Search

Power supplies have played crucial role to improve and extend plasma applications. Several dc, pulsed, and radio frequency (RF) stabilized power supplies have been developed over a wide range of frequencies and voltage waveforms. However, the influence of voltage waveform on the plasma densification, mainly due to the secondary electrons emission from the electrodes, has not been quite explored. This paper proposes an asymmetric pulsed bipolar power supply, adjustable in frequency, amplitude, pulsewidth, and number of pulses for generation of cold plasmas. Short period positive pulses, between longer negative pulses, increase greatly the secondary electron emission from the electrodes and, consequently, the plasma ionization rate. Short pulses (ns) are obtained by the phase shift between each carrier, and the high-intensity pulses are obtained by cascading the cell submodules in a half-bridge cascade topology, using a modular half-bridge converter configuration. The intensity of the positive and negative pulses can be varied independently. There is no unintended dc voltage level between the electrodes, which appear in RF plasmas. The plasma generated in this way is free of electric arc and can be kept stable within a broader range of operating parameters, mainly the voltage and the working gas pressure. [ABSTRACT FROM AUTHOR]

Series active power filters (APF) are an important solution to deal with power quality issues in weak grids under the presence of non-linear loads. The use of voltage feedback from the critical-load-bus (cload-bus) in the series APF allows for a control strategy that has performance and processing power advantages, when compared to other strategies in literature, but can cause saturation of injection transformers. This paper presents a control strategy that uses cload-bus voltage feedback with an additional control loop of the dc current in the output of the series APF voltage source converter (VSC), to avoid injection transformer saturation. The controlled dc current is additionally used for balancing the split dc-bus capacitors voltage in the VSC. The series APF and the proposed control strategy are modeled using small signal analysis for allowing controller design. Experimental results from a 3 kVA prototype are presented, with cload-bus voltage total harmonic distortion improving from 9% to 3% in each phase, while achieving the objectives of improved cload voltage waveform, controlled transformer dc current, and balanced dc-bus capacitors voltage. [ABSTRACT FROM AUTHOR]

This paper proposes an energy regeneration circuit for three-phase voltage-fed inverters using a modified Undeland snubber. The proposed system uses a quasi-square-wave zero voltage switching dc–dc auxiliary converter to regenerate the energy from snubber capacitor to the dc bus. The regenerative circuit uses a single active switch, and it operates independently of the three-phase inverter. Operation stages, theoretical waveforms, and a design methodology are presented. Experimental results based on a 4.5-kVA three-phase inverter prototype are included to validate the proposed topology. [ABSTRACT FROM PUBLISHER]