scholarly journals Multiterminal HVDC System with Power Quality Enhancement

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1306
Author(s):  
Pedro Roncero-Sánchez ◽  
Alfonso Parreño Torres ◽  
Javier Vázquez ◽  
Francisco Javier López-Alcolea ◽  
Emilio J. Molina-Martínez ◽  
...  
Keyword(s):  
Power Quality ◽  
Direct Current ◽  
Smart Grids ◽  
Computer Aided Design ◽  
Power Flow ◽  
Renewable Energy Sources ◽  
Voltage Regulation ◽  
Active Power ◽  
Voltage Source ◽  
Hvdc System

High-Voltage Direct Current (HVDC) systems are a feasible solution that allows the transmission of energy between several power networks. As a consequence of the use of HVDC systems, renewable energy sources can be integrated more easily into distribution grids and smart grids. Furthermore, HVDC systems can contribute to improving the power quality (PQ) of the grids to which they are connected. This paper presents a multiterminal HVDC system that not only controls the flows of active power between four different networks, but also compensates imbalances and harmonics in the grid currents to maintain balanced and sinusoidal voltages at the point of common coupling of the various grids. The compensation is carried out by the voltage-source converters (VSCs) connected to their respective AC grids. A control scheme based on the use of resonant regulators and proportional–integral (PI) controllers is responsible for of achieving the necessary power flow control with the amelioration of the PQ. A case study of a multiterminal HVDC system that comprises four terminals sharing a DC bus of 80 kV is simulated by means of PSCADTM/EMTDCTM (Power System Computer-Aided Design; Electromagnetic Transients including Direct Current), where the AC grids associated with the terminals suffer from voltage imbalances and voltage harmonics owing to the connection of unbalanced loads and nonlinear loads. The obtained simulation results show the performance of the complete system in terms of active power flow, voltage regulation, and harmonic distortions of the grid current and the grid voltage.

scholarly journals Analysis of Propagation Delay for Multi-Terminal High Voltage Direct Current Networks Interconnecting the Large-Scale Off-Shore Renewable Energy

Energies ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 2115 ◽  
Author(s):  
Muhammad Nadeem ◽  
Xiaodong Zheng ◽  
Nengling Tai ◽  
Mehr Gul ◽  
Sohaib Tahir
Keyword(s):  
Renewable Energy ◽  
High Voltage ◽  
Direct Current ◽  
Computer Aided Design ◽  
Large Scale ◽  
Renewable Energy Sources ◽  
Propagation Delay ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
High Voltage Direct Current

Voltage-source-converter-based multi-terminal high voltage direct current (MTDC) networks are extensively recognized as a viable solution for meeting the increasing demand of electrical energy and escalating penetration of renewable energy sources. DC faults are major limitations to the development of MTDC networks. The analysis of variable constraints has become mandatory in order to develop a reliable protection scheme. This paper contributes in assessing the propagation delay with the analytical approximation in MTDC networks. The propagation delay is analyzed in the time domain by taking only the forward traveling wave into account and considering the initial voltage step of magnitude at the fault position. Numerous simulations were carried out for different parameters and arrangements in Power System Computer Aided Design (PSCAD) to explore the proposed expressions. The results accurately depicted the time development of fault current. The results obtained from the real-time digital simulator (RTDS) confirmed that the proposed approach is capable of evaluating propagation delay in MTDC networks. Moreover, the influence of fault resistance is also taken into account for investigating its effect on the system parameters.

Power Quality Improvement of High Voltage DC Link using Modified Shunt Active Power Filter

2018 ◽  
Vol 1 (1) ◽  
pp. 54-66
Author(s):  
Rakan Khalil Antar ◽  
Basil Mohammed Saied ◽  
Rafid Ahmed Khalil
Keyword(s):  
Power Quality ◽  
High Voltage ◽  
Pulse Width Modulation ◽  
Active Power Filter ◽  
Active Power ◽  
Voltage Source ◽  
Active Power Filters ◽  
Power Filter ◽  
Power Filters ◽  
Power Quality Improvement

