Three-phase Impedance Research Articles

Low-Cost Maximum Power Point Tracking Strategy and Protection Circuit Applied to an Ayanz Wind Turbine with Screw Blades

This paper provides three different research contributions applied to a Wind Turbine patented in 1606 by the inventor Jerónimo de Ayanz y Beaumont. The windmill under study is the Ayanz Wind Turbine with screw blades. The first contribution consists of an experimental characterization of the Ayanz Wind Turbine, incorporating the enclosure proposed at the patent and showing that the efficiency of the wind turbine is increased between 70% and 90% due to the enclosure being employed. As not many details about the shape of the screw blades are provided at the patent, in this article the nowadays well-studied and commercially available Archimedes Spiral Wind Turbine blade is utilized. It has been observed that by using an enclosure with a cylindrical shape, not only the efficiency of the wind turbine is increased, but the visual impact is reduced as seeing the blades rotating is avoided, which is a very important fact for many potential individual users of this wind turbine. In addition, it also enables the use of a protective mesh for birds, almost totally reducing the probability of bird deaths. The second contribution consists in a simple and low-cost Maximum Power Point Tracking (MPPT) strategy for the wind turbine, which only uses an AC three-phase impedance to capture the maximum energy from the wind, enabling to eliminate the DC-DC converter and microprocessor employed typically for this purpose. Due to this, the cost, complexity, failure rate, and power losses of the electronic power circuit are reduced which is very welcomed for small-scale wind turbines. Finally, the last contribution is a protection electronic circuit that fulfills several objectives: to brake the wind turbine under high winds and to disconnect and protect it when over-currents occur and when the voltage range of the batteries connected to the wind turbine is outside their safety range.

Equivalent DC impedance of a three-phase impedance through an inverter

Equivalent DC impedance of a three-phase impedance through an inverter

Simulation study of pulse width modulation schemes for three-phase impedance source inverter

To avoid a short circuit of the input direct current (DC). source, a 3-phase inverter cannot run two switches in the same leg at a time, and it always operates in buck mode, with the output voltage being less than the input voltage. The Impedance source inverter features a feature that allows both switches in one leg to operate at the same time, and it can operate in buck/boost mode, which means the output voltage can be greater than the input voltage depending on the shoot-through time. In the literature, there are a few pulse width modulation (PWM) techniques for Impedance source inverter control. This research includes a simulation study as well as an examination of existing PWM schemes in the literature, as well as a proposal for TESVPWM for inverters. The inverter performance has evaluated using total harmonic distortion and fundamental components, validating by simulation findings.

Impedance Modeling and Stability Analysis of Three-Phase Four-Wire Inverter with Grid-Connected Operation

With the continuous penetration and development of renewable energy power generation, distributed grids and microgrids are becoming increasingly important in power systems. In the distribution networks and microgrids, the grid impedance is comparatively large and cannot be ignored. Usually, the parallel compensation is used to improve the grid quality. In these three-phase four-wire power systems, analyzing the impedance characteristics of the grid-connected inverter is vital to carry out the small-signal stability analysis. Thus, it is vital to consider the influence of the zero-sequence component in addition to the positive-sequence component and the negative-sequence component when it comes to analyzing system stability. In this paper, the impedances of three-phase four-wire split capacitor inverter and three-phase four-leg inverter are established. Based on the achieved impedance, the similarities and differences between the impedances of three-phase four-wire split capacitor inverter and impedance of three-phase four-leg inverter are studied. The main difference is reflected in zero-sequence impedance. Additionally, the zero-sequence impedance characteristics and the dominating factors deciding the zero-sequence impedance are analyzed. Then, the stability of the system considering the grid impedance and impedance of three-phase four-wire inverter is investigated by separately considering the stability of the positive–negative-sequence component and the stability of the zero-sequence component. Several cases of small-signal instability caused by the positive–negative-sequence component or zero-sequence component are revealed. The experimental results validate the theoretical analysis.

Comparing the Performance of Induction Machine Drive with Different Rotor-Impedance Profiles

This paper compares the performance of a wound rotor induction motor drive (WRIM) with two rotor impedance profiles. The first system involves a diode rectifier followed by variable impedance in the rotor circuit. The second system involves a three-phase variable impedance in the rotor circuit. The comparison concerns the magnitude of starting transients of stator and rotor voltages and currents, the transients settling time of the stator and rotor voltages and currents, the stator and rotor consumed active and reactive power, the electrical torque, and the stable range of operation at sub-and super-synchronous speeds. This comparison is helpful for deciding the more efficient drive to be utilized, the drive with lower harmonics in currents and voltages, and the drive allowing wider speed stable operation range. Better results are obtained for the drive with the three-phase variable impedance connected to the rotor circuit.

