Converters

In this thesis, front-end solutions with single-phase power factor correction (PFC) capability are studied. The reduction of current harmonics using various PFC techniques is investigated and related to the EN 61000-3-2 standard. Moreover, power electronics issues concerning ...

In this paper two DC-DC converters connected in parallel with the purpose of load sharing by applying droop method is considered. This method requires no communication interconnection and compensates for converter parameter variations and imbalances in line impedance. The DC-DC converter input source can be any DC source such as photovoltaic module and wind turbine or fuel cell and it is a closed loop system. In this work proportional-integral (PI) controller, will have their performance evaluated to control the paralleled converters connected to DC micro-grid. The PI controller is tuned by particle swarm optimization (PSO) method. The designing of stable DC-DC converter with primary droop current-sharing control, the stability of the interconnected parallel DC-DC converter system was studied. When the cable resistance of the paralleled DC converters differs, the interconnected system might be unstable and due to this the uneven load sharing occurs. To resolve this issue to some ext...

Solar power system finds extensive application in remote areas where access to the grid supply is impractical. From livestock watering to remote home or village water supply needs are met from the solar based water pumps system. Most of the Photovoltaic water pumping systems are connected directly to the solar arrays and use DC motor driven pumps. This system is easy to operate but is inefficient and requires frequent maintenance. Solar water pumps operated with AC drive uses an inverter with ac motor or induction motor. Induction motor offer better choice in terms of size, ruggedness, efficiency and maintainability. The DC power from solar array is boosted and fed to an inverter which gives AC. Output of inverter drives the motor coupled to a water pump. Photovoltaic power system usually require maximum power point tracking controller, which is an electronic system that operates the Photovoltaic modules in a manner that allows the modules to produce all the power they are capable of. There are different types of MPPT algorithms like Perturbation and Observation, incremental conductance etc. which can be grouped as traditional techniques. Photovoltaic powered water pumps are basically similar to any other pumping system. When there is enough sunlight, the system functions well.

Digital Decimation process plays an important task in communication system. It mostly is applied in transceiver when the frequency reduction is required. However, the decimation process for sigma delta modulator is considered in this research work. The proposed design was simulated using MATLAB software and implemented by hardware description language in Xilinx environment. Furthermore, the proposed advance arithmetic unit is applied to improve the system efficiency.

A three-stage 18-level hybrid inverter circuit and its innovative control method have been presented. The three hybrid inverter stages are the high-, medium-, and low-voltage stages. The high-voltage stage is made of a three-phase conventional inverter to reduce dc source cost and losses. The medium- and low-voltage stages are made of three-level inverters constructed using cascaded H-bridge units. The novelty of the proposed algorithm is to avoid the undesirable high switching frequency for high- and medium-voltage stages despite the fact that the inverter's dc sources are selected to maximize the inverter levels by eliminating redundant voltage states. have been developed to assure fundamental switching frequency operation of the high-voltage stages and not more than few times this frequency for the medium-voltage stage. The low-voltage stage is controlled using SVM to achieve the reference voltage vector exactly and to set the order of dominant harmonics as desired. The realization of this control approach has been enabled by considering the vector space plane in the state selection rather than individual phase levels. The inverter has been constructed, and the control algorithm has been implemented. Test results show that the proposed algorithm achieves the claimed features, and all major hypotheses have been verified.

http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=5464373

"This paper presents a multilevel multistage inverter design
and its corresponding control strategy. The hybrid inverter
has a high voltage stage composed of the six-switch
conventional three phase inverter with its output connected
in series with the outputs of three-level H-bridge medium
and low voltage stages. The voltage ratio has been selected
to enable both one state - approximation and PWM control
modes effectively. The suggested control strategy has been
developed to ensure minimum switching losses focusing
on holding the higher voltage stage state as long as it is
feasible. The reference voltage vector has been
approximated to the nearest of the 919 vectors provided by
the 18-level inverter. A special definition of state zone has
been introduced for the low voltage stage to enable the
achievement of the reference vector with minimum error.
The proposed control strategy has been tested and its short
computational time and low memory requirement has been
proven."

http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=4956745&tag=1

This paper presents the design of a CIC filters based on a low-pass filter for reducing the sampling rate, also known as decimation process. The targeted application for the filter is in the analog to digital conversion (ADC).The CIC is chosen because of its attractive property of both low power and complexity since it dose not required multipliers. Simulink toolbox available in Matlab software is used to design and simulate the functionality of the CIC filter. This paper also shows how sample frequency is decreased by CIC filter and it can be used to give enough stop-band attenuation to prevent aliasing after decimation.