A new control strategy for active power filters is proposed, modeled and implemented in order to improve the power quality of a line commutated converter High voltage DC link. The ability of reactive power and harmonics reductions are generally met by using passive and active power filters. In this paper, modified active power filter with a modified harmonics pulse width modulation algorithm is used to minimize the source harmonics and force the AC supply current to be in the same phase with AC voltage source at both sending and receiving sides of a line commutated converter high voltage DC link. Therefore, it is considered as power factor corrector and harmonics eliminator with random variations in the load current. The modified harmonics pulse width modulation algorithm is applicable for active power filter based on a three-phase five-level and seven-level cascaded H-bridge voltage source inverter. Simulation results show that the suggested modified multilevel active power filters improve total harmonics distortion of both voltage and current with almost unity effective power factor at both AC sides of high voltage DC link. Therefore, modified active power filter is an effective tool for power quality improvement and preferable for line commutated converter high voltage DC link at different load conditions.

scholarly journals A Hierarchical Control Methodology for Renewable DC Microgrids Supporting a Variable Communication Network Health

Electronics ◽  
2018 ◽  
Vol 7 (12) ◽  
pp. 418 ◽  
Author(s):  
Muhammad Shahid ◽  
Muhammad Khan ◽  
Jianming Xu ◽  
Khurram Hashmi ◽  
Salman Habib ◽  
...  
Keyword(s):  
Power Flow ◽  
Renewable Energy Sources ◽  
Hierarchical Control ◽  
Network Connectivity ◽  
Voltage Regulation ◽  
Monitoring And Control ◽  
Dc Microgrids ◽  
Communication Links ◽  
Microgrid Control ◽  
And Control

The monitoring and control of renewable energy sources (RESs) based on DC (Direct Current) microgrids (DC MG) are gaining much consideration at this time. In comparison with the isolated individual control of converters in a microgrid, DC microgrids provide better voltage regulation and harmonized energy generation/consumption. To address the inherent vulnerability of communication links, robust methods have been proposed that improve the resilience of communication-based control. However, the failure of the communication links in microgrid control layers remains a considerable issue that may lead to one or more nodes being disconnected and operating as a communication island. Such types of communication islanding may cause the unpredictable behavior of the system and further destabilization may lead to a cascaded failure. This paper proposes a fast algorithm to detect and evaluate network connectivity based on the information stored at every node in the form of a look-up table. The control structure has been modified under communication islanding, and a communication connectivity observer is used at every node to detect and address power flow issues under communication islanding. The proposed method has been verified through mathematical analysis, simulation, and experimental results.

scholarly journals Coordinated Control System between Grid–VSC and a DC Microgrid with Hybrid Energy Storage System

Electronics ◽  
2021 ◽  
Vol 10 (21) ◽  
pp. 2699
Author(s):  
Miguel Montilla-DJesus ◽  
Édinson Franco-Mejía ◽  
Edwin Rivas Trujillo ◽  
José Luis Rodriguez-Amenedo ◽  
Santiago Arnaltes
Keyword(s):  
Control Strategy ◽  
Power Flow ◽  
Storage System ◽  
Coordinated Control ◽  
Energy Storage System ◽  
Voltage Regulation ◽  
Electrical Network ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
Dc Microgrid

Direct current microgrids (DCMGs) are currently presented as an alternative solution for small systems that feed sensitive electrical loads into DC. According to the scientific literature, DCMG maintains good voltage regulation. However, when the system is in islanded mode, very pronounced voltage variations are presented, compromising the system’s ability to achieve reliable and stable energy management. Therefore, the authors propose a solution, connecting the electrical network through a grid-tied voltage source converter (GVSC) in order to reduce voltage variations. A coordinated control strategy between the DCMG and GVSC is proposed to regulate the DC voltage and find a stable power flow between the various active elements, which feed the load. The results show that the control strategy between the GVSC and DCMG, when tested under different disturbances, improves the performance of the system, making it more reliable and stable. Furthermore, the GVSC supports the AC voltage at the point of common coupling (PCC) without reducing the operating capacity of the DCMG and without exceeding even its most restrictive limit. All simulations were carried out in MATLAB 2020.

