scholarly journals Power Flow Analysis of MMC-HVDC System with Margin Voltage and Voltage Droop Control Strategies

2020 ◽  
Author(s):  
Maxwel Da Silva Santos ◽  
Luciano Sales Barros ◽  
Rafael Lucas da Silva França ◽  
Flavio Bezerra Costa ◽  
Kai Strunz
Keyword(s):  
Power Flow ◽  
Control Strategies ◽  
Flow Analysis ◽  
Open Circuit ◽  
Droop Control ◽  
Power Flow Control ◽  
Hvdc System ◽  
High Voltage Direct Current ◽  
Modular Converter ◽  
The One

High voltage direct current (HVDC) systems are an alternative for transmission of energy with higher efficiency and lower electrical losses over long distances. HVDC systems have become more common with the evolution of power electronics, promoting the interest of research in power flow control techniques. The main objective of this paper is to perform evaluations of the power flow in a meshed multiterminal HVDC (MT-HVDC) system based on the multilevel modular converter (MMC). Two different control strategies were considered; The margin voltage; and the voltage droop strategies. Two assessment scenarios were considered: when an active power reference takes place in the system; and when a DC transmission line is open-circuit due to a failure in the DC grid. For both of these test cases, the system with the margin voltage control obtained a new balance of power flow with less oscillations in power andvoltage than the one with the voltage droop control.

scholarly journals DC Voltage Adaptive Droop Control Strategy for a Hybrid Multi-Terminal HVDC System

Energies ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 380 ◽  
Author(s):  
Yingpei Liu ◽  
La Zhang ◽  
Haiping Liang
Keyword(s):  
High Voltage ◽  
Direct Current ◽  
Control Strategy ◽  
Power Flow ◽  
Influence Factor ◽  
Current System ◽  
Droop Control ◽  
Dc Voltage ◽  
Hvdc System ◽  
High Voltage Direct Current

To solve the problems of DC voltage control and power allocation in the hybrid multi-terminal high voltage direct current system effectively, a DC voltage adaptive droop control strategy based on DC voltage-current characteristics is proposed. Based on adjustment of the droop coefficient of the converter station, the proposed control strategy introduces the influence factor of the droop coefficient, which considers the dynamic power margin of the converter station according to the direction of DC current variation in the converter station. When changes in the hybrid multi-terminal high voltage direct current system power flow occur, the droop coefficient of the converter station can be adjusted by the influence factor of the droop coefficient, so that the converter station can participate in power regulation according to its own power regulating ability. Consequently, the proposed control strategy can reasonably allocate the active power and minimize the deviation of the DC voltage. Besides, the stability analysis of the proposed control strategy is also carried out. Simulation results have verified the feasibility and effectiveness of the proposed control strategy.

scholarly journals Power flow incorporating cost-based droop control strategies for ac autonomous microgrids

2020 ◽  
pp. 28-32
Author(s):  
Pham Nang Van Pham
Keyword(s):  
Power Flow ◽  
Control Strategies ◽  
Flow Analysis ◽  
Load Flow ◽  
Cost Curve ◽  
Droop Control ◽  
Test Results ◽  
Autonomous Operation ◽  
Complex Power ◽  
Flow Study

Several methods of power flow analysis for autonomous microgrids have been suggested; however, the implementation of these methods is challenging because of the lack of a swing bus and droop control characteristics. This paper puts forward an innovative technique for the load flow study of microgrids that autonomously operate according to droop control strategies incorporating cost rather than traditional droop schemes. This approach aims to extend the application of conventional power flow methodologies. In this approach, the incremental cost that is derivative of the fuel cost curve with respect to power output is embedded in droop schemes. The proposed approach deploys the iterative procedure to impose complex power that injects through the swing node to zero, which represents the autonomous operation of microgrids. Test results validate that this approach is exact and straightforward to implement; therefore, it can be highly beneficial for operating and planning microgrids

scholarly journals Impedance Matching-Based Power Flow Analysis for UPQC in Three-Phase Four-Wire Systems

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2702
Author(s):  
Xiaojun Zhao ◽  
Xiuhui Chai ◽  
Xiaoqiang Guo ◽  
Ahmad Waseem ◽  
Xiaohuan Wang ◽  
...  
Keyword(s):  
Power Flow ◽  
Control Strategies ◽  
Impedance Matching ◽  
Flow Analysis ◽  
Point Of View ◽  
Impedance Model ◽  
Power Flow Analysis ◽  
Three Phase ◽  
System Node ◽  
Power Quality Conditioner

