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Summary

Array-level calculations aggregate individual outputs, apply AC losses in sequence—auxiliary load deductions, losses, and AC collection system losses—then aggregate array outputs to the block level. Each array is calculated independently using repeater counts at both the inverter and array levels.

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Inputs

NameSymbolUnitsDescription
Inverter AC PowerPAC,invP_{AC,inv}WAC power output of each inverter (from Inverter Efficiency)
Inverter Rated AC PowerPAC,ratedP_{AC,rated}kVAInverter nameplate AC power rating
Inverter Repeater Countnrep,invn_{rep,inv}—Number of identical inverters represented
DAS LoadLDASL_{DAS}WData acquisition system power consumption
Cooling LoadLcoolL_{cool}WInverter/equipment cooling power consumption
Tracker Motor LoadLtrackL_{track}WTracker motor power consumption
MV Transformer RatingPMV,ratedP_{MV,rated}kVAArray-level MV transformer nameplate capacity
MV No-Load LossLNL,MVL_{NL,MV}%MV transformer no-load loss as a percentage of PMV,ratedP_{MV,rated}
MV Full-Load LossLFL,MVL_{FL,MV}%MV transformer full-load loss as a percentage of PMV,ratedP_{MV,rated}
AC Collection Lossfcollf_{coll}%AC collection system loss percentage at max power
Array Repeater Countnrep,arrayn_{rep,array}—Number of identical arrays represented in the block

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Outputs

NameSymbolUnitsDescription
Block PowerPblockP_{block}WAggregated AC power at block level, after all array-level losses

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Detailed Description

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Inverter Aggregation

Each array may contain multiple inverters (with repeater counts). Because all inverters in an array operate at the same AC voltage and frequency, they are connected in parallel upstream of the MV transformer and their powers add directly. The total array-level AC power is: PAC,array=∑invertersPAC,inv×nrep,invP_{AC,array} = \sum_{inverters} P_{AC,inv} \times n_{rep,inv} This aggregated power is the input to AC degradation (see Degradation Losses (AC Applied)), which produces PAC,degP_{AC,deg}, accounting for both standard degradation and losses.

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Auxiliary Loads

Auxiliary loads are constant power deductions subtracted from the degraded AC power before transformer losses. The tracker motor load (LtrackL_{track}) is aggregated from per-DC-field “Tracker Actuator Load” inputs (specified in MWh/MWp/year), scaled by each field’s DC capacity and repeater counts on DC fields and inverters; it is zero for fixed-tilt systems. Paux=PAC,deg−LDAS−Lcool−LtrackP_{aux} = P_{AC,deg} - L_{DAS} - L_{cool} - L_{track} Before the , all auxiliary loads are zero (the system is not yet commissioned). After energization:
  • DAS load is applied regardless of whether the array is producing power.
  • Cooling and tracker motor loads are applied only when the total inverter output is positive (PAC,array>0P_{AC,array} > 0); otherwise they are zero.
  • overrides all of the above: when triggered, all three auxiliary loads are set to zero (see Inverter Operating Regions for trigger conditions).

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MV Transformer

If an MV transformer is defined for the array, the Transformer Loss Model is applied to PauxP_{aux}: PMV=Paux−LMV,transP_{MV} = P_{aux} - L_{MV,trans} where LMV,transL_{MV,trans} is computed from the quadratic loss equation using PMV,ratedP_{MV,rated}, LNL,MVL_{NL,MV}, and LFL,MVL_{FL,MV}. When Nighttime Disconnect is enabled and triggered, the transformer no-load loss is set to zero, eliminating standby core losses. If no MV transformer is defined, there is no loss: LMV,trans=0L_{MV,trans} = 0 and PMV=PauxP_{MV} = P_{aux}.

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AC Collection System

AC collection losses represent resistive losses in the medium-voltage cabling between the MV transformer and the plant-level collection point. The input loss percentage fcollf_{coll} is converted to a fraction before use. Versions 3–11 (Flat Percentage Model): During daytime operation (PMV>0P_{MV} > 0): Lcoll=PMV×fcollL_{coll} = P_{MV} \times f_{coll} Pcoll=PMV−Lcoll=PMV×(1−fcoll)P_{coll} = P_{MV} - L_{coll} = P_{MV} \times (1 - f_{coll}) During nighttime operation (PMV≤0P_{MV} \leq 0), power flows in reverse—the grid supplies current through the collection system to keep transformers energized. The collection line losses compound: the grid must supply extra power to cover the losses, and that extra power itself incurs additional losses. The effective loss fraction becomes (1+fcoll)2−1≈2fcoll(1 + f_{coll})^2 - 1 \approx 2 f_{coll} for small fcollf_{coll}: Lcoll=∣PMV∣×[(1+fcoll)2−1]≥0L_{coll} = |P_{MV}| \times \left[ (1 + f_{coll})^2 - 1 \right] \geq 0 Pcoll=PMV−Lcoll=PMV×(1+fcoll)2≤0P_{coll} = P_{MV} - L_{coll} = P_{MV} \times (1 + f_{coll})^2 \leq 0 Version 12+ (Quadratic Model): Loss scales quadratically with power flow, reflecting the I²R characteristic of conductor losses: Lcoll=∣PMV2PAC,rated,array×fcoll∣L_{coll} = \left| \frac{P_{MV}^2}{P_{AC,rated,array}} \times f_{coll} \right| where PAC,rated,arrayP_{AC,rated,array} is the total inverter rated capacity for the array (scaled from kVA to VA): PAC,rated,array=∑invertersPAC,rated×nrep,invP_{AC,rated,array} = \sum_{inverters} P_{AC,rated} \times n_{rep,inv} The collection output is: Pcoll=PMV−LcollP_{coll} = P_{MV} - L_{coll}

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Block Aggregation

Array outputs are aggregated to the block level using repeater counts: Pblock=∑arraysPcoll×nrep,arrayP_{block} = \sum_{arrays} P_{coll} \times n_{rep,array}