Dynamic Load Management
The integrated Dynamic Load Management (DLM) by Bender offers a way to adapt the charging currents of multiple Charging Stations to the available current.
This DLM functions as a local load management system, where Charging Stations are interconnected through an Ethernet or WLAN network connection and configured individually via their Config UIs.
This setup is already integrated as a software function and eliminates the need for an external Load Manager.
It also allows integrating additional Charging Stations into the network, regardless of the OEM.
0.1. Functionality
The Bender DLM is overseen by a DLM Master, which can be any charge point designated within the group or installation. It manages other charge points. Communication is facilitated through various interfaces like Modbus or TCP (Ethernet), allowing the DLM Master to connect with an External Meter and communicate with all charge points.
The DLM Master receives phase-accurate measurements from the current transformers to calculate available power. The DLM Master also receives a status report by the Charge points every 30 seconds, containing information such as the occupancy of the charging station, the charging status of the vehicle, the phase or phases on which the vehicle is charging and the available charging current. Based on this information, the DLM Master calculates the available power and distributes it to the charging vehicles according to the defined charging models.
The following scenario is intended to illustrate the use of the Bender DLM:
A sub-distribution of a building has a total of 50 A available and is connected to a charging structure that consist of four charging stations. Each charging stations allocates 32 A. This limit of 50 A is known by the DLM Master. Depending on how many charging stations are being occupied at the same time, the available load is then being divided between the four charging stations.
For example:
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Scenario 1: One charge point is being occupied with 32 A The DLM Slave sends the information including the status of the charging station, the assumed maximum charging current (AMCC) and on which phase the vehicle is charging to the DLM Master. The DLM Master the provides the Charging Station with the needed 32 A
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Scenario 2: Two or more Charge points with 32 A each are being occupied at the same time The DLM Slaves communicate with the DLM Master the needed information. The DLM Master divides the available load (50 A) between the occupied charging stations.
When one charging process ends, the excessive load is then divided and added to the load of the still occupied charging stations.
1. Basic Setup
1.1. DLM Master/Slave Setup
We advise you to leave Disable Discovery Broadcasting turned Off. Otherwise the installation of a connection can not be assured.
1.2. Phase rotation
Charge points are usually designed with one or three phases. This means that a car can charge at such charge points via the phase conductor L1 (single-phase) or via the phase conductors L1/L2/L3 (three-phase). The phase relation to each other is always 120°. For the load management to optimally distribute the charging current and avoid unbalanced loads, the information of the phase position or phase rotation must be set or communicated for each Charging Station. In order to be able to distribute loads better, the phases are rotated in the sub-distribution. Example:
Charging Station 1
| L 1 | L 2 | L 3 |
|---|---|---|
| L1 | L2 | L3 |
Charging Station 2
| L 1 | L 2 | L 3 |
|---|---|---|
| L2 | L3 | L1 |
Charging Station 3
| L 1 | L 2 | L 3 |
|---|---|---|
| L3 | L1 | L2 |
This rotation is done in order to distribute the load generated by single-phase charging cars as evenly as possible to all phases.
The parameter Phase rotation of the Charge Point is set in the Charging Station itself as the installer has intended for this Charging Station.
Double Charging Stations may already be connected through phase rotation.
2. Configuration
The Setup and configuration can be done either locally via the web Interface or remotely using OCPP Change Configuration.
The following table offers an overview of the different available settings found under LOAD MANAGEMENT > Dynamic Load Management:
3. Usage Scenarios
3.1. with external meter
The DLM needs to understand the overall load at the house connection, accounting for both charging currents and other consumer loads. This allows for dynamic adjustments in current distribution to the LP.
Certain Grid Connection Points (GCPs) design may appear incompatible with additional charging stations in theory, as fixed power allocation for charging is not possible. However, variations in building load, like "load valleys" and reserves, can be identified through continuous power measurements at the GCP. The DLM then allocates these reserves to charging stations.
Electric vehicle charging current is adjustable, with the Charging Station specifying the maximum. This means the vehicle adapts its charging rate accordingly. Considering factors like charging duration and battery level, the maximum potential power (e.g. 11 kW or 22 kW) is seldom fully utilized. Load management accounts for this, ensuring any surplus is efficiently distributed among other charge points.
The additional meter can be placed directly after the grid operator's meter (Including EVSE Sub-Distribution) or in the sub-distribution after the charge point branch (Excluding EVSE Sub-Distribution). The choice may depend on installation conditions and UV design.
This approach incorporates the additional consumer load into the DLM calculations.
3.2. Load Throw-Off Management
The load throw-off feature helps manage electrical supply distribution in environments with multiple consumers, some requiring a constant electrical supply and others with variable electrical needs. This feature ensures that electrical supply is distributed efficiently, preventing overloads and optimizing the available power. Below are scenarios illustrating how this feature works.
Example Scenario 1: Factory with Staff Canteen and EV Chargers
A factory operates a staff canteen and provides 10 EV chargers for company fleet cars. Both facilities share a contract with load limits of 3 x 250A. During service hours, the kitchen consumes 150A on L1, 100A on L2, and 100A on L3. A signal is provided when the kitchen is not busy, and consumption falls below 10A.
