A Three-Phase Model Predictive Approach for Smooth Line-Switching in Islanded Microgrids

2021 ◽  
Author(s):  
Evangelos Pompodakis ◽  
Georgios C. Kryonidis ◽  
Minas Alexiadis
Keyword(s):  
Phase Model ◽  
Positive Sequence ◽  
Distributed Generators ◽  
Three Phase ◽  
Zero Sequence ◽  
Node Network ◽  
Switching Action ◽  
Switching Method ◽  
Line Switching ◽  
Distinct Features

This paper deals with a new line-switching method that facilitates the network reconfiguration of islanded microgrids. Its distinct features include the ability to handle network asymmetries and the minimization of the line current during the switching action. This is attained by developing a sensitive-based three-phase model predictive method to determine the operating set-points of the distributed generators (DGs) that minimize the current of the candidate line participating in the switching action. These set-points correspond to the positive-sequence powers as well as the negative- and zero-sequence currents of all DGs. Furthermore, the network constraints such as voltage limits and power limits of DGs are always satisfied. Simulations are performed in a balanced 33-bus islanded network as well as in the unbalanced IEEE 8500-node network to evaluate the performance of the proposed method.

A Three-Phase Model Predictive Approach for Smooth Line-Switching in Islanded Microgrids

2021 ◽  
Author(s):  
Evangelos Pompodakis ◽  
Georgios C. Kryonidis ◽  
Minas Alexiadis
Keyword(s):  
Phase Model ◽  
Positive Sequence ◽  
Distributed Generators ◽  
Three Phase ◽  
Zero Sequence ◽  
Node Network ◽  
Switching Action ◽  
Switching Method ◽  
Line Switching ◽  
Distinct Features

This paper deals with a new line-switching method that facilitates the network reconfiguration of islanded microgrids. Its distinct features include the ability to handle network asymmetries and the minimization of the line current during the switching action. This is attained by developing a sensitive-based three-phase model predictive method to determine the operating set-points of the distributed generators (DGs) that minimize the current of the candidate line participating in the switching action. These set-points correspond to the positive-sequence powers as well as the negative- and zero-sequence currents of all DGs. Furthermore, the network constraints such as voltage limits and power limits of DGs are always satisfied. Simulations are performed in a balanced 33-bus islanded network as well as in the unbalanced IEEE 8500-node network to evaluate the performance of the proposed method.

Detection of symmetrical fault and discrimination from power swing using MOPSVC approach

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Kumarraja Andanapalli ◽  
Monalisa Biswal
Keyword(s):  
Power System ◽  
Positive Sequence ◽  
Distance Relay ◽  
Security Issues ◽  
Power Swing ◽  
Three Phase ◽  
Sequence Components ◽  
Zero Sequence ◽  
Simulation Task ◽  
Eastern Regional

Abstract Distance relay are designed with swing blocking/tripping logic to maintain reliable and secure operation of power system. To prevent this from happening, the relay is functioned with a power swing blocking (PSB) logic. However, ensuring proper detection to swing event requires to overcome from the dependable situation such as three-phase fault. The relay refuses to behave normally if both swing and three-phase fault occur simultaneously. Reliable setting is essential to generate trip/block command. Unsymmetrical faults are easily detected during the swing condition due to the presence of negative and zero sequence components, but such components are absent in the case of symmetrical/three-phase fault. As a result, symmetrical fault under blocking condition is unidentified many a times by the distance relay, arising security issues. To improve the relay operation during swing and symmetrical fault conditions, a MOPSVC (multiplication of positive sequence voltage and current) based index is developed in this work. The MOPSVC index helps to discern power swing from three-phase fault. To test the efficacy of the method, a 230 kV, 50 Hz two-area four machine system, and Indian Eastern Regional Grid (IERG) network are considered. Simulation task is conducted using EMTDC/PSCAD software. To investigate the performance of the proposed method, various swing phenomena, faults, CT saturation, switching transients, and the presence of noise cases are considered, and the results demonstrate the robustness of the proposed algorithm. Responses under stressed power system conditions are also investigated, and a report on comparisons with existing methods is provided. Simulated results confirm that the proposed algorithm can balance the dependability and security aspects of the protection logic.

scholarly journals Unbalanced and Reactive Currents Compensation in Three-Phase Four-Wire Sinusoidal Power Systems

2020 ◽  
Vol 10 (5) ◽  
pp. 1764 ◽  
Author(s):  
Rafael Montoya-Mira ◽  
Pedro A. Blasco ◽  
José M. Diez ◽  
Rafael Montoya ◽  
Miguel J. Reig
Keyword(s):  
Power Systems ◽  
Positive Sequence ◽  
Electrical System ◽  
System A ◽  
Compensation Methods ◽  
Three Phase ◽  
Zero Sequence ◽  
Unbalanced Loads ◽  
Wire System

In an unbalanced linear three-phase electrical system, there are inefficient powers that increase the apparent power supplied by the network, line losses, machine malfunctions, etc. These inefficiencies are mainly due to the use of unbalanced loads. Unlike a three-wire unbalanced system, a four-wire system has zero sequence currents that circulate through the neutral wire and can be compensated by means of compensation equipment, which prevents it from being delivered by the network. To design a compensator that works with unbalanced voltages, it is necessary to consider the interactions between it and the other compensators used to compensate for negative-sequence currents and positive-sequence reactive currents. In this paper, through passive compensation, a new method is proposed to develop the zero sequence current compensation equipment. The method does not require iteration algorithms and is valid for unbalanced voltages. In addition, the interactions between all compensators are analyzed, and the necessary modifications in the calculations are proposed to obtain a total compensation. To facilitate the application of the method and demonstrate its validity, a case study is developed from a three-phase linear four-wire system with unbalanced voltages and loads. The results obtained are compared with other compensation methods that also use passive elements.

