i try to understand the theory of FOC and read a lot.
the hardware is 3 half-bridge with 6 FET and the 3 bridges are driven complementary! if UH is active then UL is OFF and if VH is OFF then VL is ON…
now for each PWM cycle the cpu computes the duty values for each phase. and the way of this foc I am now looking on: the duty values are set to the high sides. and the ON segments of all three are centred in the pwm cycle. “symetric centered” this means: at begin and end of the pwm cycle all high sides are OFF and because of the complementary: all low sides are ON. but in the middle of the pwm cycle: all High sides are ON? is this really working? i mean: if all high sides are on → then (complementary) all Low sides are OFF at this point. but then no voltages is aplied to the motor! in the text they call it sector 000 (at begin and end) and sector 111 (at middle). only in the other 6 sectors is really voltage applied to the motor. does this really work?
i look before a other way to do FOC and there they use a angle and determ from the ange only 2 phases, the sector! and apply the pwm to these 2 active high sides, acording to the angle we get 2 different duty vals for the 2 phases. this I understand.
Hey @frankers,
That is true, when all high side or low side MOSFETs are on, there is no voltage applied to the motor, or rather, the relative voltage between the phases is zero.
You can have a no centered sine pwm and space vector pwm modulation, in which case you almost never have all the high side MOSFETs on at the same time. We do have it in SimpleFOC too, we have an option for that.
The most of the modulation strategies implemented in microcontrollers are centered because in this way you get well balanced activation times of your high-side and low-side MOSFETs, they are on and off approximately the same time.
But this is a choice and you could do it otherwise.
One problem with this modulation for example is that when you set phase voltage on your motor phases, you actually set half of the power-supply voltage to all of them. (Half time low-side on, half of the time high-side is on). If you have a problem in your motor connections and for some reason one of the phases is not well connected or connected to ground, you could have a very big current passing through it.
If you would have non-centered modulation, where 0 phase voltage would correspond to 0 voltage applied (only low-side MOSFETs on all the time) this scenario would not be able to happen. 
Another reason why you usée the 111 sector (or all high-side MOSFETs on) in space vector pwm is because this type of modulation was actually designed for bang bang control, where you control the MOSFETs as digital switches. And space Vector modulation gives you a structured way to turn on or off those switches. And by allowing for the sector 111, space vector enables passing from one sector to another by only event changing the state of a single switch (high/low side pair) at a time. Making it very efficient when it commes to the switch bang bang control.
In the case of SimpleFOC, as we do not use bang bang control of the switches but we use timer synced outputs, we do not care much about that efficiency. So you can absolutely have non-centered pwm without much performance loss (at least in terms of the computational time).