Due to the negative effects of the non-linear semiconductor devices and the passive electrical components (inductor and capacitor) in the converter circuits, and that are deteriorating the power factor (PF) and total harmonics distortion (THD) of grid current, this study proposes a novel unity PF correction controller based on a new algorithm of neural network to improve the performance of a single phase boost DC-DC converter with respect to the mentioned concerns. The controller guarantees stable load voltage. The PF corrector, firstly measures the phase shift between grid voltage and grid current waveforms, then through a new artificial neural network (ANN) algorithm, a suitable duty cycle is predicted to guide and control the converter to reduce the phase shift between grid voltage and grid current as possible to have maximum PF which is unity PF, and to improve the THD level of grid current. The proposed system is simulated and evaluated via Simulink of MATLAB, the simulation re...

The main objective of the article is to provide a thorough review of currently used AC-DC converters for alkaline and proton exchange membrane (PEM) electrolyzers in power grid or wind energy conversion systems. Based on the current literature, this article aims at emphasizing the advantages and drawbacks of AC-DC converters mainly based on thyristor rectifier bridges and chopper-rectifiers. The analysis is mainly focused on the current issues for these converters in terms of specific energy consumption, current ripple, reliability, efficiency, and power quality. From this analysis, it is shown that thyristors-based rectifiers are particularly fit for high-power applications but require the use of active and passive filters to enhance the power quality. By comparison, the association combination of the chopper-rectifier can avoid the use of bulky active and passive filters since it can improve power quality. However, the use of a basic chopper (i.e., buck converter) presents several...

Most of the electricity in India comes from fossil-fuels like coal, oil and natural gas. Today the demand of Electricity in India is increasing and is already more than the production of Electricity whereas the reserves of fossil-fuel are depleting every day. There is strong need to shift for other sources and the best option is renewable energy sources. The aim of this project is to design a maximum power point tracking for wind turbine. The maximum power point tracking (MPPT) for wind energy conversation system is used for large and small scale wind turbine systems. The diversity of MPPT methods are developed, these methods vary in implementation, cost, complexity, convergence speed and faster tracking speed. This paper proposes the power characteristics curve of MPPT method in wind power systems. Proposed MPPT is implemented by applying the small-signal analysis on a nonlinear turbine-rotor mechanical system. To verify the performance of the wind turbine system, simulation system is implemented based on MPPT power control. By the variation of wind speed, the behavior of the generator speed presents good consistency among the proposed theory.

Three-stage eighteen-level hybrid inverter design with novel control method are presented. The inverter consists of main high-voltage, medium-voltage and low-voltage stages connected in series from the output side. The high voltage stage is a three-phase, six-switch conventional sub-inverter. The medium and low voltage stages are made of three-level sub-inverters constructed by H-bridge units. The proposed control strategy assumes a reference input voltage vector and aims to approximate it to the nearest inverter vector. The control concept is based on holding the high voltage state as long as it is feasible to do so. The reference voltage vector has been represented in a 60°-spaced two axis coordinate system to reduce the computational effort. The concept of the staged-control has been presented, the transformed inverter vectors and their relation to the switching variables have been defined, and the implementation process has been described. The test results verify the effectiveness of the proposed strategy in terms of computational efficiency as well as the capability of the inverter to produce very low distorted voltage with low switching losses.

http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=5523665

This paper comprehensively reviews the current status of multidisciplinary technologies in electric vehicles. Because the electric vehicle market will expand dramatically in the coming few years, research accomplishments in power electronics technology for electric vehicles will be highly attractive. Challenges in power electronics technology for driving electric vehicles, charging batteries, and circuit topologies are being explored. This paper aims primarily to address the practical issues of the future electric vehicles and help researchers obtain an overview of the latest techniques in electric vehicles, focusing on power electronics-based solutions for both current and future electric vehicle technologies. In this work, different medium-and high-voltage DC-AC inverter topologies are investigated and compared in terms of power losses and component requirements. Recent research on electric vehicle power converters is also discussed, with highlighting on soft-switching and multile...

