Control and Design of a PMSG Wind Energy Conversion System and Its Integration with Solid-State Transformer Enabled AC/DC Grid System

The Permanent Magnet Synchronous Generator (PMSG) has been widely adopted for wind renewable generation system, with the single wind turbine power rating ranging from several kilowatt to even ten megawatt. It has the advantages of high efficiency, high power density, and lower maintenance cost for wind energy conversion applications. The back-to-back converter enabled PMSG wind energy conversion system (WECS) outperforms its doubly-fed induction generator (DFIG) counterpart during grid fault situation. However, how to achieve the coordinated wind turbine control which consists of the wind generator and the turbine blade pitch angle control, is challenging. The higher penetration of wind energy poses increasing demand for grid support and power management functions of wind energy conversion system (WECS). Aiming at the maximizing the wind energy capture, necessary power curtail, and grid support functions of PMSG WECS, this dissertation addresses the wind turbine system controls, design and applications.;In this research work, a systematic literature review is first conducted for the topologies of power electronics, novel configurations, energy storage solutions, and control methods in the PMSG based WECS application. The wind turbine system control functions is then identified and analyzed; a turbine blade pitch angle regulator which considers both power and rotor speed limitations is designed. The coordinated power regulation capabilities are demonstrated with simulation verification. To carry out the wind turbine system laboratory test and experimental evaluation, a 10 Hp wind turbine emulator (WTE) testbed is designed and built. The WTE consists of a 10 Hp induction motor, an ABB ACS800 variable frequency drive (VFD), and a Microchip controller dsPIC24FJ128GA010 for turbine characteristic emulation. The studied wind turbine character is analyzed. A lookup table based method is proposed and implemented for the turbine emulator, and experimental results are provided for justification.;From the WECS control design perspective, the controller design is complicated considering the highly nonlinear properties of electric machines and power converters. How to maintain the robustness and reliable control for such system is challenging. Targeting at a controller for WECS, this dissertation adopts passivity-based control (PBC) methods, to which the stability can be analytically guaranteed. Then, a comparative study between the proposed method and a standard PI is provided. For the proposed controls, both proportional-integration PBC (PIPBC) and standard PBC (sPBC) are considered. The wind energy system consists of a wind turbine, a PMSG, a pulse width modulation (PWM) rectifier, a dc load and an equivalent distributed energy storage device, which is formed with a dc source with internal resistor. The generator rotational velocity is regulated at maximum power point (MPPT) for the investigated wind turbine. The step by step design procedures are provided for proposed PBC methods, and the control inherent stability is proved with rigorous theoretical derivation. This design methodology is aiming to provide a robust control strategy for power electronics practitioners.;From the novel interfacing power converter topology perspective, a Solid-State Transformer (SST) interfaced PMSG WECS is proposed, developed, and demonstrated. The adopted three-stage SST consists of cascaded H-bridge inverter, dual-active bridge converter (DAB) dc/dc stage and rectifier stage as the PMSG interface. Compared to conventional low-voltage WECS, the medium-voltage WECS requires less transmission current, thus resulting in lower transmission losses. As an alternative solution, this dissertation investigates a solid-state transformer (SST) interfaced permanent magnet synchronous generator (PMSG) WECS with integrated active power management and reactive power compensation functions. The SST is regarded as an emerging technology where the primary focus has been mainly from the design perspective. A high-power three-phase SST interfaced wind energy system is proposed and verified with simulation. scaled-down experiments have been carried out with a laboratory prototype. Specifically, system integration and functions are demonstrated with Silicon Carbide MOSFET based single converter cell SST and a high-voltage and high-power three converter cell based SST.;The solid-state transformer (SST) enabled dc/ac Microgrid provides an effective solution for distributed renewable energy resources (DRER) integration with conventional utility grid. This research work investigates a dc network system comprised of wind turbines, SST, and dc loads. A distributed power management algorithm based on improved dc bus signaling (DBS) is proposed for this dc network with local wind turbine controls incorporated to achieve a self-contained, power-balanced condition without the need for energy storage or communication devices. Scenarios considered include grid-connected mode, islanding mode, and the mode transitions. Simulation results are provided to verify the effectiveness of the proposed strategy.