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A 4-level flying capacitor converter (FCC) operation is considered on a base of discrete state-space model. A transition matrix is obtained for a pulse width modulation (PWM) period for large normalised voltage command values [1/3, 1). The transition matrix elements are expanded into power series by small parameters. The matrix eigenvalues are presented in the form of power series as well. Six separate transients are constructed for six possible initial FCC states on a PWM period. Inductor current and capacitors’ voltage transients are found for the voltage source power-up as the arithmetic average of the six separate transients. Finally, the discrete solutions are replaced by equivalent continuous ones. Simple and accurate formulas for inductor current and capacitors’ voltage transients demonstrate good agreement with simulation results.

A 4-level flying capacitor converter (FCC) operation is considered on a base of discrete state-space model. A transition matrix is obtained for a pulse width modulation (PWM) period for small normalised voltage command values [0, 1/3]. The transition matrix elements are expanded into power series by small parameters. The matrix eigenvalues are presented in the form of power series as well. Six separate transients are constructed for six possible initial FCC states on a PWM period. Inductor current and capacitors’ voltage transients are found for the voltage source power-up as the arithmetic average of the six separate transients. Finally, the discrete solutions are replaced by equivalent continuous ones. Simple and accurate formulas for inductor current and capacitors’ voltage transients demonstrate good agreement with simulation results.

The current research proposes an integrated framework for product design that incorporates simulation-based tools into the early design stage to achieve optimum multiscale systems. The method to determine the appropriate cellular material-property relations for the internal material structures of the system is through a topology optimization technique and a multiscale design process. Specifically, the reliability-based topology optimization (RBTO) and a multi-attribute decision design method are integrated into the inductive design exploration method (IDEM). The RBTO method is introduced to determine optimal topologies at the mesoscale. The multi-attribute decision design method is used for decision support in the design process of the macroscale systems. IDEM offers the capability for concurrent design on multiple scales providing an approach for the integration of the other two methods. An example of the developed multiscale design framework is presented in terms of a hydrogen storage tank used in a hydrogen fuel cell for automotive applications. The multiscale tank design will feature a high strength cellular structured wall, resulting in a large weight reduction. [DOI: 10.1115/1.4002294]

This study addresses the calculation of current total harmonic distortion (THD) for three-phase (3P) pulse-width modulation (PWM) inverters. First, it demonstrates how an analytical approach to PWM current ripple normalised mean square (NMS) calculation introduced in the late 1980s for a two-level (2L) inverter can be used for current THD evaluation. Second, it is shown how to evaluate current THD for a three-level (3L) 3P inverter using the current ripple NMS concept. Though considered is a 3P cascaded inverter with one H-bridge per phase, the results are applicable to popular 3L neutral point clamped (T-type) and flying capacitor inverters. [ABSTRACT FROM AUTHOR]