Research

23 pages, 1353 KiB

Open AccessArticle

Study on Energy Efficiency and Harmonic Emission of Photovoltaic Inverters

by Krzysztof Chmielowiec, Łukasz Topolski, Aleks Piszczek, Tomasz Rodziewicz and Zbigniew Hanzelka

Energies 2022, 15(8), 2857; https://0-doi-org.brum.beds.ac.uk/10.3390/en15082857 - 13 Apr 2022

Cited by 2 | Viewed by 1831

The paper presents the results of an experimental study of 26 brand new photovoltaic (PV) inverters widely available for sale on the EU market; the study was conducted in 2021 by researchers at the AGH University of Science and Technology and Tauron Dystrybucja [...] Read more.

The paper presents the results of an experimental study of 26 brand new photovoltaic (PV) inverters widely available for sale on the EU market; the study was conducted in 2021 by researchers at the AGH University of Science and Technology and Tauron Dystrybucja (Polish DSO). The purpose of the study was to compare and assess PV inverter performances in terms of their DC/AC conversion efficiencies, MPPT efficiencies, and harmonic current emissions. To examine the PV inverters, a laboratory test stand was prepared according to the standard EN 50530 and the technical report IEC/TR 61000-3-15. It was composed of a photovoltaic array simulator, a programmable regenerative AC voltage source, and a power analyzer. Each PV inverter was tested in various operating states determined by the DC voltage levels and the volume of active power generation. The results allowed for a benchmark assessment of PV inverters available on the market. The results showed how various energy efficiency indicators of individual PV inverters changed depending on their operating points. The results also revealed that, based on the performed harmonic emission tests, individual harmonics were within the normative requirements; however, in the case of several PV inverters, attention was drawn to the presence of relatively high switching frequency-related components exceeding permissible levels. Full article

(This article belongs to the Special Issue Power Electronics in Renewable, Storage, and Charging Systems)

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13 pages, 5682 KiB

Open AccessArticle

Influence of the Placement Accuracy of the Brushless DC Motor Hall Sensor on Inverter Transistor Losses

by Krzysztof Kolano, Artur Jan Moradewicz, Bartosz Drzymała and Jakub Gęca

Energies 2022, 15(5), 1822; https://0-doi-org.brum.beds.ac.uk/10.3390/en15051822 - 01 Mar 2022

Cited by 5 | Viewed by 2390

Abstract

Low-power BLDC motors are often and willingly used in many drive devices due to their functional advantages. They are also used in advanced positioning systems, where their good dynamic performance parameters are used. The control systems use shaft position sensors mounted on motors, [...] Read more.

Low-power BLDC motors are often and willingly used in many drive devices due to their functional advantages. They are also used in advanced positioning systems, where their good dynamic performance parameters are used. The control systems use shaft position sensors mounted on motors, the structure of which is based on magnetic elements and Hall sensors. The aim of this article was to investigate the influence of the BLDC motor quality on the correct operation of the control semiconductor system. The article presents the effect of BLDC motor shaft observation system’s inaccuracies on the friction and current amplitudes of individual inverter keys. Waveforms of the controller phase currents are considered and recorded on a test bench that allows precise sensor position changes. In addition, the effect of sensor misalignment on power losses in individual inverter transistors is investigated. The article shows a significant influence of the motor shaft observation system’s assembly accuracy on the current amplitudes of individual driver transistors and their power losses, which makes it necessary to consider these parameters when constructing power electronic systems. Full article

(This article belongs to the Special Issue Power Electronics in Renewable, Storage, and Charging Systems)

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14 pages, 17593 KiB

Open AccessArticle

Implementation of the Improved Active Frequency Drift Anti-Islanding Method into the Three-Phase AC/DC Converter with the LCL Grid Filter

by Krzysztof Dmitruk and Andrzej Sikorski

Energies 2022, 15(4), 1323; https://0-doi-org.brum.beds.ac.uk/10.3390/en15041323 - 11 Feb 2022

Cited by 5 | Viewed by 1401

Abstract

The article presents a modified standard Active Frequency Drift (AFD) method used to detect unintentional island operation in converters generating electricity from renewable energy sources to the power grid. The primary aim of each of the island operation detection methods is the possibility [...] Read more.

