This support article is applicable to the Congestion Management service used via the following user interface: https://energy.virtaglobal.com/.
Congestion Management is one of Virta’s solutions in the smart energy management portfolio. With Congestion Management, it is possible to create rules for controlling the amount of power delivered to EVSEs based on a specific time of day. Congestion Management enables centralized management of a wide network of EVSEs, allowing the same constraints to be applied to several charging sites, regardless of their location.
Congestion Management offers the following benefits for customers aiming to optimize power consumption of EVSEs based on grid capacity limitations and electricity production:
- Reduces electricity costs by adjusting the power consumption of the EVSEs to align with favorable electricity pricing.
- Ensures compliance with various legislations and network restrictions by modulating power consumption during specific time periods.
- Promotes the use of renewable energy sources in the grid by adapting the power consumption of EVSEs according to their availability.
- Design customized charging schedules to better manage EVSEs' power consumption based on individual customer requirements.
What you can expect to find in this article
How does it work?
Congestion Management is based on a set of "rules" applied to specific groups of EVSEs. Different event types and charging modes combine to form these rules.
The event type determines when the rule is applied. Options include: One time, Daily, and Weekly. The charging mode specifies the amount of power delivered to the EVSEs. There's no limit to the number of events that can be set for a single day.
It's worth noting that while Congestion Management is compatible with both AC and V2G chargers, the core functionalities vary based on the charger type. The table below outlines the available charging modes for AC EVSEs.
Charging modes explained
Mode |
Description |
Target power |
The user can define the target power for the EVSEs. Units to be used: kW.  In the backend, the max power is first converted to current* (as most ACs can only be adjusted by using units of electric current), and then, depending on the station capabilities, the available charging current is communicated to EVSEs either using the |
Minimum power |
The EVSEs are set to minimum power. On the Virta Hub, minimum power equals 6A per phase. This is due to the fact that many EVs have thresholds below which they might terminate charging due to too low a current (to learn more, please explore the PWM signal). And in many cases, that threshold is a value lower than 6A.Examples of the power output for different installations:
|
Local control |
Congestion Management will no longer govern the charging events. Charging will continue based on the most recent request from CM until another service provides different instructions to the EVSE. The key takeaway is that CM will no longer send adjustments to the EVSE. |
Once established, rules are assigned to EVSEs by associating specific group(s) with them. There's no limit to the number of groups that can be linked to a particular rule set. While EVSEs connect to rules through a group, it's the individual EVSEs that the rules directly influence. For instance, if a rule states "from 3 p.m. onward, the charging power is capped at 5kW," it essentially means each EVSE can draw up to a maximum of 5 kW.
The logic for re-applying the rules
The Congestion Management logic includes a fail-safe mechanism for instances when an EVSE declines initial requests or if it goes offline before a new event is activated. The currently active event is re-sent to the EVSEs every 2 minutes. To prevent unnecessary data transfers to the EVSEs, these requests are throttled. In essence, if the most recent request to the EVSE matches the current event, no further actions are initiated.
There might be a delay of a few minutes in applying new events to EVSEs, contingent upon the monitoring cycle and network quality.
Payloads
Messages for adjusting the current
DEFAULT:
As Congestion Management is not specific to a certain charging transaction (who & what you are) but rather the timing of the charging, the backend applies the smart charging profile called TxDefaultProfile to control the electric current levels instead of using the transaction-specific TxProfile. TxDefaultProfile is valid until it is either 1) erased using a clear charging profile, 2) permanently replaced by another TxDefaultProfile or 3) temporarily bypassed by a TxProfile. To learn more about the previous messages, please refer to the OCPP 1.6 protocol.
STATIONS WITH LEGACY INTEGRATIONS:
For stations that are not either tested for smart charging profiles or that do not support smart charging profiles, we use the change-configuration request combined with the vendor-specific keys for adjusting the current.
Units
With AC stations, we always use units of electric current, as many AC stations do not support adjusting power.
Limitations
Minimum current/power
Even though Congestion Management allows for controlling the charging power, the backend always converts the power to current, because many EVSEs cannot be controlled by units of power. When performing these conversions, the backend adheres to the following logic: The service will not output a current rating below 6A.
Therefore, it's impossible to set the charging current/power under this value. Given that the present OCPP implementation doesn't allow for individual phase control, an equal load is applied to all phases. Having said that, the minimum power output differs for 1-phase and 3-phase stations as follows:
For a 3-phase installation, the minimum power output is 6A * (230V * 3) = 4140 W.
For a 1-phase installation, it's 6A * 230V = 1380 W.
