Abstract
Inverter's performance and operating mode may be negatively affected by inverter input (dc-link) current and voltage ripple. It is a common experience that even theoretically balanced loads with perfectly balanced supply voltages, such as multiphase ac motors supplied by pulse-width modulation (PWM) inverters, in practice show a certain degree of current unbalance, in the range of a few percent, which introduces a low-frequency instantaneous power oscillation. This reflects in current and voltage low-frequency ripple on the dc-link inverter side (i.e. at the double-fundamental frequency). A possible method to analyse this matter is through the symmetric sequence components. In particular, based on the first negative current sequence component and by considering the equivalent dc-link impedance calculated at the dominant double-fundamental frequency, the amplitude of the corresponding dc-link voltage ripple component is calculated in this work for a general multiphase load. Finally, the design of the dc-link capacitor in multiphase inverters is proposed considering requirements referred to the double-fundamental dc voltage ripple. The feasibility of the proposed developments has been verified for three-, five- and seven-phase inverters by both numerical simulations and comprehensive experimental tests, always showing a good matching.
Highlights
During the last decades, multiphase variable speed drives have gained widespread attention, and numerous interesting developments have been published recognising their advantages over the standard three‐phase solutions [1,2,3]
It can be concluded that from the point of view of the dc‐link capacitor sizing, if the same apparent power is considered within compared multiphase inverter topologies, there are no benefits of increasing the number of phases because the amplitude of the low‐frequency voltage ripple component depends only on the level of unbalance (UF)
In order to point out the effects of the dead‐time, Figure 6 reports the harmonic spectra of the dc‐link voltage ripple considering the original simulation and a realistic case with the same dead‐time adopted as in the experiments (4 μs, blue histogram)
Summary
Multiphase variable speed drives have gained widespread attention, and numerous interesting developments have been published recognising their advantages over the standard three‐phase solutions [1,2,3].
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