The article presents a modified standard Active Frequency Drift (AFD) method used to detect unintentional island operation in converters generating electricity from renewable energy sources to the power grid. The primary aim of each of the island operation detection methods is the possibility of shortening the energising of a separate part of the power grid. The proposed method eliminates fragments of the reference current signal when it reaches a constant value for a particular time. This part of the signal is replaced with the hyperbolic sine function. It allows reducing the value of Total Harmonic Distortions (THD) while maintaining the same effectiveness of island operation detection. The article contains a detailed description of the newly proposed type of disturbance generation. The proposed solution is verified by conducting simulation and laboratory tests. The possibility of shortening the island operation detection time is proven by increasing the maximum distortion introduced into the current without exceeding the permissible THD limit for converters connected to the power grid. Full article

(This article belongs to the Special Issue Power Electronics in Renewable, Storage, and Charging Systems)

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13 pages, 7030 KiB

Open AccessArticle

Phase-Independent Reactive Power Compensation Based on Four-Wire Power Converter in the Presence of Angular Asymmetry between Voltage Vectors

by Dariusz Zieliński, Bartłomiej Stefańczak and Konrad Jędrys

Energies 2022, 15(2), 497; https://0-doi-org.brum.beds.ac.uk/10.3390/en15020497 - 11 Jan 2022

Cited by 9 | Viewed by 1570

Abstract

The paper presents the reactive power compensation method that allows for reducing the active power flow even in the presence of angular asymmetry between voltage vectors of the utility grid. Reactive power compensation ensures the reduction of power transmission losses and therefore brings [...] Read more.

The paper presents the reactive power compensation method that allows for reducing the active power flow even in the presence of angular asymmetry between voltage vectors of the utility grid. Reactive power compensation ensures the reduction of power transmission losses and therefore brings significant economic benefits to electricity consumers. The concept of the alternating current/direct current (AC/DC) converter for prosumer applications operating as a local reactive power compensator has been proposed. The system is driven by a multi-resonant algorithm, allowing for independent control of the reactive power in each phase. The proposed method was validated experimentally by using a prototype of the converter, programmable AC source, and grid impedance model. The method made it possible to cover the reactive power demand without unnecessary active power generation and thus to improve the efficiency of the analyzed prototype. This solution can be implemented particularly in radial grids and non-urban areas. Full article

(This article belongs to the Special Issue Power Electronics in Renewable, Storage, and Charging Systems)

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16 pages, 4183 KiB

Open AccessArticle

An Analysis of Electromagnetic Disturbances from an Electric Vehicle Charging Station

by Paweł Mazurek and Aleksander Chudy

Energies 2022, 15(1), 244; https://0-doi-org.brum.beds.ac.uk/10.3390/en15010244 - 30 Dec 2021

Cited by 11 | Viewed by 2797

Abstract

The electric vehicles (EVs) could potentially have a significant impact on power quality parameters and distribution networks as they are non-linear loads and their charging might result in tremendous power demand. When connected to the utility grid, a large number of EV charging [...] Read more.

