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How to define your electrical configuration

A lot of parameters affect your electrical configuration. In pvDesign this is no exception. Would you like to know more about these parameters?

Introduction

The electrical configuration is one of the main aspects to take into consideration when designing a PV plant. So don't worry, pvDesign has got you covered! Our software comes with a variety of parameters and options that can help you define said electrical configuration just the way you want. It also calculates the cross-section of all cables and locates both the low voltage and the medium voltage system elements (cables, trenches, power stations, string boxes, string inverters,…) in your PV array.

Electrical Configuration

This section will tackle all the parameters that affect the Low Voltage configuration, from the number of modules per string all the way to the power stations.

The first step is to select the inverter. pvDesign offers both central and string inverters. You can select an inverter from our public database or opt to upload your own equipment (How to upload your own equipment) to your private database. pvDesign also permits you to select a secondary central inverter if needed.

Central Inverter

If you select a central inverter, the power station will be defined by the number of central inverters inside it (and secondary inverters as well if selected). These power stations will be distributed throughout the layout and smaller ones will be used once no more can fit.

When it comes to the low voltage electrical configuration, you can select either String Box or DC Bus System in the Electrical tab, "Solar Field". 

You can also specify your preferred number of strings per string box / DC bus system. This value will be used to generate a list of 30 different electrical configurations from which you need to select one.

String Inverter

Now if you opt for string inverters, the power station will be defined by the preferred and the minimum number of these inverters.

Two different low voltage electrical configurations are available for string inverters: String Inverter in Field, and String Inverter inside the Power Station.

Modules per string

You have just selected the PV module and the inverter that you want, now what? pvDesign will recommend the optimal number of modules per string and set an interval of allowed values (all found in the Equipment tab, "Structure"). This interval depends on the minimum historical temperature found in the Location tab (this parameter can be modified).

For more information on how we calculate this, please refer to our Electrical Methodology.

 

DC/AC Ratio

The next input that we must define is the DC/AC ratio in the Layout tab, "Power Requirements".

From the value indicated at this point and according to the number of strings defined for the low voltage system, pvDesign will find the electrical configuration needed to achieve this DC/AC ratio in the PV plant, installing inverters working at different DC/AC ratios if required.

Layout Configuration

To define the size of the blocks of structures that will be installed in our design, we must select one of the following alternatives in the Layout tab, "Layout Configuration":

  • Regular Blocks: big blocks of structures will be installed with a shape as squared as possible. This will lead to a regular design that may not optimize the available area.
  • Adaptive Design: smaller blocks of structures will be installed. Blocks of structures starting from 1x1 will be installed, fitting to the perimeter as much as possible.

Cable sizing

In the Electrical tab, you can choose your preferred standard and pvDesign will automatically size your PV plant's cables according to the International Electrotechnical Commission (IEC) standard, the National Electrical Code (NEC) standard, the Australian standard, or the National Standard of the People's Republic of China. All these standards will apply the Maximum Rated Current (Ampacity) criterion, the Voltage Drop Limit criterion, and the Short-Circuit Temperature Rise criterion and will make sure that the cables are sized based on the most restrictive one.

Users can also define the maximum voltage drop limit for both the low voltage and the medium voltage systems.

A maximum of two cable cross-sections will be used for each subsystem to reduce the total installed cable volume.

Summary

With pvDesign, you can size your PV plant's cables following the IEC, NEC, the Australian, or the Chinese standard, choose a central or string Inverter, and define your Low and Medium Voltage systems with a reduced number of inputs, obtaining an optimized layout that will be adapted to fit your requirements.


For any other questions or more information regarding this topic, you can contact us at: support@ratedpower.com