Although the investigated example seems to be not very realistic so we must take into consideration also the following four conclusions. The first one is that the presented example is very simple for demonstration ofEMC consequences. The second one is that the real dimensions of the converter circuits are obviously in millimeters and so the circuit area is smaller in comparison with demonstration example, but we should take into consideration also the opposite influence resulting from the shorter switching times. Such a way the realistic final result could be that the induced voltages will reach values of few tenths of millivolts in real equipments. The third conclusion is that induced voltage in real equipment is created as sum of more circuit interactions and so it can reach also range of the volts. The fourth one is that also low-level induced voltage can have the important impact on properly work of some circuits (for example microprocessors, etc.). However the main contribution of performed analyses consist in derivation of equations by which any inductivecouplingEMC problem is possible simply analyse by computer numerical method.
The ATP program built to simulate the GIPFC scheme shown in Figure 5 is based upon the work published by Vasquez- Arnez and Zanetta (2005a), where it was presented a UPFC using similar control techniques and features. The wave- forms generated with the GIPFC scheme were obtained us- ing a 12-pulse 3-level converter configuration that utilized the phase-shift control technique, with GTOs (Gate Turn- Off thyristors) as switching devices. In this ATP program, both equivalent AC systems were assumed to operate at a rated voltage of 230 kV. The shunt converter’s rated power was set to ±200 MVA, a fair amount to fulfil the maximum real power demand from both series VSIs (each with a rated powerof 100 MVA) and to compensate, through its avail- able shunt reactive power, the bus voltage V 22 . The coupling
As mentioned already, the STATCOM is, in principle, a static (power electronic) replacement of the age-old synchronous condenser as shown in Fig.2. It shows the schematic diagram of a STATCOM connected to the utility grid at the point of common coupling (PCC) through the coupling inductors (or ac side reactors). The phasor diagram of the fundamental component of the STATCOM converter terminal voltage and the grid voltage at PCC for an inductive load in operation, (neglecting the harmonic content in the STATCOM converter terminal voltage) is presented in Fig.3 (a). However, the inter-connecting reactors have fundamental power frequency voltage at one end and PWM voltage waveform of a converter at other end. The fundamental component of the converter terminal voltage, V o 1 , may be forced
especifi camente com vários fatores sociodemográ- fi cos associados aos EMC para AF e tal estudo foi desenvolvido no Nordeste do Brasil. Como a AF é um comportamento complexo, nem sempre o que ocorre em uma região ocorre em outra. Assim, essa pesquisa tem a seguinte problematização: quais os fatores sociodemográfi cos que estão associados aos EMC para AF em acadêmicos de Educação Física de uma instituição pública do sul do Brasil?
Abstract . This paper focuses on measurement and analysis of the electromagnetic fields generated by wireless power transfer system and their possible interaction on data transmission channel. To measure the levels of electromagnetic fields and spectrum near the wireless power transfer equipment the measurement system in the frequency range 100 kHz to 3 GHz was used. Due to the advances in technology it becomes feasible to apply the wireless power transfer in the electric vehicles charging. Currently, in the Faculty of Science and Technology of the University Nova high power wireless power transfer systems are in development. Those systems need to be controlled by several microcontrollers in order to optimize the energy transmission. Their mutual communication is of extreme importance especially when high intensity fields will generate highly undesired influence. The controllers are supposed to communicate with each other through radio frequency data channels. The wireless power transfer system with the electromagnetic interference may influence or completely disrupt the communication which will be a severe problem.
Mas mesmo uma dinâmica refreada e “favorável à família” do mercado de trabalho daria conta de apenas um dos lados da questão. A convivência social das pessoas precisaria ser viabilizada de uma nova forma. A família nuclear, debilitada em suas relações sociais, representa uma enorme intensificação do trabalho. Muitos dos problemas que poderiam ser (mais) facilmente solucionados em conjunto com outras famílias acabam por se converter, se confrontados no isolamento, numa sobrecarga de longo prazo. O melhor exemplo disso são justamente as tarefas e inquietações da paternidade. Mas as situações da vida e de suporte mútuo que envolvem várias famílias no mais das vezes já são inviabilizadas pelas circunstâncias habitacionais. A mobilidade profissional e a tendência à vida de solteiro já foram cimentadas. As moradias tornam-se cada vez menores. Elas passam a ser talhadas à medida da mobilidade familiar individual. Continua completamente excluída do planejamento de apartamentos, casas e conjuntos habitacionais a possibilidade de que famílias possam querer morar e mudar-se juntas. Não apenas a arquitetura, o planejamento urbano etc. favorecem o individualismo e rejeitam uma vida social. Ainda não se impuseram limites para a transformação imaginativa da realidade. A educação das crianças, por exemplo, seria facilitada não apenas por meio do acompanhamento dos vizinhos, como também através de novas especialidades – “mães diaristas” – ou através de um sistema escolar que ainda não tenha feito do envolvimento dos pais na lição de casa uma parte integrante do “hidden curricullum”, e por aí afora. (BECK, 2010, p. 187)
The transistor parameters of DAI and NIC can be properly chosen to achieve the desirable value of equivalent inductance L (few tens µH), and the maximum-Q value at the switching frequency, and thus the efficiency ofconverter is improved. Experimental results show that the converter supplied with an input voltage of 1V, provides an output voltage of 0.74V and output ripple voltage of 10mV at 155 kHz and Q-value is maximum (≈4226) at this frequency.
