Solar inverters are devices which convert the direct current generated by solar modules into alternating current and feed it into the power supply grid. The inverter is therefore part of a photovoltaic system. The input usually features a DC-to-DC converter with a maximum power point tracker, which is controlled by a microprocessor and feeds the intermediate circuit. The output features a one to three-phase inverter which feeds into the low-voltage network or, in the case of larger devices, feeds into the medium-voltage network with the help of an integrated transformer and automatically synchronises with the power network.
This can be practical for photovoltaic systems which comprise differently aligned or partially shaded sections, as is for instance the case with vehicles and aircraft equipped with solar panels.
Usually a one-phase inverter which feeds the energy of one or more strings of solar panels into the power grid.
A one or three-phase inverter equipped with more than one MPP tracker for several strings (including different ones) of solar panels.
A large-scale electrical system, often in a switch cabinet format and less frequently as a station with a container design. The modular construction simplifies any necessary repairs. Generally used for outputs of 100 kWp and higher.
There are basically two types of solar inverter:
Devices with transformer: In this case, a transformer is responsible for the galvanic separation of DC and AC, which allows the PV generator to be earthed with a single pole. As a result, no floating potential occurs within the system. Many module types require this format, as it is legally required in some countries.
Devices without transformer: In this format, the input and output are electrically connected. As this circuit construction does not require a transformer, these devices usually offer a higher degree of efficacy. However, because there is no galvanic separation, the device requires a different electrical safety concept.
The DC input of the solar inverter usually features an input converter, which is often a boost converter with a very high degree of efficacy. The output circuit also has a high degree of efficacy, which is maintained over a wide load range. Inverters without transformers were developed to further optimise efficacy. The circuit technologies are designated H5 or HERIC Topology. However, these devices require the solar module to be earthed for personal protection.
Inverters optimised with transformers often assume the function of an input converter, making the intermediate circuit superfluous. This is referred to as direct feed-in (compare with cyclo converter). The degree of effectiveness improves as only one converter is necessary. However, these types of devices have a smaller range with optimum efficacy and this benefit quickly diminishes in systems with partial shading.