How to define Capacitor Banks in RatedPower

Do you need to compensate for the reactive power but don't want to increase the inverter quantity? Then you're in the right place!

Introduction

Not all power produced can be used for real work, and this is the case for reactive power. It can be found at the inverter, power station and substation, MV cables, as well as overhead lines. And although they play an important role in AC systems, we must consider them when sizing the PV plant, and ensure that we're obtaining (delivering) the intended active power in the POI. 

One of the ways we can ensure that is by increasing the number of inverters. This does not necessarily decrease the reactive power but ensures that we're getting the required rated power taking into account the reactive side. 

Another way to make sure we have sized the right power at the delivery point is by directly compensating the reactive power through capacitor banks. We will show you now how to do it with our tool!

Capacitor Banks

The capacitor bank solution is a great alternative to compensate for the reactive power while keeping the same amount of inverters. In our power factor tool, the users can choose if they want to use both inverters and capacitor banks, or only one of them. 

In the Grid Point tab under "Grid requirements", two options will appear when the users enable a power factor.  "Use only inverters" will be selected as default, but users can choose "Use inverters + capacitor banks" as well. 

Use only inverters

Using the first option, the users can click on "Define strategy settings" to choose where they would like their power factor to be measured, and how much it should be by typing in the number they want. Then RatedPower will calculate the resulting power factor at the inverter's output at the bottom of the window. For the measuring point, the user will be able to slide it on the bar to find the correct position among two points:

• Substation input
• Substation output

The portions of the system that reactive power will be considered for are: 

• Power Station and MV lines
• Substation

What happens here when we are sliding the measuring point? It changes the portion of the system that we consider reactive power to help size the plant's rated power ultimately. For example in the screenshot above, our measuring point is set at the substation's input. This would mean that in order to get a power factor of 1 at the substation's input when considering the reactive power coming from Power Stations and MV lines, a power factor of 0.9973 will be applied at the inverter's output.

Use inverters + capacitor bank

If we choose to have both inverters and capacitor banks, in ¨Define strategy settings¨, we'll see that we can slide two ends of a blue line on the bar to choose the portion of the system that will be compensated by the capacitor banks, and the left end of it is to determine exactly up to which point to use inverters only (yellow line). 

Just like the example below, we're choosing to use inverters up to the substation input, where the capacitor bank will take over and compensate for the reactive power from ST and OHL. Finally, we will have the point of measurement at the grid connection point with a power factor of 1. 

We could also slide the blue line all the way to the left. In this case, we wouldn't use inverters anymore and capacitor banks will compensate for all the reactive power power from the system. Ex below: 

Documents

In case capacitor banks are enabled, we should see additional information shown in the following documents:

• Energy Report
• Bill of quantities
   
• Power flow model
  
• Interconnection facility SLD 
  
• Interconnection facility layout 
  

For more information regarding this topic you can contact the Support team at support@ratedpower.com