Lipuzhin, Ivan Alekseevich

Chivenkov A.I., Sosnina E.N., Lipuzhin I.A., Trofimov I.M., Aleshin D.A.

This article presents the circuit design and research results of a prototype of low-voltage solid-state transformer based on a controlled semiconductor AC/DC/AC converter. The device allows two different AC and DC voltage sources to be connected to the network simultaneously, ensuring reliable power supply and improving the power quality of electricity delivered to the consumer. The article presents the structural and basic electrical circuit diagrams of the prototype and its design and technical characteristics, as well as the control system and the device operation algorithm, together with the operating principle of its main units: an active rectifier, dual-channel converter, autonomous voltage inverter, and DC link capacitive storage. The results of experimental research of a prototype of low-voltage solid-state transformer are shown, which makes it possible to determine the permissible range of the input voltage of power sources connected to the device, as well as the ability of the device to stabilize and balance the output voltage.

Loskutov A.B., Shalukho A.V., Lipuzhin I.A., Bedretdinov R.S., Shuvalova Y.N.

This paper presents the design and research results of prototype of a power plant based on two 1 kW hydrogen polymer proton exchange membrane fuel cells with different volt–ampere characteristics and hydrogen consumption. The power plant optimal configuration was selected, based on the analysis of existing technologies and two energy management systems for efficient power distribution between fuel cells (equal distribution and daisy-chain) were proposed. A Simulink model of the power plant was developed, and the system operating modes were simulated. Simulation results confirmed the prospects of the adopted solutions. Experimental studies of the energy management systems were conducted. Results showed that the daisy-chain is the most effective for saving hydrogen.

Rashitov I., Voropay A., Tsepilov G., Kuzmin I., Loskutov A., Osetrov E., Kurkin A., Lipuzhin I.

Vanadium redox flow batteries are promising energy storage devices and are already ahead of lead–acid batteries in terms of installed capacity in energy systems due to their long service life and possibility of recycling. One of the crucial tasks today is the development of models for assessing battery performance and its residual resource based on the battery’s present state. A promising method for estimating battery capacity is based on analyzing present voltage and current values under various load conditions. This paper analyzes the discharge characteristics of a 10 kW all-vanadium redox flow battery at fixed load powers from 6 to 12 kW. A linear dependence of operating voltage and initial discharge voltage on load power is established. It is also determined that the slope of the discharge curve linear section does not increase linearly in absolute value, and the Box–Lucas model can be used to describe it. Models for predicting current VRFB capacity based on different curve fitting functions are proposed. These models can be used to roughly estimate battery capacity at different load powers.

Lipuzhin I., Shalukho A., Bedretdinov R., Shuvalova Y.

Loskutov A., Dar'enkov A., Lipuzhin I., Shalukho A., Bedretdinov R., Vanyaev V., Shakhov A.

The article presents a developing of a 3 kW prototype of hybrid power system based on proton exchange membrane fuel cell and lithium iron phosphate batteries to energy supply remote consumers of the railway industry. The purpose is to develop an energy management system (EMS) that provides high efficiency of a fuel cell/battery hybrid power system (FCBHPS) operation as well as reduces hydrogen consumption. A FCBHPS prototype structure and characteristics of its major units are described. The choice of the required battery capacity is considered. Experimental tests of the fuel cell as a part of FCBHPS were carried out in order to determine EMS optimal settings. FCBHPS control algorithm based on finite-state machine concepts was developed with consideration of the results obtained. The article shows research results of the FCBHPS prototype in various operation modes which prove the correctness of the control algorithm and EMS settings selection, system efficiency while maintain power quality within acceptable limits. In addition, hydrogen storage technologies for stationary consumers are considered.

Chivenkov A.I., Sosnina E.N., Lipuzhin I.A.

Sosnina E., Chivenkov A., Lipuzhin I., Aleshin D., Trofimov I.

Rashitov I., Voropay A., Tsepilov G., Kuzmin I., Loskutov A., Kurkin A., Osetrov E., Lipuzhin I.

Vanadium redox flow batteries are gaining great popularity in the world due to their long service life, simple (from a technological point of view) capacity increase and overload resistance, which hardly affects the service life. However, these batteries have technical problems, namely in balancing stacks with each other in terms of volumetric flow rate of electrolyte. Stack power depends on the speed of the electrolyte flow through the stack. Stacks are connected in parallel by electrolytes to increase battery power. If one of the stacks has a lower hydrodynamic resistance, the volume of electrolytes passing through it increases, which leads to a decrease in the efficiency of the remaining stacks in the system. This experimental study was conducted on a 10 kW uninterruptible power supply system based on two 5 kW stacks of all-vanadium redox flow batteries. It was demonstrated that forced flow attenuation in a circuit with low hydrodynamic resistance leads to an overall improvement in the system operation.