A novel impedance source inverter topology with active front-end for AC drives

A unique impedance Source Inverter with an Active Front-End is proposed in this paper, that can be used for controlling AC Drives. There are a number of modulation schemes that may be used with the three-phase impedance source inverters, ultimate reduction in the switching losses makes the discontinuous modulation schemes seem most appropriate. The discontinuous modulation schemes are differentiated into two classes based on the technique used for achieving shoot-through (ST) state: single-phase-leg ST-based and three-phase-leg ST-based (3P) discontinuous modulation schemes. In this paper, we discuss the improvements in Single Phase Maximum Boost Discontinuous Space Vector modulation (1P/MB/DSVM) scheme under similar operating conditions, by simplifying gate signal generation and improving the conversion efficiency. A simulated analysis and comparison of the conventional and the enhanced 1P/MB/DSVM schemes is also discussed using PLECS. Lastly, verification of the simulation outcomes and reported analysis is carried out by making use of a three-phase quasi-Z-source inverter (qZSI) prototype which demonstrates improvement in conversion efficiency, utilizing the refined 1P/MB/DSVM scheme.

Modulation Schemes of the Three-Phase Impedance Source Inverters—Part I: Classification and Review

Impedance source inverters have experienced a fast evolution since the first release of the Z-source inverter in 2003. This evolution is not limited to improving the structure of the different topologies but also includes their modulation and control schemes in order to reinforce their performance from many perspectives. Accordingly, many modulation schemes have been proposed in different research activities, but the full differences among these modulation schemes, including their effect on the switching losses, are not clear yet to the researchers. Hence, this research activity is aimed at introducing a comprehensive review of these different modulation schemes employed for the three-phase impedance source inverters, which is enhanced with a comparative assessment. In this paper, different modulation schemes are classified and reviewed, introducing an important benchmark in order to identify the basic differences between these modulation schemes. In other words, from this paper, the concept of classifying the different modulation schemes and the mandatory equations to implement each scheme can easily be drawn. Moreover, this review is essential for the next part, i.e., Part II, in which a comparative assessment is introduced.

Modulation Schemes of the Three-Phase Impedance Source Inverters—Part II: Comparative Assessment

Three-phase impedance source inverters can be modulated using many modulation schemes, which are basically classified into two categories: three-phase-leg shoot-through-based (3P) and single-phase-leg shoot-through-based (1P) modulation schemes. These different modulation schemes have been comprehensively reviewed in Part I. Hence, in this paper, a comparative assessment among these different modulation schemes is introduced using the conventional Z-source inverter (ZSI). In this comparison, the ZSI voltage gain and stresses, current stresses, effective switching frequency of its different parts, spectrum of its output voltage, and switching losses are considered for each modulation scheme. Such comparative assessment introduces an effective benchmark for the researchers in order to determine the differences among these various modulation schemes, and easily select the appropriate one for their application. Finally, the state-of-the-art modulation schemes are experimentally assessed using a 3-kVA three-phase ZSI, where the shown results are consistent with the presented discussions and comparisons.

Can the delta-wye transformation convert an ordinary passive reciprocal three-phase impedance system into another with negative resistors?

Can the delta-wye transformation convert an ordinary passive reciprocal three-phase impedance system into another with negative resistors?

Fault location in distribution systems with DG based on similarity of fault impedance

This paper presents a new method for locating a fault in distribution systems using the similarity of fault impedance. A four-step approach is proposed to locate the fault in the networks. First, pre- and during-fault voltages from smart feeders along the primary feeders are measured. Second, three-phase impedance to calculate fault current corresponding to voltage deviation from each smart meter is achieved. Third, a relation between fault current and fault impedance for each type of fault is extracted. Finally, based on the similarity of the estimated fault impedance for each bus, an error index is calculated. Moreover, an auxiliary process is utilized to analyze the estimated fault impedance. The proposed method uses both smart meters and phasor measurement units to obtain voltage sag. Distributed generation and loads are modeled as constant impedances and then they are considered in the three-phase impedance matrix. The suggested approach is evaluated in the IEEE 34-bus test distribution network, which is simulated in the PSCAD/EMTDC environment. The obtained numerical results confirm the acceptable accuracy of the proposed methodology for all types of faults with various fault resistances.

A Fault Area Location Method in Distribution Network With DG

To precisely locate the grounded fault area in distribution network with DG, a new grounded fault area location algorithm based on three-phase impedance model and fault features in distribution network with DG is proposed in this paper. This method establishes three-phase impedance model if the distribution network with DG, analyzes and extracts the fault characteristics on the basis of the three phase impedance model of distribution network with DG. According to the characteristic of the feature value in the fault point, this method traverses all the nodes and gets the fault associated nodes. The method proposed in this paper was tested in a sixty nodal distribution system with six DGs, the result of the method verifies that the method can precisely locate the grounded fault area in distribution network with DG. DOI: http://dx.doi.org/10.11591/telkomnika.v11i11.3548 Full Text: PDF

An Islanding Detection Method Based on Dual-Frequency Harmonic Current Injection Under Grid Impedance Unbalanced Condition

This paper proposes a three-phase grid impedance detection method based on dual-frequency harmonic current injection for islanding detection. Grid impedance detection based on single harmonic current injection is reliable in three-phase impedance balanced grid. However, under impedance unbalanced condition, the harmonic voltage caused by the injected symmetric harmonic current is asymmetric, which affects the calculation of grid impedances and even leads to failed detection. The method based on dual-frequency harmonic current injection is injecting two non-characteristic symmetric harmonic currents, and then according to the different harmonic voltages caused by different frequency harmonic currents, all three-phase impedances can be calculated accurately. The implementing algorithm of the presented method is derived and its performance is analyzed in detail. Simulation and experiments are carried out under grid impedance balanced and unbalanced conditions. Theoretical analysis and experiment results proved that the proposed method is feasible.

