scholarly journals An Improved Centralized Control Structure for Compensation of Voltage Distortions in Inverter-Based Microgrids

Energies ◽  
2018 ◽  
Vol 11 (7) ◽  
pp. 1862 ◽  
Author(s):  
Morteza Afrasiabi ◽  
Esmaeel Rokrok
Keyword(s):  
Distribution System ◽  
Distribution Systems ◽  
Hierarchical Control ◽  
Control Level ◽  
Measurement Unit ◽  
Centralized Control ◽  
Secondary Control ◽  
Voltage Unbalance ◽  
Control Scheme ◽  
Centralized Controller

Recently, increased use of non-linear loads has intensified the harmonic distortion and voltage unbalance in distribution systems. Inverter Based Distributed Generators (IBDGs) can be employed as distributed compensators to improve the power quality, as well as to supply distribution systems. In this paper, an enhanced hierarchical control scheme for the compensation of voltage disturbance in an AC Micro Grid (MG) that includes of two control levels is proposed. The secondary control level is performed by a centralized controller. Data of voltage harmonics and voltage unbalance at the MG Sensitive Load Bus (SLB) is sent to the centralized controller by a measurement unit. A general case with a combined voltage harmonic and unbalance distortion is considered. The compensation coefficients for IBDG units are computed by the centralized controller, and reference commands are sent to the local controllers of the IBDG units that act as a primary level of control. In the secondary control level, harmonic analysis is performed for the MG in order to provide a guide for properly assigning the harmonics and unbalance compensation priorities to IBDGs at different locations in the distribution system. Some buses have more participation in exciting the MG resonance modes; therefore, larger harmonic compensation factors are considered for the IBDGs that are near to these buses. For other IBDGs, the voltage unbalance compensation factor is selected bigger. The control system of the IBDGs mainly includes a current controller, a virtual damping resistor loop, and a load compensation block. Effectiveness of the proposed control scheme is demonstrated through simulation studies.

scholarly journals Decentralized Fast Delayed Signal Cancelation Secondary Control for Low Voltage Ride-Through Application in Grid Supporting Grid Feeding Microgrid

2021 ◽  
Vol 9 ◽  
Author(s):  
Elutunji Buraimoh ◽  
Innocent E. Davidson ◽  
Fernando Martinez-Rodrigo
Keyword(s):  
Low Voltage ◽  
Hierarchical Control ◽  
Voltage Regulation ◽  
Power Sharing ◽  
Primary Control ◽  
Distributed Energy ◽  
Secondary Control ◽  
Low Voltage Ride Through ◽  
Control Scheme ◽  
Real Time Digital Simulator

In this study, a distributed secondary control is proposed alongside the conventional primary control to form a hierarchical control scheme for the Low Voltage Ride-Through (LVRT) control and applications in the inverter-based microgrid. The secondary control utilizes a fast Delayed Signal Cancelation (DSC) algorithm for the secondary control loop to control the reactive and active power reference by controlling the sequences generated. The microgrid consists of four Distributed Energy Resources (DER) sources interfaced to the grid through interfacing inverters coordinated by droop for effective power-sharing according to capacities. The droop also allows for grid supporting application for microgrid’s participation in frequency and voltage regulation in the main grid. The proposed decentralized fast DSC performance is evaluated with centralized secondary and traditional primary control using OPAL-RT Lab computation and MATLAB/SIMULINK graphical user interface for offline simulations and real-time digital simulator verification. This study presents and discusses the results.

scholarly journals A Comprehensive Survey on Phasor Measurement Unit Applications in Distribution Systems

Energies ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 4552 ◽  
Author(s):  
Mojgan Hojabri ◽  
Ulrich Dersch ◽  
Antonios Papaemmanouil ◽  
Peter Bosshart
Keyword(s):  
Power Systems ◽  
Data Quality ◽  
Distribution System ◽  
Distribution Systems ◽  
Measurement Unit ◽  
Wide Area Monitoring ◽  
Phasor Measurement ◽  
Comprehensive Survey ◽  
Measurement Units ◽  
Area Monitoring

Synchrophasor technology opens a new window for power system observability. Phasor measurement units (PMUs) are able to provide synchronized and accurate data such as frequency, voltage and current phasors, vibration, and temperature for power systems. Thus, the utilization of PMUs has become quite important in the fast monitoring, protection, and even the control of new and complicated distribution systems. However, data quality and communication are the main concerns for synchrophasor applications. This study presents a comprehensive survey on wide-area monitoring systems (WAMSs), PMUs, data quality, and communication requirements for the main applications of PMUs in a modern and smart distribution system with a variety of energy resources and loads. In addition, the main challenges for PMU applications as well as opportunities for the future use of this intelligent device in distribution systems will be presented in this paper.