Several efforts are being made in the field of voltage converters due to increasing focus in power electronics. This is hinged on simple fact that converters have widespread usability domain such as portable devices running on battery, PCs, industrial electronic equipment, telecoms systems, and stable power distribution. Currently, studies are focusing on developing highly effective converter systems and designs innovations that take advantage of limited energy resources to improve and increase power/voltage supply capabilities for electronic devices consumptions. Power supply mechanism is analogous to data conversion systems outcomes in which voltage is generated in circuit systems through series of conversions and reversions. This study proposes hybridization of two existing data conversion schemes in the design of highly effective voltage circuits system that can tolerate and improve energy consumptions issues. The result indicates that the hybrid voltage pin of 63V is higher than the circuits system of the single voltage source of the analog and direct voltage which generated 54V and 6V respectively. The hybrid voltage pin also outperformed another investigative paper by 63V to 32V for an input of 5V leading to the hybrid converter offering more gains for low voltage source by 66.7% (9V) to 33.3% (5V) respectively.

This paper presents a multilevel multistage inverter design and its corresponding control strategy. The hybrid inverter has a high voltage stage composed of the six-switch conventional three phase inverter with its output connected in series with the outputs of three-level H-bridge medium and low voltage stages. The voltage ratio has been selected to enable both one state approximation and PWM control modes effectively. The suggested control strategy has been developed to ensure minimum switching losses focusing on holding the higher voltage stage state as long as it is feasible. The reference voltage vector has been approximated to the nearest of the 919 vectors provided by the 18-level inverter. A special definition of state zone has been introduced for the low voltage stage to enable the achievement of the reference vector with minimum error. The proposed control strategy has been tested and its short computational time and low memory requirement has been proven.

http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=6030469&tag=1

Z-Source converter or impedance-source converter is a kind of power converters, which has the responsibility to convert the direct current to alternative current. This converter with respect to its circuit diagram acts as a buck-boost converter except it doesn’t use from DC-DC converter bridge. Γ-source inverters are one of the conventional converters based on impedance-sources; which have been under considerations of professionals at power industries due to enhanced features. These features are contained boost of output voltage level, low number of active and passive elements and low requirement to achieve the high turn's ratio of coupling transformer. This paper dealt with the survey and modeling of gamma power source systems. In this regard, the first dynamic model of converter can be extracted by writing power balance equations. In addition, with the help of dynamic equations converter performance, analysis functionality will be available in various working conditions. Final...

Resumen El creciente interes por las fuentes de energia renovables (FER) esta impulsado por factores sociales, politicos y economicos. El agotamiento de las reservas de combustibles fosiles y el cambio climatico, vienen acompanados por las complejas relaciones politicas entre los paises productores de petroleo. En la actualidad, la era de la informacion esta dando paso a la era de la energia, tal y como se manifiesta en la gran penetracion alcanzada por los productos electronicos durante la ultima decada, de tal forma, que el precio de la energia ha trascendido a numerosos aspectos de nuestra vida diaria. Todo ello, junto a la crisis economica que afecta a numerosos paises en todo el mundo, hace que muchos gobiernos se vean obligados a revisar sus politicas nucleares. Sin embargo, los recientes acontecimientos acaecidos en relacion a la seguridad de las centrales nucleares han reforzado la opinion de los grupos de presion medioambiental creando un encrucijada para el poder politico....