The electric vehicles (EVs) could potentially have a significant impact on power quality parameters and distribution networks as they are non-linear loads and their charging might result in tremendous power demand. When connected to the utility grid, a large number of EV charging stations from different manufacturers might create significant harmonic current emissions, impact the voltage profile, and eventually affect the power quality. Nevertheless, practical examples of disturbances from charging stations have not been made public. This paper aims to clarify the characteristics of conductive disturbances and levels of current harmonics generated by charging station and their severity on the quality of electric energy. The analysis was based on tests of a prototype station of an EV charging station integrated with a LED street light. The tests concern the determination of current harmonics and the values of conductive electromagnetic disturbances in the 150 kHz–30 MHz range. The test results of the prototype charger with observed exceedances of current harmonics (25th–39th range) and conducted interference exceedances are comprehensively described. After applying filtering circuits to the final version of the station, retesting in an accredited laboratory showed qualitative compliance. Full article

(This article belongs to the Special Issue Power Electronics in Renewable, Storage, and Charging Systems)

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16 pages, 7006 KiB

Open AccessEditor’s ChoiceArticle

Comparison of Two Power Converter Topologies in Wind Turbine System

by Andrzej Sikorski, Piotr Falkowski and Marek Korzeniewski

Energies 2021, 14(20), 6574; https://0-doi-org.brum.beds.ac.uk/10.3390/en14206574 - 13 Oct 2021

Cited by 7 | Viewed by 2091

Abstract

The article presents comprehensive results of research on two representative topologies of converters used in the path of processing energy generated in a wind turbine and transmitted to the grid. The topology T1 uses a two-level transistor-controlled rectifier as a converter from the [...] Read more.

The article presents comprehensive results of research on two representative topologies of converters used in the path of processing energy generated in a wind turbine and transmitted to the grid. The topology T1 uses a two-level transistor-controlled rectifier as a converter from the generator side, while the T2 topology uses DC/DC boost converter. In both topologies, a three-level back-to-back converter with a line filter L was used as a grid converter. The conclusions indicate the tendency of changes in power losses depending on the aforementioned parameters and can be used at the stage of deciding on the choice of topology, operating parameters or selection of control methods depending on the specific operating conditions of the wind turbine. Full article

(This article belongs to the Special Issue Power Electronics in Renewable, Storage, and Charging Systems)

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14 pages, 5924 KiB

Open AccessArticle

Frequency Estimation for Grid-Tied Inverters Using Resonant Frequency Estimator

by Dariusz Zieliński and Karol Fatyga

Energies 2021, 14(20), 6513; https://0-doi-org.brum.beds.ac.uk/10.3390/en14206513 - 11 Oct 2021

Cited by 2 | Viewed by 1474

Abstract

This paper introduces a new strategy of frequency estimation for grid-tied and stand-alone mode AC/DC power converters. Frequency stabilization is required, especially when operating in stand-alone mode with a Droop Control strategy, or in hybrid mode with a Diesel generator. It is also [...] Read more.

This paper introduces a new strategy of frequency estimation for grid-tied and stand-alone mode AC/DC power converters. Frequency stabilization is required, especially when operating in stand-alone mode with a Droop Control strategy, or in hybrid mode with a Diesel generator. It is also required to reduce or increase power output along with grid frequency changes. The novel strategy utilizes a resonant filter to estimate the frequency of the voltage grid and is referenced as a resonant-frequency-estimator (RFE). A mathematical background is presented for the proposed estimator and its performance is evaluated. It is compared with three common frequency estimation algorithms: SRF-FLL, DDSRF-FLL, and DSOGI-FLL. Results are presented for three cases: frequency swing, harmonics injection, and type B short-circuit. Results are analyzed and the conclusion shows that the proposed novel strategy has comparable parameters to commonly used frequency estimation algorithms while having a loopless structure. Full article

(This article belongs to the Special Issue Power Electronics in Renewable, Storage, and Charging Systems)

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10 pages, 5491 KiB

Open AccessArticle

Dual Active Bridge as a DC Link Current Pulsation Compensator in Energy Storage Applications

by Dariusz Zieliński and Karol Fatyga

Energies 2021, 14(19), 6141; https://0-doi-org.brum.beds.ac.uk/10.3390/en14196141 - 27 Sep 2021

Cited by 6 | Viewed by 1617

Abstract

This paper presents a system for compensating DC link current pulsation in four-wire inverters with energy storage operating under unbalanced load conditions. This phenomenon occurs when an inverter with an independent power control in each of the phases attempts to locally balance the [...] Read more.

