Sinusoidal Current Source Research Articles

Design of a sinusoidal current source using a sliding-mode-controlled asymmetrical full-bridge multilevel converter

An analysis and design of an asymmetrical full-bridge multilevel converter in sliding-mode operation for inverter applications in small power systems are presented. A five-level sinusoidal current source inverter is proposed with the lowest number of controllable devices and the simplest control electronics. The current source nature of the inverter is achieved by means of a sliding-mode control loop forcing the inverter output current to track a sinusoidal reference. The theoretical predictions have been verified by experiments in a 1 kW prototype in both stand-alone and grid connection operations.

Synthesis of Sinusoidal Waveform References Synchronized With Periodic Signals

This paper proposes a novel method to generate a sinusoidal waveform synchronized with any measurable periodic signal whose frequency is within a given neighborhood. The synthesized sinusoidal signal could be used as a reference current for certain applications of parallel active power filters or any other where such synchronization would be necessary (e.g., ac/dc converters for renewable energy resources, power factor correctors, power supplies, UPS, etc.) The method is based on the behavior of a dynamical system and avoids employing the usual combination of phase-locked loop (PLL) and lookup table found in most parallel active filters synthesizing a sinusoidal source current (a table also means using significant storage memory). The novel method produces two high-quality sinusoidal waveforms that are in quadrature and is applicable to those parallel active filters whose control methodology is in the reference frame, or alternatively, it produces three sinusoidal waveforms shifted 120 degrees for designs that work in the frame. Here, a th order implementation is described, including a proof of convergence. For its most simple implementation , simulated and experimental results are included.

A Novel Load Compensation Algorithm under Unbalanced and Distorted Supply Voltages

In this paper, a novel control algorithm is proposed to compensate the unbalanced and non-linear loads in a three-phase four-wire system using active power filters. The algorithm results in balanced and sinusoidal source currents under unbalanced and distorted three-phase supply voltages. The algorithm makes use of the positive sequence extraction of the supply voltage and the theory of instantaneous symmetrical components. To illustrate the concept, a three-phase four-wire system with unbalanced and non-linear load is considered for compensation. The detailed simulation and experimental results are presented to validate the proposed method.

Instantaneous Reactive Power Theory: A Comparative Evaluation of Different Formulations

This paper analyses the behavior of different active power filter (APF) control algorithms resulting from five formulations of the instantaneous power theory: p-q original theory, d-q transformation, modified or cross product formulation, p-q-r reference frame and vectorial theory are analyzed. A simulation platform with control + APF + load is built to test the different algorithms. The results obtained in an unbalanced and nonsinusoidal three-phase four-wire system are compared. The final analysis shows that from the five formulations, only the vectorial one allows balanced and sinusoidal source currents after compensation

Meeting IEEE-519 Current Harmonics and Power Factor Constraints With a Three-Phase Three-Wire Active Power Filter Under Distorted Source Voltages

An efficient steady-state compensation method and a conceptual design for sizing the three-phase three-wire shunt active power filter (APF) under nonsinusoidal source voltages are presented in this paper. Conventionally, the compensation currents injected by the APF are determined to eliminate harmonic currents of the nonlinear load as well as to compensate reactive power and maintain the sinusoidal source currents. However, the subject related to the optimal control of the APF to meet the IEEE-519 harmonic current limits and other constraints, such as minimum load power factor requirement after compensation with an optimal kilovolt-ampere rating, are rarely investigated. In this paper, an optimization-based solution algorithm is proposed to determine the three-phase three-wire APF current injections to meet different constraints with an optimal filter size, where the voltage compensation-based control strategy is formulated as a nonlinear programming problem and is solved to find the optimal compensator gains and APF current injections. Results obtained by simulations with Matlab/Simulink show that the proposed approach is very flexible and effective for compensating harmonic currents generated by the nonlinear load with an optimal size of the APF.

Single-stage electronic ballast with class-E rectifier as power-factor corrector

A single-stage high-power-factor electronic ballast with a Class-E rectifier as a power-factor corrector is proposed. A Class-E rectifier is inserted between the front-end bridge rectifier and the bulk filter capacitor to increase the conduction angle of the bridge-rectifier diode current for obtaining low line-current harmonics. The Class-E rectifier is driven by a high-frequency sinusoidal current source, which is obtained from the square-wave output voltage of the Class-D inverter through an LC series resonant circuit. A high-frequency transformer is used for impedance matching. The experimental results for a 32-W prototype ballast are given. The switching frequency was 61.3 kHz. At full power, the power factor was 0.992 and the total ballast efficiency was 88.3%. The lamp-current crest factor was about 1.36. The simulated and experimental results were in very good agreement.

