scholarly journals A Continuation Power Flow Model of Multi-Area AC/DC Interconnected Bulk Systems Incorporating Voltage Source Converter-Based Multi-Terminal DC Networks and Its Decoupling Algorithm

Energies ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 733 ◽  
Author(s):  
Wei Yan ◽  
Chong Ding ◽  
Zhouyang Ren ◽  
Wei-Jen Lee
Keyword(s):  
Power Flow ◽  
Stability Margin ◽  
Active Power ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
Continuation Power Flow ◽  
Voltage Stability Margin ◽  
Security Control ◽  
Tie Lines ◽  
Decoupling Algorithm

Existing continuation power flow (CPF) models mainly focus on the regional independent systems, which are not suitable for multi-area AC/DC interconnected systems because the market trading behaviors and security control for power allocation of tie-lines are ignored. This study presents a novel CPF model and its decoupling algorithm for multi-area AC/DC interconnected systems incorporating a voltage source converter (VSC)-based multi-terminal direct current (MTDC) network. This CPF model includes the following unique features: (1) In view of the bilateral power trading contracts among regional subsystems, the nonlinear constraint equations of directional trading active power via interface are derived, and the multi-balancing machine strategy is introduced to realize the active power balance of each subsystem. (2) An accurate simulation method for the security control behaviors of the power allocation in tie-lines is proposed, which includes a specific selection strategy for automatic generation control units and a generation re-dispatch strategy. These two strategies work together to prevent the serious overload in tie-lines during load growth and improve the voltage stability margin of the interconnected bulk systems. (3) The switching characteristic of reactive power control behaviors of VSC stations is simulated in the CPF calculation. In the end, a novel decoupling CPF algorithm based on bi-directional iteration is presented to realize the decomposition and coordination calculation. This decoupling algorithm preserves the precision and convergence of integrated CPF algorithms, and it has an apparent advantage on the calculation speed. Furthermore, this decoupling algorithm also can easily reflects the effects of the control mode changes of VSC stations to the voltage stability margin of AC system. Case studies and comparative analysis on the IEEE two-area RTS-96 system indicate the effectiveness and validity of the proposed CPF model and corresponding decoupling algorithm.

Voltage Stability Margin Assessment Using Multilayer Feed Forward Neural Network

2014 ◽  
Vol 573 ◽  
pp. 661-667 ◽  
Author(s):  
G.S. Naganathan ◽  
C.K. Babulal
Keyword(s):  
Neural Network ◽  
Power Flow ◽  
Voltage Stability ◽  
Reactive Power ◽  
Stability Margin ◽  
Feed Forward Neural Network ◽  
Continuation Power Flow ◽  
Feature Sets ◽  
Input Feature ◽  
Voltage Stability Margin

With the deregulation of electricity markets, the system operation strategies have changed in recent years. The systems are operated with smaller margins. How to maintain the voltage stability of the power systems have become an important issue.This paper presents an Artificial Feed Forward Neural Network (FFNN) approach for the assessment of power system voltage stability. This paper uses some input feature sets using real power, reactive power, voltage magnitude and phase angle to train the neural network (NN). The target output for each input pattern is obtained by computing the distance to voltage collapse from the current system operating point using a continuation power flow type algorithm. This paper compared different input feature sets and showed that reactive power and the phase angle are the best predictors of voltage stability margin. Further, the paper shows that the proposed ANN based method can successfully estimate the voltage stability margin not only under normal operation but also under N-1 contingency situations. The proposed method has been applied to the IEEE 14 and IEEE 30 bus test system. The continuation power flow technique run with PSAT and the proposed method is implemented in MATLAB.

scholarly journals Power Quality Enhancement in Windfarm by using STATCOM

2020 ◽  
Vol 8 (5) ◽  
pp. 596-601
Keyword(s):  
Wind Turbine ◽  
Power Flow ◽  
Reactive Power ◽  
Dynamic Performance ◽  
Active Power ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
Dc Microgrid ◽  
Active Power Flow ◽  
Shunt Compensation

A FACTS (Flexible AC Transmission) controlled device, STATCOM is the best solution for power compensation in the area of microgrid system. It regulates the reactive power by injecting the reactive current in to the ac/dc hybrid microgrid terminals. The STATCOM is applicable for shunt compensation which has a great role in dynamic performance by controlling its reactive power. The proposed work demonstrated about the enhancement of voltage sag during fault condition. It can improve the wind turbine performance. The main objective for the STATCOM application in windfarm is to improve the system voltage by supplying or absorbing the reactive power into hybrid ac /dc microgrid system. During steady state operation, the fundamental component of the VSC (Voltage source converter) voltage in phase with system voltage, which shows uncontrol action on active power flow. If there is change between these two voltages (lead or lag), then STATCOM can generates (or absorbs) reactive power. This phase shift leads to flow of active power which is responsible for increase or decreases of capacitor voltage. Assumption has been taken by considering the fixed speed of wind turbine. The performance of windfarm with and without STATCOM is examined and analyzed under fault condition by using MATLAB Simulink 2016.

