Directional Tuning/Detuning Control Algorithm (DTDCA)

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Environmentally friendly

Concerns have been raised regarding to whether by exposure to time-varying magnetic fields could cause harmful effects on human bodies [25-27]. Studies have been undertaken in two major frequency ranges which are the ELF ~ LF (0 ~ 100 kHz) and MF ~ EHF (100 kHz ~ 300 GHz) [28, 29]. Various reports have indicated that human bodies may be affected by high intensity magnetic fields with the result of temperature rise in tissue or body. However, this only happens in microwave range, e.g., broadcasting, telecommunications, radar, and microwave ovens. In a low frequency electromagnetic field range such as 10 ~ 100 kHz (produced in IPT systems), no observable negative biological effects has been found. Therefore IPT is regarded as hazard-free for on-site workers [30, 31].

Electric toothbrush

Electric toothbrush was initially created for orthodontic patients and claimed to have better performance than manual toothbrushes as it leaves less room for patients to brush insufficiently. There were two different ways for powering the electric toothbrush which are plugging in to a standard wall outlet and run off ac line voltage, or using rechargeable batteries. The first method requires direct cabling connection to a power source and hence, not only limited the portability of device but also created potential electrical hazards in moisturized operating environment such as bathroom. Using rechargeable batteries can allow the device to be operated cordlessly; nevertheless it still requires metal tabs to have direct electrical contact with the charging base.

Electric vehicle

In the past few decades, vast resources have been invested into developing electric vehicles with intentions to partially or completely replace petrol vehicles for providing emission-free transportations. Different approaches have been implemented, including BEV (Battery Electric Vehicles), FCEV (Fuel Cell Electric Vehicles), and HEV (Hybrid Electric Vehicles) [40, 41]. The BEV and FCEV both have emission-free feature which reduces air pollution. However, the BEV is only applicable in low speed transportation with short driving ranges (100 ~ 200 km) due to its battery management problem, and the FCEV is still at its early development stage with the cost and refueling system as major concerns. The HEV is a hybrid system using both petrol engine and electric motor to drive its wheels. It is commercially available to people and has the advantage of long driving range, better fuel economy, and very low carbon emission. Nevertheless, power management of the HEV is much more complicated compared to vehicles using a single power transmission system; in addition, the HEV requires bulky batteries for electric power storage [42-44].

Present Challenges in Power Flow Control of IPT Systems

As the IPT systems are extended to different fields, the need of a suitable power flow control method has become obvious and necessary for applications to meet their specific load requirements. Like most controllers in other systems, designing the power flow control of IPT systems needs to take aspects such as error tolerance, response speed, overshoot level, simplicity of implementation, robustness, and operating range, etc., into consideration. Other factors that may indirectly affect performance of the system such as power consumption of the controller and EMI (Electromagnetic Interference) also deserve attention. It is normally impossible to have a controller designed to be ideal in all the aspects, therefore trade-offs are often required. Nevertheless, an optimized controller design for specific operating conditions may be available if the relationship between design considerations and system parameters can be well understood.

Magnetic coupling variations

As mentioned in Section 1.2.2, the secondary movable load is common to have lateral movements along the primary current track during operations, with the reason being to obtain a fixed magnetic coupling between the primary and the secondary side so as to induce a constant and stable input voltage source (open-circuit voltage of the pickup coil) for the secondary pickup. However in some applications, planar or even spacial movements are also possible [23, 66]. These unconfined movements can cause the opencircuit voltage of the pickup coil to vary and therefore results in the output voltage fluctuation of the pickup.

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Manufacturing tolerance of tuning capacitance

In circuit simulation study, ideal components are available and the values can be chosen to be exactly the same as what user defines. However, it does not happen in the real world since there are manufacturing ranges and tolerances. In order to have the center frequency of pickup tuning circuit closely match with the primary operating frequency, high precision and low tolerance to the designated manufacturing range are normally required for tuning components such as a capacitor. But the use of high precision capacitors essentially means adding significant costs into capital and may still require tedious fine tuning process to achieve the desired capacitance value. Due to the above practical issues, it has been found to be troublesome for many manufacturers to do mass production of IPT systems.

