New generation three-phase rectifier
Thesis DisciplineElectrical Engineering
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
This thesis describes the development of a new generation of three-phase rectifier, used to power telecommunications equipment. The traditional topology for such power converters is a single-phase two-stage design, with a boost converter providing power factor correction at the input to the first stage and an isolated dc-dc converter making up the second stage. A two-stage design results in the output power being processed twice and this cascade effect results in an overall reduction in efficiency. A rectifier solution is sought that meets with all the requirements of the telecommunications industry, while not displaying the inherent weaknesses associated with a boost-derived topology, and which can be realised in a single-stage design. A number of common three-phase topologies exist that could be realised as telecommunication power supplies, however, they do not completely satisfy all the industry requirements. A new three-phase rectifier, which is a single-stage buck-derived topology, is proposed. As a consequence of incorporating a buck-derived topology, the three-phase rectifier does not exhibit any issues resulting from startup inrush currents, or high currents due to an output short circuit condition, as would result in a boost-derived topology. The new proposed rectifier is modular in nature, which has the added benefit of redundancy. As a result of the new three-phase rectifier having a single-stage topology, it is expected that the overall efficiency would able to reach close to 95%. This is due to the traditional two-stage designs having efficiencies around the 90% mark, and therefore by removing a stage, out of the power conversion process the overall losses would also be halved, resulting in the 5% gain in efficiency. The rectifier system requires only one controller as a result of being a single-stage design, thus also reducing the overall system cost. Simulations show that if this topology is combined with a three-phase phase-locked loop controller it can meet the industry compliance standards. The thesis follows the development of the three-phase power converter from the simulation stage to the realisation of the control hardware and stability modelling. It also provides a detailed report of an investigation into the power converter system’s performance. The thesis concludes with discussions concerning the viability of the new topology as a commercial product and indicates areas of possible future research and development.