Solar inverter

A solar inverter is responsible for transforming the direct current (DC) you receive from your solar panels into an alternating current (AC) compatible with the power grid. A single solar cell often has a voltage of only approximately 0.5V, which is why solar cells are often tied together into solar panels. Solar panels are often wired in such a way as to supply a voltage of 12V or 24V. Since typical inverters operate on voltages that are a multiple of 12V, it is important to adjust the wiring of your solar panels to match your inverters input voltage. Often, this means a combination of serial and parallel wiring. Here, we discuss the role of the inverter in a solar power system. We also touch upon the classes of inverters you will find and which type you need for grid-tied solar panel systems.

Direct current and alternating current

Current comes in several’flavors’, of which two are important; direct current (DC) and alternating current (AC). Direct current is provided by batteries and solar panels, where alternating current is supplied by the utility. Direct current has a constant flow direction, whereas alternating current has a flow direction which varies periodically. The inverse of the period between two AC ‘pulses’ is called the frequency of the current. The great disadvantage of direct current, is that it can’t be transformed to high voltage current. This means it can’t be transported across large distances without incurring significant losses. Since a transformer requires rapidly alternating magnetic field directions, alternating current is suitable for transformation.

Various types of current

To transport power over large distances, the utility will often ‘crank up’ the voltage to high voltages (120 kV or higher) at a frequency of 50 Hz. Such voltages are called ‘transmission’ voltages, since they allow transmission of electricity with relatively minimal heat loss. Once the current reaches your neighborhood, it is transformed down to mains power, or wall socket power (120 V in the United States).

Inverter types

Inverters can be classified according to their generated wave form or according to their ability to synchronize phase. An inverter can basically generate two wave forms:

As for phase synchronization, inverters can be further classified into two groups:

In series or parallel?

Whether you link your solar panels in series or in parallel matters a great deal. An inverter operates at a certain input voltage, which is often a multiple of 12V. In order to make the inverter work, it is necessary to adjust your circuitry in such a way that the output voltage matches the inverters required input. The below video will explain the difference between serial and parallel linking of your solar panels.