This support article is applicable to Virta Preconnect used via the following user interface: https://energy.virtaglobal.com/

Virta Preconnect - What is it and why do I need it? Sometimes, especially on large EV charging sites, the electric infrastructure cannot handle a situation where all the charging points are charging simultaneously with full power. This is where different load management solutions come to play. For standard load management solutions, the basic principle is the same: The available charging current is evenly divided between active charging points. “The available charging current” might depend on various factors, but in simple solutions, this is a static limit– These solutions are often referred to as Dynamic Load Management, Power Sharing, etc

Sometimes, having just the basic equal share methodology does not help. The available charging current per active station might end up too low: The vehicles are not able to initiate charging after a certain limit has been reached (usually 6A). If the equal share limits charging points to less than 6A, at this point, no one would be able to charge - Unless there is a sophisticated logic, that, after reaching a certain limit, starts pausing some charging transactions, and allowing some to charge. This is where Preconnect comes to play.

Virta Preconnect makes it possible to optimize the charging of the vehicles by pausing (some) charging transactions while letting others charge. It is mostly a solution for large EV charging sites with mainly long-term parking. The goal is to ensure that all plugged-in vehicles will eventually get to charge with a meaningful amount of power while making sure that the site’s infrastructure is not stressed too far.

How does it work

Overview

Pausing of charging transaction(s) takes place only when a certain parameter, minimum current, is not met. As long as this parameter – or requirement – is met, the load management solution will follow its normal sharing logic. Once the requirement is not met for all charging transactions, the Preconnect logic for queuing transactions kicks in: The latest arrivals are set in a queue and they are assigned a priority based on the time of arrival. Unless you are VIP and belong to the Priority driver group - Then you get to skip the line!

Technical details

• “Time of arrival” is defined by the moment when the OCPP status for the charging transaction changes to “Charging” for the first time

• Minimum current dictates how much current each charging point must get at a minimum. There is a separate “minimum current” parameter for both Priority and normal driver profiles.

  • The minimum current condition offers flexibility from site to site:

    • The parameter can be set to e.g., to 6A, when charging points must be able to output the minimum current a vehicle needs to start the charging transaction. This would allow a scenario where the service provider wants to allow as many simultaneous charging transactions as possible but with limited current

    • It can be set to match a station’s maximum rated current and the logic turns into a First In First Out method, where the first priorities are charged as fast as possible while others wait in line for their turn. This allows the service provider to prioritize charging power (= speed) over the number of simultaneous charging transactions

• Once the minimum current is no longer met for all charging points, the first priorities that do meet it will get to charge and the others are suspended - or queue - until more capacity frees up from the earlier priorities

• Charging for the queued transactions will resume once more capacity frees up from the previous charging transactions

• “Queuing” or “pausing” a charging transaction is basically setting the maximum current to 0A using smart charging profiles. Not all hardware support this feature, but some of them do (consult your Virta representative on the compatibility).

• Once Preconnect is enabled, all (electric) current adjustments are made using TxProfile. This is how the manufacturers have implemented the “SuspendedEVSE” feature. Using a ChangeConfiguration won’t simply work.

• Preconnect is compatible with Priority charging. When enabled, all EV drivers within Priority driver group get to charge with the minimum power configured for Priority drivers. The available capacity for non-prioritised is then reduced by equal amount to avoid exceeding the site’s limits.

  • It is possible that Prioritised drivers consume all the available charging capacity, resulting in a situation where all non-prioritised drivers are paused.

  • Once it is no longer possible for the Prioritised drivers to charge with full power without exceeding the site’s limits, the VIPs are also subjected to regular load management – During this time, all the non-prioritised drivers will wait in the queue until more capacity frees up from the  Prioritised drivers.

  • The user interface allows selecting whether Prioritised drivers are included or excluded from Preconnect. By default, Prioritised drivers are included in Preconnect. If Prioritised drivers are excluded from Preconnect, they will always get full power, regardless of the available capacity. This is a special feature that should be used with care!

• Preconnect is compatible with Dynamic Load Management, Adaptive Load Management, Boost charging, Capacity Maximiser and phase balancing.

A practical example of Preconnect in action

Enabling Preconnect to a group of charging points

• Head to Site Management

• Select the tab called Groups

• Select the group you want to enable Preconnect for

• Under Optional you’ll find a checkbox for enabling Preconnect. Enable it.
  
  
  

  

   

• Set the minimum current. The inserterd value cannot be lower than 6A.

• Click Save

• You are done!

• You can disable Preconnect at any point by unchecking the selection

Instructions for reporting issues

We need to know some basic information about the issue in order to investigate it thoroughly. Please provide at least the following information when reporting an issue:

• Problem description: How does the problem occur? What effect does the problem have?

• Which energy services were enabled during the issue?

• Were there any changes made to charger configuration or were new services enabled prior to encountering the issue?

• Date & time of the finding. This information is very important - It is used for going through the station logs.

• Make & model of the charging stations

• Charger IDs (= connector IDs)

• Make & model of the vehicle(s) charging

• What was the vehicle(s) state of charge

• Describe your actions step-by-step. If possible, link relevant OCPP logs to your actions.

Required permissions

In order to use Preconnect, the organisation (CPO) must have "Energy", "Load Management", and "Preconnect" modules activated (in Virta Hub). To be to edit Preconnect settings in Energy UI, Virta Hub User must have the role “Admin” or "Technician".