoltaic system with 3D BIM modeller

Photovoltaic system with 3D BIM modeller

What is a Photovoltaic System

Before delving into the inverter and all its features, let’s provide a brief introduction to the photovoltaic system.

A photovoltaic system is an advanced electrical system that harnesses an inexhaustible resource like the sun and can be mainly divided into two categories:

  1. Grid-connected systems
    • Integration with residential or industrial conventional electrical systems;
    • Alternate or combined use with the electrical grid to meet the energy needs of the end user;
  2. Stand-alone systems
    • Designed with battery systems to ensure service continuity, ensuring energy delivery even during nighttime or insufficient solar irradiance.

Electricity Production from a Photovoltaic System

A photovoltaic panel contains photovoltaic cells that convert solar energy into electricity. These cells, made of semiconductors like silicon, form solar modules. When they absorb sunlight, they release electrons, the basis of electricity. Electrons moved through the semiconductor create a charge imbalance, generating a voltage potential similar to a battery.

Main Components of a Photovoltaic System

The photovoltaic system consists of the following elements:

  1. Photovoltaic modules – capture solar energy to produce electricity;
  2. Module support structures – support and fix modules to the roof, optimizing solar exposure;
  3. Inverter – transforms the direct current (DC) produced by the modules into usable alternating current (AC) for residential or industrial use. It uses protection devices to ensure the safety of the system;
  4. Electrical cables – transport energy from the system to end users.

Additionally, there are additional components such as the following:

  1. Monitoring system – enables remote monitoring of production, consumption, and inverter status;
  2. Storage system – an innovative system to improve efficiency, allowing the storage of energy produced during the day for use during periods without solar production, maximizing self-consumption.

Photovoltaic systems, in addition to generating sustainable energy, incorporate additional technologies to optimize performance and offer innovative solutions in the field of energy production and storage.

What is a PV Inverter

The photovoltaic inverter, also known as a solar inverter, represents an essential component of a photovoltaic system. Without it, the electrical energy generated by solar panels would be inherently incompatible with the domestic electrical grid and the devices we intend to power through self-consumption.

Its main function is to convert the direct current (DC) produced by solar panels into alternating current (AC), making it suitable for daily use in our homes. Without this transformation, the generated energy would remain impractical for domestic use.

But the inverter is not just a current converter; it is much more. It optimizes the overall energy production, ensuring that the photovoltaic system operates at its maximum potential. This optimization not only maximizes the system’s efficiency but also allows for a smarter use of solar energy, reducing waste and maximizing performance.

Moreover, the inverter is necessary to fulfill other crucial aspects, such as:

  1. Optimization of energy production: This optimization is essential to maximize the overall performance of the system;
  2. Provision of integrated protection devices: Every PV inverter is equipped with integrated protection devices. These components are essential to ensure the safety of the solar system in case of faults or short circuits. The presence of such safety mechanisms is fundamental for the long-term protection of the entire system;
  3. Advanced monitoring function: The PV inverter is not just a converter and a protection device. It also performs a comprehensive monitoring function of the solar system. Thanks to this advanced feature, we can promptly identify faults or malfunctions in electricity production, allowing for timely interventions to maintain system efficiency.
Photovoltaic energy production scheme

Photovoltaic energy production scheme

How Does a PV Inverter Work

Now that we have outlined the fundamental functions of photovoltaic inverters, let’s take a closer look at their operational process and the requirements for correct installation.

Photovoltaic solar panels convert sunlight into electricity, but this is direct current, unsuitable for domestic use. The photovoltaic inverter becomes the protagonist, being vital for solar installations as it converts direct current into alternating current. This process allows integrating solar energy into our homes.

Some key aspects to consider before installing a PV inverter include:

  1. Proper operation of domestic electrical circuits: Ensure that domestic electrical circuits are in excellent condition to ensure effective integration of the inverter;
  2. Optimal placement of the PV inverter: The placement of the inverter is critical to ensure optimal performance. The choice of location must be carefully evaluated;
  3. Electrical connections between inverter and home electrical panel: Correct connection between the inverter and the home electrical panel is essential to ensure safe energy distribution;
  4. Adequate sizing of the inverter: Proper sizing of the inverter is crucial to adapt to the specific needs of the photovoltaic system.

To fully understand the operation of the photovoltaic inverter, it is essential to consider that the domestic grid uses alternating current with specific parameters: 230 volts and 50 Hz.

The operation of the inverter can be likened to a combination of an alternator and a transformer, with the addition of a circuit involving transistors, Mosfet, or IGBT. Components such as microcontrollers, oscillators, and amplifiers are essential to maximize efficiency and safety in converting from direct current to alternating current, preventing issues such as overvoltage and short circuits.

Types of Photovoltaic Inverters

Let’s further explore the different types and specific applications of each model.

Single-phase and Three-phase Inverters

  • Single-phase: Suitable for single-phase grids, characterized by two connectors (phase and neutral). Ideal for moderate-sized installations, up to 6 kW;
  • Three-phase: Composed of three phases and alternating currents, suitable for larger installations such as industrial or commercial ones. Their presence in residential settings is less common.

Types of Inverters for Grid-connected Systems

  1. String Inverter:
    • Common and cost-effective;
    • Suitable for systems without significant shading;
    • Easy maintenance.
  2. Centralized Inverter:
    • Preferred in large installations;
    • Connects modules in series to a single inverter;
    • Limitations in case of shading but user-friendly.
  3. Micro Inverter:
    • Installed on each individual panel;
    • Maximizes the performance of each module;
    • Higher cost but advantages in monitoring and durability.
  4. Hybrid Inverter:
    • Similar to traditional string inverters;
    • Manages the charge/discharge of batteries;
    • Introduces advanced technologies like smart inverters to maximize efficiency.

Inverters for Off-grid Systems

  • Used in systems isolated from the electrical grid;
  • Extract energy from batteries to convert it into alternating current;
  • Ideal for situations without electrical access, such as mountain cabins or recreational vehicles.

3 kW and 6 kW Photovoltaic Inverters

  • Models required for medium-sized installations;
  • The number of connectable panels depends on the power of each module and the overall system voltage;
  • Sizing considers variables such as available space, orientation, and shading.

In every choice, it is crucial to consider not only the nominal power of the inverter but also the specific requirements of the system.

How to Configure a PV Inverter

Below, you can find two videos showing you how to choose and configure an inverter, using a software for the design of photovoltaic systems.

Inverter Selection

Inverter Configuration

 

 

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