Understand the differences between each distribution strategy for evacuating the power to the grid when more than one interconnection facility is used.
In this article you'll learn:
- The different distribution strategies for the PV plant
- The different distribution strategies for BESS
- The graphical interface to set main inputs
If you want to learn how to define the interconnection facility schema of your plant, give a look to this article.
The distribution strategy: PV plant
By distribution strategy, we refer to how the software decides which lowest-level facilities are used, which of the first-level SBS or ST drawn by the user are needed to distribute the power and how they connect to the available areas. Depending on the strategy used, the software will use all the facilities or just a selection of the ones available.
There are three possible strategies:
If you know exactly the schema you want to implement, select "Minimize electrical losses" and define the MV cables between the AAs and the lowest voltage level facilities.
Bear in mind that, depending on the strategy selected, some of the drawn facilities could be discarded. Check the schema RatedPower implements in the Overview.
The options Minimize electrical losses and Assign one facility per available area connect one to one the power in a whole AA to a single facility.
The option Balance capacity distribution can connect different power stations from the same AA to different facilities.
Minimize electrical losses
With this strategy, RatedPower picks the lowest voltage level facilities that will minimize electrical losses.
In the following example, the user identified two possible SBS installation areas: one by the main access point (AC) and the other one by the secondary access point (ACb).
Choosing the Minimize electrical losses option, RatedPower selects only one of the SBS to optimally distribute the power to the substation as shown in the picture below.
- The cable length considered for the calculation of the losses is the length of the MV cable path between the lowest-level facilities and the AA.
- If no custom MV cable is defined, the cable length considered is the distance from the MV point of the facility to the one of the AA, or its AC point if there's no MV point.
- If there is a lowest voltage level facility inside the AA, it will be used even if the resulting schema yields higher electrical losses than other schema alternatives.
Balance capacity distribution
This strategy aims to distribute all the power evenly between the lowest voltage level facilities. For this strategy, the user defines all the lowest voltage level facilities to use and RatedPower decides which MV lines to connect to which facility, to have the same amount of capacity assigned to each facility.
In the following example, both facilities are utilized to distribute the power.
- This is the only strategy that allows power stations (PS) from the same AA to be connected to different facilities.
- If the total number of lowest voltage level facilities defined by the user is greater than the total number of MV lines coming out from the PV fields, one or more facilities won't be installed.
- The lowest voltage level facilities placed inside AA are used first, and afterwards, those yielding the lowest electrical losses.
- If MV cables are defined (AA-AA, AA-SBS, AA-ST), RatedPower will use those paths as much as possible.
Assign one facility per available area
This strategy assigns one facility per available area. It's particularly useful when we want to collect the power of each area in a single facility, often placed inside the AA, as in the following example.
- The number of lowest voltage level facilities must be equal to or greater than the number of available areas.
- This option is not available when custom MV lines are defined between AA and the lowest voltage level facilities. If you want to use custom MV cables and one facility per area, use the "Minimize electrical losses" option.
The distribution strategy: BESS
When you have a battery area (BA) to hybridize your PV plant with an AC-coupled BESS (Battery Energy Storage System), its capacity must be distributed too.
- With "Minimize electrical losses" or "Balance capacity distribution", the BESS capacity will be distributed through one or more of the lowest-level facilities of the PV plant, representing less than 70% of each facility's power.
- With "Assign one facility per available area", the whole BESS will be connected to the closest facility.
The interface
In the Grid Point tab you will be able to:
- Select the distribution strategy:
- Set the voltage levels and the maximum current for the MV lines going from the power stations to the first voltage level facility:
- Customize substations including the pooling substation, by selecting the corresponding box:
- Define parameters for each overhead line (OHL), by selecting the corresponding box:
Any questions? Check our Interconnection Facility methodology for more information or contact us at support@ratedpower.com