Algebraic real-time algorithm for B-Spline sinusoidal pulse width modulation in three phase voltage source inverters.

In this paper a novel algebraic real-time algorithm for implementation of sinusoidal pulse width modulation (SPWM) based on B-spline carriers is introduced and discussed. B-spline functions are used as carrier signals with the aim to to reduce harmonic content of the three phase inverter output voltage. This algorithm eliminates the problem of B-spline recursive evaluation with convolution integrals or convolution sums in digital counterpart. The pulse pattern synthesis is made with the help pre-calculated duty cycle expressions. In this way the carrier signals have not to be really synthesized, hence the hardware and the whole inverter control system becomes cheaper, more reliable and affordable. The proposed control algorithm effectiveness is finally verified by means of numerical simulations in different operating condition (e.g. for different values of the amplitude modulation index and for different values of the power factor) of a three phase inverter. Different values for voltage and current total harmonic distortion (THD) are presented comparing the B-spline SPWM control with the classical SPWM control with triangular carrier signal.