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.

scholarly journals Improvement of Power Quality Considering Voltage Stability in Grid Connected System by FACTS Devices

2013 ◽  
pp. 182-187
Author(s):  
Sarika D. Patil
Keyword(s):  
Power Generation ◽  
Wind Power ◽  
Power Flow ◽  
Voltage Stability ◽  
Low Voltage ◽  
Wind Power Generation ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
Induction Generators ◽  
Facts Devices

Recently the wind power generation has attracted special interest and many wind power stations are being in service in the world. In the wind turbine that mostly uses induction generators, tend to drain large amounts of Vars from the grid, potentially causing low voltage and may be voltage stability problems for the utility owner, especially in the case of large load variation on distribution feeder. Voltage-source converter based various FACTS devices have been used for flexible power flow control, secure loading and damping of power system oscillations. Some of those are used also to improve transient and dynamic stability of the wind power generation (WPGS).

scholarly journals Multiterminal Medium Voltage DC Distribution Network Hierarchical Control

Electronics ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 506 ◽  
Author(s):  
Patrobers Simiyu ◽  
Ai Xin ◽  
Kunyu Wang ◽  
George Adwek ◽  
Salman Salman
Keyword(s):  
Optimal Power Flow ◽  
Distribution Network ◽  
Hierarchical Control ◽  
Active Power ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
Dc Voltage ◽  
Medium Voltage ◽  
Control Scheme ◽  
Medium Voltage Dc

In this research study, a multiterminal voltage source converter (VSC) medium voltage DC (MVDC) distribution network hierarchical control scheme is proposed for renewable energy (RE) integration in a co-simulation environment of MATLAB and PSCAD/EMTDC. A DC optimal power flow (DC OPF) secondary controller is created in MATLAB. In PSCAD/EMTDC, the main circuit containing the adaptive DC voltage droop with a dead band and virtual synchronous generator (VSG) based primary controller for the VSCs is implemented. The simulation of the MVDC network under the proposed hierarchical control scheme is investigated considering variations in wind and solar photovoltaic (PV) power. The network is also connected to the standard IEEE-39 bus system and the hierarchical scheme tested by assessing the effect of tripping as well as restoration of the REs. The results show that during random variations in active power such as increasing wind and PV power generation, a sudden reduction or tripping of wind and PV power, the primary controller ensures accurate active power sharing amongst the droop-based VSCs as well as regulates DC voltage deviations within the set range of 0.98–1.02 pu with an enhanced dynamic response. The DC OPF secondary control optimizes the system’s losses by 38% regularly giving optimal droop settings to the primary controllers to ensure proper active power balance and DC voltage stability. This study demonstrates that the hierarchical control strategy is effective for RE integration in the MVDC distribution network.

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 Hopf Bifurcation Control of Subsynchronous Resonance Utilizing UPFC

2017 ◽  
Vol 7 (3) ◽  
pp. 1588-1594
Author(s):  
Μ. Μ. Alomari ◽  
M. S. Widyan ◽  
M. Abdul-Niby ◽  
A. Gheitasi
Keyword(s):  
Power System ◽  
Transmission Line ◽  
Power Flow ◽  
Operating Point ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
Unified Power Flow Controller ◽  
Subsynchronous Resonance ◽  
Wide Range ◽  
System Stabilizer

The use of a unified power flow controller (UPFC) to control the bifurcations of a subsynchronous resonance (SSR) in a multi-machine power system is introduced in this study. UPFC is one of the flexible AC transmission systems (FACTS) where a voltage source converter (VSC) is used based on gate-turn-off (GTO) thyristor valve technology. Furthermore, UPFC can be used as a stabilizer by means of a power system stabilizer (PSS). The considered system is a modified version of the second system of the IEEE second benchmark model of subsynchronous resonance where the UPFC is added to its transmission line. The dynamic effects of the machine components on SSR are considered. Time domain simulations based on the complete nonlinear dynamical mathematical model are used for numerical simulations. The results in case of including UPFC are compared to the case where the transmission line is conventionally compensated (without UPFC) where two Hopf bifurcations are predicted with unstable operating point at wide range of compensation levels. For UPFC systems, it is worth to mention that the operating point of the system never loses stability at all realistic compensation degrees and therefore all power system bifurcations have been eliminated.

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