scholarly journals A Novel Multilevel DC-Link Three-Phase T-Type Inverter

Energies ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 4186
Author(s):  
Saddam Shueai Alnamer ◽  
Saad Mekhilef ◽  
Hazlie Mokhlis ◽  
Nadia M. L. Tan
Keyword(s):  
High Efficiency ◽  
Short Circuit ◽  
Multilevel Converters ◽  
Passive Components ◽  
Medium Voltage ◽  
Three Phase ◽  
Unbalanced Voltage ◽  
Flying Capacitors ◽  
Voltage Deviation ◽  
Current Commutation

This research proposes a four-level T-type inverter that is suitable for low-power applications. The presented topology outranks other types of inverters in terms of a smaller number of semiconductor devices, absence of passive components such as clamping diodes and flying capacitors, low switching and conduction losses, and high efficiency. The proposed topology is free from voltage deviation and unbalanced voltage occurrences that are present in other multilevel converters having clamping diodes or flying capacitors. The proposed inverter can extend to N levels using unequal dc-link voltage sources for medium-voltage application. The inverter employs the simple fundamental frequency staircase modulation technique. Moreover, this paper presents a current commutation strategy to prevent the occurrences of short circuit and minimizing the number of required switching devices and switching transitions, resulting in improving the efficiency of the inverter. This paper also analyses the theoretical converter losses showing lower switching and conduction losses when compared to existing four-level inverters. The experimental validation of the proposed inverter shows its operating feasibility and a low output voltage THD.

scholarly journals A Cascaded DC-AC-AC Grid-Tied Converter for PV Plants with AC-Link

Electronics ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 409
Author(s):  
Manuel A. Barrios ◽  
Víctor Cárdenas ◽  
Jose M. Sandoval ◽  
Josep M. Guerrero ◽  
Juan C. Vasquez
Keyword(s):  
Topological Structure ◽  
Low Voltage ◽  
Low Frequency ◽  
Medium Frequency ◽  
Multilevel Converters ◽  
Voltage Inverter ◽  
Medium Voltage ◽  
Three Phase ◽  
Three Stages ◽  
Ac Converters

Cascaded multilevel converters based on medium-frequency (MF) AC-links have been proposed as alternatives to the traditional low-voltage inverter, which uses a bulky low-frequency transformer step-up voltage to medium voltage (MV) levels. In this paper, a three-phase cascaded DC-AC-AC converter with AC-link for medium-voltage applications is proposed. Three stages integrate each DC-AC-AC converter (cell): a MF square voltage generator; a MF transformer with four windings; and an AC-AC converter. Then, k DC-AC-AC converters are cascaded to generate the multilevel topology. This converter’s topological structure avoids the per-phase imbalance; this simplifies the control and reduces the problem only to solve the per-cell unbalance. Two sets of simulations were performed to verify the converter’s operation (off-grid and grid-connected modes). Finally, the papers present two reduced preliminary laboratory prototypes, one validating the cascaded configuration and the other validating the three-phase configuration.

scholarly journals Microgrid Protection Strategy Based on the Autocorrelation of Current Envelopes Using the Squaring and Low-Pass Filtering Method

Energies ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2350 ◽  
Author(s):  
Shazia Baloch ◽  
Saeed Zaman Jamali ◽  
Khawaja Khalid Mehmood ◽  
Syed Basit Ali Bukhari ◽  
Muhammad Saeed Uz Zaman ◽  
...  
Keyword(s):  
Reactive Power ◽  
Short Circuit ◽  
Backup Protection ◽  
Medium Voltage ◽  
Protection Scheme ◽  
High Penetration ◽  
Islanded Operation ◽  
Three Phase ◽  
Low Pass ◽  
Efficient Protection

To resolve the protection issues caused by high penetration of distributed energy resources, this paper proposes an efficient protection scheme for microgrids based on the autocorrelation of three-phase current envelopes. The proposed strategy uses a squaring and low-pass filtering approach for evaluating the envelope of the current signal. Then, the variance of the autocorrelation function is used to extract the hidden information of the distorted envelope to detect the fault signatures in the microgrid. Furthermore, the reactive power is used for determining the fault direction. The performance of the proposed protection scheme was verified on a standard medium-voltage microgrid by performing simulations in the MATLAB/Simulink environment (Version: R2017b). The proposed scheme was shown to be easy to implement and have good performance under looped and radial configuration for both grid-connected and islanded operation modes. The simulation results showed that the scheme could not only detect, locate, classify, and isolate various types of short-circuit faults effectively but also provide backup protection in case of primary protection failure.

scholarly journals Differential method for damage location determining in 10 kV distribution networks with isolated neutral

2019 ◽  
Vol 124 ◽  
pp. 01003
Author(s):  
V. Kozlov ◽  
E. Kirzhatskikh ◽  
R. Giniatullin
Keyword(s):  
Transmission Lines ◽  
Short Circuit ◽  
Distribution Networks ◽  
Differential Method ◽  
Medium Voltage ◽  
Damage Location ◽  
Damage Repair ◽  
Three Phase ◽  
Isolated Neutral ◽  
Emergency Mode

Half of the length of all transmission lines (TL) are medium voltage networks. Single-line-to-ground short circuit (SLGSC) in distribution networks is the most common type of damage, accounting up to 70% of all types of damage. Faults in damage repair leads to an overvoltage of two healthy phases, resulting in double shorts, two-, three-phase shorts, which contributes to consumers’ disconnection. Remote damage location (DL) determination in tree-type networks is considered to be the most relevant, since these networks are spread over large areas, crossing rivers, ravines, lakes, forests, etc. This paper presents a differential method for DL determining based on steady-state voltage of damaged phase frequency. Measuring the parameters of emergency mode at the beginning and at the ends of 10kV TL allows compact stand-alone sensors using without their synchronization.