Different from the extant power flow analysis methods, this paper discusses the power flows for the unified power quality conditioner (UPQC) in three-phase four-wire systems from the point of view of impedance matching. To this end, combined with the designed control strategies, the establishing method of the UPQC impedance model is presented, and on this basis, the UPQC system can be equivalent to an adjustable impedance model. After that, a concept of impedance matching is introduced into this impedance model to study the operation principle for the UPQC system, i.e., how the system changes its operation states and power flow under the grid voltage variations through discussing the matching relationships among node impedances. In this way, the nodes of the series and parallel converter are matched into two sets of impedances in opposite directions, which mean that one converter operates in rectifier state to draw the energy and the other one operates in inverter state to transmit the energy. Consequently, no matter what grid voltages change, the system node impedances are dynamically matched to ensure that output equivalent impedances are always equal to load impedances, so as to realize impedance and power balances of the UPQC system. Finally, the correctness of the impedance matching-based power flow analysis is validated by the experimental results.

scholarly journals Control Strategies of DC Microgrids Cluster: A Comprehensive Review

Energies ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7569
Author(s):  
Zaid Hamid Abdulabbas Al-Tameemi ◽  
Tek Tjing Lie ◽  
Gilbert Foo ◽  
Frede Blaabjerg
Keyword(s):  
Power Flow ◽  
Control Strategies ◽  
Future Research ◽  
Consensus Protocol ◽  
Power Flow Control ◽  
Dc Microgrids ◽  
Significant Control ◽  
Comparative Review ◽  
Cluster A ◽  
Research Recommendations

Multiple microgrids (MGs) close to each other can be interconnected to construct a cluster to enhance reliability and flexibility. This paper presents a comprehensive and comparative review of recent studies on DC MG clusters’ control strategies. Different schemes regarding the two significant control aspects of networked DC MGs, namely DC-link voltage control and power flow control between MGs, are investigated. A discussion about the architecture configuration of DC MG clusters is also provided. All advantages and limitations of various control strategies of recent studies are discussed in this paper. Furthermore, this paper discusses three types of consensus protocol with different time boundaries, including linear, finite, and fixed. Based on the main findings from the reviewed studies, future research recommendations are proposed.

scholarly journals Dynamic Analysis for VSG-Based Power Flow Control Applied to DG Systems

2021 ◽  
Author(s):  
THIAGO FIGUEIREDO DO NASCIMENTO ◽  
ANDRES ORTIZ SALAZAR
Keyword(s):  
Power Systems ◽  
Dynamic Analysis ◽  
Power Flow ◽  
Control Strategies ◽  
Renewable Energy Sources ◽  
Dynamic Performance ◽  
Synchronous Generator ◽  
Power Flow Control ◽  
Grid Impedance ◽  
Impedance Parameters

The integration of distributed generation (DG) systems based on renewable energy sources (RES) by using power converters is an emerging technology in modern power systems. Among the control strategies applied to this new configuration, the virtual synchronous generator (VSG) approach has proven to be an attractive solution due providing suitable dynamic performance. Thus, this paper presents a dynamic analysis of gridtied converters controlled by using VSG concept. This analysis is based on a dynamic model that describes the DG power flow transient characteristics. Based on this model, the grid impedance parameters variation effects on the VSG controllers dynamic performance are discussed. Simulation results are presented to evaluate the effectiveness of the theoretical analysis performed.

scholarly journals Research on Serial VSC-LCC Hybrid HVdc Control Strategy and Filter Design Scheme

Energies ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2260
Author(s):  
Fan Cheng ◽  
Lijun Xie ◽  
Zhibing Wang
Keyword(s):  
Reactive Power ◽  
Filter Design ◽  
Control Strategies ◽  
Short Circuit ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
Level Control ◽  
Hvdc System ◽  
High Voltage Direct Current ◽  
Design Scheme

This paper investigated the characteristics of a novel type of hybrid high voltage direct current (HVdc) converter, which is composed by line commutated converter series with voltage source converter. The system and valve level control strategies are introduced, which can provide ac system voltage support. A novel filter design scheme composed by resonant filers for hybrid HVdc are also proposed, which can decrease the capacity of reactive power compensation equipment without deteriorate harmonic characteristics. The ac voltage of HVdc fluctuation level caused by transmitted power variation will be effectively reduced, with the coordination between filter design scheme and converter control. In addition, the influence of ac grid strength is also analyzed by equivalent source internal impedance represented by short circuit ratio (SCR). Finally, the +800 kV/1600 MW hybrid HVdc system connecting two ac grids under different SCR cases are studied, and the PSCAD/EMTDC simulation results have validated the effectiveness for proposed strategy.

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