Magnitude Of Output Voltage Research Articles

Performance enhancement of an out-of-plane electret-based vibrational energy harvester with dual charged plates

This paper presents a novel out-of-plane electret-based vibrational power generator (EVPG) that has both negative and positive charged electret plates integrated into a single seismic mass system. Compared with the conventional single-charged two-plate configuration, the proposed device not only exhibits an enhanced output voltage magnitude but also has a wide operational bandwidth due to spring softening nonlinearity according to the experimental analysis. With the acceleration changes from 0.1g to 0.5g, the operating 3-dB bandwidth can be increased 2.6 times from 2.5 Hz to 6.5 Hz, which indicates higher energy conversion efficiency than a linear energy harvester in the practical scenario of broadband random vibrations.

English

Many existing and developing electrical and electronic technologies require voltages of different levels supplied from a singular available source voltage such as a battery. DC converters are devices designed specially for the purpose of changing DC voltage levels efficiently. The converters are electronic devices, it has an output voltage magnitude that is either greater than or less than the input voltage magnitude. Rising energy intensity leads to a higher cost of delivering power and low power density. Meanwhile, the demand for compact power supplies grows significantly. It requires power supplies with high efficiency, low cost and smaller size. In order to control the output voltage of the converter, the controller is designed to change the duty cycle of the converter. In this converter IGBT switch is digitally controlled by PIC microcontroller. In this work simulation and then hardware implementation is done with results. The converter is mainly used, where load is very sensitive (battery - powered products), it provides variation of _1% only.

Simplified space vector modulation technique for seven‐level cascaded H‐bridge inverter

A simplified space vector modulation (SVM) technique is proposed for the seven-level cascaded H-bridge (CHB) inverter. It is based on decomposing the seven-level space vector hexagon into a number of two-level space vector hexagons. The presented technique significantly reduces the calculation time and efforts involved in the SVM of a seven-level inverter; without any loss in the output voltage magnitude or increase in the total harmonic distortion content. A further simplified technique is also presented in this study, which significantly reduces the complexity and effort involved in the seven-level SVM. Simulation results for the seven-level CHB inverter using the proposed techniques are presented. The results are compared with results using sinusoidal pulse-width modulation (PWM) and third harmonic injection PWM to prove the validity of the proposed techniques. The proposed technique is perfectly general and can be applied to all types of multilevel inverters and extended to higher level inverters.

Analysis of the Dynamic Performance of Self-Excited Induction Generators Employed in Renewable Energy Generation

Incentives, such as the Feed-in-tariff are expected to lead to continuous increase in the deployment of Small Scale Embedded Generation (SSEG) in the distribution network. Self-Excited Induction Generators (SEIG) represent a significant segment of potential SSEG. The quality of SEIG output voltage magnitude and frequency is investigated in this paper to support the SEIG operation for different network operating conditions. The dynamic behaviour of the SEIG resulting from disconnection, reconnection from/to the grid and potential operation in islanding mode is studied in detail. The local load and reactive power supply are the key factors that determine the SEIG performance, as they have significant influence on the voltage and frequency change after disconnection from the grid. Hence, the aim of this work is to identify the optimum combination of the reactive power supply (essential for self excitation of the SEIG) and the active load (essential for balancing power generation and demand). This is required in order to support the SEIG operation after disconnection from the grid, during islanding and reconnection to the grid. The results show that the generator voltage and speed (frequency) can be controlled and maintained within the statuary limits. This will enable safe disconnection and reconnection of the SEIG from/to the grid and makes it easier to operate in islanding mode.

Voltage magnitude and frequency control of three‐phase voltage source inverter for seamless transfer

This study presents voltage magnitude and frequency control of a three-phase voltage source inverter for distributed generations to achieve a seamless transfer between grid-tied mode and intentional islanding mode. When the grid is normal, the inverter works in grid-tied mode. On the contrary, when the grid fault occurs, the breaker connecting the inverter to the grid must be turned off and the inverter just supplies the power for local loads. By varying the frequency and the magnitude of the inverter output voltage, an output power control, with which the output active and reactive power can be precisely controlled, is presented. To improve the transient response, a virtual inductor with high-pass filter in synchronous d-q frame is proposed. The effectiveness of the virtual inductor is explained by the frequency response of the inverter. Finally, experimental results are given to verify the effectiveness of the scheme.

