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Advancing Grid-Connected Renewable Generation Systems 2019
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Advancing Grid-Connected Renewable Generation Systems 2019

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Energy Science and Technology".

Deadline for manuscript submissions: closed (31 August 2020) | Viewed by 42922
Related Special Issue: Advancing Grid-Connected Renewable Generation Systems 2021

Special Issue Editors

Prof. Dr. Frede Blaabjerg

grade E-Mail Website
Guest Editor
Department of Energy Technology, Aalborg University, 9220 Aalborg, Denmark
Interests: power electronics and its applications in motor drives; wind turbines; PV systems; harmonics; reliability of power electronic systems
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Yongheng Yang

E-Mail Website
Guest Editor
College of Electrical Engineering, Zhejiang University, Zheda Rd. 38, Hangzhou 310027, China
Interests: power converter control; grid integration of renewable energy; photovoltaic power systems; reliability in power electronics and systems
Special Issues, Collections and Topics in MDPI journals
Dr. Ariya Sangwongwanich

E-Mail Website
Guest Editor
Department of Energy Technology, Aalborg University, 9220 Aalborg, Denmark
Interests: control of grid-connected converters; photovoltaic systems; reliability in power electronics and high-power multilevel converters
Special Issues, Collections and Topics in MDPI journals
Dr. Elizaveta Liivik

E-Mail Website
Guest Editor
Department of Energy Technology, Aalborg University, 9220 Aalborg, Denmark
Interests: impedance-source power electronic converters; renewable energy and distributed generation; control and reliability issues of power electronic converters in active distribution networks
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Renewables are making pace to become a major source in the energy paradigm, which has been undergoing significant shifts over the past few decades. In order to enable a wide-scale integration of renewables, advanced grid-interfacing control solutions are strongly demanded. On one hand, power conversion efficiency and reliability are the keys aspects that need to be addressed in order to maximize the total energy yield, thereby reducing the overall cost of energy. On the other hand, the stability of the energy system under a high penetration-level of renewable energy is also a concern from the system perspective. This can also be seen in the updated regulation for the grid-connected renewable energy system. Power electronics are the key enabling technology for achieving the above demands, and have been widely used for renewable energy systems such as wind turbine, solar energy, and energy storage systems. Advancing the design, control, operation, and integration of power electronics has the potential to improve the performance of the grid-connected renewable energy systems. This Special Issue, thus, serves to address the present challenging issues regarding the integration of renewable energies into a sustainable and resilient power system. Topics within, but not limited to, grid-connected renewable energy systems, in general, their control, operation, and design, are invited.

Prof. Dr. Frede Blaabjerg
Prof. Dr. Yongheng Yang
Dr. Ariya Sangwongwanich
Dr. Elizaveta Liivik
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Applied Sciences is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Renewable energy conversion
  • Power electronics converter topologies and control for grid-connected renewables
  • Energy policies, grid codes, and their development
  • Energy and power management in renewable energy systems
  • Wind power generation (onshore and offshore)
  • Photovoltaic power systems (PV, concentrator PV, and concentrated solar power plants)
  • Fuel cell systems
  • Advanced control for grid-connected renewables
  • Emerging renewable energy technology
  • Wide-bandgap power semiconductor applications in renewable energy systems

Published Papers (15 papers)

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Editorial

Jump to: Research, Review

4 pages, 194 KiB  
Editorial
Advancing Grid-Connected Renewable Generation Systems
by Elizaveta Liivik, Yongheng Yang, Ariya Sangwongwanich and Frede Blaabjerg
Appl. Sci. 2021, 11(7), 3058; https://doi.org/10.3390/app11073058 - 29 Mar 2021
Viewed by 1494
Abstract
If we look at the history of renewable energy sources (RESs), how it all began, and how rapidly they continue to develop, it can be argued that one of the main reasons is due to the rapid improvements in power electronics technology in [...] Read more.
If we look at the history of renewable energy sources (RESs), how it all began, and how rapidly they continue to develop, it can be argued that one of the main reasons is due to the rapid improvements in power electronics technology in interfacing the renewable source to the grid [...] Full article
(This article belongs to the Special Issue Advancing Grid-Connected Renewable Generation Systems 2019)