Transport of organochlorine pesticides in soil columns enhanced by dissolved organic carbon

1997 ◽  
Vol 35 (7) ◽  
pp. 139-145 ◽  
Author(s):  
Jiann-Yuan Ding ◽  
Shian-Chee Wu
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Organochlorine Pesticides ◽  
Transport Model ◽  
Phase Model ◽  
Soil Columns ◽  
Two Phase ◽  
Three Phase ◽  
Phase Transport ◽  
Remediation Of Soil

The objective of this study is to quantify the effects of humic acid solution infiltration on the transport of organochlorine pesticides (OCPs) in soil columns using a three-phase transport model. From experimental results, it is found that the dissolved organic carbon enhances the transport of OCPs in the soil columns. In the OCPs-only column, the concentration profiles of OCPs can be simulated well using a two-phase transport model with numerical method or analytical solution. In the OCPs-DOC column, the migrations of aldrin, DDT and its daughter compounds are faster than those in the OCPs-only column. The simulation with the three-phase model is more accurate than that with the two-phase model. In addition, significant decrease of the fluid pore velocities of the OCPs-DOC column was found. When DOC leachate is applied for remediation of soil or groundwater pollution, the decrease of mean pore velocities will be a crucial affecting factor.

scholarly journals Autocratisation by Term Limits Manipulation in Sub-Saharan Africa

2020 ◽  
Vol 55 (3) ◽  
pp. 228-250 ◽  
Author(s):  
Andrea Cassani
Keyword(s):  
Comparative Studies ◽  
Political Competition ◽  
Chief Executive ◽  
Term Limits ◽  
Sub Saharan Africa ◽  
Phase Model ◽  
Econometric Modelling ◽  
Three Phase ◽  
Sub Saharan ◽  
Personal Rule

Besides the introduction of multi-party elections, the sub-Saharan wave of democratic reforms of the 1990s encompassed the introduction of limits to the number of terms that a chief executive can serve. Executive term limits (ETLs) are key for democracy to advance in a continent with a legacy of personal rule. However, the manipulation of ETLs has become a recurring mode of autocratisation, through which African aspiring over-stayers weaken executive constraints, taint political competition, and limit citizens’ possibility to choose who governs. This article presents a three-phase model of autocratisation by ETL manipulation and, using new data, offers one of the first regional comparative studies of ETL manipulation in sub-Saharan Africa that rests on econometric modelling. The analysis leads to revisiting some previous findings on the drivers of ETL manipulation and highlights the relevance of other previously underestimated factors that may either discourage a leader from challenging ETLs or prevent their successful manipulation.

scholarly journals D-PMU and 5G-Network-Based Coordination Control Method for Three-Phase Imbalance Mitigation Units in the LVDN

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2754
Author(s):  
Mengmeng Xiao ◽  
Shaorong Wang ◽  
Zia Ullah
Keyword(s):  
Mobile Networks ◽  
Control Method ◽  
Low Voltage ◽  
Control Unit ◽  
Distribution Networks ◽  
Optimal Operation ◽  
Positive Sequence ◽  
Measurement Unit ◽  
Control Units ◽  
Three Phase

Three-phase imbalance is a long-term issue existing in low-voltage distribution networks (LVDNs), which consequently has an inverse impact on the safe and optimal operation of LVDNs. Recently, the increasing integration of single-phase distributed generations (DGs) and flexible loads has increased the probability of imbalance occurrence in LVDNs. To overcome the above challenges, this paper proposes a novel methodology based on the concept of "Active Asymmetry Energy-Absorbing (AAEA)" utilizing loads with a back-to-back converter, denoted as “AAEA Unit” in this paper. AAEA Units are deployed and coordinated to actively absorb asymmetry power among three phases for imbalance mitigation in LVDNs based on the high-precision, high-accuracy, and real-time distribution-level phasor measurement unit (D-PMU) data acquisition system and the 5th generation mobile networks (5G) communication channels. Furthermore, the control scheme of the proposed method includes three control units. Specifically, the positive-sequence control unit is designed to maintain the voltage of the DC-capacitor of the back-to-back converter. Likewise, the negative-sequence and zero-sequence control units are expected to mitigate the imbalanced current components. A simple imbalanced LVDN is modeled and tested in Simulink/Matlab (MathWorks, US). The obtained results demonstrate the effectiveness of the proposed methodology.

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