This paper introduces the quad-active-bridge (QAB) ac-dc converter, which provides isolation and bidirectional power flow in a single-stage topology. While matrix-based topologies commonly use bipolar voltage switches, the proposed solution allows the use of unipolar voltage switches. Compared to a six-switch inverter, the average voltage stress is reduced by a factor of 2. A modulation scheme is derived for this converter, which is analytically optimized toward minimum conduction losses to improve the conversion efficiency. The modulation scheme consists of closed-form algebraic solutions such that no lookup tables are required for implementation. Considerations for the converter design and the main component selection procedures are given. The proposed topology and modulation strategy is implemented in a 20-kW prototype. Measurements are conducted and show that the methods operate as expected. Experimental results show that the load step is stable, the power factor is close to unity, and the phase current total harmonic distortion is less than 5%. Finally, it is shown that the circulating current can be controlled independent of the output power. The methods and tools provided can be used for the design and analysis of ac-dc power converters based on the QAB topology.

This study presents the tools required to create a modular and scalable multi‐port converter structure, suitable for bidirectional power flow. A class of converters is defined based on the active bridge as basic building block. Any number of active bridges can be combined to form a multi‐port converter with any number of ports. For modelling of the converter, a Fourier‐based method is introduced to find an analytical converter model. Moreover, a scalable control method is proposed for these multi‐port converters: power‐balance control. The method uses Newton‐optimisation in order to reduce the circulating currents. Experimental verification on a prototype shows the methods operate as expected.

This paper presents a straight-forward method to compensate baseband distortion for regularly sampled PWMs, for both sawtooth and triangular carrier, aimed at high-precision power electronics applications such as medical MRI and semiconductor lithography. The method adds correction signals to the modulator input to mitigate the distortion, which is computationally lightweight, and pseudo-code is given to simplify implementation. Measurements are conducted which confirm the improvements offered by the method. It is shown that baseband distortion can be reduced by up to 60 dB. This improves the linearity and reduces audible noise of power converters.

The distortion of an H-bridge inverter can originate from many nonlinear factors, of which the most dominant one is typically the dead-time. In previous research, analytical models have been proposed to calculate the output spectrum of the H-bridge inverter. However, the existing models have not fully explored the effects of soft-switching and discontinuous conduction mode, which might severely degrade their accuracy. In this paper, the characteristics and the corresponding effects of these switching modes are analysed. Constraint functions are proposed in order to determine the time position of each switching mode. Based on this analysis, a numerical model of the output spectrum of the H-bridge inverter is then introduced. The model is shown to have a significantly improved accuracy compared to the previous analytical models especially for large inductor current ripples. The accuracy improvement is confirmed by simulation and measurements on an experimental prototype.

For atomic scale plasma processing involving precise, (an)isotropic and selective etching and deposition, it is required to precisely control the energy of the plasma ions. Tailored waveforms have been employed to bias the substrate table to accurately control this ion energy. Recent research has shown that switched-mode power converters can be used to generate this kind of waveform, with the benefit of increased energy efficiency and flexibility compared to the traditionally used linear amplifiers. In this article, an improved equivalent electric circuit model of the plasma reactor is proposed to allow simulation and bias waveform optimization. The equivalent electric circuit is analysed for different process phases, including the charge, discharge, and post-discharge phase. The proposed model is suitable for electric circuit simulation and can be used for predicting the electric waveforms and ion energy distributions. Plasma parameters are required as input for the model, thus an empirical parameter identification method based on the electrical measurements of the bias voltage and output current waveforms is introduced. Since these electrical measurements do not interact with the plasma process, the proposed parameter identification method is nonintrusive. Experiments have been carried out, which demonstrate that the proposed model and parameter identification method provide the expected accuracy.