Abstract
The total control range of asymmetric dual three-phase permanent magnet synchronous motor (ADT_PMSM) is divided into three different segments by voltage modulation range and current control dimensions and respective control strategies to get the injected voltages in harmonic subspace for three segments are presented in this paper. The three segments are sinusoidal current modulation region, sinusoidal voltage modulation region and overmodulation region. In sinusoidal current modulation region, resonant controller is adopted in the harmonic subspace to calculate the injected voltages, which can compensate the effect of six-phase voltage source inverter (VSI) dead time for two sets of three-phase windings and takes the pole correction into consideration. In sinusoidal voltage modulation region, open loop control strategy in harmonic subspace is adopted. Overmodulation region 1 and 2 are defined in overmodulation region, and the harmonic voltages which are injected into harmonic subspace to extend the modulation index are calculated based on superposition principle and VSD theory. In order to achieve smooth transition from different regions, a novel space vector pulse width modulation (SVPWM) technique for ADT_PMSM is proposed. The experimental results demonstrate the validity and feasibility of the suggested control approach.
Highlights
Multi-phase motors received considerable attention lately thanks to the unique characteristics of higher fault tolerance, smaller torque ripples, advanced control strategies and the rapid development of the multilevel inverters [1]–[6]
Based on the equations (17),(18) and vector space decomposition (VSD) theory, the current harmonics in x-y subspaces can be expressed in the following form
A lot of current harmonics exist in the phase current, nearly no current distortions exist in the α-ß subspace under load transient state, which means that the output torque performance will not be influenced even under load transient state in the overmodulation region
Summary
Multi-phase motors received considerable attention lately thanks to the unique characteristics of higher fault tolerance, smaller torque ripples, advanced control strategies and the rapid development of the multilevel inverters [1]–[6]. Two-vector space vector pulse width modulation (SVPWM) technique can be extended to the overmodulation region It injects large amount of harmonic voltages into the harmonic subspace, which will lead to heavy harmonic currents [19], [20]. PWM TECHNIQUES AND DIVISIONS OF MODULATION REGION FOR ADT_PMSM IN FULL MODULATION RANGE Fig. gives the structure of ADT-PMSM It consists of two sets of three-phase windings, which are identical and supplied by two three-phase VSIs. Based on the VSD theory [18], the motor variables (including flux, voltage and current) are mapped into three subspaces which are orthogonal to each other, i.e., α-ß (fundamental), x-y (harmonic) and O1-O2 subspaces. The on-durations for the switching vectors of two threephase windings can be given by
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