- Dettagli della rivista
- Formato
- Rivista
- eISSN
- 2255-9159
- ISSN
- 2255-9140
- Pubblicato per la prima volta
- 31 Jan 2013
- Periodo di pubblicazione
- 2 volte all'anno
- Lingue
- Inglese

#### Cerca

Accesso libero

#### AC-DC Converter with Asymmetrical Higher Harmonics Compensation Function in Sustainable AC Grid

Pagine: 5 - 13

#### Astratto

In this paper the grid current higher harmonic compensation method for two level AC-DC converters in sustainable AC grid is described. The algorithm is based on Direct Power Control with Space Vector Modulator (DPC-SVM), which was extended by additional Higher Harmonics Compensation (HHC) module. The HHC block is composed of several resonant filters tuned to appropriate frequencies. Both, symmetrical and asymmetrical types of grid currents distortions are analyzed. Operation of the HHC module in stationary αβ coordinates and rotating dq coordinates is discussed. Selected waveforms illustrating operation of the developed algorithm are presented. It is shown that in dq coordinates asymmetrical voltage distortions needs additional effort for its compensation in comparison to symmetrical higher harmonics. The subject is important because in practice asymmetrical higher harmonics usually can appear when one phase nonlinear load is connected to the grid. Even within such conditions the grid connected ACDC converter (GCC) should provide sinusoidal-like current. This assumption provides the reduction of negative impact of the GCC in power quality in Point of Common Coupling (PCC) in sustainable AC grid

#### Keywords

- Power quality
- AC-DC power converters
- pulse width modulation inverters
- bidirectional power flow
- power harmonic filters

Accesso libero

#### Simulation of Grid Connected Three-Level Neutral-Point-Clamped qZS Inverter using PSCAD

Pagine: 14 - 19

#### Astratto

This paper is focused on a single-phase three-level neutral-point-clamped quasi-z-source inverter when it is operating being connected to the electrical grid. A control strategy for injecting current synchronized in phase with the voltage at the point of common coupling has been proposed and studied. It is achieved by means of controlling the output voltage between branches adjusting the output current by using a d-q frame and the analysis of the output filter. The control strategy generates the reference to be used in the modulation technique and it has been validated with and without shoot-through switching states. A method to calculate the minimum value of the shoot-through duty cycle is also explained in order to assure the proper control of the injected current when the input voltage is less than peak value of the grid voltage. It is an important feature because 3L-NPC qZSI due to its possibility of boosting input voltage in a single stage would operate better than a traditional inverter, for instance in photovoltaic applications when the value of irradiance is decreased. The presented results have been obtained using PSCAD/EMTDC as a simulation tool.

#### Keywords

- Computer simulation
- power system simulation
- PSCAD
- pulse width modulation inverters
- voltage control

Accesso libero

#### Estimation of Semiconductor Switching Losses under Hard Switching using Matlab/Simulink Subsystem

Pagine: 20 - 26

#### Astratto

The conventional tools for the system level simulation of the switch-mode power converters (for example, MATLAB/SIMILINK) allow simulating the behavior of a power converter jointly operating with the control system in a closed automatic regulation system. This simulation tools either represent semiconductor devices as ideal switches or implement the simplest models based on volt-ampere characteristics of standard types of semiconductor devices for conducting loss estimation. This fact makes direct calculation of dynamic power losses in the semiconductor devices impossible. The MATLAB/SIMILINK subsystem that calculates the average power dissipated in the power switch during turn-on and turn-off transition is proposed in this paper. The represented approach used in the subsystem estimates by the means of MATLAB/SIMILINK the values of turn-on and turn-off energies at power switch commutation instances on the base of switching current and voltage measurements and the values of commutation energies given in datasheet on power switch. The simulation results of step-down converter with IGBT and proposed subsystem in MATLAB/SIMULINK were compared with the calculation results obtained in Semisel

#### Keywords

- Power semiconductor switches
- MATLAB
- semiconductor device modeling
- switching loss
- circuit simulation