Electrical fault diagnosis in induction motors using local extremes analysis

2016 ◽  
Vol 22 (3) ◽  
pp. 321-332 ◽  
Author(s):  
Paulo Cezar Monteiro Lamim Filho ◽  
Fabiano Bianchini Batista ◽  
Robson Pederiva ◽  
Vinicius Augusto Diniz Silva
Keyword(s):  
Induction Motors ◽  
Short Circuit ◽  
Induction Machines ◽  
Time Sequence ◽  
Content Type ◽  
Three Phase ◽  
Unbalanced Voltage ◽  
Voltage Phase ◽  
Detection And Diagnosis ◽  
Original Time

Purpose – The purpose of this paper is to introduce an algorithm based only on local extreme analysis of a time sequence to further the detection and diagnosis of inter-turn short circuits and unbalanced voltage supply using vibration signals. Design/methodology/approach – The upper and lower extreme envelopes from a modulated and oscillatory time sequence present a particular characteristic being of, theoretically, symmetrical versions with regard to amplitude reflection around the time axis. Thus, one may say that they carry the same characteristics in terms of waveforms and, consequently, frequency content. These envelopes can easily be built by an interpolation process of the local extremes, maximums and minimums, from the original time sequence. Similar to modulator signals, they contain more detailed and useful information about the required electrical fault frequencies. Findings – Results show the efficiency of the proposed algorithm and its relevance to detecting and diagnosing faults in induction motors with the advantage of being a technique that is easy to implement in any computational code. Practical implications – A laboratory investigation carried out through an experimental setup for the study of faults, mainly related to the stator winding inter-turn short circuit and voltage phase unbalance, is presented. Originality/value – The main contribution of the work is the presentation of an alternative tool to demodulate signals which may be used in real applications like the detection of faults in three-phase induction machines.

Power Quality Analysis Software Based on LabVIEW

2014 ◽  
Vol 521 ◽  
pp. 173-177
Author(s):  
Long Guang Kong ◽  
Yong Zhou
Keyword(s):  
Power Quality ◽  
High Efficiency ◽  
Frequency Deviation ◽  
Quality Analysis ◽  
Analysis Software ◽  
Design And Development ◽  
Three Phase ◽  
Quality Analyzer ◽  
Voltage Deviation ◽  
Power Quality Analysis

This paper introduces the design and development of a LabVIEW-based power quality analysis software, focusing on the four important indicators of power quality: frequency deviation,voltage deviation, three-phase unbalance and harmonics. Accuracy of the software is proven through experiment, demonstrating the high efficiency of LabVIEW in the development of power quality analyzer.

scholarly journals A Novel Cascaded Multilevel Converter Topology Based on Three-Phase Cells—CHB-SDC

Energies ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4789
Author(s):  
Renner Sartório Camargo ◽  
Daniel Santamargarita Mayor ◽  
Alvar Mayor Miguel ◽  
Emilio José Bueno ◽  
Lucas Frizera Encarnação
Keyword(s):  
Model Predictive Control ◽  
Predictive Control ◽  
Low Voltage ◽  
Short Circuit ◽  
Vector Model ◽  
Circuit Switching ◽  
Multilevel Converter ◽  
Multilevel Converters ◽  
Three Phase ◽  
Converter Topology

This paper proposes a new cascaded multilevel converter topology based on three-phase H bridge cells with a common DC-link structure. The proposed multilevel converter topology main advantages, compared with literature renowned multilevel converters topologies, are discussed in the paper, such as modularity, construction, implementation cost, and DC voltage ripple mitigation. Despite presenting an elementary structure and easy implementation, the use of classic PWM switching strategies is not feasible for this topology, causing the appearance of several short-circuit states between its capacitors. Thus, a graph theory algorithm combined with a model predictive control is also proposed in this work to identify and avoid the new cascaded multilevel converter short-circuit switching states and, concomitantly, guaranteeing the converter output power quality. In order to validate the presented topology applicability, a low voltage synchronous static compensators (STATCOM) with an optimal switching vector model predictive control (OSV-MPC) is implemented in a hardware-in-the-loop platform. The real-time experimental results prove the proposed multilevel topology and the OSV-MPC control strategy effectiveness.

Advance Protection for Three Phase Induction Motor using Microcontroller Atmega32

2018 ◽  
Vol 8 (1) ◽  
pp. 172
Author(s):  
Karan S Belsare ◽  
Gajanan D Patil
Keyword(s):  
Induction Motor ◽  
Low Cost ◽  
Short Circuit ◽  
Cost Factor ◽  
Protection Scheme ◽  
Three Phase ◽  
The Cost

A low cost and reliable protection scheme has been designed for a three phase induction motor against unbalance voltages, under voltage, over voltage, short circuit and overheating protection. Taking the cost factor into consideration the design has been proposed using microcontroller Atmega32, MOSFETs, relays, small CTs and PTs. However the sensitivity of the protection scheme has been not compromised. The design has been tested online in the laboratory for small motors and the same can be implemented for larger motors by replacing the i-v converters and relays of suitable ratings.

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