This paper presents a system for compensating DC link current pulsation in four-wire inverters with energy storage operating under unbalanced load conditions. This phenomenon occurs when an inverter with an independent power control in each of the phases attempts to locally balance the voltage imbalance in the grid. Such a condition creates a DC link current pulsation, which is destructive for energy storage connected to the DC link. The conditions when this situation appears are presented in detail in the paper. A solution to this problem is proposed in the form of a dual active bridge converter and a capacitor bank to actively compensate this pulsation. The control algorithm is proposed based on a proportional-resonant controller. This paper presents the technical background and method by which the controller parameters were calculated, implemented and tested in a real-time system. The test results are presented and discussed, concluding that the proposed solution is an attractive option for protecting the energy storage from DC link current pulsation. The dual active bridge converter combined with resonant controller can compensate the DC link current pulsation almost entirely. Full article

(This article belongs to the Special Issue Power Electronics in Renewable, Storage, and Charging Systems)

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14 pages, 4823 KiB

Open AccessArticle

Cost-Effective Power Converters for Small Wind Turbines

by Sławomir Karyś and Paweł Stawczyk

Energies 2021, 14(18), 5906; https://0-doi-org.brum.beds.ac.uk/10.3390/en14185906 - 17 Sep 2021

Cited by 8 | Viewed by 1859

Abstract

This paper presents AC/DC converters for cost-effective small wind turbine systems. The analysis focuses on reliable, sensor-less, and low-cost solutions. A recently developed type of the three phase AC/DC two-switch converter is compared, for the first time, using simulations and experiments, with two [...] Read more.

This paper presents AC/DC converters for cost-effective small wind turbine systems. The analysis focuses on reliable, sensor-less, and low-cost solutions. A recently developed type of the three phase AC/DC two-switch converter is compared, for the first time, using simulations and experiments, with two other converters. The operating principles and control methods are discussed. Simulation results are verified experimentally and interesting conclusions are drawn. It is shown that less known converters are also attractive solutions for use in small wind turbines. Full article

(This article belongs to the Special Issue Power Electronics in Renewable, Storage, and Charging Systems)

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22 pages, 9651 KiB

Open AccessArticle

A Dual Rising Edge Shift Algorithm for Eliminating the Transient DC-Bias Current in Transformer for a Dual Active Bridge Converter

by Michal Gierczynski, Lech M. Grzesiak and Arkadiusz Kaszewski

Energies 2021, 14(14), 4264; https://0-doi-org.brum.beds.ac.uk/10.3390/en14144264 - 14 Jul 2021

Cited by 8 | Viewed by 1878

Abstract

This paper deals with a well-known problem of the transient DC-bias current occurring during a phase shift transition in dual active bridge (DAB) DC/DC converters. This phenomenon, if not compensated, can cause damage to the converter or deteriorate its performance. One aim of [...] Read more.

This paper deals with a well-known problem of the transient DC-bias current occurring during a phase shift transition in dual active bridge (DAB) DC/DC converters. This phenomenon, if not compensated, can cause damage to the converter or deteriorate its performance. One aim of this paper is to present a solution which allows for the elimination of the undesired transient DC-bias component in current waveforms. This solution is the dual rising edge shift (DRES) compensation algorithm. It provides a very simple implementation and fast settling time within the first half of a switching period. Moreover, the solution is independent on any measurements or system parameter values. It is based on the double-sided single phase shift (DSSPS) modulation, which is described in detail along with a converter model in steady-state. Then, the mechanisms leading to the transient DC-bias are explained, and the compensation algorithm is derived. The performance of the algorithm has been tested using a laboratory prototype. A comprehensive set of tests, involving rapid step changes in power flow and frequency sweep, are provided. Finally, the features of the proposed algorithm are briefly discussed. Full article

(This article belongs to the Special Issue Power Electronics in Renewable, Storage, and Charging Systems)

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