Dynamic Power Limiter (DPL)
Screenshot
Settings/Parameters
Dynamic UI
Some settings may not be visiable/accessible, depending on your setup of other features, e.g., without a battery interface enabled, SoC thresholds cannot be configured.
General
Enable
Enables or disables the DPL.
Disabling
When disabling the DPL using this switch, the inverter previously managed by the DPL (if any) is shut down. Once it was shut down, the DPL does not send any more commands to that inverter.
Verbose Logging
Enable to log more information regarding the calculation of the power limit to the (serial or web) console. Definitely enable this and read the logs if the DPL does not behave as expected, and share the output in case you seek help.
Target Grid Consumption
The DPL calculates an inverter limit such that the power meter reads this amount of power. To implement a zero export policy, set this value to zero. If this value is negative, the power limit will be calculated such that the configured power is fed into the grid.
Over- and Undershooting
The inverter will over- and undershoot, especially when significant loads (water heaters, electric stoves, etc.) are switch on or off. In particular this means that energy will be fed into the grid for some time (how long depends on the setup) when loads are switched off.
Hysteresis
No limit update will be sent to the inverter if the difference between the calculated new limit and the current limit, as reported by the inverter, is less or equal to this hysteresis value.
Inverter
Target Inverter
Select the inverter to be controlled by the DPL. In the following, this inverter is refered to as the "DPL inverter".
Inverter Is Powered By Solar Modules
Enable if the DPL inverter is powered by solar panels rather than a battery. Switches and settings obsolete for these setups are hidden when this switch is enabled.
Compensate For Shading
For solar-powered inverters only
This option is only available for solar-powered inverters and is not included in the screenshot above.
Cabling limits
Do NOT enable this option if the AC cabling is potentially unable to safely handle the rated inverter output. The rated output is the inverter's AC power output while its limit is at 100% and all inputs deliver such that the inverter does output 100% of its rating, e.g., 2000W for an HMS-2000. The inverter output can surge over the configured maximum power limit if any input is no longer saturated at the expected power level, e.g., if the shading of a solar module is removed.
The calculated limit is usually sent to the inverter verbatim, and the inverter will output the amount of power equivalent to the calculated limit, as it is indeed able to draw the needed power from the battery. All inputs draw the same amount of current.
Enable this option to scale the calculated limit such that the solar-powered inverter is expected to output the calculated limit, despite significantly different power being available on the inputs. This usually happens due to shading of a subset of solar modules. This scaling means that the limit sent to the inverter is actually higher than the calculated limit, but because some inputs are saturated, the effective power output is equal to the calculated limit.
Input Used For Voltage Measurement
The battery voltage is read from the DPL inverter's input with this index if no other source is available to read the battery voltage.
Minimum Power Limit
In case the calculated limit for the inverter is smaller than this value, the inverter is actually
- shut down if the inverter is battery-powered.
- set to this minimum power limit if the inverter is solar-powered.
Stable operation
Small power limits (can) lead to oscillating power output and the inverter shutting down because of these oscillations. As a rule of thumb, the minimum limit should be greater or equal to the amount of inverter inputs times 12W.
Base Load
In case the power meter reading is unavailable (transient error) or in setups without a power meter configured, this value is assumed as the power meter reading. Choose this value such that it is close to but slightly smaller than your household's base load, i.e., the amount of power that is expected to be consumed in any case.
Maximum Power Limit
The inverter limit is set such that its AC output does not exceed this value.
Power Meter Reading Includes Inverter Output
Enable this option if the power meter reading is reduced by the inverter's output when the inverter produces AC power. This is typically true, as the metering happens between the grid and the inverter.
Automatic Restart Time
Persistent Limit
Manually set a low persistent limit when using this feature.
The daily yield of the inverter is usually reset at night when the inverter turns off due to lack of light. To reset the daily yield even though the inverter is continuously powered by the battery, the inverter can be automatically restarted at the desired time.
After the inverter restarts, it starts producing power. How much power that is depends on the value set as the persistent limit. Hence the persistent limit for inverters managed by the DPL shall be very low if they are automatically restarted. Otherwise, a possibly empty battery is drained with possibly high power for some time. The DPL will eventually set a new limit or put the inverter into standby after it restarted.
Solar-Passthrough
Enable Solar-Passthrough
Enables or disables the (Full) Solar-Passthrough feature.