A new scheme for power factor correction and active filtering for six-pulse converters loads

2009 ◽  
Vol 57 (2) ◽  
pp. 157-169 ◽  
Author(s):  
Y. Han ◽  
M. Khan ◽  
L. Xu ◽  
G. Yao ◽  
L. Zhou ◽  
...  
Keyword(s):  
Power Factor ◽  
Power Flow ◽  
Power Factor Correction ◽  
Active Power ◽  
Estimation Accuracy ◽  
Voltage Source ◽  
Current Loop ◽  
Loop Control ◽  
Proportional Integral ◽  
Active Filtering

A new scheme for power factor correction and active filtering for six-pulse converters loads This paper presents a novel harmonic-free power factor correction (PFC) topology based on T-type active power filter (APF), which is dedicated for power factor improvement and harmonic filtering for six-pulse converter loads. The cascaded controller structure is adopted for the proposed system, namely, the inner current loop and outer voltage loop. The current-loop control scheme is based on a decoupled state-space equations of the T-type APF using separate proportional-integral (PI) controllers in d-axis and q-axis of the synchronous rotating reference frame (SRRF) synchronized with grid voltages, respectively. The fundamental components of load-side currents are feed forwarded in the current-loop using two groups of synchronous frame adaptive linear neural networks (ADALINEs) to ensure estimation accuracy and a fast dynamic response. A separate proportional-integral (PI) controller is adopted in the outer voltage loop for balancing the active power flow of the voltage source inverter (VSI) dc-side capacitor. The experimental results confirm well with the theoretical analysis.

scholarly journals Mitigating power quality disturbances in smart grid using FACTS

2021 ◽  
Vol 22 (3) ◽  
pp. 1223
Author(s):  
Yahia M. Esmail ◽  
Ali H. Kasem Alaboudy ◽  
M. S. Hassan ◽  
Gamal M. Dousoky
Keyword(s):  
Renewable Energy ◽  
Smart Grid ◽  
Power Quality ◽  
Smart Grids ◽  
Renewable Energy Sources ◽  
Distribution Networks ◽  
Static Synchronous Compensator ◽  
Power Quality Disturbances ◽  
Flexible Alternating Current Transmission ◽  
Power Quality Conditioner

Power quality (PQ) assurance is a vital part of electrical distribution networks. There are many advantages and benefits of improving PQ, especially in the modern/smart grid. Smart grid (SG) has a lot of complicated and sensitive electrical components (non-linear loads) in addition to renewable energy systems (wind-solar) that may also be a source of PQ disturbances. PQ problems harm personal life and national production. Static synchronous compensator (STATCOM) and unified power quality conditioner (UPQC) are among the fastest response flexible alternating current transmission systems (FACTS) installed in smart grids to mitigate power quality disturbances such as voltage fluctuations, sag, swell, and harmonics. In this research, STATCOM and UPQC are designed and simulated in MATLAB/Simulink to overcome PQ-related disruptions in smart grids. Accordingly, the differences between the proposed two solutions are highlighted across this research and renewable energy sources' reliability during faults. Therefore, the reader will be able to choose the appropriate FACTS devices. This study emphasizes the extent of the smart grid need for the FACTS. As per the given results of this study, STATCOM and UPQC have shown exemplary performance in the PQ improvement investigations conducted in the context of smart/modern grids.

scholarly journals Analysis of Three Phase 3-Level NPC Voltage Source Converter for AC-DC Conversion

2020 ◽  
Vol 06 (09) ◽  
pp. 144-148
Author(s):  
A Divya Teja and Dr. N Sambasiva Rao
Keyword(s):  
Power Quality ◽  
Power Flow ◽  
Reactive Power ◽  
Neutral Point ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
Phase 3 ◽  
Control Techniques ◽  
Point Potential ◽  
Three Phase

