The
function calculates the appropriate duty-cycle ratios, which are
needed for generation of the given stator-reference voltage vector, using the general
sinusoidal modulation technique.
The
function for calculating the duty-cycle ratios is widely used in
modern electric drives. This function calculates the appropriate duty-cycle ratios, which
are needed for generating the given stator reference voltage vector using a special space
vector modulation technique called space vector modulation with O
111
nulls, where only
one type of null vector O
111
is used (all top switches are turned on in the invertor).
The derivation approach of the space vector modulation technique with O
111
nulls is
identical (in many aspects) to the approach presented in
distinct difference lies in the definition of variables t
1
, t
2
, and t
3
that represent switching
duty-cycle ratios of the respective phases:
Equation 48
where T is the switching period, and t_1 and t_2 are the duty-cycle ratios of the basic
space vectors defined for the respective sector in
The generally-used center-aligned PWM is discussed briefly in the following sections.
Generating the center-aligned PWM pattern is accomplished by comparing threshold
levels pwm_a, pwm_b, and pwm_c with the free-running up/down counter. The timer
counts up to 1 (0x7FFF) and then down to 0 (0x0000). It is supposed that when a
threshold level is larger than the timer value, the respective PWM output is active.
Otherwise, it is inactive (see
).
GMCLIB_SvmU7n
GMCLIB User's Guide, Rev. 2, 10/2015
60
Freescale Semiconductor, Inc.
Содержание DSP56800E
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