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Dynamic Load Management (DLM)


Managing power for multiple Charging Stations is challenging when current is limited. Bender’s Dynamic Load Management (DLM) system solves this by automatically adjusting charging currents to match available power.

Unlike traditional systems that need extra hardware or struggle with compatibility, the DLM is part of the Charge Controller's core functionality.

A designated Charging Station acts as the DLM Master, managing the others and communicating with an External Meter through standard interfaces like Modbus or Ethernet. The DLM Master collects real-time data every 30 seconds, including Charging Station occupancy, vehicle charging status, phases in use, and available power. It calculates and distributes power based on this data, ensuring efficient and balanced charging.

Example Scenarios:

  • Scenario 1: If one Charging Station is in use, the DLM Master provides the full 32A required for charging.
  • Scenario 2: If two or more Charging Stations are in use, the DLM Master divides the available 50A supply among the active stations.

1. Basic Setup

1.1. DLM Master/Slave Setup

Location in Config UIParameterValueInfo
LOAD MANAGEMENT > Dynamic Load ManagementDynamic Load Mangement - DLM Master/SlaveDLM Master (with internal DLM-Slave)The Charge Controller is part of the DLM and also regulates itself. This option is most commonly used.
DLM Master (Standalone)The Charge Controller is not part of the DLM. It only regulates other Charge Controller.
DLM Slave (Master-Auto-Discovery)The Slave Controller connects to the Master Controller with the same DLM Network Id. For this to work, the DLM Master needs to be fitted with a DLM Network Id. You can set a DLM Network Id under LOAD MANAGEMENT > Dynamic Load Management
DLM Slave (Master-Fixed-IP)The Slave Controller connects to the Master Controller that matches the DLM Master IP set under DLM Master IP and port . To set a fixed IP for the Master Controller, under NETWORK set Mode for ethernet configuration to Static. Under Static network configuration IP set your desired network IP.
caution

We advise you to leave Disable Discovery Broadcasting turned Off. Otherwise the installation of a connection can not be assured.

1.2. Phase rotation

Charging Stations are designed to work with either one phase or three phases. A car can charge using one phase (L1) or three phases (L1, L2, L3), with the phases always positioned 120° apart.

To manage the load effectively and prevent unbalanced power distribution, the system needs to know how each Charging Station’s phases are set or aligned. Without this information, it becomes harder to optimize the charging current and ensure stable operation.

The load management system uses the phase position or rotation data for each Charging Station to evenly distribute the charging current. To further balance loads, the phases are rotated in the sub-distribution system, improving efficiency and stability.

Example:

Charging Station 1

L 1L 2L 3
L1L2L3

Charging Station 2

L 1L 2L 3
L2L3L1

Charging Station 3

L 1L 2L 3
L3L1L2

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 Charging Station is set in the Charging Station itself as the installer has intended for this Charging Station.

caution

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:

SettingInfo
Dynamic Load Management - DLM Master/Slave Specifies the Charging Station's role in a DLM network. There MUST be exactly one DLM Master in a DLM network managing multiple DLM-Slaves.
DLM Network Id Several DLM groupings might coexist in one physical LAN. In case of DLM Master-Auto-Discovery, they are distinguished by Master-Auto-Discovery Network.
Disable Discovery Broadcasting Disables DLM Discovery beacons in the DLM master, preventing DLM slaves from automatically finding their DLM master using the DLM Master-Auto-Discovery feature.
Configure Solar Mode for DLM Specifies if the DLM master allows special handling of DLM slaves for solar energy. 'Only Solar Charging' enables these slaves to charge only when sufficient solar energy is available.
DLM Algorithm Sample Rate The DLM algorithm recalculates and reassigns current to its DLM slaves at this set rate, except for EVs preparing to charge, which are assigned current immediately.
EVSE Sub-Distribution Limit (L1/L2/L3) [A]Overall current limit for DLM available for distribution to EVs.
Operator EVSE Sub-Distribution Limit (L1/L2/L3) [A]Operator current limit for DLM available for distribution to EVs. The 'Operator EVSE Sub-Distribution Limit' is equal or smaller than the 'EVSE Sub-Distribution Limit'.
External Input 1 Config Adds a configurable offset to 'EVSE Sub-Distribution Limit' based on GPI External Input 1.
External Input 1 Polarity Changes the polarity of the input signal 1. "Active high" does not change the polarity, "Active low" inverts the signal.
Ext. Input 1 Current Offset (L1/L2/L3) [A]Offset added to 'EVSE Sub-Distribution Limit' case external input 1 is high.
Solar Mode on this charger Enables additional limiting for this DLM slave to use renewable production.
External Meter Support If enabled, a secondary meter considers additional load power consumption, adjusting EV charging power. Ensure 'Meter configuration (Second)' is set, preferably to a 3-phase, phase-aware meter.
Meter configuration (Second)Energy Management: the type of second meter used only for input to manage the current on the grid. For Modbus/RTU meters the address must be 2.
Main Distribution Limit (L1/L2/L3) [A]Current limit for DLM distribution to EVs and additional loads, typically higher than 'EVSE Sub-Distribution Limit.' Requires an external meter to detect additional load consumption.
External Load Headroom (L1/L2/L3) [A]Safety margin to avoid transient overload situations. The algorithm will keep headroom towards 'Main Distribution Limit'.
External Load Fallback (L1/L2/L3) [A]If the external meter fails or disconnects, 'External Load Fallback' is used as the assumed consumption. A high value will stop EVSE charging due to no available current.
External Meter Location Specifies the external meter's connection location: grid entry point, between external load and installation, or at a renewable energy source (e.g., solar panel).
External Load Averaging Length [sec]Meter values will be averaged in order to avoid transients.
Current Imbalance Prevention If enabled, DLM will not exceed the 'Current Imbalance Limit' configured.
Current Imbalance Limit [A]Maximum allowed phase imbalance. DLM will not exceed the 'Current Imbalance Limit' between phases when assigning current to.
Minimum Current Limit [A]Minimum current limit that charging should not go below.
Disconnected Limit [A]Current limit when disconnected from DLM network.
IT NetworkSet to 'On' for IT (isolé-terre) systems, accepting only 'Single-phase system (IT earthing)' DLM Slaves. Set to 'Off' for other systems, accepting only DLM Slaves with different phase rotation. Incompatible DLM Slaves will be denied.
Clear persistent DLM slave DB Immediately clears the database of known DLM slaves.
Maximum Current SchedulerIf enabled, DLM will not exceed the limit configured in the time tables. Each entry set specifies the maximum allowed current for each phase which is applied at the selected hour.

3. Usage Scenarios

3.1. with external meter

Dynamic load management (DLM) must account for the total load at the house connection, including both charging currents and other household power usage. This allows for real-time adjustments in power distribution to Charging Stations.

In some cases, Grid Connection Points (GCPs) seem unsuitable for adding Charging Stations because fixed power allocation isn’t possible. Additionally, electric vehicles rarely use their maximum charging capacity, which can lead to underutilized power. Without a system to measure and allocate unused power, efficiency suffers.

The DLM continuously measures power usage at the GCP to identify reserves during periods of lower building demand (e.g., "load valleys"). It dynamically allocates this unused power to Charging Stations.

Charging current is adjustable based on the vehicle’s requirements, and the DLM ensures any unused capacity is distributed efficiently among other stations. Depending on the setup, an additional meter can be placed either after the grid operator’s meter (including EVSE sub-distribution) or within the sub-distribution (excluding EVSE sub-distribution). This setup incorporates household loads into DLM calculations, ensuring efficient and balanced power distribution.

  • Scenario 1: If one Charging Station is in use, the DLM Master provides the full 32A required for charging.
StepDescriptionParameterValueInfo
1Specify the Charging Station's role in a DLM network. There MUST be exactly one DLM Master in a DLM network managing multiple DLM-Slaves. Typically, a Charging Station configured as DLM Master will also host an internal DLM-Slave.Dynamic Load Mangement - DLM Master/SlaveDLM Master (with internal DLM-Slave)The Charge Controller is part of the DLM and also regulates itself. This option is most commonly used.
DLM Master (Standalone)The Charge Controller is not part of the DLM. It only regulates other Charge Controller.
2When the DLM Master has been identified the remaining Charge Controllers need to be identified as the DLM Slaves.Dynamic Load Mangement - DLM Master/SlaveDLM Slave (Master-Auto-Discovery)The Slave Controller connects to the Master Controller with the same DLM Network Id. For this to work, the DLM Master needs to be fitted with a DLM Network Id. You can set a DLM Network Id under LOAD MANAGEMENT > Dynamic Load Management
DLM Slave (Master-Fixed-IP)The Slave Controller connects to the Master Controller that matches the DLM Master IP set under DLM Master IP and port . To set a fixed IP for the Master Controller, under NETWORK set Mode for ethernet configuration to Static. Under Static network configuration IP set your desired network IP.
3Set the overall current limit for DLM available for distribution to EVs.EVSE Sub-Distribution Limit (L1/L2/L3) [A]50/50/50
  • Scenario 2: If two or more Charging Stations are in use, the DLM Master divides the available 50A supply among the active stations.