Use Battery At Night Even If Only Partially Charged
The inverter may only draw power from the battery during a discharge cycle. For a discharge cycle to start, the respective start threshold must be reached first. When enabling this option, a discharge cycle also starts roughly on sunset, even if the battery charge cycle did not complete.
(Full) Solar-Passthrough Losses
Line losses are to be expected when transferring energy from the solar charge controller to the inverter. These losses can be taken into account to prevent the battery from gradually discharging in (full) solar-passthrough mode. The power limit to be set on the inverter is additionally reduced by this factor after taking its efficiency into account.
Battery Thresholds
In general, State of Charge (SoC) thresholds take priority over voltage thresholds, i.e., if the battery SoC is known (battery interface enabled, SoC value valid and not outdated) it is used to determine whether or not a particular threshold is reached.
Ignore Battery SoC
Enable this switch to have the DPL use the voltage thresholds rather than the SoC thresholds even though the battery SoC is available. As the SoC value is hard to keep accurate, it is often a good option to start and stop discharging based on the battery's voltage rather than the reported SoC.
Start Threshold for Battery Discharing
Note
This threshold is "reached" if the battery SoC or voltage value is greater or equal to this threshold value.
Drawing power from the battery is allowed once the battery reaches this threshold. Reaching this threshold starts a discharge cycle.
There is no need for this value to be close to the voltage the battery has when it is fully charged. Starting to use a partially charged battery, e.g., during the day while the battery is still being charged, is okay as well.
Stop Threshold for Battery Discharing
Note
This threshold is "reached" if the battery SoC or voltage value is smaller than this threshold value.
Avoid BMS intervention
When using the voltage stop threshold, it should be chosen such that the BMS has no need to interfere, i.e., such that the inverter stops discharging the battery long before the BMS disables dicharging the battery to protect it due to an undervoltage condition.
Battery discharging is avoided once the battery reached this threshold. Reaching this threshold starts a charge cycle.
This value must be smaller than the battery discharging start threshold.
Full Solar-Passthrough Start Threshold
Note
This threshold is "reached" if the battery SoC or voltage value is greater or equal to this threshold value.
See Full Solar-Passthrough documentation.
Set to 0% (SoC threshold) and 66V (voltage threshold) to effectively disable Full Solar-Passthrough while keeping Solar-Passthrough. Otherwise this is typically set to a value that indicates a (nearly) fully charged battery.
Full Solar-Passthrough Stop Threshold
Note
This threshold is "reached" if the battery voltage value is smaller than this threshold value.
See Full Solar-Passthrough documentation.
When starting Full Solar-Passthrough, the battery stops charging as all solar power is used by the inverter to produce AC power. This causes the battery voltage to drop (slightly). Due to fluctuations in the solar power output, the battery might be slightly discharged in Full Solar-Passthrough mode, causing the battery voltage to drop further. For that reason, this threshold shall be configured to a slightly smaller value than the Full Solar-Passthrough start threshold, such that Full Solar-Passthrough is not started and stopped repeatedly.
Load correction factor
Applicable to voltage thresholds
This settings is only applicable if the DPL is using voltage thresholds.
When the battery is discharged, its voltage drops. Additionally, depending on where the battery voltage is read, line losses can significantly influence the voltage reading, especially at high currents. In both cases, the voltage drop scales with the discharge current.
In order to not stop the inverter too early (stop threshold) while the battery is being discharged, this load correction factor can be specified to calculate (estimate) the battery voltage if it became idle. In other words: This value should be choosen such that the battery settles back to around the stop threshold voltage in the moment the DPL decides to stop discharging the battery because it hit the stop threshold.
corrected (idle) voltage = measured battery voltage + (power * correction factor)
This value depends on your setup and requires tuning. Assuming a LFP battery pack, perform the tuning procedure outside the non-linear voltage range, i.e., when the battery is neither full nor empty.
- Disable all battery loads. This possibly means to disable the DPL.
- Let the battery settle and note the idle voltage at the point where the DPL reads the voltage as well, i.e., the voltage reported by the BMS, by the charge controller, or by the inverter input, depending on your setup.
- Enable a high load with a specific power. This typically means to set your inverter to the maximum allowable limit (using the web interface).
- Observe the battery voltage drop and note this voltage (load voltage).
- Disable the load after a couple of seconds.
- The battery voltage should settle back (close) to the idle voltage noted earlier.
correction factor = (idle voltage - load voltage) / specific power