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Update voltage equations and tests to account for zero current at ful…
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…l battery, new resistance in table tests
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@brtietz
brtietz committed Oct 9, 2023
1 parent b82c6f2 commit ed71ab2
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Showing 3 changed files with 32 additions and 24 deletions.
6 changes: 5 additions & 1 deletion shared/lib_battery_voltage.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -189,6 +189,10 @@ double voltage_table_t::calculate_voltage(double DOD, double I) {
while (row < params->voltage_table.size() && DOD > params->voltage_table[row][0]) {
row++;
}
//
if (DOD < tolerance) {
I = 0.0; // At full, current must go to zero
}

return fmax(slopes[row] * DOD + intercepts[row], 0) - I * params->resistance;
}
Expand Down Expand Up @@ -291,7 +295,7 @@ 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) {
current = (q - (100. - DOD_new) * qmax / 100);
current = qmax * ((1. - DOD / 100.) - (1. - DOD_new / 100.)) / params->dt_hr;
double P = current * (a * DOD_new + b - current / params->num_strings * params->resistance);
if (std::abs(P) > std::abs(P_best)) {
P_best = P;
Expand Down
46 changes: 23 additions & 23 deletions test/shared_test/lib_battery_voltage_test.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -608,7 +608,7 @@ TEST_F(voltage_table_lib_battery_voltage_test, updateCapacityTest){
I = 5;
cap->updateCapacity(I, dt_hour); // qmx = 10, I = 4.5, q0 = 0.5
model->updateVoltage(cap->q0(), cap->qmax(), cap->I(), 0, dt_hour);
EXPECT_NEAR(model->cell_voltage(), 1.35, tol);
EXPECT_NEAR(model->cell_voltage(), 1.336, tol);
EXPECT_NEAR(cap->q0(), 0.5, tol);
}

Expand All @@ -631,7 +631,7 @@ TEST_F(voltage_table_lib_battery_voltage_test, updateCapacitySubHourly){
I = 5;
cap->updateCapacity(I, dt_hour); // qmx = 10, I = 4.5, q0 = 0.5
model->updateVoltage(cap->q0(), cap->qmax(), cap->I(), 0, dt_hour);
EXPECT_NEAR(model->cell_voltage(), 3.504, tol);
EXPECT_NEAR(model->cell_voltage(), 3.492, tol);
EXPECT_NEAR(cap->q0(), 2.5, tol);
}

Expand All @@ -654,7 +654,7 @@ TEST_F(voltage_table_lib_battery_voltage_test, updateCapacitySubMinute){
I = 5;
cap->updateCapacity(I, dt_hour); // qmx = 10, I = 4.5, q0 = 0.5
model->updateVoltage(cap->q0(), cap->qmax(), cap->I(), 0, dt_hour);
EXPECT_NEAR(model->cell_voltage(), 3.689, tol);
EXPECT_NEAR(model->cell_voltage(), 3.677, tol);
EXPECT_NEAR(cap->q0(), 4.975, 1e-3);
}

Expand Down Expand Up @@ -888,15 +888,15 @@ TEST_F(voltage_table_lib_battery_voltage_test, calculateMaxDischargeHourly){
// start at half SOC
double max_current;
double power = model->calculate_max_discharge_w(cap->q0(), cap->qmax(), 0, &max_current);
EXPECT_NEAR(power, 1194, 1); // current ~4
EXPECT_NEAR(power, 1192.6, 1); // current ~4
double max_current_calc = model->calculate_current_for_target_w(power - 1, cap->q0(), cap->qmax(), 0);
EXPECT_NEAR(max_current_calc, 2.45, 1e-2);
EXPECT_NEAR(max_current_calc, 2.44, 1e-2);
// Does not empty battery for highest power
cap->updateCapacity(max_current, dt_hour);
EXPECT_NEAR(cap->SOC(), 25.5, 1e-3);
// Check power
model->updateVoltage(cap->q0(), cap->qmax(), max_current_calc, 0, dt_hour);
EXPECT_NEAR(max_current_calc * model->battery_voltage(), power, 2);
model->updateVoltage(cap->q0(), cap->qmax(), max_current, 0, dt_hour);
EXPECT_NEAR(max_current * model->battery_voltage(), power, 2);