In this scenario, the load throw-off process operates as follows:
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When the kitchen is not busy, the EV charging infrastructure may consume up to 240A (250A – 10A). The control electronics provide a 12V DC signal, allowing the DLM system to use the full 3 x 240A.
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When the kitchen is in use, the load of 140A on L1, 90A on L2, and 90A on L3 needs to be thrown off to avoid exceeding the 3 x 250A limit. In this case, the DLM may only consume 100A on L1, 150A on L2, and 150A on L3.
Configuring the Master Controller
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Apply the following configuration:
- At the bottom of the Config UI, click , then click to apply the changes
Configuring the Slave Controller
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Apply the following configuration:
- At the bottom of the Config UI, click , then click to apply the changes
Example Scenario 2: Grid Operator with Ripple Control In this example, one or more 22kW wall boxes must reduce load to 3 x 7A (5kW) when a control signal is low.
Configuring the Master Controller
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Apply the following configuration:
- At the bottom of the Config UI, click , then click to apply the changes
Configuring the Slave Controller
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Apply the following configuration:
- At the bottom of the Config UI, click , then click to apply the changes
Limitations of the Load throw-off function
- The load can only be reduced instantly and not gradually over a time interval
- With DLM active, only the current can be reduced, not the power (reduction 32A 🡒 7A, but not 22kW 🡒 5kW)
3.3. Phase-specific load management
A rechargeable electric vehicle is equipped with a built-in charger that connects to a compatible Charging Station via a cable. This charger can draw power from either one or all three phases in a three-wire network (single-phase or three-phase).
Unlike some competitor systems that assume equal loading on all phases regardless of actual usage, the DLM detects whether the connected vehicle is single-phase or three-phase. For example, if a vehicle with a single-phase charger is drawing 1 x 16 amps, only the corresponding phase is reserved, leaving the others available for additional charging. Phase rotation is also considered. For more information, refer to the "Phase Rotation of the ChargePoint" section.
3.4. Imbalance Prevention
Many network operators in Germany are required by their technical connection conditions (TAB) not to allow the apparent power of a phase to exceed 4.6 kVA compared to the two neighboring phase conductors. This means: single-phase loads may draw a maximum current of 20 amps in total if the other two phases are not loaded. Thus, a skew load occurs when in a three-wire system one phase conductor is loaded by > 20 amperes than the other two phase conductors.
Electric vehicles vary in their charging behavior, sometimes drawing over 20 amps even at a 3 x 32 amp Charging Station. This can lead to unbalanced loads due to a lack of communication between the vehicle's on-board charger phase and the Charging Station. Bender/ebee's load management offers a solution through 'Current Imbalance Prevention,' which monitors and corrects any asymmetry above a specified threshold.
The system's skew load limit considers all managed charge points, allowing single-phase loads over 20 amps if balanced across phases. For instance, three vehicles with 32 amp on-board chargers can charge on separate phases without exceeding limits. Load management detects and adjusts the allowed current. This enables 1 x 32 ampere charge points or limits unbalanced loads for 3 x 32 ampere points.
3.5. The "Maximum Current Scheduler" function
In addition to the function of load management without or with an external metering, there is another function to (semi-)dynamically control the load management without external metering.
The function Maximum Current Scheduler under Load Management > Dynamic Load Management allows to determine the parameters of the Operator EVSE Sub-Distribution Limit via a time table depending on the time of day.
With a known and recurring load profile, the charging currents can thus be increased or decreased at times when sufficient reserves are always available. For example, in a single-family home where 60% reserve is always available at the house connection at night, the available charging currents could be ramped up at exactly these times.
- To configure the Time Profile turn
Maximum Current SchedulerOn - Click on
Add Entry
At least two entries are necessary. The set currents are always valid from the set time. That means, from the entered time to the next following time this charging current is valid for the DLM. This also applies if the times are not displayed in chronological order. In the example on the right, this means that no charging current is available from 1 o'clock to 4 o'clock. Here it does not matter that the time point '1 o'clock' is at the top and the time point '4 o'clock' is at the bottom.
The times are entered according to Coordinated Universal Time (UTC). The time in Germany is therefore in winter one hour later UTC + 1 = CET - Central European Time and in summer two hours later UTC + 2 = CEST - Central European Summer Time. The fully resolved and chronologically ordered would translate into the following table:
- At the bottom of the Config UI, click , then click to apply the changes
3.6. Solar DLM
Solar DLM extends the DLM algorithm for charging stations with PV systems, allowing them to use generated solar power for charging without needing an external energy management system.
Ensure you have a basic DLM setup, an installed PV system, and an external meter measuring positive PV energy production, placed behind the inverter or at the grid connection point.
The Solar DLM algorithm prioritizes PV energy for non-solar connectors first, then distributes remaining energy to solar-mode-enabled connectors to prevent using grid electricity. Solar connectors receive energy on a first-come, first-served basis. Non-solar connectors will charge from either the PV system or the grid, based on PV production. The algorithm uses a balancing grid meter to distribute current independently of production and consumption phases.
Configuration
- Log in to the Config UI using the Operator Login Credentials
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Apply the following configuration:
Settings for the DLM Master
Settings for the DLM Slave
- At the bottom of the Config UI, click , then click to apply the changes