Accesso libero

#### Dimmable LED Drivers Operating in Discontinuous Conduction Mode

Pagine: 27 - 33

#### Astratto

For the modern smart lighting systems one of the most attractive LED advantages is the dimming possibility. Many researchers and engineers from the field of lighting engineering are trying to find compromise between the efficiency of LED dimming process and the ease of its implementation. This paper also presents an attempt to improve LED dimmer parameters. Comparative investigation of the operation of buck LED drivers in continuous conduction mode and discontinuous conduction mode are discussed here. The first section of paper briefly describes the controllability parameters of the converter in both of these modes. The positive impact of discontinuous conduction mode on the controllability parameters as well as the results of the analytical estimation and the results of associated experiments are summarized at the end of the first section. The second section describes the impact of discontinuous conduction mode on the losses of LED dimmer. The analytical estimation of power losses in the main converter components for both operation modes as well as the summary of the experiments to identify distribution of power losses between these components are presented in this section. Finally, the conclusions about using discontinuous conduction mode for dimmable LED lamps as well as guidelines for the choosing of the components with the most appropriate parameters are drawn

#### Parole chiave

- Lighting
- LED lamps
- controllability
- electrical ballasts
- DC-DC power converters

Accesso libero

#### Evaluation of Equivalent Circuit Diagrams and Transfer Functions for Modeling of Lithium-Ion Batteries

Pagine: 34 - 39

#### Astratto

The rapid developments in the field of electrochemistry, enabled lithium-ion batteries to achieve a very good position among all the other types of energy storage devices. Therefore they became an essential component in most of the modern portable and stationary energy storage applications, where the specific energy and the life time play an important role. In order to analyze and optimize lithium-ion batteries an accurate battery model for the dynamic behavior is required. At the beginning of this paper four different categories of electrical models for li-ion cells are presented. In the next step a comparison between equivalent circuit diagrams and fractional rational functions with the complex variable s is shown for lithium-ion battery modeling. It is described how to identify the parameters of the models in the time domain and also in frequency domain. The validation of the different models is made for high and low dynamic current profiles. In the first step the dependency of all model parameters on the temperature and on the battery age is neglected. These effects will be taken into account in the continuation of this work

#### Keywords

- Batteries
- equivalent circuits
- mathematical model
- transfer functions

Accesso libero

#### Active Battery Balancing for Battery Packs

Pagine: 40 - 46

#### Astratto

In electric vehicle applications, it is necessary to use series strings of batteries since the required voltage is higher than the one that can be obtained from a single battery. Due to several factors, imbalance of batteries in these battery systems is usual and an important factor that has to be taken into account. Many balancing methods have been developed with a lot of different advantages, but all of them also have a lot of disadvantages such as complexity and/or high cost, which are the common problems that can be found in most of these equalization methods. In the present work, a low cost and very simple equalization method is proposed, in which a novel control is applied to a shunting transistor topology. It allows the transistors to regulate the amount of current that goes through each battery cell in the string depending on their State of Charge (SOC), during the charging process. This control ensures that the least charged cells to be charged faster, and the most charged ones to be charged more slowly. Design criteria are discussed and simulation results are carried out in a generic battery low power application which proves the control method. Fast equalization with a low complexity and cost is obtained

#### Keywords

- Batteries
- current control
- power MOSFET
- power dissipation

Accesso libero

#### Utilization of Electric Vehicles Connected to Distribution Substations for Peak Shaving of Utility Network Loads

Pagine: 47 - 54

#### Astratto

Use of modern electric vehicles and their effective integration into power grids depends on the technologies applied around distribution substations. Distribution substations equipped with energy storing and V2G capability enable peak load shaving and demand response, which will reduce the need to make new investments into building new power sources or power grids to meet peak demand. This paper presents a distribution substation topology for utilizing electric vehicles as energy resource units for peak shaving of utility network loads. The topology allows bidirectional energy exchange among electric vehicles, battery pack energy storage devices and utility networks. The substation acts as a service provider in a microgrid. Functions of a microgrid application were simulated with MATLAB. The evaluation of the results has shown that electric vehicles can be effectively utilized for peak shaving of utility network loads. The results of the modelling and simulation were used for the development of a microgrid prototype. Assessment of capacities of electric vehicles showed that electric vehicles can provide short term support for the utility network.

#### Keywords

- AC-DC power converters
- bidirectional power flow
- DC-DC power converters
- electric vehicles
- substations