Research

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18 pages, 4132 KiB  
Article
Estimation of Soiling Losses from an Experimental Photovoltaic Plant Using Artificial Intelligence Techniques
by Noelia Simal Pérez, Joaquín Alonso-Montesinos and Francisco Javier Batlles
Appl. Sci. 2021, 11(4), 1516; https://doi.org/10.3390/app11041516 - 08 Feb 2021
Cited by 12 | Viewed by 2403
Abstract
Fossil fuels and their use to generate energy have multiple disadvantages, with renewable energies being presented as an alternative to this situation. Among them is photovoltaic solar energy, which requires solar installations that are capable of producing energy in an optimal way. These [...] Read more.
Fossil fuels and their use to generate energy have multiple disadvantages, with renewable energies being presented as an alternative to this situation. Among them is photovoltaic solar energy, which requires solar installations that are capable of producing energy in an optimal way. These installations will have specific characteristics according to their location and meteorological variables of the place, one of these factors being soiling. Soiling generates energy losses, diminishing the plant’s performance, making it difficult to estimate the losses due to deposited soiling and to measure the amount of soiling if it is not done using very economically expensive devices, such as high-performance particle counters. In this work, these losses have been estimated with artificial intelligence techniques, using meteorological variables, commonly measured in a plant of these characteristics. The study consists of two tests, depending on whether or not the short circuit current (Isc) has been included, obtaining a maximum normalized root mean square error (nRMSE) lower than 7%, a correlation coefficient (R) higher than 0.9, as well as a practically zero normalized mean bias error (nMBE). Full article
(This article belongs to the Special Issue Advancing Grid-Connected Renewable Generation Systems 2019)
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13 pages, 1541 KiB  
Article
Common-Mode Voltage Analysis and Reduction for the Quasi-Z-Source Inverter with a Split Inductor
by Wenjie Liu, Yongheng Yang, Tamas Kerekes, Elizaveta Liivik, Dmitri Vinnikov and Frede Blaabjerg
Appl. Sci. 2020, 10(23), 8713; https://doi.org/10.3390/app10238713 - 04 Dec 2020
Cited by 4 | Viewed by 2000
Abstract
In transformerless grid-connected photovoltaic (PV) systems, leakage currents should be properly addressed. The voltage fluctuations between the neutral point of the grid and the PV array, i.e., common-mode voltage (CMV), will affect the value of the leakage currents. Therefore, the leakage currents can [...] Read more.
In transformerless grid-connected photovoltaic (PV) systems, leakage currents should be properly addressed. The voltage fluctuations between the neutral point of the grid and the PV array, i.e., common-mode voltage (CMV), will affect the value of the leakage currents. Therefore, the leakage currents can be attenuated through proper control of the CMV. The CMV depends on the converter topology and the modulation strategy. For the quasi-Z-source inverter (qZSI), the amplitude of the high-frequency components in the CMV increases due to the extra shoot-through (ST) state. The CMV reduction strategies for the conventional voltage source inverter (VSI) should be modified when applied to the qZSI. In this paper, an input-split-inductor qZSI is introduced to reduce the CMV, in which all the CMV reduction strategies for the VSI can be used directly with appropriate ST state insertion. Moreover, the proposed method can be extended to impedance source converters with a similar structure. Simulations and experimental tests demonstrate the effectiveness of the proposed strategy for the qZSI in terms of CMV reduction. Full article
(This article belongs to the Special Issue Advancing Grid-Connected Renewable Generation Systems 2019)
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22 pages, 1312 KiB  
Article
Multiple-Loop Control Design for a Single-Stage PV-Fed Grid-Tied Differential Boost Inverter
by Abdelali El Aroudi, Reham Haroun, Mohamed Al-Numay and Meng Huang
Appl. Sci. 2020, 10(14), 4808; https://doi.org/10.3390/app10144808 - 13 Jul 2020
Cited by 12 | Viewed by 2046
Abstract
This paper focuses on the control design of a differential boost inverter when used in single-stage grid-tied PV systems. The inverter performs both Maximum Power Point Tracking (MPPT) at the DC side and Power Factor Correction at the AC side. At first, the [...] Read more.