Carrier Based Pulse Width Modulation Control of a Non-Square Direct Matrix Converter with Seven-phase Input and Three-phase Output

This paper presents pulse width modulation technique for a direct ac-ac converter. The converter has seven-phase input supply and three-phase output. The input supply may be obtained from a seven-phase wind energy generation system with variable output voltage magnitude and frequency. The output of the proposed converter topology may be fed to the three-phase stiff grid system. Thus the requirement of the modulation of the ac-ac converter is to produce fixed voltage and fixed frequency output while the input can be variable. Additionally the output voltage gain should be high. Simple carrier-based PWM technique is suggested and harmonic injection scheme is proposed to enhance the output voltage magnitude. The output voltage reaches 90% of the input supply voltage with the proposed technique. An additional control block is used to stabilize the output voltage and frequency of the converter. Simulation results are shown in the paper for the verification of the proposed scheme.

Modeling and simulation of a wind farm in the presence of power electronic devices for the enhancement of transient stability

A comprehensive comparative study is made of a pitch control system and shunt flexible AC transmission system (FACTS) devices in order to improve large wind farm operation. Transient stability analysis of a large wind farm in the presence of superconducting magnetic energy storage (SMES), static synchronous compensator (STATCOM), static var compensator (SVC) and pitch controller is performed. The proposed control strategy of the STATCOM is based on PWM control; both the angle and the magnitude of the converter output voltage and the proposed SMES control system is based on a PWM voltage-source converter and a two-quadrant DC–DC chopper using an insulated-gate bipolar transistor (IGBT). Furthermore, robust control systems are designed for SVC and pitch controllers. To investigate the operation of the wind farm with contribution of these devices, two scenarios are considered and simulated. First, extensive analysis of a symmetrical three-phase fault and its effects on system operation is carried out. A permanent fault due to unsuccessful reclosing is analysed; this is one of the most noticeable features of this study. PSCAD/EMTDC software is used for modeling and simulation of the system components and proposed control strategies for power electronic interfaces. System performance analysis under different operating conditions and performance indices show the effectiveness of the proposed controllers even when a severe fault is applied.

Parallel DC/DC converters system with a novel primary droop current sharing control

In this study, a primary droop current sharing controller with output current commitment capability for a stand-alone renewable energy source was proposed. The specially designed DC/DC converter for renewable energy source consists of feedforward, voltage and droop current sharing control loops; furthermore, the droop voltage compensated scheme is also designed to improve current sharing performance under variation of the input voltage. When the renewable energy is abundant, the DC/DC converter with respect to this energy source can provide more load current and also can save energy bill from utility. The output voltage magnitude of the maximum power point tracking (MPPT)-controlled converter is used to signal the status of the renewable energy for the output current commitment judgment, and then shifts the output voltage droop characteristics to adjust output current through an 8 bits microprocessor PIC16F876. Finally, the design and analysis of the proposed scheme are introduced in this paper and some simulation and experimental results are also provided.

Hybrid excitation synchronous generator in embedded applications: Modeling and control

The paper deals with the modeling and the control of the hybrid excitation synchronous machine operating as a variable frequency generator that supplies an isolated load in embedded applications such as aircraft electrical power generation. The elaborated model is suitable for simulation and is adapted to the generator mode. In addition, it includes the magnetic circuit saturation effect. The aim of the control is to maintain the output voltage magnitude constant when the load and/or the speed of the rotor vary. Simulation results and experiments validate the approach. The electrical parameters of the laboratory prototype machine are identified prior to the control test.

A Carrier-Based Pulse Width Modulation Method for Indirect Matrix Converters

This paper proposes a carrier-based pulse width modulation (PWM) method to control an indirect matrix converter (IMC) by analyzing the relationship between the space vector PWM (SVPWM) and the carrier-based PWM. The complexity of the SVPWM method for an IMC can be reduced by using an equivalent carrier-based PWM method. The advantage of the proposed algorithm is its ability use only one symmetrical triangular carrier signal to generate the gate signals for all of the power switches in both the rectifier and inverter stages as compared to the conventional method where the carrier signal used in the rectifier stage is different from that of the inverter stage. In addition, by using a suitable offset voltage component in the modulation signals, the output voltage magnitude reaches 0.866 of the input voltage magnitude. Simulation and experimental results are provided in order to validate the proposed method.

