7. Multiphase regulation - further information
7.1. Introduction
Use the multiphase regulation setting in systems with a three-phase connection to the utility grid. The setting defines how the ESS interacts with the different phases.
By default, the "Total of all phases" option is selected. All phases are adjusted to convert the same power both from and to DC. It divides the work equally across the phases, thereby making the full capacity available and optimal billing.
This setting has no effect on single-phase systems and can therefore be ignored.
When the ESS mode is set to Keep batteries charged, this setting has no effect.
Single-phase connection to the utility grid
Phase compensation setting has no effect and can be ignored.
Single-phase ESS in a system with a three-phase connection to the utility grid
Single-phase ESS is a single inverter/charger.
"Total of all phases" selected - ESS regulates total power L1 + L2 + L3 to 0.
"Individual phase" selected - ESS regulates only the power of L1 to 0.
Three-phase ESS in a system with a three-phase connection to the utility grid
A three-phase ESS consists of at least three inverters/chargers, one in each phase.
"Total of all phases": ESS symmetrically outputs the same power on all phases, attempting to keep the sum total to 0.
"Individual phase": ESS regulates each separate phase to 0 W. This may result in ESS discharging on one phase whilst charging on another via the DC bus, which is much less efficient.
7.2. Single-phase ESS in a three-phase system
With "Total of all phases" selected, the (single-phase) ESS uses the battery to balance the combined power of all phases to 0 W (zero watts).
See the following example: ESS is connected to L1, and by compensating for phases L2 and L3 as well, it regulates the total power at the distribution panel to 0 W.
L1 | L2 | L3 | Total | |
|---|---|---|---|---|
Load | 100 W | 400 W | 200 W | 700 W |
ESS | -700 W | 0 W | 0 W | -700 W |
Distribution box | -600 W | 400 W | 200 W | 0 W |
With "Individual phase" option selected , the (single-phase) ESS uses the battery to balance only L1 to 0 W. L2 and L3 are visible on the CCGX, but not used by the ESS in any way.
(Make sure you install the ESS on L1. If it's installed on another phase, the visualisation will be wrong and the function impaired.)
7.3. Three-phase ESS
A three-phase ESS system has at least one Multi installed on each phase. We recommend leaving the Multiphase regulation setting to its default: "Total of all phases".
Installation details
The Multis need to be configured as a three-phase system. Use VE.Bus Quick Configure or VE.Bus System Configurator for this.
Install the ESS Assistant in all units …all the phase-masters and also all slaves (if any).
Three-phase loads: it is possible to connect three-phase loads to the AC-out of the Multis. Those loads will be powered from the battery during a power failure.
Multiphase Regulation - "Total of all phases" (default & recommended)
ESS balances the total power (L1 + L2 + L3) to be net 0 W on the meter, and symmetrically loading the inverters.
In the example below the loads on L1 are 6000 W, exceeding capacity of the inverter on that phase. L2 and L3 have loads of 0 W. Looking at the sum of all three phases: the ESS system is able to provide surplus from the L2, and L3, to displace the load on the L1. This is optimal for billing efficiency.
Load | ESS | On the meter | |
|---|---|---|---|
L1 | 6000 W | 2000 W | 4000 W |
L2 | 0 W | 2000 W | -2000 W |
L3 | 0 W | 2000 W | -2000 W |
Sum | 6000 W | 6000 W | 0 W |
Similarly in a PV with Load situation: if there would be 6kW excess PV on L1, and the same inverter/charger configuration, all inverter/chargers will be charging at approximately equal power:
PV + Load | ESS | On the meter | |
|---|---|---|---|
L1 | -6000 W | 1800 W | -4200 W |
L2 | 600 W | 1800 W | 2400 W |
L3 | 0 W | 1800 W | 1800 W |
Sum | -5400 W | 5400 W | 0 W |
Note: Excess PV power from solar chargers is not actively made symmetrical across phases.
PV + Load | ESS | On the meter | |
|---|---|---|---|
L1 | -6000 W | 0 W | -6000 W |
L2 | 0 W | 0 W | 0 W |
L3 | 0 W | 0 W | 0 W |
Sum | -6000 W | 0 W | -6000 W |
"Individual phase" mode selected
ESS balances the power of each separate phase to 0 W.
Beware: using the system this way causes significant losses as power will flow from one AC phase to another via the DC connections. This incurs losses caused by converting from AC to DC on one phase, and then back again from DC to AC on the other phase.
Note on the maximum charge current
In a multi-phase system, the charge current is configured per phase - rather than for the whole system. A limitation of this arrangement, for example, is where a relatively small battery bank is installed, and at a certain moment a significant over-supply of PV power is available on L1 - but not on the other phases, then only a part of that excess PV power on L1 will be used to charge the battery.
Note on Energy meters in a 3-phase system
It is generally recommended to install an EM24 Energy Meter in a 3-phase system instead of an ET340 Energy Meter. The reason is the different aggregation methods used by them. The EM24 creates a net sum count of grid energy, which is not the case with the 3 Multis and the ET340 and therefore also affects the VRM evaluation of the imported and exported energy. This then can lead to discrepancies between the data displayed on the VRM portal and the grid meter of your provider. See also FAQ Q14: Why does my split- and 3-phase ESS VRM data not match my billing.