High-voltage pulse generator using sequentially charged full-bridge modular multilevel converter Sub-modules, for water treatment applications

This paper proposes a new high-voltage pulse generator (PG) fed from a low-voltage DC supply Vs, which charges one arm of N series-connected full-bridge (FB) modular multilevel converter (MMC) sub-module (SM) capacitors sequentially, through a resistive-inductive branch. By utilising FB-SMs, the proposed PG is able to generate bipolar rectangular pulses of peak NVs and unipolar rectangular pulses of either polarity, at high repetition rates. Asymmetrical pulses are also possible. The proposed topology is assessed via simulation and scaled-down experimentation, which establish the viability of the topology for water treatment applications

High-voltage pulse generators incorporating modular multilevel converter sub-modules

Recent research established the effectiveness of applying a pulsed electric field to deactivate harmful microorganisms (such as bacteria and E. coli). Successful deactivation is achieved by lethal electroporation; a process that produces electric pores in the biological cell membrane of the harmful microorganisms when subjected to high-voltage (HV) pulses. The HV pulses are designed to create pores beyond a critical size at which the biological cell can reseal.;In contrast when applying non-lethal electroporation, the cell-membrane survives after the electroporation process. This is required, for example, when inserting protein cells in the cell-membrane. In both lethal and non-lethal electroporation, HV pulses in the kilo-Volt range (1-100 kV) with durations ranging between nanoseconds and milliseconds are required.;This thesis proposes nine pulse generator (PG) topologies based on power electronic devices and modular multilevel converter sub-modules. The proposed topologies are divided into two main groups namely: PGs fed from a HV DC supply and PGs fed from an LV DC supply. The first group presents a new family of HV DC fed topologies that improve the performance of existing HV DC fed PGs, such as flexible pulse-waveform generation and full utilisation of the DC link voltage.;The second group is dedicated to a new family of LV DC fed PG topologies which have flexible pulse-waveform generation, controlled operation efficiency, and high voltage gain.;All the proposed PG topologies share the important aspect in the newly developed HV PGs, that is modularity, which offers redundancy and robust pulse generation operation.;The presented PG topologies are supported by theoretical analysis, simulations, and experimentation.Recent research established the effectiveness of applying a pulsed electric field to deactivate harmful microorganisms (such as bacteria and E. coli). Successful deactivation is achieved by lethal electroporation; a process that produces electric pores in the biological cell membrane of the harmful microorganisms when subjected to high-voltage (HV) pulses. The HV pulses are designed to create pores beyond a critical size at which the biological cell can reseal.;In contrast when applying non-lethal electroporation, the cell-membrane survives after the electroporation process. This is required, for example, when inserting protein cells in the cell-membrane. In both lethal and non-lethal electroporation, HV pulses in the kilo-Volt range (1-100 kV) with durations ranging between nanoseconds and milliseconds are required.;This thesis proposes nine pulse generator (PG) topologies based on power electronic devices and modular multilevel converter sub-modules. The proposed topologies are divided into two main groups namely: PGs fed from a HV DC supply and PGs fed from an LV DC supply. The first group presents a new family of HV DC fed topologies that improve the performance of existing HV DC fed PGs, such as flexible pulse-waveform generation and full utilisation of the DC link voltage.;The second group is dedicated to a new family of LV DC fed PG topologies which have flexible pulse-waveform generation, controlled operation efficiency, and high voltage gain.;All the proposed PG topologies share the important aspect in the newly developed HV PGs, that is modularity, which offers redundancy and robust pulse generation operation.;The presented PG topologies are supported by theoretical analysis, simulations, and experimentation

A comparative review of three different power inverters for DC–AC applications

This paper presents a comparative review of three different widely used power inverters, namely the conventional six-switch inverter; the reduced switch count four-switch inverter; and the eight-switch inverter. The later inverter can be reconfigured as a neutral-point diode-clamped inverter at the failure of one inverter leg. The three power inverters are compared and discussed with respect to cost, complexity, losses, common mode voltage, and control techniques. The paper is intended to serve as a guide regarding selecting the appropriate inverter for each specific application. Simulation results are presented to demonstrate the performance of the three power inverters, followed by a comprehensive comparison between the three power inverters

Current-source single-phase module integrated inverters for PV grid-connected applications

