Pulse-Amplitude-Modulation Full-Bridge Diode-Clamped Multilevel LLC Resonant Converter Using Multi-Neighboring Reference Vector Discontinuous PWM

Abstract

A full-bridge diode-clamped multilevel LLC resonant converter suitable for power conversion systems that use high input voltage, such as railway vehicles, is proposed in this paper. In order to eliminate the voltage deviations of the capacitors connected in series to the high voltage input DC link, a novel modulation strategy referred to as multi-neighboring reference vector discontinuous pulse-width modulation (MNRV DPWM) is proposed. Unlike the existing two-level resonant converter that varies the operating frequency to hold the output voltage constant, the proposed multilevel resonant converter modulates the amplitude of the fundamental wave input to a resonance tank while fixing the operating frequency at the resonance point. Therefore, the design of passive elements becomes easier, and stable operation is possible over a wide operating range with only one power conversion stage. In this paper, the control algorithm and operation characteristics of the newly proposed full-bridge diode-clamped four-level LLC resonant converter are analyzed in detail and design guidelines are presented. The feasibility of the proposed converter is verified through a simulation and an experiment with a prototype converter.

Full-Bridge Diode-Clamped Four-Level Symmetric Switching Converter

“…The switching patterns in the end sag type that adopt either down or up counting carrier depending on the magnitude of modulation index m=Vcmd/Vdc (−1≤m≤1) and CM are expressed in ( 2) and ( 3) [31]. When Vcmd is greater than 0.5Vdc in UCM, the switching pair (AB) changes as follows: because the A phase is clamped to the positive DC rail, the switching status of A always remains at "3", while the switching status of the B phase changes from "0", "1", to "2" because the B phase is located in SVR.…”

“…Mode 3 [t2, t3]: At t2, QB6 turns off and the switching state becomes (31). The capacitor charge state becomes DDC, which means Cdc1 and Cdc2 are discharged with a current of 1/3•ILS and Cdc3 is charged with a current of 2/3•ILS.…”

“…Meanwhile, multi-neighboring reference vector discontinuous PWM (MNRV DPWM) applicable to fullbridge (FB) DC/DC converters has been reported recently [31,32]. It is characterized in that several reference voltage vectors having different charge/discharge characteristics of the capacitors are selected and combined according to the position of the command voltage.…”

“…FB diode-clamped four-level LLC resonant converter using MNRV DPWM controls the output voltage by modulating the amplitude of the switching leg voltage instead of the conventional switching frequency sweep method [31]. Pulse-amplitude-modulation (PAM) allows the switching frequency to be fixed at the resonant frequency, facilitating passive component design.…”

Identifying the Technology Opportunities and the Technology Taxonomy for Railway Static Inverters With Patent Data Analytics

“…As a static inverter is an important device for ensuring the reliability and safety of vehicles and improving passenger convenience, performance verification must be secured [5][6][7]. Therefore, it is necessary to understand the technology of static inverter for railway vehicles in detail, analyze future technology trends, and use this information to establish the technical strategy for railway R&D. Static inverter for railway vehicles has attracted great interest since the 1990s, leading to many patents focused on improving system efficiency and reducing operating costs.…”