Bidirectional Electric Vehicles Service Integration in Smart Power Grid with Renewable Energy Resources

As electric vehicles (EVs) become more popular, the utility companies are forced to increase power generations in the grid. However, these EVs are capable of providing power to the grid to deliver different grid ancillary services in a concept known as vehicle-to-grid (V2G) and grid-to-vehicle (G2V), in which the EV can serve as a load or source at the same time. These services can provide more benefits when they are integrated with Photovoltaic (PV) generation. The proper modeling, design and control for the power conversion systems that provide the optimum integration among the EVs, PV generations and grid are investigated in this thesis. The coupling between the PV generation and integration bus is accomplished through a unidirectional converter. Precise dynamic and small-signal models for the grid-connected PV power system are developed and utilized to predict the system’s performance during the different operating conditions. An advanced intelligent maximum power point tracker based on fuzzy logic control is developed and designed using a mix between the analytical model and genetic algorithm optimization. The EV is connected to the integration bus through a bidirectional inductive wireless power transfer system (BIWPTS), which allows the EV to be charged and discharged wirelessly during the long-term parking, transient stops and movement. Accurate analytical and physics-based models for the BIWPTS are developed and utilized to forecast its performance, and novel practical limitations for the active and reactive power-flow during G2V and V2G operations are stated. A comparative and assessment analysis for the different compensation topologies in the symmetrical BIWPTS was performed based on analytical, simulation and experimental data. Also, a magnetic design optimization for the double-D power pad based on finite-element analysis is achieved. The nonlinearities in the BIWPTS due to the magnetic material and the high-frequency components are investigated rely on a physics-based co-simulation platform. Also, a novel two-layer predictive power-flow controller that manages the bidirectional power-flow between the EV and grid is developed, implemented and tested. In addition, the feasibility of deploying the quasi-dynamic wireless power transfer technology on the road to charge the EV during the transient stops at the traffic signals is proven

Power Converters in Power Electronics

In recent years, power converters have played an important role in power electronics technology for different applications, such as renewable energy systems, electric vehicles, pulsed power generation, and biomedical sciences. Power converters, in the realm of power electronics, are becoming essential for generating electrical power energy in various ways. This Special Issue focuses on the development of novel power converter topologies in power electronics. The topics of interest include, but are not limited to: Z-source converters; multilevel power converter topologies; switched-capacitor-based power converters; power converters for battery management systems; power converters in wireless power transfer techniques; the reliability of power conversion systems; and modulation techniques for advanced power converters

Measurements, Models, Systems and Design

531 s.

Passive Stability And Actuation Of Micro Aerial Vehicles

Micro Aerial Vehicles (MAVs) have increased in popularity in recent years. The most common platform, the quadrotor, has surpassed other MAVs like traditional helicopters and ornithopters in popularity mainly due to their simplicity. Yet the quadrotor design is a century old and was intended to carry people. We set out to design a MAV that is designed specifically to be a MAV, i.e. a vehicle not intended to carry humans as a payload. With this constraint lifted the vehicle can continuously rotate, which would dizzy a human, can sustain larger forces, which would damage a human, or can take advantage of scaling properties, where it may not work at human scale. Furthermore, we aim for simplicity by removing vehicle controllers and reducing the number of actuators, such that the vehicle can be made cost effective, if not disposable. We begin by studying general equations of motion for hovering MAVs. We search for vehicle configurations that exhibit passive stability, allowing the MAV to operate without a controller or actuators to apply control, ideally a single actuator. The analysis suggests two distinct types of passively stabilized MAVs and we create test vehicles for both. With simple hovering achieved, we concentrate on controlled motion with an emphasis on doing so without adding actuators. We find we can attain three degree of freedom control using separation of time scales with our actuator via low frequency for control in the vertical direction and high frequency for control in the horizontal plane. We explore techniques for achieving high frequency actuator control, which also allow the compensation of motor defects, specifically cogging torque. We combine passive stability with the motion control into two vehicles, UNO and Piccolissimo. UNO, the Underactuated-propeller Naturally-stabilized One-motor vehicle, demonstrates the capabilities of simple vehicles by performing maneuvers like conventional quadrotors. Piccolissimo, Italian for “very little”, demonstrates the merits of passive stability and single actuator control by being the smallest, self-powered, controllable MAV

Revving up for the future: an inductive power transfer system geared for vehicular applications

Energized by the prospect of decluttering the charging infrastructure by severing the bulky power cords used to charge an Electric Vehicle (EV), an innovative technique to wirelessly charge an EV battery known as Inductive Power Transfer (IPT) has garnered widespread acceptance. This thesis introduces the design of an integrated stationary IPT system with an optimized power control algorithm and efficiency maximization to transfer power from a transmitter pad positioned on the ground and the receiver pad embedded under the chassis of an EV. Magnetic analysis for the charging coil architecture is facilitated via simulations in Ansys Maxwell. The power electronics design focuses on implementation of an H-bridge converter incorporating Series-Series (SS) compensation topology to utilize a novel control algorithm to prioritize battery charging operation. The system is validated through a simulation model in PSIM and a hardware-in-the-loop simulation in Typhoon HIL before hardware implementation and testing of the developed prototype