This paper focuses on the control design of a differential boost inverter when used in single-stage grid-tied PV systems. The inverter performs both Maximum Power Point Tracking (MPPT) at the DC side and Power Factor Correction at the AC side. At first, the state-space time-domain averaged model of the inverter is derived and the small signal frequency domain model is obtained using a quasi-static approximation in which the inverter is treated as a DC–DC converter with a slowly varying output voltage. Then, the controllers are designed using a three-loop strategy in which the inverter inductor currents loop is used for suitable compensation, the DC Photovoltaic (PV) voltage loop is used for MPPT and the output grid current loop is used for Power Factor Correction (PFC) and active power control. The selection of the control parameters is based on a compromise among suitable system performances such as settling time of the input PV voltage, the sampling period of the MPPT, total harmonic distortion of the output grid current, power factor as well as suppression of subharmonic oscillation for all the range of the operating duty cycle. The resulting design ensures that the oscillations of the voltage, current and power at the DC side and the grid current at the AC side are effectively controlled. The validity of the proposed control design is verified by numerical simulations performed on the switched model of the system demonstrating its robustness and fast response under irradiance variations and MPPT perturbations despite the nonlinearity and complexity of the system. Full article
(This article belongs to the Special Issue Advancing Grid-Connected Renewable Generation Systems 2019)
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21 pages, 55223 KiB  
Article
Light Load Efficient Silicon Power Converters Based on Wide Bandgap Circuit Extensions
by Markus Makoschitz and Sumanta Biswas
Appl. Sci. 2020, 10(14), 4730; https://doi.org/10.3390/app10144730 - 09 Jul 2020
Cited by 2 | Viewed by 2574
Abstract
A power electronics converter is generally designed for a specific load condition. However, depending on the applications and its mission profiles, the operating load conditions can be distinctly lower than the specified ones (PV cell under shading conditions, etc.). During this light load [...] Read more.
A power electronics converter is generally designed for a specific load condition. However, depending on the applications and its mission profiles, the operating load conditions can be distinctly lower than the specified ones (PV cell under shading conditions, etc.). During this light load condition, the efficiency diminishes considerably, especially if Si–IGBT devices are considered within the power circuit. This study explains a light-load circuit extension based on wide-bandgap (WBG, silicon carbide and gallium nitride) material, which can improve the light-load efficiency and transient response of the conventional IGBT-based active rectifiers and inverter. Such an additional circuit extension is, in general, associated with additional cost. Numerous factors, such as the power electronics application itself, mission profiles, converter power rating and sizing of passive components, etc., can shift the break-even point of the upgraded power electronics system in terms of time. Therefore, a profound investigation of the relevant areas of interest is required in advance to ensure the most efficient amortization of the additional incurred costs of the applied circuitry. A 125 kW 3-phase six-switch inverter is discussed to highlight relevant effects in light-load operation that must be considered for final product design. Full article
(This article belongs to the Special Issue Advancing Grid-Connected Renewable Generation Systems 2019)
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12 pages, 5818 KiB  
Article
Thermal Mapping of Power Semiconductors in H-Bridge Circuit
by Dao Zhou, Yingzhou Peng, Francesco Iannuzzo, Michael Hartmann and Frede Blaabjerg
Appl. Sci. 2020, 10(12), 4340; https://doi.org/10.3390/app10124340 - 24 Jun 2020
Cited by 7 | Viewed by 2774
Abstract
In this paper, a universal H-bridge circuit is used as a loading emulator to investigate the loss and thermal models of the power semiconductor. Based on its operation principle and modulation method, the dominating factors’ (e.g., power factor, loading current, fundamental frequency, and [...] Read more.
In this paper, a universal H-bridge circuit is used as a loading emulator to investigate the loss and thermal models of the power semiconductor. Based on its operation principle and modulation method, the dominating factors’ (e.g., power factor, loading current, fundamental frequency, and switching frequency) impact on the thermal stress of power semiconductors is considerably evaluated. The junction temperature in terms of the mean value and its swing is verified by using Piecewise Linear Electrical Circuit Simulation (PLECS) simulation and experimental setup. It helps to allocate the loading condition in order to obtain the desired thermal stress. Full article
(This article belongs to the Special Issue Advancing Grid-Connected Renewable Generation Systems 2019)
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17 pages, 3542 KiB  
Article
Practical Submodule Capacitor Sizing for Modular Multilevel Converter Considering Grid Faults
by Zhijian Yin, Huan Qiu, Yongheng Yang, Yi Tang and Huai Wang
Appl. Sci. 2020, 10(10), 3550; https://doi.org/10.3390/app10103550 - 20 May 2020
Cited by 5 | Viewed by 2295
Abstract
Submodule (SM) capacitors are key elements in the modular multilevel converter (MMC), the design of which influences the entire system performance. In practical cases, SM capacitor sizing must consider the abnormal system operation (e.g., grid faults). In order to find a clear design [...] Read more.
