All solid-state rectangular pulse generator for corona discharge in water

Abstract

Industrial pollutants and in particular pharmaceutical residues have caused large-scale pollution to the potable water in China. Many pharmaceuticals and macromolecular organic matter withstand conventional water treatment technologies. Consequently, advanced oxidation processes (AOP), and especially low-temperature plasmas with their ability to create reactive species including the hydroxyl radical which is currently one of the strongest oxidants in nature directly in water, may offer a promising solution. We developed a plasma reactor with a coaxial geometry to generate large volume corona discharges directly in water. To avoid that the corona discharges develop into arc discharges, high-voltage pulses with the duration of only a few hundreds of nanoseconds are required. Moreover, since the impedance of the waste water in the plasma reactor varies all the time, it is better not to require the impedance matching for the pulse generator. Therefore, an all solid-state nanosecond pulse generator using IGBTs is constructed in Marx topology. FPGA is utilized to generate the nanosecond signals and the driving circuits are precisely designed to trigger 12 IGBTs synchronously in a few nanoseconds. Finally, nanosecond pulses with voltage amplitude up to 10 kV, duration of 1–100 μs and frequency up to 10 kHz are generated. Besides, all these parameters can be adjusted easily and the whole system is very compact and portable.