The control and operation of the five level diode clamped inverter

This thesis describes an investigation of three and five level diode clamped inverters for motor drive applications. The work was completed as a PhD project at the University of Nottingham with funding from EPSRC and Heenan Drives Ltd. The investigation of the three level converter describes the design, development, control and operation of an 11kW prototype. Included in the design is a review of typical switching strategies employed for control of the output voltage. New improvements to the sub-harmonic pulse width modulation method are presented which allow an improved output waveform to be obtained. The problem of DC link capacitor voltage balancing (Neutral Point Control) is addressed and a novel balancing control method is presented based on the addition of a DC offset to the modulation pattern. This method is verified through mathematical analysis and experimental operation. The operational limits of the control are analysed. Improvements to the technique are presented to expand its operating limits. The development of a prototype five level converter is then described. The design again features improvements to the sub-harmonic modulation strategy to provide enhanced output waveform generation, particularly for transient operation. The current demands on the DC link capacitors for the five level arrangement are analysed and it is concluded that the capacitors cannot be regulated by simple modifications to the output switching pattern. A novel circuit is presented to achieve capacitor balancing within the DC link. The circuit behaviour is described and analysed. Operation is confirmed through simulation and experimental implementation. High dynamic performance is demonstrated via the use of a vector controlled induction motor. Neutral point control is successfully achieved through a similar method to that used for the three level inverter. Having demonstrated the principle of operation of the three and five level inverters on low voltage prototypes, the thesis concludes with a review of the main considerations required to implement the configurations as medium voltage drives

Power quality improvement utilizing photovoltaic generation connected to a weak grid

Microgrid research and development in the past decades have been one of the most popular topics. Similarly, the photovoltaic generation has been surging among renewable generation in the past few years, thanks to the availability, affordability, technology maturity of the PV panels and the PV inverter in the general market. Unfortunately, quite often, the PV installations are connected to weak grids and may have been considered as the culprit of poor power quality affecting other loads in particular sensitive loads connected to the same point of common coupling (PCC). This paper is intended to demystify the renewable generation, and turns the negative perception into positive revelation of the superiority of PV generation to the power quality improvement in a microgrid system. The main objective of this work is to develop a control method for the PV inverter so that the power quality at the PCC will be improved under various disturbances. The method is to control the reactive current based on utilizing the grid current to counteract the negative impact of the disturbances. The proposed control method is verified in PSIM platform. Promising results have been obtaine

The control and operation of the five level diode clamped inverter

This thesis describes an investigation of three and five level diode clamped inverters for motor drive applications. The work was completed as a PhD project at the University of Nottingham with funding from EPSRC and Heenan Drives Ltd. The investigation of the three level converter describes the design, development, control and operation of an 11kW prototype. Included in the design is a review of typical switching strategies employed for control of the output voltage. New improvements to the sub-harmonic pulse width modulation method are presented which allow an improved output waveform to be obtained. The problem of DC link capacitor voltage balancing (Neutral Point Control) is addressed and a novel balancing control method is presented based on the addition of a DC offset to the modulation pattern. This method is verified through mathematical analysis and experimental operation. The operational limits of the control are analysed. Improvements to the technique are presented to expand its operating limits. The development of a prototype five level converter is then described. The design again features improvements to the sub-harmonic modulation strategy to provide enhanced output waveform generation, particularly for transient operation. The current demands on the DC link capacitors for the five level arrangement are analysed and it is concluded that the capacitors cannot be regulated by simple modifications to the output switching pattern. A novel circuit is presented to achieve capacitor balancing within the DC link. The circuit behaviour is described and analysed. Operation is confirmed through simulation and experimental implementation. High dynamic performance is demonstrated via the use of a vector controlled induction motor. Neutral point control is successfully achieved through a similar method to that used for the three level inverter. Having demonstrated the principle of operation of the three and five level inverters on low voltage prototypes, the thesis concludes with a review of the main considerations required to implement the configurations as medium voltage drives

Power conversion for a modular lightweight direct-drive wind turbine generator

A power conversion system for a modular lightweight direct-drive wind turbine generator has been proposed, based on a modular cascaded multilevel voltage-source inverter. Each module of the inverter is connected to two generator coils, which eliminates the problem of DC-link voltage balancing found in multilevel inverters with a large number of levels.The slotless design of the generator, and modular inverter, means that a high output voltage can be achieved from the inverter, while using standard components in the modules. Analysis of the high voltage issues shows that isolating the modules to a high voltage is easily possible, but insulating the generator coils could result in a signicant increase in the airgap size, reducing the generator effciency. A boost rectier input to the modules was calculated to have the highest electrical effciency of all the rectier systems tested, as well as the highest annual power extraction, while having a competitive cost. A rectier control system, based on estimating the generator EMF from the coil current and drawing a sinusoidal current in phase with the EMF, was developed. The control system can mitigate the problem of airgap eccentricity, likely to be present in a lightweight generator. A laboratory test rig was developed, based on two 2.5kW generators, with 12 coils each. A single phase of the inverter, with 12 power modules, was implemented, with each module featuring it's own microcontroller. The system is able to produce a good quality AC voltage waveform, and is able to tolerate the fault of a single module during operation. A decentralised inverter control system was developed, based on all modules estimating the grid voltage position and synchronising their estimates. Distributed output current limiting was also implemented, and the system is capable of riding through grid faults