scholarly journals Control Strategy for a Grid Connected Converter in Active Unbalanced Distribution Systems

Energies ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1362
Author(s):  
Boris Dumnic ◽  
Bane Popadic ◽  
Dragan Milicevic ◽  
Nikola Vukajlovic ◽  
Marko Delimar
Keyword(s):  
Power Systems ◽  
Experimental Verification ◽  
Control Strategy ◽  
Distribution Systems ◽  
System Stability ◽  
Control Technique ◽  
Distributed Resources ◽  
Abc Classification ◽  
Point Of Common Coupling ◽  
Common Coupling

The development in distributed energy resources technology has led to a significant amount of non-linear power electronics converters to be integrated in the power system. Although this leads to a more sustainable system, it also can have adverse impacts on system stability and energy power quality. More importantly, the majority of the distribution power systems currently are unbalanced (with asymmetrical voltages) due to load unbalance, while the most common fault types are unbalanced grid faults that can have many adverse effects on distributed resource operations. In that regard, proper control of the grid connected converters in active unbalanced distribution systems will become very important. This paper aims to present the behavior of the advanced grid connected converter control technique under different voltage states at the point of common coupling (according to the ABC classification). The main insufficiencies of the classical control technique will be highlighted, while the paper will propose an appropriate solution for mitigation of negative sequence currents under asymmetrical voltages at the point of common coupling. An extensive experimental verification of the proposed techniques is performed using an advanced laboratory prototype for research in grid integration of distributed resources. The experimental verification clearly demonstrates the benefits offered by the advanced control strategy.

scholarly journals TSO-DSO Coordination Schemes to Facilitate Distributed Resources Integration

2021 ◽  
Author(s):  
Fatemeh Najibi ◽  
Dimitra Apostolopoulou ◽  
Eduardo Alonso
Keyword(s):  
Power Systems ◽  
Power Flow ◽  
Distribution Systems ◽  
Optimal Power Flow ◽  
Optimal Solution ◽  
Distributed Resources ◽  
Optimal Power ◽  
Conflicting Objectives ◽  
Marginal Prices ◽  
Transmission And Distribution

The incorporation of renewable energy into power systems poses serious challenges to the transmission and distribution power system operators (TSOs and DSOs). To fully leverage these resources there is a need for a new market design with improved coordination between TSOs and DSOs. In this paper we propose two coordination schemes between TSOs and DSOs: one centralised and another decentralised that facilitate the integration of distributed based generation; minimise operational cost; relieve congestion; and promote a sustainable system. To this end, we approximate the power equations with linearised equations so that the resulting optimal power flows (OPFs) in both the TSO and DSO become convex optimisation problems. In the resulting decentralised scheme, the TSO and DSO collaborate to optimally allocate all resources in the system. In particular, we propose an iterative bi-level optimisation technique where the upper level is the TSO that solves its own OPF and determines the locational marginal prices at substations. We demonstrate numerically that the algorithm converges to a near optimal solution. We study the interaction of TSOs and DSOs and the existence of any conflicting objectives with the centralised scheme. More specifically, we approximate the Pareto front of the multi-objective optimal power flow problem where the entire system, i.e., transmission and distribution systems, is modelled. The proposed ideas are illustrated through a five bus transmission system connected with distribution systems, represented by the IEEE 33 and 69 bus feeders.

scholarly journals A stabilising control strategy for Cyber-Physical Power Systems

2018 ◽  
Author(s):  
Etinosa Ekomwenrenren ◽  
Hatem Alharbi ◽  
Taisir Elgorashi ◽  
Jaafar Elmirghani ◽  
Petros Aristidou
Keyword(s):  
Power Systems ◽  
Power System ◽  
Control Strategy ◽  
Physical Nature ◽  
System Stability ◽  
Wide Area ◽  
Equivalent Model ◽  
Communication Infrastructure ◽  
Damping Controllers ◽  
And Control

The cyber-physical nature of electric power systems has increased immensely over the last decades, with advanced communication infrastructure paving the way. It is now possible to design wide-area controllers, relying on remote monitor and control of devices, that can tackle power system stability problems more effectively than local controllers. However, their performance and security relies extensively on the communication infrastructure and can make power systems vulnerable to disturbances emerging on the cyber side of the system. In this paper, we investigate the effect of communication delays on the performance and security of wide-area damping controllers (WADC) designed to stabilise oscillatory modes in a Cyber-Physical Power System (CPPS). We propose a rule-based control strategy that combines wide-area and traditional local stabilising controllers to increase the performance and maintain the security of CPPS. The proposed strategy is validated on a reduced CPPS equivalent model of Great-Britain (GB).

scholarly journals A Composite Nonlinear Controller for Power Systems with STATCOM under External Disturbances

2020 ◽  
Vol 18 (2) ◽  
pp. 107-117
Author(s):  
Adirak Kanchanaharuthai ◽  
Piraporn Konkhum ◽  
Kruwan Wongsurith
Keyword(s):  
Power Systems ◽  
State Feedback Control ◽  
System Stability ◽  
Control Technique ◽  
Nonlinear Controller ◽  
Static Synchronous Compensator ◽  
External Disturbances ◽  
Loop Dynamics ◽  
Dynamic Performances ◽  
Better Than