The use of Inductive Wireless Power Transfer (IWPT) varies from low-power applications such as mobile phones and tablets chargers to high-power electric vehicles chargers. DC–DC converters are used in IWPT systems, and their design needs to consider the demand of high efficiency in the power transfer. In this paper, a DC–DC power converter for IWPT is proposed. Its topology uses a DC–AC converter in the transmitter circuit and an AC–DC converter in the receptor. The transmitter has an interleaved coupled-Buck converter that integrates two Buck converters connected to a half inverter bridge and a parallel resonant load. The control strategy implemented for the semiconductor switching devices allows two operating modes to obtain a sinusoidal output voltage with a low distortion that makes it suitable in high-efficiency power transfer systems. To obtain a DC output voltage, a full wave bridge rectifier is used in the receptor circuit. The proposed topology and the control strategy are ...

Multiple-output DC–DC converters are essential in a multitude of applications where different DC output voltages are required. The interest and importance of this type of multiport configuration is also reflected in that many electronics manufacturers currently develop integrated solutions. Traditionally, the different output voltages required are obtained by means of a transformer with several windings, which are in addition to providing electrical isolation. However, the current trend in the development of multiple-output DC–DC converters follows general aspects, such as low losses, high-power density, and high efficiency, as well as the development of new architectures and control strategies. Certainly, simple structures with a reduced number of components and power switches will be one of the new trends, especially to reduce the size. In this sense, the incorporation of devices with a Wide Band Gap (WBG), particularly Gallium Nitride (GaN) and Silicon Carbide (SiC), will establi...

ABSTRACT In this paper, a method to synthesize a dc power gyrator, based on cascaded connection of two dc-dc converters is introduced. The dc power gyrator is synthesized by means of a sliding-mode control that imposes a proportionality between the input current of the first stage and the output voltage of the second stage. Only one sliding surface is used to drive both the switches of the system. A systematic procedure for designing the system is presented and its stability analysis is performed analytically and validated by numerical simulations using PSIM software. As an example of application, it is shown that a gyrator based on the cascade connection of two boost converters can be a good candidate for the impedance matching between a photovoltaic (PV) generator and a resistive load.

In the framework of the Italian In-Kind Contribution (IKC) to the construction of the European Spallation Source (ESS), Elettra Sincrotrone Trieste is in charge of providing some key equipment for the accelerator. Among them, there are the magnets and the associated power converters for the Linac Warm Units (LWU), the High Energy Beam Transport (HEBT) dogleg, the Dump Line (DmpL) and the Accelerator to Target (A2T) sections of the neutron source. Magnets and their power converters are complementary parts of common systems. Their design cannot be totally separated, requiring iterations for an optimal solution that should include also power cable standardization. This work will describe the power converters' solutions adopted for the magnets of the abovementioned sections. They comprise 4-Quadrant power converters for the correctors, compact DC power converters for the small quadrupole magnets and more powerful DC power converters for the dipole and large quadrupole magnets. INTRO...

With the expansion of renewable energy sources worldwide, the need for developing more economical and more efficient converters that can operate on a high frequency with minimal switching and conduction losses has been increased. In power electronic converters, achieving high efficiency is one of the most challenging targets to achieve. The utilization of wideband switches can achieve this goal but add additional cost to the system. LLC resonant converters are widely used in different applications of renewable energy systems, i.e., PV, wind, hydro and geothermal, etc. This type of converter has more benefits than the other converters such as high electrical isolation, high power density, low EMI, and high efficiency. In this paper, a comparison between silicon carbide (SiC) MOSFET and silicon (Si) MOSFET switches was made, by considering a 3KW half-bridge LLC converter with a wide range of input voltage. The switching losses and conduction losses were analyzed through mathematical c...