Submodule (SM) capacitors are key elements in the modular multilevel converter (MMC), the design of which influences the entire system performance. In practical cases, SM capacitor sizing must consider the abnormal system operation (e.g., grid faults). In order to find a clear design boundary for SM capacitors, a practical capacitor sizing method is presented for the first time in this paper, considering the grid-fault-ride-through operation of the MMC, impact of MMC control system, and aging mechanism of capacitors. The SM capacitor rated voltage, capacitance, ESR, thermal resistance, and lifetime can be decided to ensure reliable operations of the MMC during grid faults. The effectiveness of the proposed method has been verified through experimental tests on a down-scale MMC system. Full article
(This article belongs to the Special Issue Advancing Grid-Connected Renewable Generation Systems 2019)
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25 pages, 12788 KiB  
Article
Research on Multi-Scenario Variable Parameter Energy Management Strategy of Rural Community Microgrid
by Lidong Guo, Zilong Yang, Yibo Wang and Honghua Xu
Appl. Sci. 2020, 10(8), 2730; https://doi.org/10.3390/app10082730 - 15 Apr 2020
Cited by 4 | Viewed by 1775
Abstract
Many rural communities in western China use renewable energy-based clean energy supply methods, and the community microgrid system of “photovoltaic + energy storage + electric heating” has been widely used. However, the energy management effect of such a typical rural community microgrid system [...] Read more.
Many rural communities in western China use renewable energy-based clean energy supply methods, and the community microgrid system of “photovoltaic + energy storage + electric heating” has been widely used. However, the energy management effect of such a typical rural community microgrid system is not very satisfactory. Aiming at the problem of the comprehensive economic operation of the microgrid system in rural communities, a method for optimizing the operation strategy parameters of typical operating scenarios is proposed, and critical parameters of the real-time energy management strategy of the microgrid system are optimized. Through the evaluation of the annual time-scale simulation results, it is proved that the proposed strategy can improve the comprehensive economic benefits of the operation of the rural community microgrid system (comprehensive economic benefits include electricity bills and energy storage system (ESS) life loss). Relying on the actual community microgrid demonstration project system in western China, a community-level microgrid energy management monitoring system is built. The control strategy proposed in this paper is applied to the demonstration system for experimental verification. The operational data of the demonstration system shows that the proposed method is feasible and effective. Full article
(This article belongs to the Special Issue Advancing Grid-Connected Renewable Generation Systems 2019)
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20 pages, 5141 KiB  
Article
Adaptive Performance Tuning for Voltage-Sourced Converters with Frequency Responses
by Weichao Zhang, Xiangwu Yan and Hanyan Huang
Appl. Sci. 2020, 10(5), 1884; https://doi.org/10.3390/app10051884 - 10 Mar 2020
Cited by 2 | Viewed by 2186
Abstract
Renewable generation brings both new energies and significant challenges to the evolving power system. To cope with the loss of inertia caused by inertialess power electronic interfaces (PEIs), the concept of the virtual synchronous generator (VSG) has been proposed. The PEIs under VSG [...] Read more.
Renewable generation brings both new energies and significant challenges to the evolving power system. To cope with the loss of inertia caused by inertialess power electronic interfaces (PEIs), the concept of the virtual synchronous generator (VSG) has been proposed. The PEIs under VSG control could mimic the external properties of the traditional synchronous generators. Therefore, the frequency stability of the entire system could be sustained against disturbances mainly caused by demand changes. Moreover, as the parameters in the emulation control processes are adjustable rather than fixed, the flexibility could be enhanced by proper tuning. This paper presents a parameter tuning method adaptive to the load deviations. First, the concept and implementation of the VSG algorithm performing an inertia response (IR) and primary frequency responses (PFR) are introduced. Then, the simplification of the transfer function of the dynamic system of the stand-alone VSG-PEI is completed according to the distributed poles and zeros. As a result, the performance indices during the IR and PFR stages are deduced by the inverse Laplace transformation. Then, the composite influences on the performances by different parameters (including the inertia constant, the speed droop, and the load deviations) are analyzed. Based on the composite influences and the time sequences, an adaptive parameter tuning method is presented. The feasibility of the proposed method is verified by simulation. Full article
(This article belongs to the Special Issue Advancing Grid-Connected Renewable Generation Systems 2019)
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24 pages, 3337 KiB  
Article
Emulation Strategies and Economic Dispatch for Inverter-Based Renewable Generation under VSG Control Participating in Multiple Temporal Frequency Control
by Weichao Zhang, Xiangwu Yan and Hanyan Huang
Appl. Sci. 2020, 10(4), 1303; https://doi.org/10.3390/app10041303 - 14 Feb 2020
Cited by 3 | Viewed by 1940
Abstract