In summary, any values under 6A are automatically adjusted to 6A by the backend. Additionally, Congestion Management does not support the pausing or suspending of charging transactions
The conversion logic’s effect on the power output
-
Effect on power output:
- For a 3-phase charging transaction/station, the minimum power is calculated as 6 Amps times 230 Volts times 3, which equals 4140 Watts.
- For a 1-phase charging transaction/station, it’s 6 Amps times 230 Volts, equaling 1380 Watts
- Uniform phase load: The maximum current is applied to all phases, as many chargers don’t enable controlling individual phases.
-
Limitations on adjusting power:
- When a power limit is set, such as 8 kW, the system first converts this into a current value assuming a 3-phase and 230V system. For example, 8 kW converts to approximately 11.6 Amps on a 3-phase, 230V system.
- In 1-phase systems, this conversion results in a lower actual power output than intended. Using the above conversion, 11.6 Amps on a 1-phase system equals about 2668 Watts or 2.7 kW, not the full 8 kW.
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Key Points:
- The minimum current is always adjusted to 6 Amps.
- The minimum power output varies between 1-phase and 3-phase installations.
- Power limits are converted to current assuming a 3-phase system, affecting actual output o 1-phase systems.
- The system doesn't pause or suspend charging.
Offline EVSEs
As Congestion Management is a cloud-based solution, there is no way of controlling EVSEs that are offline. If an EVSE loses its internet connection, it will continue charging according to the latest request it accepted before losing its connection. CM will resume active control of the charging event once the EVSE re-establishes an online connection and begins reporting OCPP status changes to the backend.
Requirements & compatibility
| Prerequisites |
|
| Requirements regarding meter values |
Note: The core CM logic does not rely on meter values; however, the aforementioned meter values are required for displaying the data and for troubleshooting purposes. Without the meter values, the platform lacks visibility into the total load and power draw
|
| Requirements regarding the ability to change the maximum current/power rating during an active charging transaction |
|
A practical example of Congestion Management in action
The rules are created using a calendar-like tool, as demonstrated in the screenshot below:
In this example, the rules are applied to each individual EVSE that is connected to this rule through a group. First, the EVSEs are grouped together, and then the group is linked to the rule.
When a rule becomes active, it sends a corresponding payload message to each EVSE, intending to adjust their current rating according to what is defined in the rule. You can track how the EVSEs respond to Congestion Management by either examining the OCPP logs or by observing the graphs that EnergyUI generates from the meter values reported by the EVSEs. The latter method offers a more effective way to analyze EVSE behavior.
Here is an example of how the meter values reported by an EVSE are visualized:
Setting up a group and enabling Congestion Management for ACs
- Head to Congestion Management
- Click Create a new rule
- Name your rule
- Select the group type as CHARGER, which essentially defines the group type as AC
- In order to create new events to your rule, select Add new event
- The event calendar opens up. First, you need to select the Event type, which defines when and how often the event occurs. Then you need to define the Charging mode, which defines what exactly happens at the given time.
- Once the Event type and Charging mode have been selected and defined, click Add and the event is added to the Event calendar.
- You can continue adding new events now or do it later. You can add new events to your rule at any given time.
- Congestion Management is applied to group(s) of EVSEs. To connect group(s) to follow the rule, click Connect more groups.
- Select the group(s) you wish to follow the rule and click Connect selected groups.
- Click Save from the bottom of the page. The Congestion Management rule is now created and activated.
- It is possible to disable/enable rules on the page that lists all your Congestion Management rules.
Troubleshooting guide
If you believe that Congestion Management is failing to control one or more EVSEs, check the following:
- Is the EVSE connected to a group that is linked to the CM rule? If not, connect the EVSE to a group and ensure that the group is linked to the rule.
- Is the EVSE online? Congestion Management is a cloud-based service, which means that the EVSE must be online and connected to the Virta backend to receive control commands.
- Are other energy management features enabled simultaneously? For example, if you have Dynamic Load Management enabled and it requests a lower power rating from the EVSE than what Congestion Management does, then the requests made by DLM are prioritized.
- Are the EVSEs displayed as Supported (either Basic support or Full support) in EnergyUI? If not, then it means that the specific station type has not been integrated for energy services. If this is the case, please reach out to your Virta point of contact.
If you continue to face issues, please contact Virta support at support@virta.global. Ensure to include all the information described in the "Instructions for reporting issues" section.
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 the EVSE configurations?
- 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 detailed logs.
- Make & model of EVSEs
- EVSE 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 access Congestion Management, the user must have the role “V2G Congestion Management”. This role is assigned by our Support team.