In islanding mode, to synchronize the backup generator with the microgrid, the generator output voltage and frequency must comply with parameterized limits. During this mode, the system voltage depends on the generator voltage when it is running. With regard to the frequency, the bi-directional inverter implements an automatic frequency adjustment in order to prevent malfunction of frequency-sensitive loads (SMA, 2007). In addition, the output powerof other source devices may be individually limited in case the upper and lower frequency limits are not complied. This kind of situation arises, for instance, when the battery bank is fully charged and the power from available renewable sources exceeds the power required by the loads. To prevent the overcharging of the battery, the bi-directional inverter changes the microgrid frequency. This frequency adjustment is monitored by the inverters of the distributed generation systems and, as soon as the grid frequency increases beyond a 51 Hz, they decrease their output power linearly in order to bring the frequency back to the rated frequency of the grid. This process, called “Frequency-Shift Power Control”, ends whenever the microgrid frequency reaches 52 Hz (SMA, -). The inverters become inactive, i.e., are disconnected from the microgrid, if the frequency outranges the 50 Hz ±4,5 Hz.
Os EMC referem-se, então, à condição na qual o indivíduo se encontra com relação aos seus hábitos e intenções de iniciar ou manter a prática da atividade física. Os EMC são normalmente classificados como: 1) Pré- contemplação: O indivíduo não pratica atividade física regular, e não tem a intenção de mudar o seu comportamento; 2) Contemplação: O indivíduo não pratica, mas apresenta intenções de iniciar a prática em até seis meses; 3) Preparação: O indivíduo tem intenção de iniciar a prática de AF nos próximos 30 dias, ou a pratica, mas irregularmente; 4) Ação: o indivíduo pratica atividade física regularmente, mas há menos de 6 meses; 5) Manutenção: O indivíduo pratica AF regularmente por seis meses ou mais (MARCUS et al., 1994).
Abstract— This paper describes a power amplifier system for testing of distance relay operating characteristic. This power amplifier is based on two three phase inverters with a neutral wire. The output power currents and voltages are controlled by a sliding mode controller. A developed matlab/simulink digital simulator generates the test signals. This test signals are converted in current and voltage references using a microcontroller to connect the digital simulator to the powerconverter amplifier. Experimental results from a laboratory prototype are presented and discussed.
Abstract. A recent trend in automotive industry is adding electrical drive systems to conventional drives. The electri- fication allows an expansion of energy sources and provides great opportunities for environmental friendly mobility. The electrical powertrain and its components can also cause dis- turbances which couple into nearby electronic control units and communication cables. Therefore the communication can be degraded or even permanently disrupted. To mini- mize these interferences, different approaches are possible. One possibility is to use EMC filters. However, the diversity of filters is very large and the determination of an appropriate filter for each application is time-consuming. Therefore, the filter design is determined by using a simulation tool includ- ing an effective optimization algorithm. This method leads to improvements in terms of weight, volume and cost.
The harmonics generated by nonlinear load when added with reactive load causes more problematic to supply system as it not only affects transformer at supply end, but also to other consumers connected to same supply. Because of these problems, the power quality is an issue and an object of great concern not only for consumers but also for distributors . This paper presents modeling and simulation of a Synchronous Link Converter (SLC) using PWM connected to a single-phase system having both reactive and non-linear load. The SLC acts as Active Power Filter for harmonics compensation and static Synchronous Compensator for variable compensation of load. The proposed model is designed and simulated using MATLAB/Simulink. The relevant results are presented for justifications.
Climate change threats and energy crisis leads to look for alternate sources of energy [1-3]. The world is virtually on the hunt of promising renewable and sustainable sources of energy. In recent years, renewable energy sources like solar, wind, tidal, have attracted the researchers, as it is limitless, non- pollutant and available free of cost. Due to rapid improvement in advancement in power electronics and reduction in the manufacturing cost of PV cell, solar energy is becoming more promising source of energy [4-8]. Solar PV exhibits nonlinear characteristics and its efficiency is also low. It becomes essential to extract maximum power from solar PV under all ambient conditions. MPPT (Maximum Power Point Tracking) algorithm is used to extract maximum power from solar PV [9-10]. The control of MPPT is implemented in the control circuit ofPower electronics converters. A converter without MPPT system only regulates the output voltage of PV module, but it does not ensure that PV system is operating at the maximum power point MPP . The operation of MPPT depends on the type ofconverter used [12-14]. In this paper a buck dc-dc converter is used and the performance of MPPT is evaluated.
