Solar inverter photovoltaic

The inverter or PV power convertor is an important and also indispensable part of the photovoltaic energy installation. The DC converter has two main functions: The most important function is converting direct voltage (DC) to alternating voltage (AC).

  • PV panels are connected to the DC input side.
  • The PV modules deliver direct voltage.
  • On the other side, the power grid is connected that is based on AC voltage.

The main function of an inverter is to optimize the yield given the conditions such as:

  • The amount of sun irradiation
  • Shadow trap and possibly
  • Desired payload if a battery system is connected.

Solar inverter photovoltaic

An DC converter is equipped with Maximum Power Point Tracking (MPPT) or Global Maximum Power Point Tracking (GMPPT). In order to extract as much electrical power from a PV panel as possible, it constantly searches for the point where the product of panel current (voltage) and voltage (amperage) is maximum (voltage x amperage = wattage).

This is called the MPP. The MPP shifts as soon as the irradiation on or the temperature of the panel changes. An inverter is therefore always provided with one or more MPP trackers. GMPPT has the added advantage that it can determine the optimal yield over multiple panels in a string. Also in case one or more panels are shaded. 

A string is a series of connected panels that are linked as a group. Other important functions of the inverter are process monitoring and system protection both on the side of the panels (AC side) and on the side of the power supply (DC side)

Photovoltaic inverter

The following protections may be present on the DC side:

  • Overvoltage protection.; Protection against lightning and overvoltage. It is important to coordinate this type of security with an installer because surge protection has different levels. Overvoltage protection must also be installed in the correct places in the installation.
  • Reversal protection. 
    Protection against incorrect connection of the + and - poles.
  • Electronic Switich (ESS). 
    Device function for safe disconnection of the DC side of the inverter. Even if there is still some tension there as a result of not following the right procedures or short circuit.
  • AC short-circuit resistance or function to automatically switch off the inverter in the event of a short-circuit.
  • Earth leak monitoring.
    On the AC side, among other things, the frequency and voltage of the power grid are monitored in accordance with the applicable (national) regulations.
  • If the voltage on the mains is too high, he will switch off. Even in the absence of a power network frequency, this can be the case in the event of power failure or if there is a fault in the local power circuit, it will switch itself off.
  • Inverter power systems that directly inject into the medium voltage network (1 kV - 50 kV) must have a phase shift function. In this way, large photovoltaic power systems are compatible with the capacity of the distribution network and there is no useless load on the power network. The generation of network-usable PV power is an important condition for the success of renewable energy sources.
  • Most of the manufacturers also produce hybrid inverters. In addition to a PV converter, these also have a charging function.

Power inverter photovoltaic

Photovoltaic system DC converters are mostly grid tie inverters. They need electricity from the grid to function. If there is a grid failure, they stop to deliver energy. ( grid tie = connected to the network)

A solution for this is to have an off-grid battery system like the SMA sunny island. This grid & off-grid inverter will have an AC output from a low voltage lithium battery. It is also using the generated solar energy, what's going usually into the grid, to load the battery. So in case of an electrical failure from the electricity company, it is keeping the AC power by level monitoring.

That is how energy storage works in your advantage — saving electricity during the day from the string inverters into lithium storage. Using it by night or if the power has a breakdown.

Note: Not every inverter is standard equipped with all safety and monitoring systems. A check on the specifications and options is therefore necessary.