Symmetrical six-phase drives with common-mode voltage elimination based on synchronized PWM

Abstract

Novel methodology of synchronized pulsewidth modulation (PWM) has been disseminated for control of symmetrical six-phase (dual three-phase) induction motor drives fed by two three-phase inverters with single DC voltage source. Control algorithms are based in this case on the 60 0 -phaseshifting of control signals of two standard voltage source inverters. Four basic schemes of synchronized continuous and discontinuous PWM, applied for control of symmetrical dual three-phase systems, have been analyzed and compared. All these schemes allow providing cancellation of undesirable commonmode voltages in systems during the whole control range. Simulations give the behavior of symmetrical dual three-phase system with synchronized PWM. The spectra of the phase voltage of six-phase drives with algorithms of synchronized PWM do not contain even harmonics and sub-harmonics, which is especially important for the high power/high current applications.

Combined synchronised PWM for symmetrical split-phase drives with low switching frequency

“…Control of symmetrical six-phase induction machine drives is based on the 60 0 -phase-shift of the corresponding signals of two three-phase inverters of sixphase system [7]- [10]. In accordance with the theory of vector space decomposition, the basic six-dimensional space (as, bs, cs, xs, ys, zs) of a dual three-phase induction machine with isolated neutral points can be transformed into two orthogonal two-dimensional subspaces (sa, sb) and (m1, m2) [4].…”

“…Symmetrical Six-Phase Systems with Two Identical Schemes of Synchronised PW The use of two identical PWM schemes for control of inverters of symmetrical six-phase system allows special order of switching sequences of two three-phase inverters providing elimination of undesirable alternative commonmode voltage V 0 in the system [8], [10]. As an illustration of this control principle, Figs.…”

“…Last decades have been marked by fast application of methods of spacevector modulation, which are some of the most suitable for adjustable speed drives [1], including the developed methods of space-vector PWM, applied for control of multiphase drives [2]. Some interesting and perspective topologies of converters and drives are now six-phase (split-phase or dual three-phase) converters feeding six-phase induction motors [3]- [10]. Dual three-phase power conversion systems have several advantages over their three-phase counterparts, such as reduction of torque pulsations, of the rotor harmonic losses, and of the rated current of power switches; improved reliability at system level [5].…”

“…In particular, asymmetrical sixphase systems are based on asymmetrical six-phase machine which has two sets of windings spatially shifted by 30 electrical degrees [3]- [6]. And symmetrical sixphase drive systems are based on symmetrical induction motor, which has two sets of windings spatially shifted by 60 electrical degrees [7]- [10]. In particular, Fig.…”

“…To provide increased efficiency of dual three-phase drives fed by six-phase power converters, novel spacevector-based control and modulation strategies have been proposed for both asymmetrical and symmetrical systems [3]- [10].…”