Loskutov A.B., Lipuzhin I.A., Bedretdinov R.S.

Loskutov A., Kurkin A., Shalukho A., Lipuzhin I.

A reliable and efficient power supply for critical infrastructure customers is key to ensuring energy security. Critical infrastructure requires local power sources. Currently, performance requirements for such sources have significantly increased. Apart from high energy efficiency, important requirements include quick start-up time, small size, environmental friendliness, low noise, etc. These may be provided by fuel cells, which are considered the most prospective sources of electric power. However, it is necessary to overcome a number of obstacles limiting fuel cell efficiency in power supply systems for critical infrastructure customers. This paper presents the results of design analysis in the field of fuel cell, hydrogen conversion and power storage technologies. An assessment is given of promising studies aimed at combining the abovementioned technologies to create local power sources to ensure reliable power supply to critical infrastructure objects.

Sosnina E., Dar’enkov A., Kurkin A., Lipuzhin I., Mamonov A.

The article contains current information on the development of energy-efficient technologies of wind–diesel hybrid systems (WDHS) for decreasing organic fuel consumption. As a result of the review, three research directions are identified: WDHS design optimization, the main equipment and control system improvements. A comparison of their effectiveness is presented. The methods of selecting WDHS configuration, equipment capacities and location, the optimization algorithms and objective functions used are described and WDHS project feasibility calculation results are presented. The methods to improve energy efficiency of WDHS major units’ (diesel generator (DG) and wind turbine (WT)) are considered. The methods to decrease diesel fuel consumption using special devices and energy storage system are presented. Special attention is paid to WDHS operating modes’ control methods and strategies, as well as to algorithms providing the efficient system operation. As a result, recommendations for the design of both isolated and on-grid WDHS are formulated.

Chivenkov A., Sosnina E., Lipuzhin I.

Shalukho A.V., Bedretdinov R.S., Lipuzhin I.A., Shuvalova Y.N.

Loskutov A., Kurkin A., Shalukho A., Lipuzhin I., Bedretdinov R.

The article is devoted to the problem of proton-exchange membrane fuel cells (PEMFCs) integration into power supply systems. A hybrid energy complex (HEC) based on PEMFCs and lithium iron phosphate batteries can be used as a reliable energy source. It is necessary to properly determine the PEMFC characteristics in order to develop a PEMFC-based HEC prototype and its control algorithms. This paper presents a 1 kW PEMFC’s test results in steady and dynamic modes. The dependences of the average hydrogen consumption per 1 min, the volume of hydrogen for the generation of 1 kWh, the PEMFC efficiency on the load current were obtained and an analysis of these dependences for steady operation modes was performed. A range of load changes beyond which the efficiency of the PEMFC significantly decreased and it was recommended to switch to the joint operation of the PEMFCs and batteries (or only batteries) was established. Diagrams of the PEMFC output voltage during the dynamic changes in loads are presented and an analysis of transient response characteristics was carried out. The air supply fans were found to affect the performance of PEMFCs.

Loskutov A., Kurkin A., Kuzmin I., Lipuzhin I.

Vanadium redox flow batteries are a highly efficient solution for long-term energy storage. They have a long service life, low self-discharge, are fire safe and can be used to create a large-scale storage system. The characteristics of the flow battery are determined by the parameters of its main components: a stack determines the battery power and its efficiency, and an electrolyte determines the battery’s capacity and service life. Several stacks must be combined into one system to create a powerful energy storage system; however, the discharge characteristics differ even for two identical stacks connected in parallel. This article proposes hydrodynamic and electrotechnical methods for ensuring the parallel operation of several flow stacks under the same conditions.

Peyrani G., Marocco P., Gandiglio M., Biga R., Santarelli M.

Mu X., Wang X., Sang X., Yuan P., Yuan Y., Chen R.