A line-interactive UPS system implementation with series-parallel active power-line conditioning for three-phase, four-wire systems

This paper presents a three-phase line-interactive uninterruptible power supply (UPS) system with active series-parallel power-line conditioning capabilities. Synchronous reference frame (SRF)-based controller is used for harmonic and reactive power compensation generated from any configuration of non-linear loads. Under normal line conditions the UPS system works with universal filtering capabilities, such as compensating the input currents and output voltages. Two three-phase pulsewidth modulation (PWM) converters, called series and parallel active filters, are used to perform the series and parallel active power-line compensation. The series active filter works as sinusoidal current source in phase with the input voltage, drawing from utility sinusoidal and balanced input currents with low total harmonic distortion (THD). The parallel active filter works as sinusoidal voltage source in phase with the input voltage, providing regulated and sinusoidal output voltages with low THD. The performance of the UPS system is evaluated in three-phase, four-wire systems. Experimental results are presented to confirm the theoretical studies.

Optimisation-based strategy for shunt active power filter control under non-ideal supply voltages

A new theory and a conceptual design for the three-phase shunt active power filter (APF) control strategy under imbalanced and distorted supply voltages are presented. Conventionally, the compensation currents injected by the APF are determined according to reference frame transformation-based approaches, where the load instantaneous real and reactive powers are calculated in the new reference frame. The APF injection currents are then computed to maintain the balanced and sinusoidal source currents, as well as the least active power consumption by the APF. However, if current harmonics set by harmonic standards or other constraints are considered, the load harmonic currents after APF compensation can be controlled to meet the requirements. Therefore, the APF may have an adjustable performance. An optimal algorithm for the APF control in steady state is proposed, in which the individual and total harmonic current distortion limits, the minimum load power factor, levels of current imbalance and the size of the APF can be taken into account. The planned APF does not consume or produce active power and only the passive energy-storage elements are required in the new APF design. Results obtained by simulations with Matlab and Simulink show that the proposed approach is more flexible than conventional approaches for compensating reactive power and harmonic/neutral currents of the load, even if the source voltages are severely distorted and imbalanced. The new control strategy is very suitable for planning the APF when several alternative objective functions and constraints are under considerations.

Volume Conduction in an Anatomically Based Surface EMG Model

A finite-element model to simulate surface electromyography (EMG) in a realistic human upper arm is presented. The model is used to explore the effect of limb geometry on surface-detected muscle fiber action potentials. The model was based on magnetic resonance images of the subject's upper arm and includes both resistive and capacitive material properties. To validate the model geometry, experimental and simulated potentials were compared at different electrode sites during the application of a subthreshold sinusoidal current source to the skin surface. Of the material properties examined, the closest approximation to the experimental data yielded a mean root-mean-square (rms) error of the normalized surface potential of 18% or 27%, depending on the site of the applied source. Surface-detected action potentials simulated using the realistic volume conductor model and an idealized cylindrical model based on the same limb geometry were then compared. Variation in the simulated limb geometry had a considerable effect on action potential shape. However, the rate of decay of the action potential amplitude with increasing distance from the fiber was similar in both models. Inclusion of capacitive material properties resulted in temporal low-pass filtering of the surface action potentials. This effect was most pronounced in the end-effect components of action potentials detected at locations far from the active fiber. It is concluded that accurate modeling of the limb geometry, asymmetry, tissue capacitance and fiber curvature is important when the specific action potential shapes are of interest. However, if the objective is to examine more qualitative features of the surface EMG signal, then an idealized volume conductor model with appropriate tissue thicknesses provides a close approximation.

Simulations of ion transport in a collisional radio-frequency plasma sheath.

A hybrid theoretical model, capable of describing the characteristics of a collisional sheath driven by a sinusoidal current source and determining the energy and angular distributions of ions incident onto the substrate, is proposed. The model consists of one-dimensional time-dependent fluid equations coupled with the Poisson equation determining spatiotemporal evolution of the sheath and the Monte Carlo simulation predicting the energy and angular distributions of ions striking the electrode, in which charge-exchange collisions between ions and neutrals are included. Additionally, an equivalent circuit model in conjunction with the fluid equations is adopted to self-consistently determine the relationship between the instantaneous potential at a rf-biased electrode and the sheath thickness. It is found that the collisional effects would influence the height of the energy peaks in the ion energy distributions and the ion angular distributions.

