关于TI2812中SVPWM程序的问题

只看该作者 · 2009-12-10 23:19

/*=====================================================================================
File name:       SVGEN_DQ.C
Description:  空间矢量PWM产生函数

=====================================================================================*/

#include "IQmathLib.h"
#include "dmctype.h"
#include "svgen_dq.h"

void svgendq_calc(SVGENDQ *v)
{

      _iq Va,Vb,Vc,t1,t2;
      Uint32 Sector = 0;

// 反CLARK变换
Va = v->Ubeta;
Vb = _IQmpy(_IQ(-0.5),v->Ubeta) + _IQmpy(_IQ(0.8660254),v->Ualpha);  // 0.8660254 = sqrt(3)/2
Vc = _IQmpy(_IQ(-0.5),v->Ubeta) - _IQmpy(_IQ(0.8660254),v->Ualpha);  // 0.8660254 = sqrt(3)/2

//用Sector判断所在扇区
if (Va>_IQ(0))
   Sector = 1;
if (Vb>_IQ(0))
   Sector = Sector + 2;
if (Vc>_IQ(0))
   Sector = Sector + 4;

// X,Y,Z (Va,Vb,Vc) 计算
Va = v->Ubeta;                                                    // X = Va
Vb = _IQmpy(_IQ(0.5),v->Ubeta) + _IQmpy(_IQ(0.8660254),v->Ualpha); // Y = Vb
Vc = _IQmpy(_IQ(0.5),v->Ubeta) - _IQmpy(_IQ(0.8660254),v->Ualpha); // Z = Vc

if (Sector==0)  // Sector 0: 当(Ualpha,Ubeta) = (0,0)
{
   v->Ta = _IQ(0.5);
   v->Tb = _IQ(0.5);
   v->Tc = _IQ(0.5);
}
if (Sector==1)  // Sector 1: t1=Z and t2=Y (abc ---> Tb,Ta,Tc)
{
   t1 = Vc;
   t2 = Vb;
   v->Tb = _IQmpy(_IQ(0.5),(_IQ(1)-t1-t2));    // tbon = (1-t1-t2)/2
   v->Ta = v->Tb+t1;                            // taon = tbon+t1
   v->Tc = v->Ta+t2;                            // tcon = taon+t2
}
else if (Sector==2)  // Sector 2: t1=Y and t2=-X (abc ---> Ta,Tc,Tb)
{
   t1 = Vb;
   t2 = -Va;
   v->Ta = _IQmpy(_IQ(0.5),(_IQ(1)-t1-t2));    // taon = (1-t1-t2)/2
   v->Tc = v->Ta+t1;                            // tcon = taon+t1
   v->Tb = v->Tc+t2;                            // tbon = tcon+t2
}
else if (Sector==3)  // Sector 3: t1=-Z and t2=X (abc ---> Ta,Tb,Tc)
{
   t1 = -Vc;
   t2 = Va;
   v->Ta = _IQmpy(_IQ(0.5),(_IQ(1)-t1-t2));    // taon = (1-t1-t2)/2
   v->Tb = v->Ta+t1;                            // tbon = taon+t1
   v->Tc = v->Tb+t2;                            // tcon = tbon+t2
}
else if (Sector==4)  // Sector 4: t1=-X and t2=Z (abc ---> Tc,Tb,Ta)
{
   t1 = -Va;
   t2 = Vc;
   v->Tc = _IQmpy(_IQ(0.5),(_IQ(1)-t1-t2));    // tcon = (1-t1-t2)/2
   v->Tb = v->Tc+t1;                            // tbon = tcon+t1
   v->Ta = v->Tb+t2;                            // taon = tbon+t2
}
else if (Sector==5)  // Sector 5: t1=X and t2=-Y (abc ---> Tb,Tc,Ta)
{
   t1 = Va;
   t2 = -Vb;
   v->Tb = _IQmpy(_IQ(0.5),(_IQ(1)-t1-t2));    // tbon = (1-t1-t2)/2
   v->Tc = v->Tb+t1;                            // tcon = tbon+t1
   v->Ta = v->Tc+t2;                            // taon = tcon+t2
}
else if (Sector==6)  // Sector 6: t1=-Y and t2=-Z (abc ---> Tc,Ta,Tb)
{
   t1 = -Vb;
   t2 = -Vc;
   v->Tc = _IQmpy(_IQ(0.5),(_IQ(1)-t1-t2));    // tcon = (1-t1-t2)/2
   v->Ta = v->Tc+t1;                            // taon = tcon+t1
   v->Tb = v->Ta+t2;                            // tbon = taon+t2
}

// 转换无符号全局Q格式(0,1)为有符号全局Q格式 (-1,1)
v->Ta = _IQmpy(_IQ(2.0),(v->Ta-_IQ(0.5)));
v->Tb = _IQmpy(_IQ(2.0),(v->Tb-_IQ(0.5)));
v->Tc = _IQmpy(_IQ(2.0),(v->Tc-_IQ(0.5)));

}
上面加粗的部分,作用是什么?为什么要将无符号全局Q格式,换为有符号的全局Q格式.??谢谢了!