scholarly journals Coordinated single-phase control scheme for voltage unbalance reduction in low voltage network

2017 ◽  
Vol 375 (2100) ◽  
pp. 20160308 ◽  
Author(s):  
Deepak Pullaguram ◽  
Sukumar Mishra ◽  
Nilanjan Senroy
Keyword(s):  
Distribution Systems ◽  
Single Phase ◽  
Reactive Power ◽  
Low Voltage ◽  
Power Sharing ◽  
Voltage Unbalance ◽  
Line Configuration ◽  
Control Scheme ◽  
Multi Agent ◽  
Proper Power

Low voltage (LV) distribution systems are typically unbalanced in nature due to unbalanced loading and unsymmetrical line configuration. This situation is further aggravated by single-phase power injections. A coordinated control scheme is proposed for single-phase sources, to reduce voltage unbalance. A consensus-based coordination is achieved using a multi-agent system, where each agent estimates the averaged global voltage and current magnitudes of individual phases in the LV network. These estimated values are used to modify the reference power of individual single-phase sources, to ensure system-wide balanced voltages and proper power sharing among sources connected to the same phase. Further, the high X / R ratio of the filter, used in the inverter of the single-phase source, enables control of reactive power, to minimize voltage unbalance locally. The proposed scheme is validated by simulating a LV distribution network with multiple single-phase sources subjected to various perturbations. This article is part of the themed issue ‘Energy management: flexibility, risk and optimization’.

scholarly journals Optimal Micro-PMU Placement Using Mutual Information Theory in Distribution Networks

Energies ◽  
2018 ◽  
Vol 11 (7) ◽  
pp. 1917 ◽  
Author(s):  
Zhi Wu ◽  
Xiao Du ◽  
Wei Gu ◽  
Ping Ling ◽  
Jinsong Liu ◽  
...  
Keyword(s):  
Distribution System ◽  
Distribution Systems ◽  
Estimation Method ◽  
Distribution Networks ◽  
Point Estimation ◽  
Optimal Placement ◽  
Measurement Unit ◽  
Selection Strategy ◽  
Smart Meters ◽  
Point Estimation Method

Micro-phasor measurement unit (μPMU) is under fast development and becoming more and more important for application in future distribution networks. It is unrealistic and unaffordable to place all buses with μPMUs because of the high costs, leading to the necessity of determining optimal placement with minimal numbers of μPMUs in the distribution system. An optimal μPMU placement (OPP) based on the information entropy evaluation and node selection strategy (IENS) using greedy algorithm is presented in this paper. The uncertainties of distributed generations (DGs) and pseudo measurements are taken into consideration, and the two-point estimation method (2PEM) is utilized for solving stochastic state estimation problems. The set of buses selected by improved IENS, which can minimize the uncertainties of network and obtain system observability is considered as the optimal deployment of μPMUs. The proposed method utilizes the measurements of smart meters and pseudo measurements of load powers in the distribution systems to reduce the number of μPMUs and enhance the observability of the network. The results of the simulations prove the effectiveness of the proposed algorithm with the comparison of traditional topological methods for the OPP problem. The improved IENS method can obtain the optimal complete and incomplete μPMU placement in the distribution systems.

scholarly journals A Voltage-Based Approach for Series High Impedance Fault Detection and Location in Distribution Systems Using Smart Meters

Energies ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 3022 ◽  
Author(s):  
Francinei L. Vieira ◽  
Pedro H. M. Santos ◽  
José M. Carvalho Filho ◽  
Roberto C. Leborgne ◽  
Marino P. Leite
Keyword(s):  
Distribution System ◽  
Distribution Systems ◽  
New Technologies ◽  
Low Voltage ◽  
Real Life ◽  
Distribution Networks ◽  
Smart Meters ◽  
Voltage Unbalance ◽  
High Impedance ◽  
High Impedance Faults

High impedance faults (HIFs) have been a major concern for protecting distribution systems and public safety hazards when involving downed conductors. The deployment of smarter grids brings new technologies for smart monitoring, automation, and protection of distribution networks. This paper presents a new method for a series of HIF detection and location in primary distribution feeders, using voltage unbalance measurements collected from smart meters (SMs) installed at low-voltage end-users. The methodology was tested in MATLAB and Simulink through steady-state simulations of a typical 13.8 kV distribution system, under load unbalance and different fault scenarios. Results show that the proposed method is robust and accurate for the detection of blown fuses and broken conductors, with or without ground faults, located either at the source or the load-side. The ease of implementation in SM design, formulation of parameters, and reliable simulation results show potential real-life applications.

