Comparative Analysis of Two and Four Current Loops for Vector Controlled Dual-Three Phase Permanent Magnet Synchronous Motor

Abstract

Dual three-phase (DTP) permanent magnet synchronous motors (PMSMs) are specialized machines which are commonly used for high power density applications. These machines offer the merits of high efficiency, high torque density, and superior supervisor fault tolerant capability compared to conventional three-phase AC-machines. However, the electrical structure of such machines is very complicated, and as such, control becomes challenging. In conventional vector controlled DTP-PMSMs drives, the components of the dq-subspace are associated with electromechanical energy conversion, and two currents, i.e., Id and Iq belonging to this subspace, are used in feedback-loops for control. Such orthodox control methods can cause some anomalies e.g., the voltage source inverter’s (VSI) dead time effect and other nonlinear factors, and can induce large harmonics. These glitches can be greatly alleviated by the introduction of the two-extra current loops to directly control the currents in Z1Z2-subspace in order to suppress the insertion of harmonics. In this paper, two approaches—one with two-current loops and other with four-current loops—for vector controlled DTP-PMSMs are investigated with the aid of different MATLAB-based simulations. Furthermore, in the paper, the influence of additional current loops is quantified using simulation-based results.

Current Control Methods for an Asymmetric Six-Phase Permanent Magnet Synchronous Motor

“…Two modeling and control methods have been adopted for the ASP_PMSM. They are the double d-q approach [5][6][7] and the vector space decomposition (VSD) approach [8][9][10]. The former scheme has the advantages of modeling and control schemes of traditional three-phase motors and each set of three-phase winding is regarded as a basic unit.…”

“…Only in α-β subspace does the electromechanical energy take place, while the x-y and O 1 -O 2 subspaces are only pertinent to the loss. Because the VSD Because the VSD scheme reveals the characteristics of multi-degree freedom for the ASP_PMSM [8][9][10], the current control becomes more flexible compared to the double d-q transformation. Therefore, most of the recent research studies pertinent to ASP_PMSM are based on the VSD method.…”

“…Therefore, most of the recent research studies pertinent to ASP_PMSM are based on the VSD method. Two dimensional current control which only controls the torque producing α-β currents is insufficient [8]. Four-dimensional current control based on the VSD approach can be used not only for torque control but also for the inverter dead time effect [8][9][10][11].…”

“…Four-dimensional current control based on the VSD approach can be used not only for torque control but also for the inverter dead time effect [8][9][10][11]. In α-β subspace, the currents are controlled in the rotor coordinates to achieve vector control [8][9][10][11][12][13][14]. This coordinate system is a natural selection because not only are the controllable currents direct currents in steady state but also, the inductance matrix can be decoupled.…”

“…In α-β subspace, internal model control (IMC) with a state observer is adopted to reduce the current fluctuations of d and q axes currents. In x-y subspace, an adaptive-linear-neuron (ADALINE)-based control algorithm is employed to suppress the current harmonics due to the dead time and the nonlinearity of the inverter, which is independent of the current polarity and avoids the multiple Two dimensional current control which only controls the torque producing α-β currents is insufficient [8]. Four-dimensional current control based on the VSD approach can be used not only for torque control but also for the inverter dead time effect [8][9][10][11].…”