Table of Contents :

Abstract
Acknowledgement
Table of Contents
Nomenclature
List of Figures
List of Tables
Chapter 1: Introduction
- 1.1 Background
- 1.2 Introduction to IPT Systems
  - 1.2.1 Basic Structure and Operating Principle
  - 1.2.2 General Features
  - 1.2.3 Related Applications
- 1.3 Present Challenges in Power Flow Control of IPT Systems
- 1.4 Objectives and Scope of the Thesis
Chapter 2: Overview of Power Flow Control Techniques in IPT Systems
- 2.1 Introduction
- 2.2 Fundamentals of IPT Systems
  - 2.2.1 Primary Track Power Supply
  - 2.2.2 Secondary Power Pickups
- 2.3 Control of Primary Track Current
  - 2.3.1 Magnitude Control of Track Current
  - 2.3.2 Operating Frequency Control of Track Current
- 2.4 Existing Power Flow Control Methods of Secondary Power Pickup
  - 2.4.1 Voltage Regulator
  - 2.4.2 ShortingControl
  - 2.4.3 Dynamic Tuning/Detuning Control
- 2.5 Summary
Chapter 3: Directional Tuning/Detuning Control Algorithm (DTDCA)
- 3.1 Introduction
- 3.2 Basic Concept and Control Law of Directional Tuning/Detuning Control Algorithm (DTDCA)
- 3.3 Sampling Frequency and Tuning StepSize of DTDCA
- 3.4 Standard Procedure of DTDCA
- 3.5 Summary
Chapter 4: DTDCA Control of LCL Power Pickup
- 4.1 Introduction
- 4.2 LCL Tuning Power Pickup
  - 4.2.1 Basic Structure of LCL Tuning Pickup
  - 4.2.2 Characteristics of LCL Tuning Circuit in Steady State
  - 4.2.3 Controllable Power Transfer Capacity
- 4.3 Effects of LCL Circuit Parameter Variations on Pickup Output Voltage
  - 4.3.1 Operating Frequency Variation
  - 4.3.2 Magnetic Coupling Variation
  - 4.3.3 Tuning Capacitance Variation
  - 4.3.4 Load Variation
  - 4.3.5 Choice of kVR and rk
  - 4.3.6 Operating Range of Variable LS
- 4.4 Implementation of DTDCA Controlled LCL Power Pickup
  - 4.4.1 LinearMode Saturable Inductor
  - 4.4.2 General Structure of LinearMode Saturable Inductor Controlled LCL Power Pickup
  - 4.4.3 Sampling Frequency for LCL Power Pickup
  - 4.4.4 Tuning StepSize for LCL Power Pickup
- 4.5 Simulation/Experimental Results and Discussion
  - 4.5.1 Simulation Study of DTDCA Controlled LCL Power Pickup
  - 4.5.2 Experimental Study of DTDCA Controlled LCL Power Pickup
  - 4.5.3 Discussion
- 4.6 Summary
Chapter 5: Fuzzy Logic DTDCA Control of LCL Power Pickup
- 5.1 Introduction
- 5.2 Fuzzy Logic Controller Design for Tuning StepSize Automation
  - 5.2.1 Fuzzification of Output Voltage Error and Rate of Error
  - 5.2.2 Control Rule Base
  - 5.2.3 Defuzzification of Output Fuzzy Sets
  - 5.2.4 Analytical Structure of Fuzzy Logic Controller
  - 5.2.5 Choice of Scaling Factors
  - 5.2.6 Standard Procedure of Fuzzy Logic Based (FLB) DTDCA
- 5.3 Simulation and Experimental Results