Subsea power transmission and distribution has been widely accepted by the offshore oil and gas industry for boosting the production and reducing the cost. To support various processing loads such as pumps and compressors, the subsea power demand is increasing rapidly from kW to tens of MWs and with a step-out distance of few kilometers to hundreds of kilometers. The reactive power burden on the system due to the charging currents limit the conventional ac power transmission to smaller step-out distances. At PEMSES, we study various subsea power system architectures and propose to use HVDC based subsea transmission architectures. We also propose a novel hybrid circuit breaker for HVDC systems to reduce the breaking time and the losses. This project also investigates various variable frequency drives (VFDs) suitable for driving the electrical submersible pumps (ESP) for subsea applications.
Voltage Source Converters (VSCs) have been widely used in renewable energy, distributed power generation and microgrid applications. VSCs can not only control the power transfer among the sources, grid and loads but also make it possible to improve the power quality via the converter control. At PEMSES, we investigate the interfacing VSC control methods that can effectively share the active/reactive load power demand in islanded microgrid as well as actively mitigate the LCL filter resonance and harmonics caused by non-linear loads in grid-connected microgrid system. A 5kW experimental prototype comprises IGBT-based three phase VSC, dSPACE MicroLab Rapid Control Prototyping (RCP) controller and Chroma Regenerative Grid Simulator is developed to verify the ideas.
With the ever increasing demand for making electric vehicles (EVs) more powerful, higher capacity battery packs are going to be installed in the EV. Fast charging of these battery are crucial for bringing parity between the EV and conventional vehicles. At PEMSES, a single stage EV charger is being developed to achieve more efficiency by using lesser number of semiconductor switches compared to conventional chargers having multiple power conversion stage. Higher power density will also be achieved by minimizing the use of magnetic components and using Wide Bandgap (WBG) devices like SiC with high switching frequency. Bidirectional power flow feature is being considered to pump excess power from the vehicle back to the grid to cater to peak loading conditions.
In a three phase microgrid, due to asymmetric loading of the individual phases, the phase currents are unequal. This results in appreciable negative sequence and zero sequence current through the phases, which may falsely trip the line circuit breakers and damage three phase machines which are connected to the microgrid. Several inverter topologies like four half bridges and three separate full bridges, are being investigated to compensate for this unbalance, such the power quality and reliability in the microgrid is maintained. At PEMSES, we are working on developing several PWM techniques and control methods using four leg inverter to compensate for the negative sequence and zero sequence current.
Energy management in microgrids is a highly researched topic especially after the impact of increased renewable energy penetration. At PEMSES, we develop a novel hierarchical Multi-Agent System (MAS) based controller for Energy Management in microgrids. The proposed control architecture will provide faster response and enhanced resiliency even during controller faults. We test the robustness of the controller using real-time simulation tools. We are also working towards electric vehicle integration to grid.
In recent years, SiC MOSFET has been the most preferred power semiconductor device for medium voltage range due to its improved switching response and high temperature (HT) operation capabilities. This HT operation capability of SiC MOSFET increases its application in HT environments like motor drives, hybrid electrical vehicles and industrial drilling tools. Though SiC MOSFET has the capability to operate at a higher junction temperature (150°C to 200°C), it requires a robust gate drive and protection circuit for its reliable operation. Our work at PEMSES focuses on development of HT gate driver for SiC MOSFET. The proposed gate driver consists of an improved desaturation and under voltage lock out circuit.
There are big advantages to 5G networks. In addition to faster speeds, 5G offers greater bandwidth and network capacity, paving the way for a future of driverless cars, connected devices and more high-definition connections for virtual meetings and tele-medicine. But the roll out in the United States and elsewhere has been stymied by gaps in available technology that could operate at the high frequencies required by 5G.
Envelope tracking is a type of power supply modulation technique that continuously adjusts the converter voltage used by the radio frequency power amplifier in order to keep it running at peak efficiency. Boosting both frequency and power at the same time is technically challenging, in part because of the excess heat produced. The continuous adjustment via envelop tracking can significantly reduce the amount of waste heat produced by the system, despite the higher power output.