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In industry, adjustable speed drives (ASDs) are widely employed in driving AC motors for variable speed applications due to the high performance and high energy efficiency obtained in such systems. However, ASDs have an impact on the power quality and utilisation of AC power feeds by injecting current harmonics and causing resonances, additional losses, and voltage distortion at the point of common coupling. Due to these problems, electric power utilities have established stringent rules and regulations to limit the effects of this distortion. As a result, efficient, reliable, and economical harmonic mitigation techniques must now be implemented in practical systems to achieve compliance at reasonable cost. A variety of techniques exist to control the harmonic current injected by ASDs, and allow three-phase AC-line-connected medium-power systems to meet stringent power quality standards. Of these, the broadband harmonic passive filter deserves special attention because of its good harmonic mitigation and reactive power compensation abilities, and low cost. It is also relatively free from harmonic resonance problems, has relatively simple structural complexity and involves considerably less engineering effort when compared to systems of single tuned shunt passive filters or active filters and active rectifier solutions. In this thesis, passive broadband harmonic filters are investigated. In particular, the improved broadband filter (IBF) which has superior overall performance and examples of its application are increasing rapidly. During this research project, the IBF operating principle is reviewed and its design principles are established. As the main disadvantage of most passive harmonic filters is the large-sized components, the first proposed design attempts to optimize the size of the filter components (L and C) utilized in the existing IBF topology. The second proposed design attempts to optimize the number and then the size of filter components resulting in an Advanced Broadband passive Filter (ABF) novel structure. The proposed design methods are based on frequency domain modelling of the system and then using a genetic algorithm optimization technique to search for optimal filter component values. The results obtained are compared with the results of a linear searching approach. The measured performance of the optimal filter designs (IBF and ABF) is evaluated under different loading conditions with typical levels of background voltage distortion. This involves assessing input current total harmonic distortion, input power factor, rectifier voltage regulation, efficiency, size and cost. The potential resonance problem is addressed and the influence of voltage imbalance on performance is investigated. The assessment is based on analysis, computer simulations and experimental results. The measured performance is compared to various typical passive harmonic filters for three-phase diode rectifier front-end type adjustable speed drives. Finally, the broadband filter design’s effectiveness and performance are evaluated by involving them in a standard IEEE distribution network operating under different penetration levels of connected nonlinear total loads (ASD system). The study is conducted via detailed modelling of the distribution network and the linked nonlinear loads using computer simulations.

"In this thesis, based on the existing researches on power factor correction technology, I analyze, design and study the Boost type power factor correction technology, which is applied in the in-board two-stage battery charger. First I analyzed the basic working principle of the active power factor corrector. By comparing several different topologies of PFC converter main circuit and control methods, I specified the research object to be the average current control (ACM) boost power factor corrector. Then I calculated and designed the PFC circuit and the ACM controller applied in the first level charging of EVs. And I run the design in Simulink and study the important features like power factor, the input current waveform and the output DC voltage and the THD and odd harmonic magnitude."

As power electronic based controllers and loads become more prevalent in power systems, there is a growing concern about how the harmonics generated by these controllers and loads affect the power quality of the system. One widely used power electronic based load is the Variable Frequency Drive (VFDs) used to vary the speed of an induction motor; whereas a common example of a power electronic based controller used in power systems is the Static VAR Compensator (SVC) for improving a system’s power factor. In this thesis, the harmonic content and overall performance of a system including both a VFD and a SVC will be studied and analyzed. Specifically, the cases of no compensation, static capacitor compensation, and power electronic based static VAR compensation are examined. A small-scale model of a system for study was constructed in lab. Several cases were then performed and tested to simulate a system which contained both fixed and power electronic based harmonic generating loads. The performance of each case was determined by total harmonic current and voltage distortions, true power factor, and RMS current levels at different points in the system.

