Featured in low-speed and high-torque operation, outer-rotor switched reluctance motors (OSRMs) have the potential to be widely deployed in low-speed commuter and logistics vehicle applications. In this paper, a five-phase OSRM and the control method featuring torque ripple reduction has been proposed, which can be applied as the wheel hub motor in the electric vehicles. The simulation was carried out to analyze the OSRM operation. The electromagnetic characteristics of single-phase and two-phase hybrid excitation mode, as well as step current excitation mode, were compared and analyzed. To solve the problem of the large torque ripple of OSRMs under traditional excitation modes, the torque ripple suppression method based on step current excitation was also studied. The experiment design, including motor start-up control, speed control, and torque ripple reduction, are presented to verify the system torque ripple mitigation method.
The series-connected offshore wind farm (SC-OWF) is a promising offshore wind generation solution to mitigate the need of centralized offshore high-voltage/power converter stations. Predominantly, researchers have focused on the steadystate operation and control of SC-OWFs, without considering the system-level characteristics and ability to ride-through dc side and ac network faults. This paper proposes an enhanced system for SC-OWF applications with fault-resilient capability, where comprehensive circuit configuration and protection strategies are articulated to minimize the negative effects caused by various types of dc and ac faults. For the offshore wind farm architecture, a grouping scheme is adopted where a substation based on disconnectors and diodes is proposed to realize prompt fault bypass/isolation and protection functions in the event of offshore system faults. Additionally, an onshore fault-tolerant modular multilevel converter (MMC) with modified dc-system-oriented control is employed to enable smooth and secure operation under steady-state and fault conditions. The proposed SC-OWF system is quantitatively substantiated by time-domain simulations where four ac/dc fault cases are considered, and the results consolidate the feasibility of the proposed configuration and control, indicating fault resilience of the SC-OWF system. Additionally, size, weight and cost estimations of the proposed offshore substation are presented and compared to a conventional MMC offshore station, to further highlight the merits of the proposed solution.
This article presents a gate driver circuit with all-magnetic isolation for driving silicon carbide (SiC) power devices in a three-level T-type bridge-leg. Gate driver circuitry for SiC devices has to be tolerant of rapid common-mode voltage changes. With respect to the resultant potentially problematic common-mode current paths, an arrangement of transformers is proposed for supplying the power devices with drive signals and power for their local floating gate driver circuits. The high-frequency carrier phase-switching technique is used to reduce the number of transformers. Signal timing and other implementation issues are addressed when using this arrangement with the T-type converter. The circuit is demonstrated in a 540 V bridge-leg constructed around 650 V and 1200 V cascode-connected normally-on SiC junction field effect transistors (JFETs).
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