PFC Topologies for AC to DC Converters in DC Micro-Grid

With increasing dominance of renewable energy resources and DC household appliances, the novelty of DC micro grid is attracting significant attention. The key interface between the main supply grid and DC micro grid is AC to DC converter. The conventional AC to DC converter with large output capacitor introduces undesirable power quality problems in the main supply current. It reduces system efficiency due to low power factor and high harmonic distortion. Power Factor Correction (PFC) circuits are used to make supply currents sinusoidal and in-phase with supply voltages. This paper presents different PFC topologies for single phase AC to DC converters which are analyzed for power factor (PF), total harmonic distortion (THD) and system efficiency by varying output power. Two-quadrant shunt active filter topology attains a power factor of 0.999, 3.03% THD and 98% system efficiency. Output voltage regulation of the presented active PFC topologies is simulated by applying a step load. Two-quadrant shunt active filter achieves better output voltage regulation compared to other topologies and can be used as grid interface

Small-scale hybrid alternative energy maximizer for wind turbines and photovoltaic panels

This thesis describes the creation of a small-scale Hybrid Power System (HPS) that maximizes energy from a wind turbine and photovoltaic array. Small-scale HPS are becoming an increasingly viable energy solution as fossil fuel prices rise and more electricity is needed in remote areas. Modern HPS typically employ wind speed sensors and three power stages to extract maximum power. Modern systems also use passive rectifiers to convert AC from the wind turbine to DC that is usable by power electronics. This passive system inefficiently wastes power and introduces damaging harmonic noise to the wind turbine. The HPS described in this thesis does not require external wind speed sensors, and has independent wind and solar Maximum Power Point Tracking (MPPT). It converts AC from the wind turbine to DC with a Vienna rectifier that can be controlled to improve efficiency, allow MPPT, and allow Power Factor Correction (PFC). PFC all but eliminates the harmonic noise that can damage the wind turbine. A prototype HPS was built and evaluated that combines the two renewable sources in such a way that only two power stages are necessary, the Vienna rectifier and a step-down converter. This thesis describes the prototype and reports the results obtained

Co-Simulation of IBC Type PFC Converter with Fuzzy Logic Controller

Many electronic power systems use bridge rectifiers, which are nonlinear, resulting in low power factor activity and high harmonic distortion due to the existence of nonlinear devices. To conform to harmonic standard requirements, longer device lifetime, and smooth operation of other devices in the system, power factor correction is required in these devices. The proposed system with an input power supply linked to a bridge rectifier which transforms ac to dc in this analysis, which is then linked to an Interleaved Boost Converter (IBC) with two parallel boost converters. The Interleaved Boost Converter uses Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) to work with the switches. The proportional controller gain has the effect of minimizing the time of increase and does not remove the error of steady-state. The result of removing the steady-state error is an integral control gain but deteriorate the transient response. The fuzzy controller takes inputs from the actual signals feedback values. Using the membership functions in the fuzzification method, the data provided to the fuzzy system is transformed into linguistic variables. To evaluate the performance, a series of rules that mimic the decision-making process of the human expert running the machine is then implemented using such inference mechanisms. Finally, a defuzzification block that transforms the output to a crisp value in such a manner that both structures are consistent. The proposed method is implemented using the software of MATLAB/Simulink and PSIM. The co-simulation result shows that the power factor achieved here is 0.9988, the Total Harmonic Distortion (THD) maintained is less than 5% and the average efficiency concluded here is 98% respectively. To verify the feasibility of the proposed scheme, a prototype model of a 5kW IBC type PFC converter is developed which is converting 230V AC input voltage to 400V DC output voltage, is implemented using a Microchip IC dsPIC33FJ16GS504. The experimental results are satisfactory, which uncover that a power factor is 0.9992 (close to unity), THD is 4.11; less than 5% and 98% overall efficiency at 100 kHz switching frequency, 230Vrms input voltage. With the higher performance, as a result, topology with high switching frequency makes a more compact, but costlier converter

Design and implementation of a 1.3 KW, single-phase, seven-level, GaN AC-DC converter