Experimental Study of Nonequilibrium Electrodeposition of Nanostructures on Copper and Nickel for Photochemical Fuel Cell Application

To increase the performance of photochemical fuel cells, nonequilibrium electrodeposition has been performed on Cu and Ni to make photosensitive anodes. Processing parameters including electrolyte concentration, and electrode potential were studied using cyclic voltammetry. Scanning electron microscopy (SEM) and X-ray Spectroscopy (EDS) were performed to understand the formation of the nanostructures during the nonequilibrium deposition of copper fractals. An increase in the deposition rate was observed with the increase in electrolyte concentration (from 0.05 M to 1.0 M). Similar trend was found when the cathode potential was decreased from −0.5 V to −4.5 V. The effect of substrate material was also examined. Porous fractal structures on copper were achieved, while the deposited material showed high density of surface cracks on nickel. The fractal structures deposited on copper electrode with the increased surface area were converted into copper oxide by oxidation in air. Such oxide samples were made into anodes for photochemical fuel cell application. We demonstrated that an increase in the magnitude of open circuit output voltage is associated with the increase in the fractal surface area under the ultraviolet irradiation test conditions. However, the electrodeposited fractals on nickel showed very limited increase in the magnitude of open circuit voltage.

A Novel High-Voltage Pulsed-Power Supply Based on Low-Voltage Switch–Capacitor Units

This paper presents a high-voltage pulsed-power system based on low-voltage switch-capacitor units that are connected to a current source for several applications such as plasma systems. A modified positive buck-boost converter topology is used to utilize the current source concept, and a series of low-voltage switch-capacitor units is connected to the current source in order to provide a high voltage with a high voltage stress (dv/dt) as demanded by the loads. This pulsed-power converter is flexible in terms of energy control because the stored energy in the current source can be adjusted by changing the current magnitude to significantly improve the efficiency of various systems with different requirements. The output-voltage magnitude and stress (dv/dt) can be controlled by a proper selection of components and control algorithm to turn on and off the switching devices.

Fault-Tolerant Structure and Modulation Strategies With Fault Detection Method for Matrix Converters

This paper proposes a fault-tolerant matrix converter with reconfigurable structure and modified switch control schemes, along with a fault diagnosis technique for open-circuited switch failures. The proposed fault recognition method can detect and locate a failed bidirectional switch with voltage error signals dedicated to each switch, based on a direct comparison of the input and the output voltages. Following the fault detection, the designed converter architecture isolates the faulty parts and bypasses the remaining load phase, resulting in a 3 × 2 matrix configuration with six bidirectional switches. Based on the reconfigured hardware topology, novel fault-tolerant modulation strategies are developed to produce three-phase balanced sinusoidal output voltages/currents with only six bidirectional switches, but at a reduced output voltage magnitude as compared with the normal matrix converter. Thus, the developed switching function matrices for the reconfigurable converter structure, containing an appropriate positive- and negative-sequence set of matrices with input voltage vector, can preserve continuous operation even after switch failures and improve reliability of the drives.

A Compensation Technique for Smooth Transitions in a Noninverting Buck–Boost Converter

With the advent of battery-powered portable devices and mandatory adoption of power factor correction, noninverting buck-boost converters are garnering lots of attention. Conventional two-switch or four-switch noninverting buck-boost converters choose their operation modes by measuring input and output voltage magnitude. The criterion for the selection of the operation mode can cause higher output voltage transients in the neighborhood, where input and output are close to each other. For the mode selection, due to the voltage drops raised by the parasitic components, it is not enough just to compare the magnitude of input and output voltages. In addition, the difference in the minimum and maximum effective duty cycles between controller output and switching device yields discontinuity at the instant of mode change. Moreover, the different properties of output voltage versus a given duty cycle of buck and boost operating modes contribute to the output voltage transients. In this paper, the effect of the discontinuity due to the effective duty cycle derived from the device switching time at the mode change is analyzed. A technique to compensate the output voltage transient due to this discontinuity is proposed. In order to attain additional mitigation of output transients and a linear input/output voltage characteristic in buck and boost modes, the linearization of DC gain of the large-signal model in boost operation is analyzed as well. Analytical, simulation, and experimental results are presented to validate the proposed theory.

