63 implement cell by cell electrical model in fvs

FullVehicleSim/battery_model.py

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+import numpy as np
+from paramLoader import *
+import matplotlib.pyplot as plt
+
+np.random.seed(42)
+
+class Cell:
+    def __init__ (self, soc, resistance, capacity_Ah = 5, hysteresis = 0):
+        self.soc = soc
+        self.resistance = resistance
+        self.capacity_Ah = capacity_Ah
+        self.hysteresis = hysteresis
+
+    def ocv(self, T_K = 298.15):
+        #code from powertrain
+        F = Parameters["FaradaysConstant"]
+        R = Parameters["GasConstant"]
+
+        V0 = Magic["cellModel_V0"]
+        C1 = Magic["cellModel_C1"]
+        C2 = Magic["cellModel_C2"]
+        C3 = Magic["cellModel_C3"]
+        C4 = Magic["cellModel_C4"]
+
+        eps = 1e-9
+
+        soc_shift = self.soc - (0.1 ** 3)
+
+        denom = np.clip(1.0 - soc_shift + C4, eps, None)
+        numer = np.clip(C1 * soc_shift + C3, eps, None)
+
+        log_term = np.log(numer / denom)
+        return V0 + (C2 * (R * T_K / F) * log_term) + Magic["cellModel_bias"]
+
+    def terminal_voltage(self, current):
+        #main function
+        return (self.ocv() - self.hysteresis - (current * self.resistance))
+
+    def update_soc(self, current, dt, capacity_Ah):
+        #change w time
+        change_soc = (current * dt / 3600) / capacity_Ah
+        self.soc = np.clip(self.soc - change_soc, 0.0, 1.0)
+
+class Parallel_Groups:
+    def __init__(self, cells):
+        self.cells = cells
+
+    def solve_currents(self, pack_current):
+        sum_rhs_over_R = 0  ##rhs is ocv - hysteris (right hand side of equation)
+        sum_1_over_R = 0
+
+        for cell in self.cells:
+            rhs = cell.ocv() - cell.hysteresis
+            sum_rhs_over_R += rhs/cell.resistance
+            sum_1_over_R += 1/cell.resistance
+
+        V_group = (sum_rhs_over_R - pack_current)/sum_1_over_R
+        currents = []
+        for cell in self.cells:
+            rhs = cell.ocv() - cell.hysteresis
+            current = (rhs - V_group)/cell.resistance
+            currents.append(float(current))
+
+        return currents, V_group
+
+    def step(self, pack_current, dt, capacity_Ah):
+        #for each timestep
+        currents, V_group = self.solve_currents(pack_current)
+        for cell, current in zip(self.cells, currents):
+            cell.update_soc(current, dt, capacity_Ah)
+        return currents, V_group
+
+class Module:
+    def __init__(self, groups):
+        self.groups = groups
+
+    def step(self, pack_current, dt, capacity_Ah):
+        total_voltage = 0
+        all_currents = []
+        for group in self.groups:
+            currents, V_group = group.step(pack_current, dt, capacity_Ah)
+            total_voltage += V_group
+            all_currents.append(currents)
+        return all_currents, total_voltage
+
+def build_modules(width = 4, height = 2, resistances = None):
+    #if no given csv
+    if resistances is None:
+        resistances = np.random.normal(0.008, 0.0005, (height, width))
+    #with importing a csv
+    else:
+        resistances = np.asarray(resistances)
+        if resistances.shape != (height, width):
+            raise ValueError(f"Expected shape ({height}, {width}), got {resistances.shape}")
+    groups = []
+    for h in range(height):
+        cells = []
+        for w in range(width):
+            soc = np.random.uniform(0.85, 0.95)
+            cells.append(Cell(soc=soc, resistance=resistances[h, w]))
+        groups.append(Parallel_Groups(cells))
+    return Module(groups)    
+
+module = build_modules(width=4, height=2)   
+##sim
+
+pack_current = 100.0
+dt = 1.0
+capacity_Ah = 5.0
+
+num_steps = 10
+
+for step in range(num_steps):
+    all_currents, module_voltage = module.step(pack_current, dt, capacity_Ah)
+    print(f"\nStep {step}")
+    print(f"Module Voltage: {module_voltage:.2f} V")
+
+    for g, group_currents in enumerate(all_currents):
+        print(f"  Group {g}: {group_currents}")
+        print(f"  Group {g} Sum: {np.sum(group_currents):.2f} A")