AN2388 datasheet(44/54 Pages) STMICROELECTRONICS

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Software design

AN2388

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Adjusting the PI gain

The gains of the controller set the overall system response. At the beginning when the P

gain is set, the I term should be set to zero . The P gain can then be increased until the

system responds well to set-point changes without excessive overshoot or oscillations. After

a reasonable P gain is selected, the I term gain can be slowly increased to force the system

error to zero. Only a small amount of I gain is required in most systems. This application

includes a term to limit integral wind-up which will occur if the integrated error saturates the

output parameter. Any further increase in the integrated error won’t effect the output.

Take into consideration that the PI regulator for the Flux components is essentially the same

as that for the torque.

4.6

Clark and Park transformation

In the next two paragraphs, the ST10F276 code for Clark and Park transformation is

presented. The corresponding theoretical background explanations have already been

handled.

4.6.1

(a,b)->(

α,β) projection (Clark transformation)

In the following code the considered constant and variables are implemented in 1.15 format.

************************************************************************************

*************************

Clark Transformation

(a, b) ->(alfa, beta)

iSalfa = ia

.....*

iSbeta = (2*ib+ia)/sqrt(3)

void Clark (void)

{

qIalfa=qIa;

//qIalfa component in Q1.15 format

mul_q15_q15_q31 (qSqrt3, qIa, &qIa_Sqrt3_tmp);

mul_q15_q15_q31 (qSqrt3, qIb, &qIb_Sqrt3_tmp);

qI_tmp_a = (short) (qIa_Sqrt3_tmp>>16);

qI_tmp_b = (short) (qIb_Sqrt3_tmp>>16);

I_beta_tmp = (qI_tmp_a+qI_tmp_b+qI_tmp_b);

qIbeta = I_beta_tmp;// qIbeta component in Q1.15 Format

}

************************************************************************************

*************************

END Routine

************************************************************************************

************************

where qSqrt3 is the following constant:

qSqrt

577

⇔

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