Simplified spice vector pulse width modulation algorithm for asynchronous motor speed control
The paper presents algorithms for voltage generation at induction motor (IM) windings in vector pulse width modulation (PWM) mode while IM rotation frequency regulating. These algorithms ensure smaller amount of computation, allowing eliminate through currents in the inverter power stage. Vector PWM (VPWM) employs 8 states of inverter switches for IM control. The paper considers the possibility of extra intermediate vector states of the switches, which would not cause through currents occurrence in the inverter and allow include them into IM speed control algorithm. For through current elimination in transition periods between zero vectors and basic and non-zero basic vectors the authors suggest implementation of intermediate switches conditions of the switches, which will be operated on as vectors. Let us consider treat these vector as variables. The authors analyzed the usage of a group of vectors V01, V02, V03, V04, V05, V06 or V10, V20, V30, V40, V50, V60. It allows obtain two most promising algorithm. To control IM output voltage and frequency parameters employing PWM mode, the assemblage of the transitions between acceptable ones, when at least one syllable of a control word would be inverted, will be referred to as vector subset of permitted dangerous bilateral transitions. The simultaneous switching of both switches of a totem pole corresponds to the dangerous transition. In the suggested algorithms, the transitions are in parallel with Karnaugh map sides, which means that they do not cause through currents. Vector PWM voltage and frequency parameters will be considered only in the time interval corresponding to the half of the sector. Simulation was carried out varying time interval of vector V0 existence for regulating generated voltage value under invariable TV4/TV6 ratio (for s the first sector). The effect of n parameter on the quality of IM drive in VPWM mode. The simulation was performed with MATLAB Simulink. Simulation results are presented.