A line-interactive UPS system implementation with series-parallel active power-line conditioning for three-phase, four-wire systems

This paper presents a three-phase line-interactive uninterruptible power supply (UPS) system with active series-parallel power-line conditioning capabilities. Synchronous reference frame (SRF)-based controller is used to harmonic and reactive power compensation generated from any configuration of non-linear load. Under normal line conditions the UPS system works with universal filtering capabilities, such as compensating the input currents and output voltages. Two three-phase pulse width modulation (PWM) converters, called series and parallel active filters, are used to perform the series and parallel active power-line compensation. The series active power filter works as sinusoidal current source in phase with the input voltage, drawing from utility sinusoidal and balanced input currents with low total harmonic distortion (THD). The parallel active power filter works as sinusoidal voltage source in phase with the input voltage, providing regulated and sinusoidal output voltages with low THD. Operation of a three-phase phase-locked loop (PLL) structure, used in the proposed line-interactive UPS implementation, is presented and experimentally verified under distorted utility conditions. The performance of the UPS system is evaluated in three-phase, four-wire systems. Digital simulations and experimental results are presented to confirm the theoretical studies.

Modeling of quartz crystal oscillators by using nonlinear dipolar method

A quartz crystal oscillator can be thought of as a resonator connected across an amplifier considered as a nonlinear dipole the impedance of which depends on the amplitude of the current that flows through it. The nonlinear amplifier resistance and reactance are obtained by using a time domain electrical simulator like SPICE (Simulation Program with Integrated Circuit Emphasis): the resonator is replaced with a sinusoidal current source of the same frequency and a set of transient analyses is performed by giving the current source a larger amplitude. A Fourier analysis of the steady-state voltage across the dipolar amplifier is performed to calculate both real and imaginary parts of the dipolar impedance as a function of the current amplitude. From these curves, it is then possible to accurately calculate the oscillation amplitude and frequency without having to perform unacceptably long transient analyses needed by a direct oscillator closed loop simulation. This method implemented in the Analyse Dipolaire des Oscillateurs a Quartz or Quartz Crystal Oscillators Dipolar Analysis (ADOQ) program calculates the oscillation start-up condition, the oscillation steady-state features (oscillation amplitude and frequency), and the oscillator sensitivity to various parameters. The oscillation nonlinear differential equation is solved by using the slowly varying function method so that the program quickly and accurately calculates the current amplitude and frequency transients. Measurements performed on an actual amplifier show a very good agreement with the results obtained by the simulation program.

A three-phase line-interactive UPS system implementation with series-parallel active power-line conditioning capabilities

This paper presents a three-phase line-interactive uninterruptible power supply (UPS) system with series-parallel active power-line conditioning capabilities, using a synchronous reference frame (SRF) based controller, which allows an effective power factor correction, load harmonic current suppression and output voltage regulation. The three-phase UPS system is composed of two active power filter topologies. The first one is a series active power filter, which works as a sinusoidal current source in phase with the input voltage. The other is a parallel active power filter, which works as a sinusoidal voltage source in phase with the input voltage, providing to the load a regulated and sinusoidal voltage with low total harmonic distortion (THD). Operation of a three-phase phase-locked loop (PLL) structure, used in the proposed line-interactive UPS implementation, is presented and experimentally verified under distorted utility conditions. The control algorithm using SRF method and the active power flow through the UPS system are described and analytically studied. Design procedures, digital simulations and experimental results for a prototype are presented to verify the good performance of the proposed three-phase line-interactive UPS system.

A New Method for Determining Reference Compensating Currents of Three-Phase Shunt Active Power Filters

Among various solutions to electric power quality problems, the use of a shunt active power filter (SAPF) has been proven as an effective method to compensate reactive power and to mitigate harmonic currents of nonlinear loads. When designing a SAPF, it is crucial to generate reference currents for determining actual compensating current injections to the point of common coupling. In contrast to the conventional instantaneous reactive power theory that needs coordinate transformations, the new method proposed in this paper is to determine reference compensating currents based on the balance of the instantaneous reactive and active power generated in the SAPF. It is shown that the proposed method is suitable for reactive and harmonic power compensation by using a SAPF. In addition to maintaining the sinusoidal source currents, this method also eliminates the need for installing an energy storage device for reactive power compensation as well as the DC source for the harmonic compensation in the active power filter. Therefore, a simpler design of the SAPF with the minimal line losses can be expected.