This paper presents a modular grid-connected single-phase system based on series-connected current-source module integrated converters (MICs). The modular configuration improves the reliability, redundancy and scalability of photovoltaic (PV) distributed generators. In this system, each PV panel is connected to a dc/ac inverter to permit individual Maximum Power Point Tracking (MPPT) operation for each panel. Thus, the harvested power from the PV system will increase significantly. There are four different inverter topologies suitable to be used as MICs with different performances in terms of filtering elements size, power losses, efficiency, output voltage range, and high frequency transformers’ size. For the MPPT control, the oscillating even order harmonic components should be eliminated from the inverter’s input side otherwise the maximum power cannot be extracted. The proposed modulation scheme in this paper will ease the control of inverter’s input and output sides. Therefore, the 2nd order harmonic in the input current can be eliminated without adding new active semiconductor switches. A repetitive controller coupled with proportional-resonant controllers are employed to achieve accurate tracking for grid side as well as input side currents. Comparisons and performance evaluations for the proposed MICs are presented and validated with 1 kVA prototype controlled by TMS320F29335 DSP

Review of switched reluctance motor converters and torque ripple minimisation techniques for electric vehicle applications

This paper presents a review of the most common power converters and torque ripple minimisation approaches for switched reluctance motors (SRMs). Unlike conventional three-phase AC motors, namely squirrel cage induction motors and permanent magnet synchronous motors, which require a typical three-phase inverter for operation, the switched reluctance motor requires a different topology power converter for reliable and efficient operation. In addition, due to the non-linear, discrete nature of SRM torque production, torque ripple is severely pronounced, which is undesirable in servo applications like electric vehicles. Hence, deploying a proper torque control function for smooth and quiet motor operation is crucial. This paper sheds light over the most popular SRM power converters as well as torque ripple minimisation methods, and it suggests an optimal SRM drive topology for EV applications.</p

A new torque control approach for torque ripple minimisation in switched reluctance drives

The switched reluctance motor (SRM) has many merits, such as robustness, a simple construction, low cost, and no permanent magnets. However, its deployment in servo applications is restrained due to acoustic noise and torque ripple (TR). This paper presents a new torque control approach for TR reduction in switched reluctance drives. The approach is based on the maximum utilisation of the available dc-link voltage, hence extending the zero torque-ripple speed range. The approach is suitable for an SRM with any number of phases and stator/rotor poles. Soft switching control is deployed, which reduces switching losses. At any instant (regardless of the number of phases being conducted simultaneously), only one phase current is controlled. The well-established torque-sharing function concept is adapted and generalised to cater for more than two phases conducting simultaneously. MATLAB/Simulink confirmation simulations are based on the widely studied four-phase 8/6, 4 kW, 1500 rpm SRM.</p

A review of modular electrical sub-systems of electric vehicles

Climate change risks have triggered the international community to find efficient solutions to reduce greenhouse gas (GHG) emissions mainly produced by the energy, industrial, and transportation sectors. The problem can be significantly tackled by promoting electric vehicles (EVs) to be the dominant technology in the transportation sector. Accordingly, there is a pressing need to increase the scale of EV penetration, which requires simplifying the manufacturing process, increasing the training level of maintenance personnel, securing the necessary supply chains, and, importantly, developing the charging infrastructure. A new modular trend in EV manufacturing is being explored and tested by several large automotive companies, mainly in the USA, the European Union, and China. This modular manufacturing platform paves the way for standardised manufacturing and assembly of EVs when standard scalable units are used to build EVs at different power scales, ranging from small light-duty vehicles to large electric buses and trucks. In this context, modularising EV electric systems needs to be considered to prepare for the next EV generation. This paper reviews the main modular topologies presented in the literature in the context of EV systems. This paper summarises the most promising topologies in terms of modularised battery connections, propulsion systems focusing on inverters and rectifiers, modular cascaded EV machines, and modular charging systems

Electroporation for water disinfection: a proof of concept experimentation

This paper is a proof of concept showing the effectiveness of using irreversible electroporation (IRE) as a stage of water disinfection in the water treatment process. The IRE process essentially requires relatively high voltage pulses to pose a pulsed electric field across harmful microorganisms. In this paper, a laboratory-based solid-state Marx generator was built for this purpose and untreated water samples have been used to test the effectiveness of applying variable pulse width, magnitude and rate. All the pulses are unipolar rectangular. The tested samples are all from the same water source with the same coliform count. After performing the electroporation disinfection process the coliform count reached zero proving the effectiveness of IRE