The Research On Dual Three Phase Permanent Magnet Synchronous Motor Drives

Because of small torque ripple and high reliability, multi-phase motor drive system in essence could satisfy the requirement of high-power electric drive systems. Multi-phase motor drive system focused on the military, high-reliability requirement and high-power application, and such drive system had been widely used in the ship propulsion system. However, there were still a lot of problems in theory and in practice as an emerging technology.Dual three-phase permanent magnet synchronous motor (PMSM) was a symmetric twelve-phase system according to motor windings and an asymmetric six-phase system by motor outside. So dual three-phase PMSM was a six-phase system toward design of main circuit and control circuit. It only needed six inverter bridges and six cables. However, it was shown that this winding configuration resulted in the elimination of all air-gap flux time harmonics of the order k=6m±l(m=1,3,5...). Consequently, all rotor copper losses were produced by these harmonics as well as all torque harmonics of the order k=6m±l(m=1,3,5...) were eliminated. It was the same as the twelve-phase motor. These advantages made dual three-phase PMSM a most promising structure.In this paper, several key issues of dual three-phase PMSM drive system were deeply and comprehensively studied. This paper included the following contents:1Mathematical model and basic control method for dual three-phase PMSMThis paper utilized dual-reaction theory to derive self inductance and mutual inductance of the dual three-phase PMSM, built mathematical model on natural coordinates, found a group of standard orthogonal basis consisting of six-dimensional vector as well as obtained the mathematical model on dq axises and αβ axises by coordinate transformation. Several approaches to vector control of dual three-phase PMSM were elaborated. For the convenience of engineering application, an engineering approximate algorithm for the maximum ratio of torque to current was advanced by using optimization method. Dual three-phase PMSM sensorless control system based on sliding mode observer was constructed. The simulation and experiment demonstrated the effectiveness and feasibility of the proposed method.2Space-Vector PWM techniques for dual three-phase PMSMIn this paper, the traditional space vector modulation techniques for dual three-phase PMSM was introduced. Taking into account unnecessary harmonic losses in the z1-z2plane brought by traditional space vector modulation techniques, two basic voltage vector was increased, offsetting harmonic voltage on the z1-z2plane. Three approaches to space vector control of dual three-phase PMSM were elaborated. To further improve the utilization of DC voltage, a novel over-modulation technique for space-vector pulse-width modulation inverter was proposed. The over-modulation range was divided into four modes depending on the modulation index. Output voltage and harmonic components were analyzed by simulation. The simulation and experiment confirmed validity of these methods.3Direct Torque Control for dual three-phase PMSMFirstly, mathematical modeling and direct torque control theory for dual three-phase PMSM was discussed in detail. Its flux equation and torque equation was almost consistent with an ordinary three-phase PMSM. Considering the problem of torque ripples and harmonic currents with k=6m±l(m=1,3,5...), a novel direct torque control strategy, which based on fuzzy logic and rebuilding voltage vector, was proposed. In order to obtain accurate torque and flux linkage control, space vector modulation (SVM) technique was introduced to the conventional PMSM direct torque control system. Direct torque control based on SVM was established. Moreover, direct torque control PMSM system based on rotor flux observation sensorless was constituted.4Multi-level dual three-phase PMSM control systemThis paper presented the most important topologies like diode-clamped inverter (neutral-point clamped), capacitor-clamped (flying capacitor) and cascaded multicell with separate dc sources. Diode-clamped three-level inverter space vector modulation control method for dual three-phase PMSM control system was proposed. The simulation result had been verified.5The development of dual three-phase permanent magnet synchronous motor drive systemThe design of the dual three-phase permanent magnet synchronous motor drive system based on the TMS320F2812was provided and developed. The experimental results demonstrated that the system could reliably perform.