Add internal resistance to voltage table calculations

NREL · Apr 21, 2023 · f7972b9 · f7972b9
1 parent 9b08216
commit f7972b9
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Showing 2 changed files with 11 additions and 10 deletions.
diff --git a/shared/lib_battery_voltage.cpp b/shared/lib_battery_voltage.cpp
@@ -178,7 +178,7 @@ voltage_t *voltage_table_t::clone() {
     return new voltage_table_t(*this);
 }
 
-double voltage_table_t::calculate_voltage(double DOD) {
+double voltage_table_t::calculate_voltage(double DOD, double I) {
     DOD = fmax(0., DOD);
     DOD = fmin(DOD, 100.);
 
@@ -187,22 +187,22 @@ double voltage_table_t::calculate_voltage(double DOD) {
         row++;
     }
 
-    return fmax(slopes[row] * DOD + intercepts[row], 0);
+    return fmax(slopes[row] * DOD + intercepts[row], 0) - I * params->resistance;
 }
 
 void voltage_table_t::set_initial_SOC(double init_soc) {
-    state->cell_voltage = calculate_voltage(100. - init_soc);
+    state->cell_voltage = calculate_voltage(100. - init_soc, 0.0);
 }
 
 double voltage_table_t::calculate_voltage_for_current(double I, double q, double qmax, double) {
     double DOD = (q - I * params->dt_hr) / qmax * 100.;
-    return calculate_voltage(DOD) * params->num_cells_series;
+    return calculate_voltage(DOD, I / params->num_strings) * params->num_cells_series;
 }
 
 
-void voltage_table_t::updateVoltage(double q, double qmax, double, const double, double) {
+void voltage_table_t::updateVoltage(double q, double qmax, double I, const double, double) {
     double DOD = 100. * (1 - q / qmax);
-    state->cell_voltage = calculate_voltage(DOD);
+    state->cell_voltage = calculate_voltage(DOD, I / params->num_strings);
 }
 
 // helper fx to calculate depth of discharge from current and max capacities
@@ -212,7 +212,7 @@ double voltage_table_t::calculate_max_charge_w(double q, double qmax, double, do
     double current = (q - qmax) / params->dt_hr;
     if (max_current)
         *max_current = current;
-    return calculate_voltage(0.) * current * params->num_cells_series;
+    return calculate_voltage(0., current / params->num_strings) * current * params->num_cells_series;
 }
 
 double voltage_table_t::calculate_max_discharge_w(double q, double qmax, double, double *max_current) {
@@ -227,7 +227,7 @@ double voltage_table_t::calculate_max_discharge_w(double q, double qmax, double,
         dod = fmin(100, dod);
         dod = fmax(0, dod);
         double current = qmax * ((1. - DOD0 / 100.) - (1. - dod / 100.)) / params->dt_hr;
-        double p = calculate_voltage(dod) * current;
+        double p = calculate_voltage(dod, current / params->num_strings) * current;
         if (p > max_P) {
             max_P = p;
             max_I = current;
@@ -288,7 +288,8 @@ double voltage_table_t::calculate_current_for_target_w(double P_watts, double q,
         auto DOD_upper = params->voltage_table[upper][0];
         auto DOD_lower = params->voltage_table[lower][0];
         if (DOD_new <= DOD_upper && DOD_new >= DOD_lower) {
-            double P = (q - (100. - DOD_new) * qmax/100) * (a * DOD_new + b);
+            current = (q - (100. - DOD_new) * qmax / 100);
+            double P = current * (a * DOD_new + b - current / params->num_strings * params->resistance);
             if (std::abs(P) > std::abs(P_best)) {
                 P_best = P;
                 DOD_best = DOD_new;

diff --git a/shared/lib_battery_voltage.h b/shared/lib_battery_voltage.h
@@ -165,7 +165,7 @@ class voltage_table_t : public voltage_t {
     std::vector<double> slopes;
     std::vector<double> intercepts;
 
-    double calculate_voltage(double DOD);
+    double calculate_voltage(double DOD, double I);
 
 private:
     void initialize();