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SVPWM with midpoint clamp #309

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Merged
merged 5 commits into from
Sep 23, 2023
Merged

SVPWM with midpoint clamp #309

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e60cdf5
SVPWM with midpoint clamp
Candas1 Sep 13, 2023
717480b
Merge pull request #315 from simplefoc/dev
runger1101001 Sep 22, 2023
0e7434b
Merge branch 'simplefoc:master' into SVPWM_midpoint
Candas1 Sep 23, 2023
f9e9a2d
Merge pull request #318 from simplefoc/dev
runger1101001 Sep 23, 2023
6cbbf03
Merge branch 'simplefoc:master' into SVPWM_midpoint
Candas1 Sep 23, 2023
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106 changes: 16 additions & 90 deletions src/BLDCMotor.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -545,6 +545,7 @@ void BLDCMotor::setPhaseVoltage(float Uq, float Ud, float angle_el) {
break;

case FOCModulationType::SinePWM :
case FOCModulationType::SpaceVectorPWM :
// Sinusoidal PWM modulation
// Inverse Park + Clarke transformation
_sincos(angle_el, &_sa, &_ca);
Expand All @@ -553,107 +554,32 @@ void BLDCMotor::setPhaseVoltage(float Uq, float Ud, float angle_el) {
Ualpha = _ca * Ud - _sa * Uq; // -sin(angle) * Uq;
Ubeta = _sa * Ud + _ca * Uq; // cos(angle) * Uq;

// center = modulation_centered ? (driver->voltage_limit)/2 : Uq;
center = driver->voltage_limit/2;
// Clarke transform
Ua = Ualpha + center;
Ub = -0.5f * Ualpha + _SQRT3_2 * Ubeta + center;
Uc = -0.5f * Ualpha - _SQRT3_2 * Ubeta + center;
Ua = Ualpha;
Ub = -0.5f * Ualpha + _SQRT3_2 * Ubeta;
Uc = -0.5f * Ualpha - _SQRT3_2 * Ubeta;

center = driver->voltage_limit/2;
if (foc_modulation == FOCModulationType::SpaceVectorPWM){
// Midpoint Clamp
float Umin = min(Ua, min(Ub, Uc));
float Umax = max(Ua, max(Ub, Uc));
center -= (Umax+Umin) / 2;
}

if (!modulation_centered) {
float Umin = min(Ua, min(Ub, Uc));
Ua -= Umin;
Ub -= Umin;
Uc -= Umin;
}else{
Ua += center;
Ub += center;
Uc += center;
}

break;

case FOCModulationType::SpaceVectorPWM :
// Nice video explaining the SpaceVectorModulation (SVPWM) algorithm
// https://www.youtube.com/watch?v=QMSWUMEAejg

// the algorithm goes
// 1) Ualpha, Ubeta
// 2) Uout = sqrt(Ualpha^2 + Ubeta^2)
// 3) angle_el = atan2(Ubeta, Ualpha)
//
// equivalent to 2) because the magnitude does not change is:
// Uout = sqrt(Ud^2 + Uq^2)
// equivalent to 3) is
// angle_el = angle_el + atan2(Uq,Ud)

float Uout;
// a bit of optitmisation
if(Ud){ // only if Ud and Uq set
// _sqrt is an approx of sqrt (3-4% error)
Uout = _sqrt(Ud*Ud + Uq*Uq) / driver->voltage_limit;
// angle normalisation in between 0 and 2pi
// only necessary if using _sin and _cos - approximation functions
angle_el = _normalizeAngle(angle_el + atan2(Uq, Ud));
}else{// only Uq available - no need for atan2 and sqrt
Uout = Uq / driver->voltage_limit;
// angle normalisation in between 0 and 2pi
// only necessary if using _sin and _cos - approximation functions
angle_el = _normalizeAngle(angle_el + _PI_2);
}
// find the sector we are in currently
sector = floor(angle_el / _PI_3) + 1;
// calculate the duty cycles
float T1 = _SQRT3*_sin(sector*_PI_3 - angle_el) * Uout;
float T2 = _SQRT3*_sin(angle_el - (sector-1.0f)*_PI_3) * Uout;
// two versions possible
float T0 = 0; // pulled to 0 - better for low power supply voltage
if (modulation_centered) {
T0 = 1 - T1 - T2; // modulation_centered around driver->voltage_limit/2
}

// calculate the duty cycles(times)
float Ta,Tb,Tc;
switch(sector){
case 1:
Ta = T1 + T2 + T0/2;
Tb = T2 + T0/2;
Tc = T0/2;
break;
case 2:
Ta = T1 + T0/2;
Tb = T1 + T2 + T0/2;
Tc = T0/2;
break;
case 3:
Ta = T0/2;
Tb = T1 + T2 + T0/2;
Tc = T2 + T0/2;
break;
case 4:
Ta = T0/2;
Tb = T1+ T0/2;
Tc = T1 + T2 + T0/2;
break;
case 5:
Ta = T2 + T0/2;
Tb = T0/2;
Tc = T1 + T2 + T0/2;
break;
case 6:
Ta = T1 + T2 + T0/2;
Tb = T0/2;
Tc = T1 + T0/2;
break;
default:
// possible error state
Ta = 0;
Tb = 0;
Tc = 0;
}

// calculate the phase voltages and center
Ua = Ta*driver->voltage_limit;
Ub = Tb*driver->voltage_limit;
Uc = Tc*driver->voltage_limit;
break;

}

// set the voltages in driver
Expand Down