After the solar PV panels themselves, Solar Power Inverters are the next most significant part of a grid-connected PV system and so the DC input power rating of the inverter ought to be chosen to match the PV panel or array.

by Lincoln Electric Systems, Lincoln Nebraska
Photo by American Public Power Association / Unsplash

Generally, power inverters are chosen for a specific system based on the maximum load, the maximum surge needed, AC output voltage needed, input battery voltage and any optional features required. the dimensions of AN electrical converter are measured by its maximum continuous output in watts and this rating must be larger than the full wattage of all of the AC loads connected at the same time.

Moreover, electrical appliances like washing machines, dries, fridge’s and freezers that use electric motors need a lot of power to begin themselves than they require to run. This high starting power consumption can be over twice the normal power consumption so this must be considered once sizing an inverters wattage. Most power inverters are capable of delivering 3 to 5 times their rated power for brief term surges and overload conditions.

Let's assume that we have calculated the total AC power consumption of our home which we would need a 2,500W or 2.5kW solar inverter. The PV solar panels we are interested in are 24V monocrystalline silicon panels rated at 140 Watts peak. Then dividing two,500W by 140 watts means that 18 PV panels are required, yielding 2,520W in total. however, can we connect these eighteen panels to the inverter? We know from previous tutorials that PV solar panels will be connected along rather like batteries, and in an exceedingly series combination the voltage adds, with a constant current through every panel, and in a parallel combination, this adds with a constant voltage across every panel.

We first need to calculate how many modules can be connected along with a series branch. The datasheet for our inverter tells us that the maximum power point tracking (MPPT) input voltage is between 175 and 480 volts at a maximum current of fifteen amps. The electrical circuit Vage (Voc) of every twenty four volt PV panel at 25oC is given as 36.8 Volts. Then the maximum number of panels we can connect with a single series branch is calculated as 480/36.8 = 13 panels. Likewise, the minimum variety of 24V PV panels needed to keep the MPPT tracking voltage above the minimum 175 volts is there calculated as 175/24 = 7.3, or 8 panels.

Then, to stay within the inverters input voltage limits for our simple example so that the PV array voltage isn't lower than 175V or bigger than 480V requires an array branch of between 8 and 13 solar PV panels. Since our calculated array consists of 18 panels, 2 branches or strings of 9, 24V PV panels every is appropriate. The short current, Isc of our 24 V monocrystalline silicon panels is given as 5.8 amps. Two branches will, therefore, provide a total most current of eleven.6 amps, well inside the inverters specification.

To find out the number of panels that may be connected on one series PV branch, check that the sum of the electrical circuit voltage of all the panels doesn't exceed the most electrical outlet pursuit DC input voltage which the minimum number of panels in the series branch does not fall below the minimum MPPT voltage not forgetting that the voltage in a series branch varies up and down with temperature. Additionally, check that the short circuit current (Isc) of the array is less than the maximum DC input current of the power inverter.