A new DC-DC converter linking LCC-HVDC transmission networks

Transferring bulk power via high voltage direct current (HVDC) transmission is dominated by line commutated converters (LCC). This is due to the robustness and higher ratings of the thyristors as well as the higher converter efficiency. Nevertheless, most of these transmission networks are point to point. This is due to the challenges of allowing multi-terminal LCC based networks and power reversal. This paper introduces a new dc-dc converter topology that allows connecting two independent LCC networks. The proposed converter is based on insulated gate commutated thyristors (IGCTs). Utilizing IGCTs allow mimicking similar control and performance as in insulated gate bipolar transistor (IGBT) based voltage source dc-dc converters. However, IGCTs have more superior features over IGBTs such as higher efficiency, higher short circuit current and higher power ratings. Detailed analysis and simulations are provided to validate the proposed converter topology, which confirms its potential in connecting HVDC-LCC networks

Sinusoidal PWM modulation technique of five-phase current-source-converters with controlled modulation index

Applications such as multiphase machine drives and wind energy conversion systems are normally based on voltage source converters (VSCs) which feature a convenient and familiar control scheme. In high-power medium voltage drives, three-phase current source converters (CSCs) are widely used owing to its simple topology, motor-friendly waveforms, power reversal capability, and short-circuit-inherited protection. Although controlling CSCs in three-phase is a troublesome, multi-phase CSCs gating generation and control are challenging. In this paper, a sinusoidal PWM-based controlled modulation index gating signal generator is introduced for five-phase CSCs. Two different simulation models have been built, using MATLAB/SIMULINK, to verify the proposed concept on rectification and inversion modes of the CSCs. The proposed controller provides a controllable linear modulation index with the availability of over modulation.Qatar National Research FundScopu

Advances in Converter Control and Innovative Exploitation of Additional Degrees of Freedom for Multiphase Machines

Multiphase variable-speed drives and generation systems (systems with more than three phases) have become one of the mainstream research areas during the last decade. The main driving forces are the specific applications, predominantly related to the green agenda, such as electric and hybrid electric vehicles, locomotive traction, ship propulsion, ‘more-electric’ aircraft, remote offshore wind farms for electric energy generation, and general high-power industrial applications. As a result, produced body of significant work is substantial, making it impossible to review all the major developments in a single paper. This paper therefore surveys the recent progress in two specific areas associated with multiphase systems, namely power electronic supply control and innovative ways of using the additional degrees of freedom in multiphase machines for various non-traditional purposes

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