This paper concentrates on the design of a composite nonlinear stabilizing state feedback control for power systems with static synchronous compensator (STATCOM) with the help of a combination of backstepping strategy and a nonlinear disturbance approach. The disturbance observer is used to estimate unavoidably external disturbances. Thus, the obtained control law can be used to successfully stabilize the system stability and reject undesired external disturbances. In order to demonstrate the effectiveness of the developed process design, numerical simulation results are provided to indicate that the presented composite controller can improve dynamic performances, rapidly suppress system oscillations of the overall closed-loop dynamics, and despite having inevitably external disturbances, performs better than a conventional backstepping control technique.

scholarly journals An Enhanced Control Strategy for Mitigation of State-Transition Oscillation Phenomena in Grid-Forming Self-Synchronized Converter System with Islanded Power System

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8453
Author(s):  
Ki Ryong Kim ◽  
Sangjung Lee ◽  
Jong-Pil Lee ◽  
Jaesik Kang
Keyword(s):  
Power System ◽  
Control Strategy ◽  
State Transition ◽  
Reactive Power ◽  
Phase Synchronization ◽  
Control Method ◽  
System Stability ◽  
Electromagnetic Transient ◽  
Point Of Common Coupling ◽  
Hardware In Loop

This paper proposes an enhanced control strategy for mitigating state-transition oscillations in active and reactive power responses of self-synchronized converter system to secure the islanded power system stability. The self-synchronized converter is well known for “grid-forming” that is able to operate to stand-alone mode (SAM) providing grid voltage and frequency without phase synchronization units. Although the grid-forming (GFM) is self-synchronized, the inherent synchronization principle causes system degradation in which should maintain a point of common coupling (PCC) voltage for critical loads as well as transitions from grid-connected mode (GCM) to SAM and vice versa. Therefore, this paper focuses on resolving the inherent oscillatory issues in GFM self-synchronized converter system (especially adopted ‘synchronverter’ principle), and proposes a control strategy for controllability improvement based on stability analysis for smooth state-transition under islanded power system. The efficacy of the proposed control method is verified through a high-fidelity electromagnetic transient (EMT) simulation with case studies on 30kW synchronverter system and further experimental hardware-in-loop system (HILS) test with Opal-RT (OP-5707) platform.

scholarly journals Simulation of Grid Connected Three-Level Neutral-Point-Clamped qZS Inverter using PSCAD

2013 ◽  
Vol 2 (1) ◽  
pp. 14-19
Author(s):  
Carlos Roncero-Clemente ◽  
Enrique Romero-Cadaval ◽  
Oleksandr Husev ◽  
Dmitri Vinnikov ◽  
Serhii Stepenko
Keyword(s):  
Control Strategy ◽  
Input Voltage ◽  
Neutral Point ◽  
Electrical Grid ◽  
Photovoltaic Applications ◽  
Point Of Common Coupling ◽  
Common Coupling ◽  
Output Filter ◽  
Better Than ◽  
Peak Value

AbstractThis paper is focused on a single-phase three-level neutral-point-clamped quasi-z-source inverter when it is operating being connected to the electrical grid. A control strategy for injecting current synchronized in phase with the voltage at the point of common coupling has been proposed and studied. It is achieved by means of controlling the output voltage between branches adjusting the output current by using a d-q frame and the analysis of the output filter. The control strategy generates the reference to be used in the modulation technique and it has been validated with and without shoot-through switching states. A method to calculate the minimum value of the shoot-through duty cycle is also explained in order to assure the proper control of the injected current when the input voltage is less than peak value of the grid voltage. It is an important feature because 3L-NPC qZSI due to its possibility of boosting input voltage in a single stage would operate better than a traditional inverter, for instance in photovoltaic applications when the value of irradiance is decreased. The presented results have been obtained using PSCAD/EMTDC as a simulation tool.

scholarly journals On-Site Engineering Test of Active Support Control for the PV Station and Wind Farm in the AC-DC Hybrid Power Grid under Extreme Fault Conditions

Complexity ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Xiao-ling Su ◽  
Lai-jun Chen ◽  
Jun Yang ◽  
Zhengxi Li ◽  
Peng Zhou ◽  
...  
Keyword(s):  
Power Systems ◽  
Power System ◽  
Control Strategy ◽  
Wind Farm ◽  
Power Grid ◽  
Renewable Energy Sources ◽  
Wind Farms ◽  
System Stability ◽  
Test Results ◽  
Hybrid Power

Power systems have developed significantly because of the increasing share of renewable energy sources (RESs). Despite the advantages, they also bring inevitable challenges to power system stability, especially under extreme fault conditions. This paper presents a practical active support control strategy for RESs to support the power grid under extreme fault conditions. The proof process is taken in an AC-DC hybrid power grid integrated with large capacity of PV stations and wind farms. The on-site engineering test results reflect that RESs bring potential risks in the AC-DC hybrid power grid operation and validate the excellent engineering practical features of the proposed control strategy. In addition, test results also reveal predisposing factors of power system instability which are missing in the simulation and fault simulation device-based testing results. They prove the outstanding advantages of on-site engineering tests.

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