ABSTRACT This paper discusses a comparative investigation of the three basic nonisolated DC-DC converters used as interfaces for maximum power point tracking (MPPT) in photovoltaic (PV) generators using the direct duty ratio control tracking algorithm. Analysis of buck, boost, and buck-boost converters is undertaken to study the behavior of converter performance with respect to changing atmospheric conditions, in-turn duty ratio variation (as a result of MPPT), and tracking efficiency. As atmospheric conditions change, the operating value of resistance at the maximum power point (R mpp) changes. To effectively drive the system at the maximum power yield point, the MPPT algorithm has to drive the system operation point close to the value of R mpp for the varying atmospheric profile of change in insolation and temperature. The efficiency of the MPPT algorithm lies in meeting this very requirement. The simulation study shows that, although buck, boost, and buck-boost converters are used as power converters in MPPT applications, not all converters perform with high efficiency. The effect of different resistive loads that have values other than R mpp on converter-side output is considered for the three topologies, and it is observed that the buck-boost converter is the only one that is able to track the maximum power point (MPP) under variations in insolation, temperature, and loading effect with the highest tracking efficiency.

Digital control methods for switching power converters offer greater robustness, more flexibility to changing operating characteristics, and better system performance than conventional techniques, which are often model-limited and only work well in a small range of conditions. Digital controllers are broadly classified into five generations, from 0 through 4. Generation 4 methods, such as the three techniques proposed in the present work, use new system formulations to achieve advanced control objectives. The first proposed technique ...

An analysis and implementation of delta modulation (DM) technique in the control of ac-dc converters is studied here in this project. The DM technique offers advantages of easy implementation, continues converter voltage control, and a direct control on the line harmonics. A simple circuit of the delta modulator is proposed, designed and fabricated in the laboratory. This proposed modulation scheme, fundamentally differs from conventional PWM technique, by virtue of its self carrier generating ability. Results of the parametric variation of the modulator are reported. Simulated and experimental results of the single phase DM ac-dc converters validate the analytical results.

In this paper, a novel approach is presented for an integrated analysis of power distribution networks, including dc–dc converters, power transmission lines (PTLs), and multiple loads. The effect of power interconnects is investigated on the dynamic characteristics of a pulsewidth-modulated buck converter. A closed-form relation is developed for control-to-output transfer function including the power interconnects as a transmission line model. The effect of PTLs is demonstrated on converter’s open-loop transfer function and its stability. For analysis of distributed power loads on printed circuit board PTLs, a model is developed based on cascaded matrix representation of interconnects. The model is successfully tested against planar electromagnetic simulation results.

An impedance source buck-boost converter (BBC) prototype for renewable energy (RE) application in the transportation industry is proposed. Its functions include stabilizing the variable output voltage of the RE sources such as fuel cells and photovoltaic cells. The converter utilized a topology of DC-DC quasi-impedance source converters (q-ZSCs) to achieve the gain curve of the BBC. With BBC gain curve, the converter earned advantages over the two other classes of non-isolated DC-DC q-ZSCs. These advantages include ecient buck-boost capability at the ecient duty ratio range of 0:35-0:65 and continuous and non-zero gain at the ecient duty ratio range. The converter's q-ZSC topology implies using two capacitors and two inductors. These two capacitors and inductors formed two separate LC filters that provides second order filtering compared to the first order filtering in BBC. Its other advantages over the traditional BBC include elim-ination of dead and overlap-time, simple contol...

A double output port DC-DC quasi impedance source converter (q-ZSC) is proposed. Each of the outputs has a different voltage gain. One of the outputs is capable of bidirectional (four-quadrant) operation by only varying the duty ratio. The second output has the gain of traditional two-switch buck-boost converter. Operation of the converter was verified by simulating its responses for different input voltages and duty ratios using MATLAB SIMULINK software. Its average steady-state output current and voltage values were determined and used to determine the ripples that existed. These ripples are less than 5% of the average steady-state values for all the input voltage and duty ratio ranges considered.

A double output port DC-DC quasi impedance source converter (q-ZSC) is proposed. Each of the outputs has a different voltage gain. One of the outputs is capable of bidirectional (four-quadrant) operation by only varying the duty ratio. The second output has the gain of traditional two-switch buck-boost converter. Operation of the converter was verified by simulating its responses for different input voltages and duty ratios using MATLAB SIMULINK software. Its average steady-state output current and voltage values were determined and used to determine the ripples that existed. These ripples are less than 5% of the average steady-state values for all the input voltage and duty ratio ranges considered.