In today's world, electrical energy meets an increasing amount of the world's power needs as more countries are transitioning from traditional energy sources such as fossil fuels to renewable energy sources. The importance of power electronics has substantially increased due to their key roles in harnessing and delivering energy efficiently from renewable energy sources. As many modern applications of power electronics such as renewable energy harnessing, electric vehicle, and data center energy management require high-performance power electronics, innovative approaches to more robust, smaller, and efficient power converters are in great demand. This work presents detailed design process and hardware implementation of 1.3 kW, 90-264 Vrms (60 Hz) to 400 VDC converter. As a part of the trend in power electronics, the proposed converter features an innovative topology optimized for size miniaturization and high efficiency: a seven-level flying capacitor multilevel design with gallium nitride MOSFETs operating at 120 kHz. The converter is currently in competition for the IEEE International Future Energy Challenge 2016. It has achieved over 96% conversion efficiency at about 300 W output power. The development of fully functional power factor correction and digital control is in steady progress. With the sophisticated digital control and heat sink for better heat dissipation, this converter is projected to have a power density greater than 2 W/cubic-cm (32.8 W/cubic-inch) with over 98% efficiency.Ope

SENSORLESS DIRECT POWER CONTROL FOR THREE-PHASE GRID SIDE CONVERTER INTEGRATED INTO WIND TURBINE SYSTEM UNDER DISTURBED GRID VOLTAGES

Wind turbines with permanent magnet synchronous generator (PMSG) are widely used as sources of energy connected to a grid. The studied system is composed of a wind turbine based on PMSG, a bridge rectifier, a boost converter, and a controlled inverter to eliminate low-order harmonics in grid currents under disturbances of grid voltage. Traditionally, the grid side converter is controlled by using the control VFOC (Virtual Flux Oriented Control), which decouple the three-phase currents indirect components (id) and in quadratic (iq) and regulate them separately. However, the VFOC approach is dependent on the parameters of the system. This paper illustrates a new scheme for the grid-connected converter controller. Voltage imbalance and harmonic contents in the three-phase voltage system cause current distortions. Hence, the synchronization with the network is an important feature of controlling the voltage converter. Thus, a robust control method is necessary to maintain the adequate injection of the power during faults and/or a highly distorted grid voltage. The proposed new control strategy is to use the direct power control based virtual flux to eliminate side effects induced by mains disturbances. This control technique lowers remarkably the fluctuations of the active and reactive power and the harmonic distortion rate. The estimated powers used in the proposed control approach is calculated directly by the positive, negative, and harmonic items of the estimated flux and the measured current without line sensor voltage.Ветряные турбины с синхронным генератором на постоянных магнитах (PMSG) широко используются в качестве источников энергии, подключенных к сети. Исследуемая система состоит из ветряной турбины на основе PMSG, мостового выпрямителя, повышающего преобразователя и управляемого инвертора для устранения гармоник низкого порядка в токах сетки при возмущениях напряжения сети. Традиционно преобразователь на стороне сети управляется с помощью виртуального потокоориентированного управления VFOC (Virtual Flux Oriented Control), который разделяет трехфазные токи на косвенные компоненты (id) и на квадратичные компоннеты (iq) и регулирует их отдельно. Однако подход VFOC зависит от параметров системы. Данная статья иллюстрирует новую схему для контроллера преобразователя, подключенного к сети. Дисбаланс напряжения и содержание гармоник в трехфазной системе напряжения вызывают искажения тока. Следовательно, синхронизация с сетью является важной особенностью управления преобразователем напряжения. Таким образом, надежный метод управления необходим для поддержания адекватной подачи энергии во время неисправностей и/или значительно искаженного напряжения сети. Предложенная новая стратегия управления заключается в использовании виртуального потока на основе прямого управления мощностью для устранения побочных эффектов, вызванных помехами в сети. Этот метод управления значительно снижает колебания активной и реактивной мощности и уровень гармонических искажений. Оценочные мощности, используемые в предлагаемом подходе к управлению, рассчитываются непосредственно по положительным, отрицательным и гармоническим элементам оцененного потока и измеренного тока без напряжения линейного датчика

A Single-phase Rectifier With Ripple-power Decoupling and Application to LED Lighting

