Novel control method for magnetic suspension and motor drive with one three-phase voltage source inverter using zero-phase current

Abstract

independent d-and q-axis currents are actively regulated by one three-phase inverter. If three current components, such as d-, q-, and zero-axis currents, are independently regulated by only one three-phase inverter that has six power switching devices, further motor downsizing, and energy saving can be achieved. The zero-phase current flowing through the non-contact linear generator coils for the super-conducting Maglev was actively controlled to increase a magnetic damping between the bogies and ground (Sakamoto, et al., 2006). This paper focuses on both three-phase permanent magnet synchronous motor (PMSM) drive and a one-DOF actively controlled actuator using only one three-phase voltage source inverter. The final goal of this study is to apply the proposed control method to a one-DOF actively regulated bearingless machine, which consists of, for example, a three-phase PMSM, repulsive type passive magnetic bearings, and an axial magnetic bearing. As a first step of this study, we are aiming to drive an interior permanent magnet synchronous motor (IPMSM) and to magnetically suspend an iron ball using only one three-phase voltage source inverter in this paper. We propose a novel concept that the suspension winding can be connected between a neutral point of the Y-connected three-phase winding and a middle point of the dc voltage sources, and resulting zero-phase current generates the suspension force. Since one actively controlled DOF is increased without any inverter circuits, the proposed control method can contribute to magnetically suspended machines. In section 2, the proposed control method of the zero-phase current with motor operation is analytically derived, and the control block diagrams are shown. To verify the proposed control method, we fabricated the experimental apparatus which consists of a three-phase interior permanent magnet synchronous motor (IPMSM) and a single active magnetic suspension system with an iron ball. Section 3 presents the experimental apparatus and results. A part of this paper was presented in [Asama, et al., 2014]. Significant revisions with additional theoretical analysis results, derivation voltage-current equation, and improved test results are included in this paper.