As the increasing penetration of inverter-based generation (IBG) and the consequent displacement of traditional synchronous generators (SGs), the system stability and reliability deteriorate for two reasons: first, the overall inertia decreases since the power electronic interfaces (PEIs) are almost inertia-less; second, renewable generation [...] Read more.
As the increasing penetration of inverter-based generation (IBG) and the consequent displacement of traditional synchronous generators (SGs), the system stability and reliability deteriorate for two reasons: first, the overall inertia decreases since the power electronic interfaces (PEIs) are almost inertia-less; second, renewable generation profiles are largely influenced by stochastic meteorological conditions. To strengthen power systems, the concept of the virtual synchronous generator (VSG) has been proposed, which controls the external characteristics of PEIs to emulate those of SGs. Currently, PEIs could perform short-term inertial and primary frequency responses through the VSG algorithm. For renewable energy sources (RES), deloading strategies enable the generation units to possess active power reserves for system frequency responses. Additionally, the deloading strategies could provide the potential for renewable generation to possess long-term frequency regulation abilities. This paper focuses on emulation strategies and economic dispatch for IBG units to perform multiple temporal frequency control. By referring to the well-established knowledge systems of generation and operation in conventional power systems, the current VSG algorithm is extended and complemented by the emulation of secondary and tertiary regulations. The reliability criteria are proposed, considering the loss of load probability (LOLP) and renewable spillage probability (RSP). The reliability criteria are presented in two scenarios, including the renewable units operated in maximum power point tracking (MPPT) and VSG modes. A LOLP-based economic dispatch (ED) approach is solved to acquire the generation and reserve schemes. The emulation strategies and the proposed approach are verified by simulation. Full article
(This article belongs to the Special Issue Advancing Grid-Connected Renewable Generation Systems 2019)
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19 pages, 7452 KiB  
Article
Global MPPT Based on Machine-Learning for PV Arrays Operating under Partial Shading Conditions
by Christos Kalogerakis, Eftichis Koutroulis and Michail G. Lagoudakis
Appl. Sci. 2020, 10(2), 700; https://doi.org/10.3390/app10020700 - 19 Jan 2020
Cited by 32 | Viewed by 4794
Abstract
A global maximum power point tracking (GMPPT) process must be applied for detecting the position of the GMPP operating point in the minimum possible search time in order to maximize the energy production of a photovoltaic (PV) system when its PV array operates [...] Read more.
A global maximum power point tracking (GMPPT) process must be applied for detecting the position of the GMPP operating point in the minimum possible search time in order to maximize the energy production of a photovoltaic (PV) system when its PV array operates under partial shading conditions. This paper presents a novel GMPPT method which is based on the application of a machine-learning algorithm. Compared to the existing GMPPT techniques, the proposed method has the advantage that it does not require knowledge of the operational characteristics of the PV modules comprising the PV system, or the PV array structure. Additionally, due to its inherent learning capability, it is capable of detecting the GMPP in significantly fewer search steps and, therefore, it is suitable for employment in PV applications, where the shading pattern may change quickly (e.g., wearable PV systems, building-integrated PV systems etc.). The numerical results presented in the paper demonstrate that the time required for detecting the global MPP, when unknown partial shading patterns are applied, is reduced by 80.5%–98.3% by executing the proposed Q-learning-based GMPPT algorithm, compared to the convergence time required by a GMPPT process based on the particle swarm optimization (PSO) algorithm. Full article
(This article belongs to the Special Issue Advancing Grid-Connected Renewable Generation Systems 2019)
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17 pages, 5604 KiB  
Article
Phase Balancing and Reactive Power Support Services for Microgrids
by Anastasis Charalambous, Lenos Hadjidemetriou, Lazaros Zacharia, Angelina D. Bintoudi, Apostolos C. Tsolakis, Dimitrios Tzovaras and Elias Kyriakides
Appl. Sci. 2019, 9(23), 5067; https://doi.org/10.3390/app9235067 - 24 Nov 2019
Cited by 22 | Viewed by 3312
Abstract
Alternating current (AC) microgrids are expected to operate as active components within smart distribution grids in the near future. The high penetration of intermittent renewable energy sources and the rapid electrification of the thermal and transportation sectors pose serious challenges that must be [...] Read more.
