1,721,105 research outputs found
A hexagonal hysteresis space vector current controller for single Z-source network multilevel inverter with capacitor balancing
No full textZ-source neutral-point clamped multilevel inverter (Z-NP-MLI) used in solar grid connected applications due to their better performance related to conventional inverters. Normally, current controller based Pulse Width Modulation (PWM) approach is expected for any grid connected system. The space vector pulse width modulation (SVPWM) strategy is a prominent modulation technique for Z-source multilevel inverters (MLIs) due to their appropriate voltage vector selection opportunity. Previous publications have shown the control of a ZNPMLI inverter using the SVPWM with and without modification of shoot through switching. However, the current controller based SVPWM is not attempted. This paper presents hexagonal space vector hysteresis current control (SVHCC) for ZNPMLI with DC-link capacitors balancing. This proposed SVHCC scheme uses reduced shoot through switching and finding the current reference based on the error. With respect to the error vector position, the choice of the adjacent vector is acted to minimize the error vector. In addition to the error vector selection, the capacitor voltage is also equilibrated by controlling the degree of freedom existing in selecting the switching vectors. The proposed scheme is asserted through MATLAB/Simulink and validated. The results are confirming the advantages of the proposed current control method and the line voltage and output current THD profile is lesser than conventional methods
An Adaptive Overcurrent Coordination Scheme to Improve Relay Sensitivity and Overcome Drawbacks due to Distributed Generation in Smart Grids
Full text linkDistributed Generation (DG) brought new challenges for protection engineers since standard relay settings of traditional system may no longer function properly under increasing presence of DG. The extreme case is coordination loss between primary and backup relays. The directional overcurrent relay (DOCR) which is the most implemented protective device in the electrical network also suffers performance degradation in presence of DG.
Therefore, this paper proposes the mitigation of DG impact on DOCR coordination employing adaptive protection scheme (APS) using differential evolution algorithm (DE) while improving overall sensitivity of relays .
The impacts of DG prior and after the application of APS are presented based on interconnected 6 bus and IEEE 14 bus system. As a consequence, general sensitivity improvement and mitigation scheme is proposed
Protection Interface Concept for LV Grids with an Efficient Dynamic Voltage Restorer
Full text linkPower quality (PQ) issues are often the reason for malfunctions and interruptions in the low-voltage (LV) utility grid. Protection from voltage sags and swells can be achieved using dynamic voltage restorer (DVR) circuits. The diffusion of grid scale energy storage has renewed interest for battery-fed DVR converters for voltage support, where sensitive loads are connected to the grid. At the same time, the next generation smart grid calls for the design of efficient and compact power converters with minimum impact on the grid. In this paper, a concept design for a battery-fed DVR is proposed with particular focus on energy efficiency and power density. The layout, operation and control strategy of the converter are presented and supported by simulation results. The study lays the basis for the implementation of a 30-kVA prototype
Zdjęcia pracowników Zakładu Elektrotechniki Teoretycznej
No full textSiedzą od lewej: Leszek Peszyński, Adam Gubański, Piotr Ruczewski, prof. Tadeusz Łobos, prof. Adam Skopec, Jarosław Szymańda, Czesław Stec. Stoją: Tomasz Sikorski, Jacek Rezmer, Paweł Kostyła, Zbigniew Leonowicz, Zbigniew Wacławek, Przemysław Janik, Lesław Ładniak
Mitigating the impact of distributed generation on directional overcurrent relay coordination by adaptive protection scheme
No full textDistributed Generation (DG) brought new challenges for protection engineers since standard relay settings of traditional system may no longer function correctly under the new conditions of DG. The extreme case is coordination loss between primary and backup relays. The directional overcurrent relay (DOCR) which is the most implemented protection device in the electrical network also suffers performance degradation in presence of DG. Therefore, the paper proposes the mitigation of DG impact on DOCR coordination employing adaptive protection scheme (APS) using differential evolution algorithm (DE). The impacts of DG prior and after the application of APS are presented and a new mitigation scheme is proposed
Investigation of Machine Learning Classifiers for Diagnostics of Induction Motors
