Power supply design and waveform targeting for dielectric barrier discharge reactors

This thesis explores the development of efficient power supplies for high-efficacy dielectric barrier discharge (DBD) ozonisers, with a focus on designing and generating controllable waveforms to optimise ozone production.

One useful technology for building DBD power supplies is the piezoelectric transformer, a two-port electromechanical device similar to a magnetic transformer, that can be modelled with an electrical equivalent circuit. A global-optimiser-based method to determine the equivalent circuit parameters of piezoelectric transformers and resonators is developed to aid in power supply design. Three parameterisation methods are explored, including an improved cost function, refinement of parameters, and particle swarm optimisation (PSO). The research shows that these methods can more accurately extract the circuit parameters than those shown previous literature, aiding design and simulation of DBD reactor power supplies.

Piezoelectric resonators are one-port electromechanical devices which are high Q-factor resonators. A novel piezoelectric-resonator-based power supply for operation with low input voltage is also designed. A dielectric barrier discharge reactor is parameterised to determine its equivalent linear-model component values, which are used in conjunction with parameters from three different piezoelectric resonators to develop a new system model. This model is then used to design a novel power supply which uses only the piezoelectric resonator for voltage gain. This power supply is then tested in conjunction with the DBD reactor to validate its performance.

This thesis also explores how a biharmonic waveform can be used to change the frequency spectrum of the reactor input waveform to improve the efficacy of the reactor and overall system efficacy. A technique called selective harmonic generation (SHG) is presented to create a periodic pulse-train containing precisely controllable harmonics up to the switching frequency. Two experiments with DBD reactors are performed, one using a high-voltage magnetic transformer as the voltage gain device and the other using a piezoelectric transformer to validate this technique.

Finally, global optimisers using hardware in the loop tune the biharmonic input waveform parameters and flowrate of the input gas to improve the efficacy of ozone production in a DBD reactor. A novel hardware-in-the-loop system is developed to explore the effects of varying these parameters on reactor conditions.

The main contribution of this work comes from the development of a new biharmonic tailored waveform technique which is shown to improve ozone generation. A second contribution includes the novel piezoelectric resonator-based power supply that has many applications beyond chemical reactors. Other contributions include the piezoelectric and reactor modelling which have applications beyond ozonisers.