// start at empty SOC
power = model->calculate_max_discharge_w(cap->q0(), cap->qmax(), 0, &max_current);
Expand All @@ -915,15 +915,15 @@ TEST_F(voltage_table_lib_battery_voltage_test, calculateMaxDischargeHourly){
while (cap->SOC() < 95)
cap->updateCapacity(I, dt_hour);
power = model->calculate_max_discharge_w(cap->q0(), cap->qmax(), 0, &max_current);
EXPECT_NEAR(power, 3569, 1);
EXPECT_NEAR(power, 3553, 1);
max_current_calc = model->calculate_current_for_target_w(power - 1, cap->q0(), cap->qmax(), 0);
EXPECT_NEAR(max_current_calc, max_current, 1e-2);
EXPECT_NEAR(max_current_calc, max_current, 1e-1);
// Does not empty battery for highest power
cap->updateCapacity(max_current, dt_hour);
EXPECT_NEAR(cap->SOC(), 27.02, 1e-2);
// Check power
model->updateVoltage(cap->q0(), cap->qmax(), max_current_calc, 0, dt_hour);
EXPECT_NEAR(max_current_calc * model->battery_voltage(), power, 2);
model->updateVoltage(cap->q0(), cap->qmax(), max_current, 0, dt_hour);
EXPECT_NEAR(max_current * model->battery_voltage(), power, 2);
}

TEST_F(voltage_table_lib_battery_voltage_test, calculateMaxDischargeHourlyInputErrors) {
Expand Down Expand Up @@ -962,17 +962,17 @@ TEST_F(voltage_table_lib_battery_voltage_test, calculateMaxDischargeSubHourly){
// start at half SOC
double max_current;
double power = model->calculate_max_discharge_w(cap->q0(), cap->qmax(), 0, &max_current);
EXPECT_NEAR(power, 2388, 1); // current ~4
EXPECT_NEAR(power, 2381, 1); // current ~4
double max_current_calc = model->calculate_current_for_target_w(power - 1, cap->q0(), cap->qmax(), 0);
EXPECT_NEAR(max_current, 4.9, 1e-2);
EXPECT_NEAR(max_current_calc, 4.9, 1e-2);
EXPECT_NEAR(max_current, 4.90, 1e-2);
EXPECT_NEAR(max_current_calc, 4.90, 1e-1); //4.88 as of 10/9/2023
// Does not empty battery for highest power
cap->updateCapacity(max_current, dt_hour);
EXPECT_NEAR(cap->SOC(), 25.5, 1e-3);

// start at empty SOC
power = model->calculate_max_discharge_w(cap->q0(), cap->qmax(), 0, &max_current);
EXPECT_NEAR(power, 1163, 1);
EXPECT_NEAR(power, 1161, 1);
max_current_calc = model->calculate_current_for_target_w(power - 1, cap->q0(), cap->qmax(), 0);
EXPECT_NEAR(max_current, 2.44, 1e-1);
EXPECT_NEAR(max_current_calc, 2.44, 1e-1);
Expand All @@ -985,9 +985,9 @@ TEST_F(voltage_table_lib_battery_voltage_test, calculateMaxDischargeSubHourly){
while (cap->SOC() < 95)
cap->updateCapacity(I, dt_hour);
power = model->calculate_max_discharge_w(cap->q0(), cap->qmax(), 0, &max_current);
EXPECT_NEAR(power, 7139, 1);
EXPECT_NEAR(power, 7073, 1);
max_current_calc = model->calculate_current_for_target_w(power - 1, cap->q0(), cap->qmax(), 0);
EXPECT_NEAR(max_current_calc, max_current, 1e-2);
EXPECT_NEAR(max_current_calc, max_current, 2e-1);
// Does not empty battery for highest power
cap->updateCapacity(max_current, dt_hour);
EXPECT_NEAR(cap->SOC(), 27.02, 1e-2);
Expand All @@ -1000,7 +1000,7 @@ TEST_F(voltage_table_lib_battery_voltage_test, calculateMaxDischargeHourly_table
// start at half SOC
double max_current;
double power = model->calculate_max_discharge_w(cap->q0(), cap->qmax(), 293, &max_current);
EXPECT_NEAR(power, 719.25, 1); // current ~4
EXPECT_NEAR(power, 714.44, 1); // current ~4
double max_current_calc = model->calculate_current_for_target_w(power, cap->q0(), cap->qmax(), 293);
EXPECT_NEAR(max_current, 3.94, 1e-2);
EXPECT_NEAR(max_current_calc, 3.94, 1e-2);
Expand Down Expand Up @@ -1028,7 +1028,7 @@ TEST_F(voltage_table_lib_battery_voltage_test, calculateMaxDischargeHourly_table
while (cap->SOC() < 95)
cap->updateCapacity(I, dt_hour);
power = model->calculate_max_discharge_w(cap->q0(), cap->qmax(), 293, &max_current);
EXPECT_NEAR(power, 1480.35, 1);
EXPECT_NEAR(power, 1462.98, 1);
max_current_calc = model->calculate_current_for_target_w(power, cap->q0(), cap->qmax(), 293);
EXPECT_NEAR(max_current, 7.5, 1e-2);
EXPECT_NEAR(max_current_calc, 7.5, 1e-2);
Expand All @@ -1047,7 +1047,7 @@ TEST_F(voltage_table_lib_battery_voltage_test, calculateMaxDischargeSubMinute){
// start at half SOC
double max_current;
double power = model->calculate_max_discharge_w(cap->q0(), cap->qmax(), 0, &max_current);
EXPECT_NEAR(power, 238891, 1); // current ~8
EXPECT_NEAR(power, 164727, 1); // current ~8
double max_current_calc = model->calculate_current_for_target_w(power, cap->q0(), cap->qmax(), 0);
EXPECT_NEAR(max_current_calc, max_current, 0.2);
// Does not empty battery for highest power
Expand All @@ -1059,7 +1059,7 @@ TEST_F(voltage_table_lib_battery_voltage_test, calculateMaxDischargeSubMinute){