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Using a shunt active power filter (SAPF) has been proved as an effective method to compensate reactive power and to mitigate harmonic currents of nonlinear loads. When designing a SAPF, it is crucial to generate reference currents for determining actual compensating current injections to the point of common coupling. In contrast to the conventional instantaneous reactive power theory, which needs coordinate transformations, the new method proposed in this letter is to determine reference compensating currents based on the balance of the instantaneous reactive and active power generated in the SAPF. It is shown that the proposed method is suitable for reactive and harmonic power compensation by using a SAPF In addition, to maintain the sinusoidal source currents this method also eliminates the need for installing energy storage devices for reactive power compensation as well as the DC source for the harmonic compensation in the active power filter. Therefore, a simpler design of the SAPF with minimal line losses can be expected.

Spatiotemporal characteristics of the collisionless rf sheath and the ion energy distributions arriving at rf-biased electrodes.

A self-consistent fluid model is proposed for describing collisionless radio-frequency (rf) sheaths driven by a sinusoidal current source. This model includes all time-dependent terms in ion fluid equations, which are commonly ignored in some analytical models and numerical simulations. Moreover, an equivalent circuit model is introduced to determine self-consistently the relationship between the instantaneous potential at a rf-biased electrode and the sheath thickness. The time-dependent voltage wave form, the sheath thickness and the ion flux at the electrode as well as the spatiotemporal variations of the potential, the electric field and the ion density inside the sheath are calculated for various rf powers and ratios of the rf frequency to the ion plasma frequency. The ion energy distributions ( IEDs) impinging on the rf-biased electrode are also calculated with the ion flux at the electrode. The numerical results show that the frequency ratio is a crucial parameter determining the spatiotemporal variations of the rf sheath and the shape of the IEDs.

Collisional effects on the radio-frequency sheath dynamics

Using the hydrodynamic model, we have derived a self-consistent model describing the dynamics of a collisional rf sheath driven by a sinusoidal current source. Numerical results have been obtained for the dependence of ion density, ion kinetic energy, sheath thickness, and sheath electric field, on the collision parameter and the current source parameter.

A new method for determining reference compensating currents of the three-phase shunt active power filter

Among various solutions to electric power quality problems, the use of a shunt active power filter (SAPF) has been proven as an effective method to compensate reactive power and to mitigate harmonic currents of nonlinear loads. When designing a SAPF, it is crucial to generate reference currents for determining actual compensating current injections to the point of common coupling. In contrast to the conventional instantaneous reactive power theory that needs coordinate transformations, the new method proposed in this paper is to determine reference compensating currents based on the balance of the instantaneous reactive and active power generated in the SAPF. It is shown that the proposed method is suitable for reactive and harmonic power compensation by using a SAPF. In addition to maintaining the sinusoidal source currents, this method also eliminates the need for installing an energy storage device for reactive power compensation as well as the DC source for the harmonic compensation in the active power filter. Therefore, a simpler design of the SAPF with the minimal line losses can be expected.

DYNAMICAL MODEL OF THE RADIO-FREQUENCY PLASMA SHEATH

A self-consistent model for the dynamics of the capacitive radio-frequency (RF) plasma sheath driven by a sinusoidal current source is obtained under the assumptions of time-dependent,collisionless ion motion and inertialess electrons. The model consists of fluid equations describing the charge transport in the sheath coupled to an equivalent circuit model of the sheath to predict the characteristics of it at any RF frequency. Some numerical results have been obtained for the instantaneous sheath thickness, the instantaneous voltage and the ion flux density on the substrate, etc. It has been shown that when the RF frequency is less than the ion plasma frequency, the ion flux density will strongly depend on the time.

Design sensitivity of transient electro-thermal problems for the specific temperature distribution

This paper presents a design sensitivity algorithm for the temperature distribution control in transient induction heating problems that require the electro-thermal analysis. It is assumed that the induction heating system is in the steady state electromagnetically and in the transient state thermally, and it is driven by a sinusoidal current source. The eddy current and the temperature distribution are obtained using the 2D finite element method. In this paper, the design goal is to have the desired temperature distribution on a surface of heated metal. The steepest descent method is used as an optimization algorithm.