Alternating current (AC) microgrids are expected to operate as active components within smart distribution grids in the near future. The high penetration of intermittent renewable energy sources and the rapid electrification of the thermal and transportation sectors pose serious challenges that must be addressed by modern distribution system operators. Hence, new solutions should be developed to overcome these issues. Microgrids can be considered as a great candidate for the provision of ancillary services since they are more flexible to coordinate their distributed generation sources and their loads. This paper proposes a method for compensating microgrid power factor and loads asymmetries by utilizing advanced functionalities enabled by grid tied inverters of photovoltaics and energy storage systems. Further, a central controller has been developed for adaptively regulating the provision of both reactive power and phase balancing services according to the measured loading conditions at the microgrid’s point of common coupling. An experimental validation with a laboratory scale inverter and a real time hardware in the loop investigation demonstrates that the provision of such ancillary services by the microgrid can significantly improve the operation of distribution grids in terms of power quality, energy losses and utilization of available capacity. Full article
(This article belongs to the Special Issue Advancing Grid-Connected Renewable Generation Systems 2019)
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15 pages, 3409 KiB  
Article
Classifying Power Quality Disturbances Based on Phase Space Reconstruction and a Convolutional Neural Network
by Kewei Cai, Taoping Hu, Wenping Cao and Guofeng Li
Appl. Sci. 2019, 9(18), 3681; https://doi.org/10.3390/app9183681 - 05 Sep 2019
Cited by 23 | Viewed by 2724
Abstract
This paper presents a hybrid approach combining phase space reconstruction (PSR) with a convolutional neural network (CNN) for power quality disturbance (PQD) classification. Firstly, a PSR technique is developed to transform a 1D voltage disturbance signal into a 2D image file. Then, a [...] Read more.
This paper presents a hybrid approach combining phase space reconstruction (PSR) with a convolutional neural network (CNN) for power quality disturbance (PQD) classification. Firstly, a PSR technique is developed to transform a 1D voltage disturbance signal into a 2D image file. Then, a CNN model is developed for the image classification. The feature maps are extracted automatically from the image file and different patterns are derived from variables in CNN. A set of synthetic signals, as well as operational measurements, are used to validate the proposed method. Moreover, the test results are also compared with existing methods, including empirical mode decomposition (EMD) with balanced neural tree (BNT), S-transform (ST) with neural network (NN) and decision tree (DT), hybrid ST with DT, adaptive linear neuron (ADALINE) with feedforward neural network (FFNN), and variational mode decomposition (VMD) with deep stochastic configuration network (DSCN). Based on deep learning algorithms, the proposed method is capable of providing more accurate results without any human intervention for PQDs. It also enables the planning of PQ remedy actions. Full article
(This article belongs to the Special Issue Advancing Grid-Connected Renewable Generation Systems 2019)
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18 pages, 4493 KiB  
Article
GA Optimization Method for a Multi-Vector Energy System Incorporating Wind, Hydrogen, and Fuel Cells for Rural Village Applications
by Xiangping Chen, Wenping Cao and Lei Xing
Appl. Sci. 2019, 9(17), 3554; https://doi.org/10.3390/app9173554 - 30 Aug 2019
Cited by 8 | Viewed by 2828
Abstract
Utilization of renewable energy (e.g., wind, solar, bio-energy) is high on international and governmental agendas. In order to address energy poverty and increase energy efficiency for rural villages, a hybrid distribution generation (DG) system including wind, hydrogen and fuel cells is proposed to [...] Read more.
Utilization of renewable energy (e.g., wind, solar, bio-energy) is high on international and governmental agendas. In order to address energy poverty and increase energy efficiency for rural villages, a hybrid distribution generation (DG) system including wind, hydrogen and fuel cells is proposed to supplement to the main grid. Wind energy is first converted into electrical energy while part of the generated electricity is used for water electrolysis to generate hydrogen for energy storage. Hydrogen is used by fuel cells to convert back to electricity when electrical energy demand peaks. An analytical model has been developed to coordinate the operation of the system involving energy conversion between mechanical, electrical and chemical forms. The proposed system is primarily designed to meet the electrical demand of a rural village in the UK where the energy storage system can balance out the discrepancy between intermittent renewable energy supplies and fluctuating energy demands so as to improve the system efficiency. Genetic Algorithm (GA) is used as an optimization strategy to determine the operational scheme for the multi-vector energy system. In the work, four case studies are carried out based on real-world measurement data. The novelty of this study lies in the GA-based optimization and operational methods for maximized wind energy utilization. This provides an alternative to battery energy storage and can be widely applied to wind-rich rural areas. Full article
(This article belongs to the Special Issue Advancing Grid-Connected Renewable Generation Systems 2019)
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Review