3.2. Load Throw-Off Management

In environments with multiple consumers, some need a constant electrical supply, while others have variable electrical needs.

Without proper management, electrical supply distribution can lead to overloads or inefficient use of available power.

The load throw-off feature ensures efficient distribution of electrical supply, preventing overloads and optimizing power usage. 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:

  • 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.

  • 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

  1. Apply the following configuration:

Location in Config UIParameterValue
Load Management >
Dynamic Load Management
Dynamic Load Management - DLM Master/Slave DLM Master (With internal DLM-Slave)
EVSE Sub Distribution (L1/L2/L3)[A]
L 1L 2L 3
240240240
External Input 1 Config Enable Opto 1 in
External Input 1 Polarity Active low
External Input 1 Current Offset
L 1L 2L 3
-140-90-90
  1. At the bottom of the Config UI, click , then click to apply the changes

Configuring the Slave Controller

  1. Apply the following configuration:

Location in Config UIParameterValue
Load Management >
Dynamic Load Management
Disconnected Limit [A]10
  1. 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

  1. Apply the following configuration:

Location in Config UISet Parameterto
Load Management >
Dynamic Load Management
Dynamic Load Management - DLM Master/Slave DLM Master (With internal DLM-Slave)
EVSE Sub Distribution Limit (L1/L2/L3)[A]
L 1L 2L 3
323232
External Input 1 Config Enable Opto 1 in
External Input 1 Polarity Active low
External Input 1 Current Offset
L 1L 2L 3
-25-25-25
Disconnected Limit [A]7
  1. At the bottom of the Config UI, click , then click to apply the changes

Configuring the Slave Controller

  1. Apply the following configuration:

Location in Config UIParameterValue
Load Management >
Dynamic Load Management
Disconnected Limit [A]7
  1. 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, and can draw power from a single-phase or three-phase network.

Many competitor systems assume equal loading on all phases, regardless of actual usage, which leads to inefficient power distribution.

The DLM system detects whether the vehicle is using a single-phase or three-phase charger. For example, if a vehicle with a single-phase charger draws 16A, only the corresponding phase is used, keeping other phases available for additional charging. The system also takes phase rotation into account. For more details, see the "Phase Rotation of the Charging Station" section.

3.4. Imbalance Prevention

In Germany, network operators must comply with technical connection conditions (TAB), which limit the apparent power of a phase to 4.6 kVA compared to the neighboring phases.

This means single-phase loads can draw a maximum of 20A if the other phases are not loaded. A skew load occurs when one phase conductor is loaded by more than 20A compared to the other two phases in a three-wire system.

To avoid skew load, it is essential to ensure that the phase currents are balanced, keeping the load within the required limits.

ExamplesPhase setupResult
1
L 1L 2L 3
101520
No difference between all outer conductors by > 20 amperes. Thus, there is no violation of the maximum allowed asymmetry.
2
L 1L 2L 3
101536
L3 is loaded 21A > L2 and 26A > L1. As a result, the max. permissible unbalanced load of 20 A is exceeded.

Electric vehicles can vary in their charging behavior, sometimes drawing over 20A even at a 3 x 32 amp Charging Station, which can lead to unbalanced loads due to a lack of communication between the vehicle's on-board charger phase and the Charging Station.

This imbalance occurs because the vehicle and Charging Station may not coordinate properly, potentially causing overloads or inefficient power usage.

Our Dynamic Load Management (DLM) system provides a solution through Current Imbalance Prevention, which monitors and corrects any asymmetry above a specified threshold. The system’s skew load limit ensures that single-phase loads over 20A are allowed if balanced across phases.
For example, three vehicles with 32-amp chargers can charge on separate phases without exceeding limits. The system detects and adjusts the current, enabling 1 x 32-amp Charging Stations or limiting unbalanced loads for 3 x 32-amp 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.

  1. To configure the Time Profile turn Maximum Current Scheduler On
  2. 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:

Time: from - toDLM Current Limit (L1/L2/L3)
01:00 - 04:00
L 1L 2L 3
000
04:00 - 18:00
L 1L 2L 3
909090
18:00 - 23:00
L 1L 2L 3
100100100
23:00 - 01:00
L 1L 2L 3
150150150
  1. At the bottom of the Config UI, click , then click to apply the changes