F.S. Dos Reis

Using PFC for harmonic mitigation in wind turbine energy conversion systems

Permanent magnet synchronous generators (PMSG) wind energy conversion system (WECS) using variable speed operation is being used more frequently in wind turbine application. Variable speed systems have several advantages over the traditional method of operating wind turbines, such as the reduction of mechanical stress and an increase in energy capture. To allow the variable speed operation of the PMSG WECS a conventional three-phase bridge rectifier (BR) with a bulky capacitor associated with voltage source current controlled inverter (VS-CCI) is used. This simple scheme introduces a high intensity low frequency current harmonic content into the PMSG and consequently increases the total loses in it. Subsequently, decreases the power capability of the system. In this paper a simulation study using a single-switch three-phase boost rectifier (PFC) applied to harmonic mitigation in this systems is presented.

Characterization of conducted noise generation for Sepic, Cuk and Boost converters working as power factor preregulators

The influence of the electromagnetic interference in the electronic design is becoming more and more important. The current and future regulations limit the generation of conducted and radiated noise. These regulations also limit the minimum power factor for the equipment connected to the AC line. All these facts show the importance of the analysis of power converters working as power factor preregulators (PFP). In this paper the authors present a characterization of conducted noise generated by Sepic and Cuk converters as PFP in the discontinuous conduction mode (DCM). A comparison of conducted noise generated between Sepic and Cuk converters as PFP in DCM, and a Boost converter as PFP in continuous conduction mode (CCM) and DCM is made. The results show that the conducted noise generated by Sepic and Cuk converters in DCM is lower than the conducted noise generated by the Boost converter in DCM and CCM, for the same input inductor. This fact has important influence in the selection of the optimum topology for PFP.<<ETX>>

A single-switch three-phase boost rectifier to reduce the generator losses in wind energy conversion systems

Low and medium power wind energy conversion systems (WECS) are expected to be simple, low cost and reliable. They are usually implemented with fixed pitch wind turbines. In such a case, operation with variable speed for increased capture of wind energy requires a power electronics converter capable of adjusting the shaft speed. This is done by controlling the active power drawn from the generator. Permanent magnet synchronous generators (PMSG) are a good option for low power variable speed WECS since they do not require external excitation nor reactive power to operate. Typically, an ac-dc converter composed of a diode rectifier and a capacitive filter, connected to a voltage source inverter is used as an interface to a grid or to a load. The highly distorted input currents of the diode rectifier with capacitive filters produce additional power losses in the generator that can reduce its lifetime. This paper discusses the use of a single-switch three-phase boost rectifier in the front end of the power electronic interface. It provides means for regulating the shaft speed by duty cycle variation while reducing the generator losses when compared to the standard diode and capacitive filter scheme. Simulation and experimental results show the effectiveness of the proposed scheme for reducing the generator copper and core losses and also the internal temperature.

Integrated System for Intelligent Street Lighting

This reports the study and hardware implementation of a dimmable electronic ballast for high pressure sodium lamps, and a microprocessor-based system for control and energy measurement for this ballast, which uses a power line communications system to send and receive status and commands from another ballasts plugged in the same mains subcircuit. These ballasts are connected in the topology of a logic network, one of them being defined as the master of the subcircuit, and the others as slaves. The master unit distinguishes from the slaves by the additional communications system, which works through a cell phone, and enables the wireless connection to a PC-based central supervisory system. This way, any locale or town becomes able to control its entire main lighting system, in addition to the obtainment of more accurate data about energy billing, which together with the ability to control luminosity and the better power factor, will result in financial and energetic economy

Power factor preregulators employing the flyback and zeta converters in FM mode

The flyback and zeta converters can work as power factor preregulators (PFP). These converters can be designed to obtain unitary power factor, that is, they are resistance emulators. In this paper, a method for high frequency electromagnetic interference reduction using the frequency modulation (FM) approach is described for these converters. Results show that a reduction of conducted electromagnetic interferences (EMI) generated by these converters is possible using the FM technique. The price for this EMI reduction is a small reduction in the power factor (PF).

An Electric Fence Energizer Design Method

This paper introduces fundamental concepts of electric fence technology, presents a new design method for a livestock electric fence energizer circuit and impulse transformer as well a mathematic analyze of the circuit. A new expression for design single impulse transformers for this kind of application is presented who has different project criteria from conventional transformer applications. The energizer equipment is rounded about many concepts, safety standards and data performance that are discussed. An electric circuit prototype of electric fence energizer equipment for livestock use was implemented and the results are showed. This work is based on a study developed in a Master Thesis

Full Bridge Single Stage Electronic Ballast for a 250 W High Pressure Sodium Lamp

In this paper is reported the study and implementation of a single stage, high power factor (HPF) electronic ballast for high pressure sodium (HPS) lamps using a LCC filter. In the recent years, many authors are working to obtain single stage HPF electronic ballast for fluorescent lamps. Normally, to obtain HPF in electronic ballast for high-pressure sodium lamps, a power factor pre-regulator (PFP) is used between the mains and the electronic ballast. The main idea of this work is to present a simple and low-cost electronic ballast with HPF for HPS lamps, which does not require an additional PFP converter. To get all this advantages the price to be paid is accepting a high crest factor on the lamp

Analog signal processing for photovoltaic panels grid-tied by Zeta converter

In this paper it is presented a detailed description of the analog implementation of the control for a DC-AC converter composed by a DC-DC Zeta converter and a low frequency inverter. Using only analog components, it was developed the MPPT technique based on linearization of solar panel characteristic around the MPP, a feedforward control and a robust PWM sine wave modulator. This simple and low cost solution was designed to be used in grid connected rooftop photovoltaic panels (PV). In scenery where an entire city area could be used to generate extra power, reducing the necessity of huge central power plants, module integrated inverters will play an important role on grid connection of PV systems with high reliability due to the high level of redundancy. The experimental results show that this simple cost effective solution is able to extract maximum power from PVs with low current harmonic content.

Nonlinear Loads Parameters Estimation and Modeling

This paper describes the study and development of two estimation methods for the values of electrical components concerning the input rectifier present in most of the electronic equipments available in the market. Through these methods, it is possible to identify the values of the EMI filter parasitic inductance, the input filtering capacitance Ccc, and the equivalent load connected to the rectifier. This study will be performed from the analysis of the voltage and current waveforms obtained from an oscilloscope in the input of the equipment under measure. The resulting data will be processed through a mathematical analysis in the time domain. This process will permit the subsequent analysis, modeling and simulation of the complex electrical systems in time domain employing commercial simulators like PSIM, Matlab and ORCAD aiming essentially the study of the influence of these loads over the mains harmonic distortion and power quality.

Tool for conducted EMI and filter design

In this paper a simulation tool that allows us to determine the conducted electromagnetic interference (EMI), generated for the basic PFP converters (Cuk, buck, boost, buck-boost, sepic, and zeta converters) will be presented. Using this software, we can determine full EMI spectrum in dB//spl mu/V in accordance with the CISPR 16 standard. An EMI filter design methodology that allow us to accommodate the conducted electromagnetic interference (EMI) generated by power factor correctors to international standards in the design step is also presented. Therefore, this can be an useful aid for power electronics designers.