Jump to: Editorial, Research

26 pages, 1074 KiB  
Review
Leakage Current Reduction in Single-Phase Grid-Connected Inverters—A Review
by Adyr A. Estévez-Bén, Alfredo Alvarez-Diazcomas, Gonzalo Macias-Bobadilla and Juvenal Rodríguez-Reséndiz
Appl. Sci. 2020, 10(7), 2384; https://doi.org/10.3390/app10072384 - 31 Mar 2020
Cited by 36 | Viewed by 6371
Abstract
The rise in renewable energy has increased the use of DC/AC converters, which transform the direct current to alternating current. These devices, generally called inverters, are mainly used as an interface between clean energy and the grid. It is estimated that 21% of [...] Read more.
The rise in renewable energy has increased the use of DC/AC converters, which transform the direct current to alternating current. These devices, generally called inverters, are mainly used as an interface between clean energy and the grid. It is estimated that 21% of the global electricity generation capacity from renewable sources is supplied by photovoltaic systems. In these systems, a transformer to ensure grid isolation is used. Nevertheless, the transformer makes the system expensive, heavy, bulky and reduces its efficiency. Therefore, transformerless schemes are used to eliminate the mentioned disadvantages. One of the main drawbacks of transformerless topologies is the presence of a leakage current between the physical earth of the grid and the parasitic capacitances of the photovoltaic module terminals. The leakage current depends on the value of the parasitic capacitances of the panel and the common-mode voltage. At the same time, the common-mode voltage depends on the modulation strategy used. Therefore, by the manipulation of the modulation technique, is accomplished a decrease in the leakage current. However, the connection standards for photovoltaic inverters establish a maximum total harmonic distortion of 5%. In this paper an analysis of the common-mode voltage and its influence on the value of the leakage current is described. The main topologies and strategies used to reduce the leakage current in transformerless schemes are summarized, highlighting advantages and disadvantages and establishing points of comparison with similar topologies. A comparative table with the most important aspects of each converter is shown based on number of components, modes of operation, type of modulation strategy used, and the leakage current value obtained. It is important to mention that analyzed topologies present a variation of the leakage current between 0 to 180 mA. Finally, the trends, problems, and researches on transformerless grid-connected PV systems are discussed. Full article
(This article belongs to the Special Issue Advancing Grid-Connected Renewable Generation Systems 2019)
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