This thesis mainly presents the design and implementation of a flyback converter with single-stage power factor correction. In the beginning, we propose different power factor collection (PFC) techniques referring to the inductor current of converter under three kinds of operation modes. In the continuous mode, we adopt the nonlinear-carrier control (NLC). Then, in the discontinuous mode and boundary mode, voltage-follower control (VFC) and transition mode technique control (TM) are adopted respectively. As to the converter analysis, we derive and verify the results of a small-signal model and perform equivalent circuit analysis by state-space averaging method, loss-free resistor (LFR) model, averaging method for two-time-scale system (AM), and current injected equivalent circuit approach (CIECA). Results derived from the above-mentioned models are compared and verified to be accurate of the system model. Furthermore, the control function and element design are implemented by simulation. We perform a PI controller to achieve better power factor based on results of analysis of the time and frequency domains analysis. Finally, three sets of different hardware are fabricated and verified depending on measured result and theoretical simulation.

Due to development of industries, power factor and harmonic pollution have become serious concerns in the power system. This thesis presents an adaptive linear neuron (ADALINE) - based static synchronous compensator (STATCOM) to cope with power quality issues in the industrial power system. The targeted compensating current of the STATCOM is generated based on the so-called LMS algorithm, thus the compensated system current becomes balanced and active even in reactive, unbalanced or distorted loads. In this thesis, the STATCOM is realized by using a three-level neutral point-clamped (NPC) inverter with the in-phase level-shifted sinusoidal pulse width modulation (IPLSPWM). Theoretical analysis of ADALINE method is detailed and hardware implementation of STATCOM is conducted to validate effectiveness of the proposed approach.

This study aims to design a Shunt Semi-Active Power Factor Correction Circuits , which can be applied to high power circuit by low switching frequency. The designed circuit can avoid power loss working with high switching frequency when using the method of active power factor correction .The experimental configuration based on DSP is applied to a compressor of air conditioner with varied load. The simulation check the developed circuit using Ispice . Both of the experimental and simulation results have guaranteed the derived configuration reach the expected goals.

This thesis presented a sensor-less permanent magnet synchronous motor (PMSM) driver for controlling air-conditioner rotary compressor speed. In this thesis, a quasi-sine pulse-width modulation (PWM) driving method was proposed. Furthermore, the current feedback control scheme and rotor magnet pole position detection were included. The system structure was implemented by using a digital signal processing (DSP) platform. The proposed driving scheme was compared with the square-wave driving without current feedback and six-step square-wave driving method with current feedback. Moreover, the passive and shunt semi-active power factor correction (PFC) technique were researched for the air-conditioner application. Experimental results demonstrated that the system power factor could be improved by the proposed shunt semi-active PFC method. Besides, the proposed sensor-less quasi-sine PWM driving method implemented in an air-conditioner compressor driver was capable of reducing the magnitude of rotational speed ripples, compressor vibration, and system power consumption.

The traditional AC/DC rectifier usually results in low power factor and serious harmonic distortion and it will bring about the serious pollution to power system. This thesis proposes boost power factor correction technique to solve these problems. First, we aim at power factor correction circuit which need input voltage sensing, to study its operating principle and design consideration, then design applicable voltage compensator by the frequency analysis and perform the simulation and implementation using the developed criterion. In order to prevent the shortcoming that power factor correction circuits with input voltage sensing and complexity is raised for a multiplier must be added to controller, we develop the power factor correction circuit without input voltage sensing. We perform the operating principle and control function by simulation, develop hardware scheme by analog components and place load variation to measure power factor and total harmonic distortion. According to experimental results and simulation, we confirm the new power factor correction circuit. When the full load is placed, the power factor can achieve 0.99 and the total harmonic distortion is lower than 8%.

A single-stage high-power-factor electronic ballast is designed for fluorescent lamps with dimming capability. The circuit configuration is originated from the integration of the half-bridge resonant inverter and the buck-boost converter. The buck-boost converter is designed to operate in discontinuous conduction mode (DCM) to provide nearly unit power factor at a fixed switching frequency. With asymmetrical pulse-width-modulation (APWM), the lamp power can be effectively regulated. The power switches of the inverter exhibit either zero-voltage-switching (ZVS) or zero-current-switching (ZCS) over the whole dimming range. Design equations are derived and computer analyses are performed based on a power-dependent lamp model and fundamental approximation. Design guidelines for determining circuit parameters are provided. A prototype circuit for a T8-36W fluorescent lamp is built and tested to verify the analytical predictions.