Similar to the VI control method, (1) can be used to obtain the gain curves as function of . In this case, is not considered and is set to be zero in (1). The variation of is made by knowing that % = 2 ∗ I ∗ . Fig. 5 presents the gain curves as function of , &@ A considering a design for 10 FG and 100 FG. Fig. 5a) presents these curves for different load values. In this case unlike the previous case it is possible to observe that considering the design for a lower frequency leads to a narrower voltage gain peak. At and around resonance, the voltage gain is independent of the load and frequency variation. As the resonant filter components are constant, is always constant even with variation. Since the converter is designed initially to operate at resonance considering the maximum power in the output at this point, and that in normal operation, it will only operate at or above to regulate the output, ZVS is always guaranteed. From Fig. 5b) it can be seen that for a given voltage gain variation, ∆&, when the design frequency is higher @100 FGA the variation of needed to obtain that gain variation @∆ A is higher when compared to a lower frequency design @10 FGA gain curve. Therefore, for the same range, when the design is for a lower value of it will lead to a higher controllable range of the output. Nevertheless, from Fig. 5a) above resonance, if the frequency of design is higher, the operation is less load dependent although it allows less output regulation with the same variation of . Another advantage of increasing the design frequency is that enables circuit miniaturization.
This work follows previous research where sliding-mode controllers, based on switched state-space models, to achieve cross-decoupled (independent) control of active and reactive power flow were presented and two different DPFC series converter topologies were proposed , . This paper proposes a power transformer and a third-order LCL filter to be part of a DPFC device. DPFC devices can contribute to sustainability of electrical power. This research work on energy management and smart grids might benefit from future collective awareness systems in order to implement cooperative control, or perform informed decision making or the effective involvement of the electrical or sustainable energy systems.
Analog-to-digital converter (ADC) has become essential structure for most of the electronics and communication systems. Comparator constitutes the main component in analog to digital conversion (ADC). It is basically the first stage in ADC, which converts the signal from analog to digital domain. The Flash ADC is the fastest ADC among all types of available ADC architectures. An N-Bit Flash ADC employs the 2 N -1 comparators for data conversion. However, these comparators consume large power as they work simultaneously in parallel fashion. The Flash ADC also requires resistor ladder circuit or capacitor array circuit for reference voltage generation , which again makes the converter more power hungry & therefore Flash ADC consumes highest power among all types of ADCs. For low power data conversion circuits, the power dissipation has become one of the most important limitations. In reality, power efficiency has been considered as an essential design criterion in many battery employed applications such as wireless sensor node, pacemakers and other implanted RFID chips as biomedical imaging devices in the human body . The objective in such cases is minimum power consumption for maximum battery life time. The designed 6-Bit Flash ADC in this paper meets the requirement for such low power applications.
Hysteresis current control is the easiest techniques to implement; this is developed by Brod and Novotny in 1985.One disadvantage of this technique is that there is no limit on switching frequency. An additional circuitry is required to limit the maximum switching frequency. An error signal E (t) is used to control the switches of the inverter. When the error reaches at upper limit, the transistors are switched to force the current down. When the error reaches at lower limit the current is forced to increase. The maximum and minimum values of the error signal are Emax and Emin respectively. The range of the error signal, Emax – Emin, controls the amount of ripple in the output current from the inverter.
Generally transistors are used as the switches of the DC-DC converters. In traditional PWM converters, power transistors such as MOSFET, IGBT are adopted as the switching devices. MOSFET is preferable for low voltage and high current applications where as IGBT is preferable for high voltage applications. The duty cycle of the power switch is controlled to achieve buck/boost topology. During the turn on instant current increases linearly results in switching losses. Although the traditional PWM converter is efficient than conventionally adopted linear powerconverter, it has some drawbacks. The operating frequency of conventional PWM converter must be raised to high value to minimize the volume and weight of the converter. But increase in switching frequency leads to increases the switching losses and it also increases the severity of switching stress and EMI. So there is a frequency limitation on traditional PWM converter (hard switching converter).
The new converter has a simple structure, low cost and ease of control. The effect of parasitic elements and reverse recovery losses in diodes are the major problem in this type of converters. In this type of converters the snubber circuit is made for the lowest input voltage and the highest load current. The diodes used in the proposed snubber circuits have low reverse recovery time period. This helps in eliminating stored charges in diodes during turn off. The snubber circuit does not have any coupled inductor or bulky transformers and thus magnetic losses are reduced. The proposed converter can be used for Electric vehicles, Portable Lighting systems, charger Circuits, in Desert Agriculture, in Air Conditioning Systems, PV power generation scheme without step-up transformer.