In recent years, Light-Emitting-Diode (LED) is widely used in lighting applications for its high efficacy and high reliability. However, the rectifier, which is required by the LEDs to convert the AC power from the grid into DC power, suffers from low-reliability caused by the filtering capacitor. In order to fully utilize the long operational hours of the LEDs, this thesis proposes a rectifier that has improved reliability by adding a ripple-port to eliminate the non-reliable electrolytic capacitor. The ripple-port is capable of decoupling the ripple-power inherited in a single-phase rectifier, which enables using the reliable film capacitor to replace the electrolytic capacitor. To guarantee that the ripple-port can effectively decouple the ripple-power, a closed-loop control scheme is designed and implemented in a digital controller. Simulation and experimental results show that the proposed rectifier can reduce the required capacitance by 70%, which results in a 60% increase in lifetime. The proposed ripple-port circuit can be considered as an add-on module to be integrated into the rectifiers used in applications that require long lifetime. A detailed analysis of the efficiency, cost and reliability of applying the ripple-port in LED lighting applications supports the feasibility of the proposed circuit

Housing equilibrium price framework for Malaysian middle Class group in affordable housing market

Failure in getting housing equilibrium price for affordable housing market has become a hot topic that is often discussed in the press due to the imbalance between housing demanded and supplied. The basic purpose of the research was to investigate the relationship between macroeconomic housing demand and supply detenninant factors and affordable housing needs in Malaysia, and to dete1111ine the equilibrium house price for middle-class income in the affordable housing market. The research involved the development of theoretical framework by synthesising the models and framework developed by past researchers on the housing equilibrium price framework. It also uses time series analysis together with regression analysis to collect and analyse data. As initial, 371 respondents from household's side and 32 respondents from developer's side in Melaka Tengah were selected as samples as case study in Melaka. During data analysed, around 200 questionnaires from households and 32 questionnaires from developers can be used. The data was analysed using SPSS software to investigate the relationship between macroeconomic housing demand and supply determinant factors towards the needs f and supply of afordable housing market. From the investigation, current house price, monetary status and population changes are the most critical factors that lead to the needs of affordable housing supplies. Meanwhile, developers put the interest rate, government interventions and population changes as the catalyst to develop the affordable housing projects. On the other hand, the empirical data of housing prices are collected from NAPIC from 2006 to 2015. The equilibrium price calculated from the sales perfonnance within four quarter reported by NAPIC is examined using linear regression method. Based on these themes, the research contended that the housing equilibrium price can be achieved using empirical data from demand and supply with supported from current house price, monetary status and population changes the interest rate, government interventions and population changes. Hence, government is the key player and be a pulling effect in controlling the housing price by using the housing demand and supply determinant factor to create a win-win situation between middle-class income and housing developers

A high performance three-phase telecom supply incorporating a HF switched mode rectifier with a phase shifted PWM controller

Telecom supplies need to conform to low Total Harmonic Distortion (THD) and high Power Factor (PF) as per IEC 61000-3-2 and IEEE 519-1992 standards. These high rating power supplies use a three phase utility in which low THD and high PF are realized via various passive and active wave shaping schemes. In this paper, a new design for three phase telecom power supplies is presented with circuit parameter values optimized for high performance in terms of a low THD, high PF, low ripple and high line and load regulation using a suitable combination of various strategies. The performance of the power supply is validated by extensive simulations

Technical Challenges and Solutions of a three-phase bidirectional two stage Electric Vehicle charger

The sustainability of the power grid owing to the building strain of the ever-growing demand for electrical energy urges innovative and more practical solutions that enable active participation of end-users in stable and reliable management of power systems. One of the emerging projections of such a two-way exchange of electrical power between the grid and consumers is the developing field of bidirectional energy trade between power providers and electric vehicle owners. A bidirectional, three-phase, two-stage off-board electric vehicle EV charger design is proposed in this research. The first stage acts as alternating current AC to direct current DC converter during charging operation and behaves as three phase inverter and power factor corrector when energy exchange is from vehicle to grid. The second stage is a bidirectional DC-DC level converter linked to the first stage by a DC bus. The grid side filter is designed to enable the grid interfacing without any significant power quality problems. The proposed design, topology and the devised control infrastructure are tested through simulations on MATLAB/Simulink platform by interfacing the charger to a three-phase AC microgrid and the results approve the performance of the proposed charging topology