Cooperative fuzzy controllers for autonomous voltage regulation in Smart Grids

<p>With the advent of smart grids, voltage fluctuation has increased, especially in active distribution networks with a high penetration of distributed energy resources and a large deployment of electric vehicles. In this context, on-load tap-changer (OLTC) distribution transformers have become a key component, mainly because they provide automatic voltage regulation capability. In order to maximise the lifetime of OLTC devices, the number of tap operations should be minimised, avoiding unnecessary changes, but ensuring the main requirement: to keep the voltage within the limits permitted. Therefore, when the automatic mode is active, the control policy followed by the automatic voltage regulator is decisive. This paper presents a novel form of functional approximation of these policies. Furthermore, by means of a unified framework, a methodology for the simulation of policies based on control theory is proposed. The unified framework has been validated using real data. The results confirm the ability of the introduced framework to simulate different scenarios, optimising and validating both existing and new policies by observing their effect on transformer behavior. In addition, it allows the determination of the best fit policies depending on characteristics such as the pre-selected voltage set point or the voltage variation between transformer taps.</p>

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Multiterminal HVDC System with Power Quality Enhancement

Energies ◽

10.3390/en14051306 ◽

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.

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Effect of Series Active Voltage Conditioners on Modernized Grid

10.26686/wgtn.17012342 ◽

2021 ◽

Author(s):

◽

Mostafa Ahmed Nazih Ahmed

Keyword(s):

Smart Grids ◽

Communication Systems ◽

Fossil Fuels ◽

Renewable Energy Sources ◽

Interaction Mechanism ◽

Voltage Regulation ◽

Initial Attempt ◽

Pv Systems ◽

Operational Characteristics ◽

The Subject

<p>Modernized “Smart” grids incorporate renewable energy sources on a widespread scale. Foreseen expansion in integrating more renewables is driven by global CO₂ emission concerns and depletion of fossil fuels. Active elements/devices are added to smart grids to enhance power availability and quality with the aid of advances in power electronics and communication systems. Active Voltage Conditioner (AVC) represents state-of-the-art in the field of voltage regulation and conditioning, however; integrating it into modernized grids has not been the subject of detailed study yet. This thesis details the AVC-Grid interaction mechanism and associated performance parameters. ABB PCS100 AVC computer model based on MATLAB/PLECS platform is used as a basis for the proposed mathematical model. Accordingly, operational V-I characteristics is derived and impact of equivalent grid stiffness is analyzed. In this thesis, the modeling of AVC has been introduced as seen by the grid in light of MATLAB/PLECS simulations. The conditioning ratio to describe the “depth” of load conditioning had been introduced. Modeling of AVC operational characteristics has been developed and dependency on conditioning ratio and equivalent grid stiffness had been investigated. Also, the analysis of grid behavior due to AVC operation during overvoltages and undervoltages has been carried out as well as discussing the envisaged impact on tied WTG/PV systems. The thesis represents an initial attempt to model the AVC and discusses its envisaged impact on smart grids.</p>

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Analysis of the number of switches of on-load tap changer of a power transformer for field substation, taking into account discrete time and voltage level sampling

E3S Web of Conferences ◽

10.1051/e3sconf/202022001056 ◽

2020 ◽

Vol 220 ◽

pp. 01056

Author(s):

T.V. Tabachnikova ◽

L.V. Shvetskova ◽

A.V. Yumalin

Keyword(s):

Smart Grids ◽

Oil And Gas ◽

Reactive Power ◽

Power Transformer ◽

Voltage Regulation ◽

Electrical Network ◽

Universal Method ◽

Voltage Level ◽

Tap Changer ◽

Load Tap Changer

The introduction of “smart grids” technologies poses the problems of multi-criteria determination of the optimum voltage in the main substation of the object under study. In this study the busbar sections of the field substation of the oil and gas company is considered as the main substation. This paper studies regulation of voltage level in an electrical network using on-load tap changer (OLTC) of a power transformer for field substation of an oil and gas enterprise. Considered are approaches for voltage regulation taking into account the development of smart grid technologies. The authors have developed a universal method for determining the optimal voltage level on the busbar sections of a field substation, which allows for selection of the optimum voltage in accordance with certain parameters: loss of active, reactive power, voltage, electricity consumption, specific consumption or efficiency factor of artificial oil lift. The actual daily graphs of consumption of active, reactive power and voltage level at one of the field substations of PJSC Tatneft were studied. The operation mode of on-load tap-changer drive of the field transformer was modeled, taking into account the calculated optimal values of voltage and the dead zone. The paper presents the results of study of automatic voltage regulation on busbar sections of a field substation, taking into account the constraints for tap changer switches of a power transformer.

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