Embedded Software and Motor Control Libraries for PXR40xx

Function GMCLIB_SvmStd_F16
Figure 4-65 depicts the u α and u β components of the stator reference voltage vector U S
that were calculated by the equations u α = cos( θ) and u β = sin( θ), respectively.
Figure 4-66. Reference voltages u_ref1, u_ref2 and u_ref3
The Sector Identification Tree, shown in Figure 4-67, can be a numerical solution of the
approach shown in Figure 4-66.
Figure 4-67. Identification of the sector number
It should be pointed out that, in the worst case, three simple comparisons are required to
precisely identify the sector of the stator reference voltage vector. For example, if the
stator reference voltage vector resides according to the one shown in Figure 4-61, the
stator reference voltage vector is phase-advanced by 30 ° from the α-axis, which results
in the positive quantities of u ref1 and u ref2 and the negative quantity of u ref3; refer to
Figure 4-66. If these quantities are used as the inputs to the Sector Identification Tree, the
product of those comparisons will be Sector I. Using the same approach identifies Sector
II, if the stator reference voltage vector is located according to the one shown in Figure
4-64. The variables t 1, t 2 and t 3, representing the switching duty-cycle ratios of the
respective three-phase system, are given by the following equations:
Embedded Software and Motor Control Libraries for PXR40xx, Rev. 1.0
524 Freescale Semiconductor, Inc.