Functions

The direct current supplied by the solar generator is converted into single or multi-phase alternating current by an inverter. This is necessary because German power grids are only designed for alternating current.

Inverters are available in many performance classes and differ depending on the system concept

Central, string, multistring and module inverters.

Depending on the circuit concept, devices with or without a transformer are used.

In addition to converting the generator voltage, an inverter searches for the operating point on the generator characteristic curve with the highest power.

This point is known as the Maximum Power Point (MPP) and has a different combination depending on solar radiation and temperature

Amperage and voltage.

In addition, an inverter has monitoring and protection devices to ensure compliance with the relevant guidelines and regulations. In the event of voltage deviations, frequency changes and fault currents, for example, it ensures that the system is disconnected from the power grid.

Interconnection

In principle, photovoltaic modules can be connected in a system in parallel, in series or in a combination of both. In connection with different module orientations and shading, this affects the voltage and amperage of the system and influences the choice of the appropriate inverter.

In principle, when individual modules are connected in parallel, the currents add up and the voltages remain the same. In the case of a series connection, the voltages are added and the currents remain the same. The different temperature coefficients of the modules play an important role in determining limit values, since a photovoltaic module also supplies different voltages and currents at different temperatures.

Furthermore, the reverse current resistance of the modules must be taken into account in order not to risk damaging them. The efficiency of a system also depends on the correct overload ratio of the inverter to the generator.