Fault Tolerant Control in Z-Source Inverter Fed Induction Motor

This paper discusses about the detection and replacement of the switches in inverter under fault. The detection of switch is done through measuring the phase and line voltages of inverter. The replacement of the open switch is done through the extra arm provided in the circuit. The firing of the extra arm is done by detecting the open switch fault and interrupting the processor to provide the firing to the extra arm switch. This paper gives simple and effective detection and replacement of open switch. The replacement of switch will be done without stopping the whole system and saves the unspecified time. Simulation results are provided to demonstrate the detection and replacement. A feasible test is implemented by building a proto type three-phase impedance source inverter, which is designed and controlled on the basis of proposed considerations. It is verified from the practical point of view that this new approach is more effective and acceptable to minimize the distortion. Keywords: SMPS – Switch Mode Power Supply, pulse width modulation (PWM), VSI –Voltage Source Inverter. DOI: http://dx.doi.org/10.11591/ijpeds.v1i1.67

FLC based adjustable speed drives for power quality enhancement

This study describes a new approach based on fuzzy algorithm to suppress the current harmonic contents in the output of an inverter. Inverter system using fuzzy controllers provide ride-through capability during voltage sags, reduces harmonics, improves power factor and high reliability, less electromagnetic interference noise, low common mode noise and extends output voltage range. A feasible test is implemented by building a model of three-phase impedance source inverter, which is designed and controlled on the basis of proposed considerations. It is verified from the practical point of view that these new approaches are more effective and acceptable to minimize the harmonic distortion and improves the quality of power. Due to the complex algorithm, their realization often calls for a compromise between cost and performance. The proposed optimizing strategies may be applied in variable-frequency dc-ac inverters, UPSs, and ac drives.

Computer aided analytical study of the transient operation of an exciter-alternator-rectifier set

The transient operation of a rectified output double-star synchronous machine excited by a single-star rectified output synchronous generator is studied. An equivalent transient three-phase impedance is defined. It accounts for the particular structure of the rectifier bridge, including the effect of overlapping. All quantities are given by rational transfer functions including polynomials of high degree (up to 27). All expressions are analytically derived from Park equations of the machines and their loads. This is achieved by means of a program which can handle the multiplications and additions of the polynomials, and step-by-step integration techniques are avoided. Experimental verification was obtained in two cases. The field voltage of the exciter was suddenly varied, and the load impedance was suddenly changed. In both cases, theoretical results tally with experimental curves.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Development of a three-phase bus impedance matrix in the complex frequency domain for transient analysis in unbalanced distribution systems

Abstract Untransposed feeders, a combination of single-phase, two-phase and unequal three-phase loads impose imbalance in distribution systems. This paper presents a generalized computer technique to develop the three-phase bus impedance matrix Z bus3 (s) in the complex frequency domain. The method utilizes the phase-frame representation of the network elements. Consequently, the transient response due to line removals or additions, asymmetrical shunt faults, series faults, and capacitor switching can be simulated by modifying Z bus3 (s) . Thus, the proposed method makes it possible to analyze a power system network considering imbalance and the frequency dependence of the feeder parameters, and to obtain the transient response due to fault or capacitor switching conditions in the presence of harmonic distortion.

A generalized computer technique for the development of the three-phase impedance matrix for unbalanced power systems

Abstract This paper presents the development of the three-phase bus impedance and bus admittance matrices for unbalanced power systems. The imbalance conditioned by large single-phase loads, untransposed feeders, bundled conductors, etc., is reflected in the polyphase impedance or admittance matrix. The method utilizes the phase frame representation of network elements. Consequently, line removals or additions, impedance changes, conductor and phase openings can be simulated easily by modifying the bus impedance matrix. Thus, the proposed method makes it possible to analyze any type of single- or three-phase loads and unequal mutual coupling between the phases for large-scale power systems.

Analysis of Distribution Line Carrier Propagation Using the Bus Impedance Matrix

Distribution line carrier (DLC) is a communication system used in automated distribution systems to transmit data between the substation and certain locations on the distribution primary and secondary. Extensive DLC propagation measurements have shown that the propagation of signals on a power distribution line is difficult to predict because of the complexity and variability of distribution systems. This paper presents an efficient and comprehensive analytical tool for predicting DLC signal propagation over complex distribution systems. This paper develops a three-phase bus impedance matrix, which consists of 3×3 transfer impedance submatrices. These submatrices represent the general transfer function which relates the three-phase received voltage vector at any point of interest to any three-phase transmitted (injected) current vector at any point of interest. The method described here is an extension of the three-phase bus impedance approach used for 60 Hz power distribution.