Calculate number of combiner boxes during electrical sizing (#125)

examples/Detailed_PV_Layout/detailed_pv_config.py

@@ -35,6 +35,7 @@ class PVLayoutConfig:
     interrack_spac: float       # m
 
     # Wiring config
+    nb_inputs_combiner: int     # count
 
     # Road config
     perimetral_road: bool   

examples/Detailed_PV_Layout/detailed_pv_layout.py

@@ -58,6 +58,7 @@ def __init__(self,
         self.substation_coord = None
         self.modules_per_string = None
         self.n_strings = None
+        self.n_combiners = None
         self.n_inverters = None
         self.calculated_system_capacity = None
         self.flicker_loss = 0
@@ -125,7 +126,7 @@ def _compute_string_config(self,
             module_power = self.config.module_power
             inverter_power=self.config.inverter_power
 
-        self.n_strings, self.n_inverters, self.calculated_system_capacity = size_electrical_parameters(
+        self.n_strings, self.n_combiners, self.n_inverters, self.calculated_system_capacity = size_electrical_parameters(
             target_system_capacity=target_solar_kw,
             target_dc_ac_ratio=self.parameters.dc_ac_ratio,
             modules_per_string=self.modules_per_string,

hybrid/layout/pv_design_utils.py

@@ -77,19 +77,21 @@ def size_electrical_parameters(
     modules_per_string: float,
     module_power: float,
     inverter_power: float,
-    n_inputs_inverter: float=50
+    n_inputs_inverter: float=50,
+    n_inputs_combiner: float=32,
     ):
     """
-    Calculates the number of strings and number of inverters to best match target dc_ac_ratio.
+    Calculates the number of strings, combiner boxes and inverters to best match target capacity and DC/AC ratio
 
     :param target_system_capacity: target system capacity, kW
     :param target_dc_ac_ratio: target DC-to-AC ratio
     :param modules_per_string: modules per string
     :param module_power: module power at maximum point point at reference conditions, kW
     :param inverter_power: inverter maximum AC power, kW
-    :param n_inputs_inverter: number of inverter DC inputs
+    :param n_inputs_inverter: number of DC inputs per inverter
+    :param n_inputs_combiner: number of DC inputs per combiner box
 
-    :returns: calculated system capacity, kW
+    :returns: number of strings, number of combiner boxes, number of inverters, calculated system capacity, kW
     """
     n_strings_frac = target_system_capacity / (modules_per_string * module_power)
     n_strings = max(1, round(n_strings_frac))
@@ -104,11 +106,10 @@ def size_electrical_parameters(
         inverter_power=inverter_power,
         )
 
-    # Ensure there are enough enough inverters for the number of field connections
-    # TODO: implement get_n_combiner_boxes() and/or string inverter calculations to compute n_field_connections
-    n_field_connections = 1
-    while math.ceil(n_field_connections / n_inverters) > n_inputs_inverter:
-        n_inverters += 1
+    n_combiners = math.ceil(n_strings / n_inputs_combiner)
+
+    # Ensure there are enough enough inverters for the number of combiner boxes
+    max(n_inverters, math.ceil(n_combiners / n_inputs_inverter))
 
     # Verify sizing was close to the target size, otherwise error out
     calculated_system_capacity = verify_capacity_from_electrical_parameters(
@@ -118,7 +119,7 @@ def size_electrical_parameters(
         module_power=module_power
     )
 
-    return n_strings, n_inverters, calculated_system_capacity
+    return n_strings, n_combiners, n_inverters, calculated_system_capacity
 
 
 def verify_capacity_from_electrical_parameters(

tests/hybrid/test_hybrid.py

@@ -196,7 +196,7 @@ def test_hybrid_detailed_pv_only(site):
     solar_only['grid']['interconnect_kw'] = 150e3
 
     # autosize number of strings, number of inverters and adjust system capacity
-    n_strings, n_inverters, calculated_system_capacity = size_electrical_parameters(
+    n_strings, n_combiners, n_inverters, calculated_system_capacity = size_electrical_parameters(
         target_system_capacity=solar_only['pv']['tech_config']['system_capacity'],
         target_dc_ac_ratio=1.34,
         modules_per_string=solar_only['pv']['tech_config']['subarray1_modules_per_string'],
@@ -207,6 +207,7 @@ def test_hybrid_detailed_pv_only(site):
         inverter_power=solar_only['pv']['tech_config']['inv_snl_paco'] * 1e-3
     )
     assert n_strings == 13435
+    assert n_combiners == 420
     assert n_inverters == 50
     assert calculated_system_capacity == approx(50002.2, 1e-3)
     solar_only['pv']['tech_config']['subarray1_nstrings'] = n_strings
@@ -334,6 +335,7 @@ def test_custom_layout(site):
         # These are not:
         nb_inputs_inverter=10,
         interrack_spac=1,
+        nb_inputs_combiner=16,
         perimetral_road=False,
         setback_distance=10,
     )

tests/hybrid/test_layout.py

@@ -240,23 +240,26 @@ def test_system_electrical_sizing(site):
     module_power = 0.310149     # [kW]
     inverter_power = 753.2      # [kW]
     n_inputs_inverter = 50
+    n_inputs_combiner = 16
 
-    n_strings, n_inverters, calculated_system_capacity = size_electrical_parameters(
+    n_strings, n_combiners, n_inverters, calculated_system_capacity = size_electrical_parameters(
         target_system_capacity=target_solar_kw,
         target_dc_ac_ratio=target_dc_ac_ratio,
         modules_per_string=modules_per_string,
         module_power=module_power,
         inverter_power=inverter_power,
         n_inputs_inverter=n_inputs_inverter,
+        n_inputs_combiner=n_inputs_combiner,
     )
     assert n_strings == 26869
+    assert n_combiners == 1680
     assert n_inverters == 99
     assert calculated_system_capacity == pytest.approx(1e5, 1e-3)
 
     with pytest.raises(Exception) as e_info:
         target_solar_kw_mod = 33
         modules_per_string_mod = 24
-        n_strings, n_inverters, calculated_system_capacity = size_electrical_parameters(
+        n_strings, n_combiners, n_inverters, calculated_system_capacity = size_electrical_parameters(
             target_system_capacity=target_solar_kw_mod,
             target_dc_ac_ratio=target_dc_ac_ratio,
             modules_per_string=modules_per_string_mod,