Design of an Autonomous Control for Parallel-Connected Uninterruptible Power Supplies

This paper proposes an autonomous control for parallel-connected uninterruptible power supply (UPS) systems based on electrical power system interrelations. The controllable variables are the output voltage phase angle and magnitude. Relation between active current and output voltage phase angle is derived from a synchronous machine model. Electrical power systems suggest that voltage regulation and reactive current can be proportionally related to yield another control equation. The resulted control scheme is very simple and only requires an output current measurement to provide a voltage reference signal locally in synchronism with other UPSs without communication signal exchange. A small-signal model represents the entire system and constitutes proof of its stability. Feasibility is confirmed by an experimental setup with three UPSs connected in parallel with different output power ratings. In the experiments, voltage limiters (1%) are employed and three cases are verified. Under all conditions, the results show excellent performance in terms of stability, and active and reactive load sharing.

TRIAC Dimmable Ballast With Power Equalization

A two-stage, two-wire TRIAC dimmable electronic ballast for fluorescent lamps is presented in this paper. It is constructed by using a flyback converter as the input power factor corrector to supply a half-bridge series-resonant parallel-loaded inverter to ballast the lamp. The flyback converter is operated in discontinuous conduction mode so that the filtered input current profile is the same as the TRIAC-controlled voltage waveform. The switches in the inverter are switched at a constant frequency slightly higher than the resonant frequency of the resonant tank. Based on the constant average input current characteristics of the inverter, the dimming operation is simply achieved by pulsewidth modulation control of the magnitude of the flyback converter output voltage. No synchronization network is required between the input and output stages. In addition, a linear power equalization scheme is developed so that the dc-link voltage (and hence the lamp power) is in a linear relationship with the firing angle of the TRIAC. The average output voltage of the dimmer controls the equalized flyback converter output voltage. Modeling, analysis, and design of the ballast will be described. A prototype was implemented to verify the experimental measurements with the theoretical predictions.

Dynamic hysteresis band control of the buck converter with fast transient response

A dynamic hysteresis control of the buck converter for achieving high slew-rate response to disturbances is proposed. The hysteresis band is derived from the output capacitor current that predicts the output voltage magnitude after a hypothesized switching action. Four switching criteria are formulated to dictate the state of the main switch. The output voltage can revert to the steady state in two switching actions after a large-signal disturbance. The technique is verified with the experimental results of a 50 W buck converter.

Design and Dynamic Performance of Modified Series-Parallel Resonant Converter

This paper deals with modified series-parallel resonant converter (MSPRC). Leakage inductance and winding capacitance of high-frequency transformer are incorporated in the analysis of basic operation of circuit. MSPRC is well suited to high-voltage dc applications, and is operated just above the resonant frequency to maintain zero-voltage switching (ZVS). Sampled-data technique of the MSPRC is presented, and small signal modelling of the converter is obtained. Steady-state behaviour using complex ac-circuit analysis is used for design of resonant tank circuit. The magnitude of output voltage is regulated by using variable frequency control. An experimental prototype unit is developed using high frequency switches (MOSFETs). Simulation results are compared with those obtained experimentally.

Analogue fault detectability comparison between power supply current and output voltage magnitude and phase spectrum components

A method using magnitude and phase spectrum components for fault detection of catastrophic and parametric faults is presented. A procedure is developed, discrimination factors are defined and their values are adjusted to include circuit parameter deviations. Comparative results from linear and nonlinear configurations of operational amplifier circuits are given, showing a significant increase in fault detectability over a previous method and also an improvement in fault coverage by the use of the power supply current against the output voltage signal.

Ac chopper with harmonics elimination and phase control

AbstractA switching strategy for the A C chopper is presented. With this strategy, it is possible to control the phase angle of the output voltage, besides the possibility of controlling the output voltage magnitude. Furthermore, selected lower order harmonics can be eliminated. Profiles of switching angles of the proposed technique are given. Theoretical analysis of the performance of the A C chopper under this strategy along with experimental results verifying the analysis is detailed.