// start at empty SOC
power = model->calculate_max_discharge_w(cap->q0(), cap->qmax(), 0, &max_current);
EXPECT_NEAR(power, 116333, 1);
EXPECT_NEAR(power, 97792, 1);
max_current_calc = model->calculate_current_for_target_w(power, cap->q0(), cap->qmax(), 0);
EXPECT_NEAR(max_current_calc, max_current, 1e-1);
// Does not empty battery for highest power
Expand All @@ -1074,12 +1074,12 @@ TEST_F(voltage_table_lib_battery_voltage_test, calculateMaxDischargeSubMinute){
while (cap->SOC() < 95)
cap->updateCapacity(I, dt_hour);
power = model->calculate_max_discharge_w(cap->q0(), cap->qmax(), 0, &max_current);
EXPECT_NEAR(power, 685795, 1);
EXPECT_NEAR(power, 207281, 1);
max_current_calc = model->calculate_current_for_target_w(power, cap->q0(), cap->qmax(), 0);
EXPECT_NEAR(max_current_calc, max_current, 0.3);
// Does not empty battery for highest power
cap->updateCapacity(max_current, dt_hour);
EXPECT_NEAR(cap->SOC(), 24.52, 1e-3);
EXPECT_NEAR(cap->SOC(), 48.0, 1e-3);
// Check power
model->updateVoltage(cap->q0(), cap->qmax(), max_current_calc, 293, dt_hour);
EXPECT_NEAR(max_current_calc * model->battery_voltage(), power, 1e-2);
Expand Down
4 changes: 4 additions & 0 deletions test/shared_test/lib_battery_voltage_test.h
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Original file line number Diff line number Diff line change
Expand Up @@ -127,6 +127,8 @@ class voltage_table_lib_battery_voltage_test : public lib_battery_voltage_test
88.9, Vnom, 99, 0});
table = util::matrix_t<double>(4, 2, &vals);

R = 0.02;

cap = std::unique_ptr<capacity_lithium_ion_t>(new capacity_lithium_ion_t(10, 50, 95, 5, dt_hr));
model = std::unique_ptr<voltage_t>(new voltage_table_t(n_cells_series, n_strings, voltage_nom, table, R, dt_hr));
model->set_initial_SOC(50);
Expand All @@ -137,6 +139,7 @@ class voltage_table_lib_battery_voltage_test : public lib_battery_voltage_test
std::vector<double> voltage_vals = { 0, 1.7, 4, 1.69, 5, 1.58, 60, 1.5, 85, 1.4, 90, 1.3, 93, 1.2, 95, 1, 96, 0.9 };
util::matrix_t<double> voltage_table(9, 2, &voltage_vals);

R = 0.02;
voltage_nom = 1.5;
cap = std::unique_ptr<capacity_lithium_ion_t>(new capacity_lithium_ion_t(10, 50, 95, 5, dt_hr));
model = std::unique_ptr<voltage_t>(new voltage_table_t(n_cells_series, n_strings, voltage_nom, voltage_table, R,
Expand Down Expand Up @@ -174,6 +177,7 @@ class voltage_table_lib_battery_voltage_test : public lib_battery_voltage_test
n_cells_series = 6;
n_strings = 28;
voltage_nom = 12;
R = 0.02;

cap = std::unique_ptr<capacity_lithium_ion_t>(new capacity_lithium_ion_t(10, 50, 95, 5, dt_hr));
model = std::unique_ptr<voltage_t>(new voltage_table_t(n_cells_series, n_strings, voltage_nom, voltage_table, R,
Expand Down

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