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The inductance gradient reflects the armature thrust in the electromagnetic rail launcher (EML). The inductance gradient is separated into two components: one is the armature thrust inductance gradient $L'_{a}$ that affects armature velocity and position and another is the rail inductance gradient $L'_{r}$ that affects the rail’s forward thrust, when combined with armature inductance gradient gives the total time-varying inductive load for the pulsed power. Thus, an accurate estimate of the system current can be created, which feeds back to the armature thrust and velocity calculation. The velocity frequency $f_{v}$ is introduced to interpret the velocity skin effect (VSE). The energy storage inductance gradient $L_{u}$ varying with $f_{v}$ is obtained in the 2-D finite-element model (FEM), which is used to calculate the time-varying inductance, and $L'_{a}$ can be obtained in the 3-D FEM, which is used to calculate the armature thrust. A simulate diagram is introduced to interpret how all the system components are calculated and fit together. Launch simulations reproduce experiments to about 1%. [ABSTRACT FROM AUTHOR]

As energy storage elements in modular multilevel converter (MMC) sub-module of a unified power flow controller (UPFC), metallized film capacitors endure ac and dc superimposed voltages, which brings new challenges to insulation performance of the dielectric film. In this article, an experimental setup was created to investigate the breakdown characteristics of the dielectric film for sub-module capacitors. Factors which may affect breakdown strength under ac and dc superimposed voltages were studied experimentally. The results reveal that, as the dc voltage component increases in the range of 0–3200 V, the breakdown strength gradually increases by 16.36%; as the ac voltage component increases in the range of 0–1800 V, the breakdown strength slightly decreases by 3.52%; the breakdown strength is more affected by frequency as the ac voltage component increases and decreases with increasing frequency; as temperature increases from 20 °C to 95 °C, the breakdown strength substantially decreases by 31.12%; as the thickness of the film increases from 7 to $10~\mu \text{m}$ , the breakdown strength slightly increases by 6.32%. For capacitors in 500-kV UPFC, the dc voltage component is approximately 1600 V; the ac voltage component, whose peak-to-peak value is within 800 V, mainly contains power frequency and the second harmonic components. According to the experimental results, since the ac voltage component is small and the order of harmonic is low, the breakdown strength of capacitors in UPFC has little difference compared with that of the dc capacitors. This article can provide a reference for insulation design optimization of capacitors in UPFC. [ABSTRACT FROM AUTHOR]

The development of pulsed power puts forward new requirements on volume and weight of generators. To develop a compact and lightweight high-voltage pulse generator, this work proposed a new modular pulse forming topology with high voltage gain and a reduced number of energy storage capacitors. The topology is realized by charging a set of capacitors cyclically step-by-step and discharging repetitively in series. A voltage gain of $2^{n-1}$ can be achieved with $2n\,+\,1$ all-solid-state switches, $n$ fast recovery diodes, and n capacitors. An experimental prototype built around five capacitors generates high-voltage pulses with adjustable voltage level, pulse frequency, and pulsewidth. Meanwhile, it is verified that the prototype has a certain capacity with a capacitive load. [ABSTRACT FROM AUTHOR]