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Add internal resistance to voltage table calculations #1016

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merged 14 commits into from
Oct 10, 2023
Merged

Add internal resistance to voltage table calculations #1016

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b28f443
Address loss diagram issue for POA reference cell in SAM issue 1366
sjanzou Mar 4, 2023
75c059d
Working without pressure column
sjanzou Mar 6, 2023
d050a8d
Reset POA_P mode - uses decomposition with and without pressure column
sjanzou Mar 7, 2023
803f6bb
Add wfpoa to reported outputs to facilitate troubleshooting
cpaulgilman Mar 7, 2023
a301701
Merge pull request #1000 from NREL/SAM_1366
sjanzou Mar 8, 2023
ddd00f9
Merge pull request #1001 from NREL/SAM_1367
sjanzou Mar 8, 2023
9c319bb
Size the collector loop mass flow based on n_collectors (#1004)
Matthew-Boyd Mar 9, 2023
60554d5
Update to GitHub Actions to latest Ubuntu
sjanzou Apr 4, 2023
9b08216
Merge pull request #1009 from NREL/github_actions_patch
sjanzou Apr 6, 2023
f7972b9
Add internal resistance to voltage table calculations
brtietz Apr 21, 2023
4506a6e
Merge branch 'develop' of https://github.com/NREL/ssc into ssc_831_vo…
brtietz Jul 14, 2023
b82c6f2
Merge branch 'develop' of https://github.com/NREL/ssc into ssc_831_vo…
brtietz Oct 9, 2023
ed71ab2
Update voltage equations and tests to account for zero current at ful…
brtietz Oct 9, 2023
3222a5b
update resilience tests and fix voltage at 100 percent dod
brtietz Oct 9, 2023
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23 changes: 14 additions & 9 deletions shared/lib_battery_voltage.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -181,31 +181,35 @@ 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.);

size_t row = 0;
while (row < params->voltage_table.size() && DOD > params->voltage_table[row][0]) {
row++;
}
//
if (DOD < tolerance || DOD > 100. - tolerance) {
I = 0.0; // At full or empty, current must go to zero
}

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
Expand All @@ -215,7 +219,7 @@ 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) {
Expand All @@ -230,7 +234,7 @@ 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;
Expand Down Expand Up @@ -291,7 +295,8 @@ 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 = 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;
DOD_best = DOD_new;
Expand Down
2 changes: 1 addition & 1 deletion shared/lib_battery_voltage.h
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Original file line number Diff line number Diff line change
Expand Up @@ -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();
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
8 changes: 4 additions & 4 deletions test/shared_test/lib_resilience_test.cpp
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Expand Up @@ -329,13 +329,13 @@ TEST_F(ResilienceTest_lib_resilience, VoltageTable)
cap.updateCapacity(current, 1);
volt.updateVoltage(cap.q0(), cap.qmax(), cap.I(), 0, 0.);
EXPECT_NEAR(cap.SOC(), 44.445, 1e-3);
EXPECT_NEAR(volt.cell_voltage(), 1.773, 1e-3);
EXPECT_NEAR(volt.cell_voltage(), 1.873, 1e-3);

current = -1;
cap.updateCapacity(current, 1);
volt.updateVoltage(cap.q0(), cap.qmax(), cap.I(), 0, 0.);
EXPECT_NEAR(cap.SOC(), 88.889, 1e-3);
EXPECT_NEAR(volt.cell_voltage(), 2.777, 1e-3);
EXPECT_NEAR(volt.cell_voltage(), 2.877, 1e-3);
}

TEST_F(ResilienceTest_lib_resilience, DischargeVoltageTable){
Expand All @@ -359,7 +359,7 @@ TEST_F(ResilienceTest_lib_resilience, DischargeVoltageTable){
cap.updateCapacity(req_cur, 1);
volt.updateVoltage(cap.q0(), cap.qmax(), cap.I(), 0, 1);
double v = volt.cell_voltage();
EXPECT_NEAR(req_cur * v, 0.5, 1e-2);
EXPECT_NEAR(req_cur * v, 0.48, 1e-2);

// test max discharge
cap = capacity_lithium_ion_t(2.25, 50, 100, 0, 1);
Expand Down Expand Up @@ -397,7 +397,7 @@ TEST_F(ResilienceTest_lib_resilience, ChargeVoltageTable){
cap.updateCapacity(req_cur, 1);
volt.updateVoltage(cap.q0(), cap.qmax(), cap.I(), 0, 1);
double v = volt.cell_voltage();
EXPECT_NEAR(req_cur * v, -1.5, 1e-2);
EXPECT_NEAR(req_cur * v, -1.58, 1e-2);

// test max charge
double max_p = volt.calculate_max_charge_w(cap.q0(), cap.qmax(), 0, &current);
Expand Down
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