No full textModern shipboard SCADA systems monitoring many thousands of parameters of shipboard equipment. These systems arrange parameters, monitor ranges and dynamics of their changes. The collected information provides control and diagnostics of ship systems and equipment. Induction electric drives and induction motors are the largest part of ships electrical equipment. The article proposes to use a machine learning classifier for diagnosing induction motors. Using the proposed universal model of an induction motor, it is possible to simulate any motor malfunctions: in the stator, in the rotor, in the mechanical part. A part of the diagnostics of an induction motor obtained as a result of simulations and machine learning is presented.</p
Comparative analysis of common MPPT techniques for solar PV system with soft switched, interleaved isolated converter
No full textThis paper presents the comparative analysis of most commonly used Maximum Power Point Tracking (MPPT) techniques viz Open Circuit Voltage (OCV), Perturb and Observe (PnO) and Incremental Conductance (INC) methods that are capable of extracting maximum power from the PV generation system with Soft Switched Interleaved Flyback(SSIFB) converter. The OCV technique is an indirect MPPT method that tracks the Maximum Power Point (MPP) using empirical data or mathematical expressions with numerical corrections and approximations. The direct methods such as PnO and INC techniques measure the actual instantaneous values of PV voltage and PV current to seek the MPP. The steady state performance of each of the MPPT algorithms on PV-SSIFB system under different solar irradiations is compared in terms of accuracy, MPPT efficiency and tracking speed. MATLAB/SIMULINK software is used to simulate and investigate the suitability and limitations of the PV - SSIFB system implemented with MPPT algorithm. The simulation results prove that the OCV MPPT method provides an effective MPP tracking at low irradiations and INC MPPT method offers the better steady state performance at medium and higher irradiations
Investigating the effects of selecting different slack bus on power systems
No full textThe load-flow study is a numerical analysis of the flow of electric power in an interconnected system in power engineering. Simplified notation such as the one-line diagram and per-unit system is used for power-flow study and focuses on various features of AC power parameters, such as voltages, voltage angles, real power and reactive power. It analyses the power systems in normal steady-state operation. So, the load flow studies play a major role in analyzing of the power systems. Generally, power system buses are categorized into three classes named load bus, power grid bus and slack bus or swing bus. In fact, slack buses in the power system are chosen among PV buses and also voltage value and phase angle of slack buses must be set 1 and 0, respectively. In this study, analysis of power flow was performed on six bus bar system using Gauss Seidel method. The study analyzed the change of effects that come from choosing different slack buses to determine the critical stress points, voltage stability, in the multi-bus systems. At the beginning of the each power flow analysis, different busses which have generator were determined as the slack bus and the analysis was performed without increasing the load. The effects of changes in critical points were examined at the end of the all possible analysis
Advanced Control of the Dynamic Voltage Restorer for Mitigating Voltage Sags in Power Systems
Full text linkThe paper presents a vector control with two cascaded loops to improve the properties of Dynamic Voltage Restorer (DVR) to minimize Voltage Sags on the grid. Thereby, a vector controlled structure was built on the rotating dq-coordinate system with the combination of voltage control and the current control. The proposed DVR control method is modelled using MATLAB-Simulink. It is tested using balanced/unbalanced voltage sags as well as fluctuant and distorted voltages. As a result, by using this controlling method, the dynamic characteristics of the system have been improved significantly. The system performed with higher accuracy, faster response and lower distortion in the voltage sags compensation. The paper presents real time experimental results to verify the performance of the proposed method in real environments
Configurations of Modified SEPIC Converter with Switched Inductor Module (MSCsI) for Photovoltaic Application: Part-II
No full textThe proposed work is extended configurations of Modified SEPIC Converter (MSC) and Modified SEPIC Converter with Switched Module (MSCSI). The proposed three configurations are derived by replacing two inductor of MSC by two Switched Inductor (SI) modules, namely Modified SEPIC Converter with XYL configuration (MSCSI-XYL), Modified SEPIC Converter with LYZ configuration (MSCSI-LYZ) and Modified SEPIC Converter with XLZ configuration (MSCSI-XLZ) to improve or increase the overall gain of the converter. The key feature of proposed configuration is: (i) single switch topologies, (ii) no reverse current flow from load to source due to large inductor at the input side, (iii) high voltage conversion ratio. The detailed analysis of three configurations is done in terms of component count, voltage conversion ratio and efficiency. The mathematical analysis and simulation results validates the functionality of three configurations
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