scholarly journals Secondary Control Scheme for Voltage Unbalance Compensation in an Islanded Droop-Controlled Microgrid

2012 ◽  
Vol 3 (2) ◽  
pp. 797-807 ◽  
Author(s):  
Mehdi Savaghebi ◽  
Alireza Jalilian ◽  
Juan C. Vasquez ◽  
Josep M. Guerrero
Keyword(s):  
Secondary Control ◽  
Voltage Unbalance ◽  
Control Scheme

scholarly journals A Hybrid State Estimator Based on SCADA and PMU Measurements for Medium Voltage Distribution System

2018 ◽  
Vol 8 (9) ◽  
pp. 1527 ◽  
Author(s):  
Xiangyu Kong ◽  
Ying Chen ◽  
Tao Xu ◽  
Chengshan Wang ◽  
Chengsi Yong ◽  
...  
Keyword(s):  
Data Acquisition ◽  
State Estimation ◽  
Robust Estimation ◽  
Distribution System ◽  
Distribution Systems ◽  
Measurement Unit ◽  
State Estimator ◽  
Hybrid State ◽  
Linear State ◽  
And Performance

With the increasing importance of renewable energy and flexible loads, the operation of the distribution system is becoming more stochastic and complex, and it is necessary to monitor the power system in real-time. Considering the gradual applications of intelligent electronic devices in the distribution systems, a hybrid state estimator based on supervisory control and data acquisition (SCADA) and phasor measurement unit (PMU) measurements is proposed in this paper, which consists of the improved robust estimation and linear state estimation. At the time of SCADA data acquisition, the improved robust estimation combining the SCADA measurements with PMU measurements is performed. To eliminate the effect of bad data, the internal student residual method is introduced, and the robust thresholds are adjusted adaptively. Then the linear state estimation is performed at the time of PMU data acquisition based on the results of the previous estimation time and the PMU measurements, which can quickly correct the robust estimation results and track the changes of the distribution system. Finally, the effectiveness and performance of the proposed method are verified in a modified IEEE 33-bus distribution system and a real distribution system in China.

scholarly journals Resilient Self-Triggered Control for Voltage Restoration and Reactive Power Sharing in Islanded Microgrids under Denial-of-Service Attacks

2020 ◽  
Vol 10 (11) ◽  
pp. 3780
Author(s):  
Gang Xu ◽  
Liang Ma
Keyword(s):  
Information Exchange ◽  
Reactive Power ◽  
Denial Of Service ◽  
Control Level ◽  
Power Sharing ◽  
Accurate Estimation ◽  
Secondary Control ◽  
Dos Attacks ◽  
Control Scheme ◽  
Average Information

This paper addresses the problem of voltage restoration and reactive power sharing of inverter-based distributed generations (DGs) in an islanded microgrid subject to denial-of-service (DoS) attacks. Note that DoS attacks may block information exchange among DGs by jamming the communication network in the secondary control level of a microgrid. A two-layer distributed secondary control framework is presented, in which a state observer employing the multiagent system (MAS)-based ternary self-triggered control is implemented for discovering the average information of voltage and reactive power in a fully distributed manner while highly reducing communication burden than that the periodic communication way. The compensation for the reference signal to the primary control is acquired according to the average estimates to achieve voltage restoration while properly sharing reactive power among DGs. An improved ternary self-triggered control strategy integrating an acknowledgment (ACK)-based monitoring mechanism is established, where DoS attacks are modeled by repeated cycles of jamming and sleeping. A new triggering condition is developed to guarantee the successful information exchange between DGs when the sleep period of DoS attacks is detected. Using the Lyapunov approach, it is proved that the proposed algorithm allows agents to reach consensus regardless of the frequency of the DoS attacks, which maintains the accurate estimation of average information and the implementation of the secondary control objectives. The performance of the proposed control scheme is evaluated under simulation and experimental conditions. The results show that the proposed secondary control scheme can highly reduce the inter-agent communication as well as improve the robustness of the system to resist DoS attacks.

Three-phase to Single-phase Matrix Converter for Improvement of Three-phase Voltage Unbalance in Distribution System

2015 ◽  
Vol 135 (3) ◽  
pp. 168-180 ◽  
Author(s):  
Ryota Mizutani ◽  
Hirotaka Koizumi ◽  
Kentaro Hirose ◽  
Kazunari Ishibashi
Keyword(s):  
Distribution System ◽  
Single Phase ◽  
Matrix Converter ◽  
Phase Voltage ◽  
Voltage Unbalance ◽  
Three Phase
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