The use of power electronic converters influences the generation of harmonics and reactive power flow in power system. Therefore, three-phase multilevel improved power quality AC-DC converters are gaining lot of popularity in power conversion applications. This work deals with critical problem of multilevel structure i.e neutral point potential (NPP) variation. In this paper, a simplified current controlled scheme is presented to ensure unity power factor operation. Neutral point potential (NPP) of three-phase, 3-level NPC AC-DC converter is controlled by modifying control signal in the controller using NPP regulator. An auxiliary circuit is being presented in this paper as an alternative option for controlling the neutral point potential of the converter. Comparison has been carried out between these control techniques in terms of power quality. A complete mathematical model is presented for better understanding of both techniques used for NPP control. The presented control techniques has been verified through simulation investigations and validated

scholarly journals Operation and Challenges of Multi-Infeed LCC–HVDC System: Commutation Failure, AC/DC Power Flow, and Voltage Stability

2021 ◽  
Vol 11 (18) ◽  
pp. 8637
Author(s):  
Bilawal Rehman ◽  
Atiq ur Rehman ◽  
Waqar Ahmad Khan ◽  
Irfan Sami ◽  
Jong-Suk Ro
Keyword(s):  
Power Systems ◽  
Power Flow ◽  
Voltage Stability ◽  
Power Transmission ◽  
Voltage Source ◽  
Future Research ◽  
Long Distance ◽  
Hvdc System ◽  
Dc Power ◽  
Commutation Failure

This paper presents a detailed analysis of commutation failure, AC/DC power flow, and voltage stability of multi-infeed high-voltage direct current (HVDC). The use of HVDC power transmission technology has become common in modern power systems. During the past two decades, HVDC technology has been extensively used for long-distance bulk power transmission to remote areas. Throughout the world, the demand for power has drastically increased in recent years due to industrialization; such situations make HVDC an economic candidate because the distance between power generation plants and load areas is significantly very long. The line-commutated converter (LCC) technology-based HVDC system is well more mature than other available conversion schemes (i.e., voltage source converters), and it is widely used in high-power projects. China had approximately 50 HVDC–LCC links in 2020, and a single LCC-based link with the highest capacity is 12 GW. The installation of several HVDC links in an existing power network has led to a situation where two or more HVDC links terminate in the electric vicinity of each other’s AC network or even in same AC busbar. Such scenarios are termed multi-infeed HVDC system. Multi-infeed HVDC systems bring various challenges related to voltage stability, local and concurrent commutation failure, and AC/DC power flow. Here, the literature available on these phenomena of LCC-based HVDC is discussed for future research. The assumptions and drawbacks of various techniques used for investigating the mentioned phenomena are also highlighted.

scholarly journals Dynamic analysis of voltage angle droop controlled HVDC systems in curative congestion management scenarios

2019 ◽  
Vol 217 ◽  
pp. 01004
Author(s):  
Yang Zhou ◽  
Stefan Dalhues ◽  
Ulf Häger
Keyword(s):  
Power System ◽  
Dynamic Behavior ◽  
Transmission Lines ◽  
Power Flow ◽  
Congestion Management ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
Management Scenarios ◽  
Hvdc System ◽  
Good Ability

The integration of the voltage-source converter based high voltage direct current (VSC-HVDC) system makes the set-point of its active power adaptive to the changes in the power flow, and contributes to the curative congestion management. To further exploit the dynamic behavior of a hybrid AC/DC power system in curative congestion management scenarios, this paper investigates a novel control scheme for voltage angle droop controlled HVDC (VAD-HVDC) systems. The proposed scheme to alleviate the circuit overload is estimated firstly by calculating the severity index when the power flow changes under N-1 situations. Then the voltage angle controlled HVDC system is applied on the modified IEEE 39-bus 10-machine test power system for the time-domain simulation. The dynamic behavior in the HVDC station validates that the VAD control can stabilize the DC voltage and possess a good ability against interference. In addition, the dynamic characteristics analysis on the AC transmission lines proves that the hybrid AC/DC system integrated with the VAD controlled HVDC system are in possession of good stability after the N-1 contingency event. The VAD controller employed in the HVDC system is capable of effective congestion management to mitigate the critical loadings on the transmission lines.

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