An Advanced Three-Level Active Neutral-Point-Clamped Converter With Improved Fault-Tolerant Capabilities

A resilient fault-tolerant silicon carbide (SiC) three-level power converter topology is introduced based on the traditional active neutral-point-clamped converter. This novel converter topology incorporates a redundant leg to provide fault tolerance during switch open-circuit faults and short-circuit faults. Additionally, the topology is capable of maintaining full output voltage and maximum modulation index in the presence of switch open and short-circuit faults. Moreover, the redundant leg can be employed to share load current with other phase legs to balance thermal stress among semiconductor switches during normal operation. A 25-kW prototype of the novel topology was designed and constructed utilizing 1.2-kV SiC metal-oxide-semiconductor field-effect transistors. Experimental results confirm the anticipated theoretical capabilities of this new three-level converter topology

Medium Voltage DC Network Modeling and Analysis with Preliminary Studies for Optimized Converter Configuration Through PSCAD Simulation Environment

With the advancement of high capacity power electronics technologies, most notably in high voltage direct current (HVDC) applications, the concept of developing and implementing future transmission networks through a DC backbone presents a realistic and advantageous option over traditional AC approaches. Currently, most consumer electrical equipment requires DC power to function, thus requiring an AC/DC conversion. New forms of distributed generation, such as solar photovoltaic power, produce a direct DC output. Establishing an accessible and direct supply of DC power to serve such resources and loads creates the potential to mitigate losses experienced in the AC/DC conversion process, reduce overall electrical system infrastructure, and lessen the amount of power generated from power plants, as well as other advantages. For the reasons listed, medium voltage DC (MVDC) networks represent a promising, initial platform for interconnecting relatively low voltage generation resources such as photovoltaic panels, serving loads, and supplying other equipment on a common DC bus bar. Future industrial parks, ship power systems, hybrid plug-in vehicles, and energy storage systems are all avenues for future implementation of the concept. This thesis introduces an initial design and simulation model of the MVDC network concept containing renewable generation, power electronic converters, and induction machine loads. Each of the equipment models are developed and modeled in PSCAD and validated analytically. The models of the represented system equipment and components are individually presented and accompanied with their simulated results to demonstrate the validity of the overall model. Finally, the equipment models are assembled together into a meshed system to perform traditional preliminary studies on the overall power system including wind speed adjustments, load energizing, and fault-clearing analysis in order to evaluate aspects of various operational phenomena such as potential overvoltages, system stability issues, and other unexpected occurrences

Cost and losses associated with offshore wind farm collection networks which centralise the turbine power electronic converters

Costs and losses have been calculated for several different network topologies, which centralise the turbine power electronic converters, in order to improve access for maintenance. These are divided into star topologies, where each turbine is connected individually to its own converter on a platform housing many converters, and cluster topologies, where multiple turbines are connected through a single large converter. Both AC and DC topologies were considered, along with standard string topologies for comparison. Star and cluster topologies were both found to have higher costs and losses than the string topology. In the case of the star topology, this is due to the longer cable length and higher component count. In the case of the cluster topology, this is due to the reduced energy capture from controlling turbine speeds in clusters rather than individually. DC topologies were generally found to have a lower cost and loss than AC, but the fact that the converters are not commercially available makes this advantage less certain

Power Converter of Electric Machines, Renewable Energy Systems, and Transportation

Power converters and electric machines represent essential components in all fields of electrical engineering. In fact, we are heading towards a future where energy will be more and more electrical: electrical vehicles, electrical motors, renewables, storage systems are now widespread. The ongoing energy transition poses new challenges for interfacing and integrating different power systems. The constraints of space, weight, reliability, performance, and autonomy for the electric system have increased the attention of scientific research in order to find more and more appropriate technological solutions. In this context, power converters and electric machines assume a key role in enabling higher performance of electrical power conversion. Consequently, the design and control of power converters and electric machines shall be developed accordingly to the requirements of the specific application, thus leading to more specialized solutions, with the aim of enhancing the reliability, fault tolerance, and flexibility of the next generation power systems

Power Electronics Applications in Renewable Energy Systems

The renewable generation system is currently experiencing rapid growth in various power grids. The stability and dynamic response issues of power grids are receiving attention due to the increase in power electronics-based renewable energy. The main focus of this Special Issue is to provide solutions for power system planning and operation. Power electronics-based devices can offer new ancillary services to several industrial sectors. In order to fully include the capability of power conversion systems in the network integration of renewable generators, several studies should be carried out, including detailed studies of switching circuits, and comprehensive operating strategies for numerous devices, consisting of large-scale renewable generation clusters

Multi-Level Medium Voltage Inverter for Dc Distributed Wind Farm to Establish Grid Interface and Provide Ancillary Support

Wind energy has gained in popularity in recent years due to cost, security and environmental concerns associated with conventional energy sources like fossil fuels. However, the utilization of wind energy in power systems creates many technical and non-technical challenges that need to be addressed for successful integrations. The main technical issues related to wind energy are its uncertainty and variability and their impacts on stability, reliability and quality of the electric power. In systems with high wind energy penetrations, unlike conventional generations, sudden changes in active and/or reactive power demand cannot be supported by wind energy. This lack of demand support may create unwanted voltage and frequency variations in the grid. On the hand, the existing AC distributed wind farms have several drawbacks including complexity, higher cost, and lower efficiency. In this dissertation, a medium voltage direct current (MVDC) distribution system for wind farms is investigated. The proposed system offers higher reliability, lower cost, higher efficiency and more importantly grid support. It also allows for easier integration of energy storage systems at DC level. Design, control, implementation, and testing of a three-level medium voltage inverter are presented. The inverter can provide active and reactive power support to the grid in case of frequency and voltage droops. Simulation and experimental results are presented to verify the viability of the proposed system and control techniques

Grid emulator for wave energy converter testing

Power generation has been an ever growing exigency since the invention of electric power. The world is gradually inching away from conventional generation toward renewable generation. Advancements in renewable energy generation have been at a steady positive pace over the past few decades with different resources developing to be feasible alternatives. A smooth and gradual transition from conventional generation to predominantly renewable energy sourced generation is what the world is looking toward in the next couple of centuries. The grid emulator is a device that will facilitate the testing and development of wave energy generators, thereby enabling the inclusion of energy generated using wave power into the existing generation mix, without causing adverse effects to the host system. The grid emulator will enable testing of wave energy devices under different grid disturbances as well as provide isolation between the devices and the grid during initial testing. This thesis presents the preliminary functions planned using the grid emulator, the specifications of the device, the design details and simulation results. The grid emulator under development is currently limited to wave energy devices, however, anomalous devices could be developed for the research and development of other under developed and untapped renewable resources