In more electric aircraft (MEA) weight reduction and energy efficiency constitute the key figures. Additionally, the safety and continuity of operation of its electrical power distribution system (EPDS) is of critical importance. These sets of desired features are in disagreement with each other, because higher redundancy, needed to guarantee the safety of operation, implies additional weight. In fact, EPDS is usually divided into isolated sections, which need to be sized for the worst-case scenario. Several concepts of EPDS have been investigated, aiming at enabling the power exchange among separate sections, which allows better optimization for power and weight of the whole system. In this paper, an approach based on the widespread use of multi-port power converters for both DC/DC and DC/AC stages is proposed. System integration of these two is proposed as a multiport power conversion system (MPCS), which allows a ring power distribution while galvanic isolation is still maintained, even in fault conditions. Thus, redundancy of MEA is established by no significant weight increase. A machine design analysis shows how the segmented machine could offer superior performance to the traditional one with same weight. Simulation and experimental verifications show the system feasibility in both normal and fault operations.
Common-mode voltage (CMV) in electric drives causes leakage current causing consequently EMI problems, loss and reduction of their components' lifetime. Several solutions have been proposed which usually lead to higher cost because additional components are used. This paper is focused on the mitigation of the resulting CMV produced by the operation of the VSD by means of a specifically designed PWM method. The proposal is based on the analysis of the CMV harmonic spectrum using the Fourier analysis. The CMV mitigation is achieved by modifying the time-shift displacement of the carriers each sampling time considering a multi-carrier PWM technique. The resulting method has been evaluated in a down scaled experimental setup and it is easily implementable on mostly off-the-shelf mid-range microcontroller control platforms.
Electric variable speed drives (VSDs) based on two VSDs connected to a multiphase machine are an attractive solution to replace high-power mechanic and hydraulic systems in many sectors of industry and transportation because they present high performance with reduced cost, volume and weight. Among the causes which affect the reliability of dual VSDs, the common-mode current flowing through the machine bearing is an important issue. This paper faces the mitigation of the common-mode current by reducing the common-mode voltage (CMV) generated by the operation of a dual VSD. The CMV reduction is carried out without introducing any extra device and/or passive filtering method. This CMV reduction is performed by applying a specific phase-displacement between the modulation strategies of each single inverter drive. The proposed technique has been evaluated in a down scaled experimental setup in order to test its effectiveness.INDEX TERMS Harmonic analysis, Pulse width modulation, Common-mode voltage.
There is a growing attention in the industrial and academic sectors for the multi-phase drive for high power and high-speed applications. The multi three-phase drive with independent neutral points is a popular option for this application, as it allows for the usage of standard control and standard power electronics for the individual three-phase systems. This work presents a novel model of multi three-phase drive. The mathematical modelling of multi three-phase permanent magnet synchronous machine (PMSM) and modular three-phase converters is presented. The electromagnetic torque equations of multi three-phase PMSM fed by modular converters are calculated. Finally, numerical results in a dual three-phase drive are presented to validate the analytical models.
Multiphase drives are entering the spotlight of the research community for transportation applications with their high power density and the possibility of high fault tolerance. The multi three-phase drive is one of the main types of multiphase drives that allows for the direct adoption of commercial three-phase converters and high control flexibility. The elimination of high-frequency current harmonics will reduce the flux linkage harmonics, torque ripple, vibration and noise in machine drives. Therefore, this work introduces a new method to the modelling of equivalent phase current in multi three-phase drives with the double integral Fourier analysis method. A new carrier-based pulse-width modulation (CPWM) method is introduced to reduce the equivalent phase current harmonics by applying proper carrier phase angle to each subsystem in the multi three-phase drives. The proposed angles of carrier signals are analyzed for quadruple three-phase drives, and the corresponding experimental results confirm the significance of the proposed phase-shifted CPWM method to eliminate the equivalent phase current harmonics.
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