With the continuous improvement of new energy penetration and the significant improvement of terminal electrification level, the role of distribution network as the basic power energy carrying network has become increasingly prominent. However, the operation mode of “closed-loop design and open-loop operation” exposes the problems of weak new energy consumption capacity and poor power supply reliability of the traditional distribution network. The existing flexible loop closing technology generally has the problems of high cost, large land occupation and poor reliability, which is not suitable for promotion in distribution network. From the perspective of practical technology and easy popularization and application, this paper analyzes and studies a multi-level voltage regulating device with both functionality and economy based on the flexible closed-loop model of medium voltage distribution network, and then studies the flexible closed-loop control strategy of medium voltage distribution network based on the device, and proposes a fast mapping method of power command. Finally, the control strategy is verified by the hardware in the loop simulation platform.

Ding J., Liu F., Jia S.

Magro N., Vázquez J.R., Sánchez-Herrera R.

Nowadays, the proliferation of distributed renewable energy sources is a fact. A microgrid is a good solution to self-manage the energy generation and consumption of electrical loads and sources from the point of view of the consumer as well as the power system operator. To make a microgrid as versatile as necessary to carry that out, a flexible inverter is necessary. In this paper, an algorithm is presented to control an inverter and make it complete and versatile to work in grid-connected and in isolated modes, injecting or receiving power from the grid and always compensating the harmonics generated by the loads in the microgrid. With this inverter, the microgrid can work while optimizing its energy consumption or according to the power system operator instructions. The inverter proposed is tested in a designed Matlab/Simulink simulation platform. After that, an experimental platform designed and built ad hoc, including a DC source, AC linear and non-linear loads, and a Semikron power inverter, is used to test the proposed control strategies. The results corroborate the good system performance. The replicability of the system is guaranteed by the use of low-cost devices in the implementation of the control.

Lin J., Zhang Z., Qiu J., Wu Y., Yu J., Li Y., Ren X., Zhang L., Song Z.

Dong F., Qin W., Xu S., Ni H.

Poli D., Barsali S.

Sung M., Yi H., Han J., Lee J.B., Yoon S., Park J.

This study addresses the critical challenge of carbon corrosion in proton exchange membrane fuel cells (PEMFCs) by developing hybrid supports that combine the high surface area of carbon black (CB) with the superior crystallinity and graphitic structure of carbon nanofibers (CNFs). Two commercially available CB samples were physically activated and composited with two types of CNFs synthesized via chemical vapor deposition using different carbon sources. The structure, morphology, and crystallinity of the resulting CNF–CB hybrid supports were characterized, and the performances of these hybrid supports in mitigating carbon corrosion and enhancing the PEMFC performance was evaluated through full-cell testing in collaboration with a membrane electrode assembly (MEA) manufacturer (VinaTech, Seoul, Republic, of Korea), adhering to industry-standard fabrication and evaluation procedures. Accelerated stress tests following the US Department of Energy protocols revealed that incorporating CNFs enhanced the durability of the CB-based hybrid supports without compromising their performance. The improved performance of the MEAs with the hybrid carbon support is attributed to the ability of the CNF to act as a structural backbone, facilitate water removal, and provide abundant edge plane sites for anchoring the platinum catalyst, which promoted the oxygen reduction reaction and improved catalyst utilization. The findings of this study highlight the potential of CNF-reinforced CB supports for enhancing the durability and performance of PEMFCs.

Chen H., Li S., Zhao Y., Li X., Zhao H., Cheng L., Li R., Dai P.

The integration of intermittent renewable energy sources into the energy supply has driven the need for large-scale energy storage technologies. Vanadium redox flow batteries (VRFBs) are considered promising due to their long lifespan, high safety, and flexible design. However, the graphite felt (GF) electrode, a critical component of VRFBs, faces challenges due to the scarcity of active sites, leading to low electrochemical activity. Herein, we developed a bismuth nanoparticle uniformly modified graphite felt (Bi-GF) electrode using a bismuth oxide-mediated hydrothermal pyrolysis method. The Bi-GF electrode demonstrated significantly improved electrochemical performance, with higher peak current densities and lower charge transfer resistance than those of the pristine GF. VRFBs utilizing Bi-GF electrodes achieved a charge-discharge capacity exceeding 700 mAh at 200 mA/cm2, with a voltage efficiency above 84%, an energy efficiency of 83.05%, and an electrolyte utilization rate exceeding 70%. This work provides new insights into the design and development of efficient electrodes, which is of great significance for improving the efficiency and reducing the cost of VRFBs.

Hu J., Zhang N., Yang L., Hu C.

Feng R., Yu J., Zhao Z., Hua Z., He J., Shu X.

Filipkowski J., Skibko Z., Borusiewicz A., Romaniuk W., Pisarek Ł., Milewska A.

Renewable electricity sources are now widely used worldwide. Currently, the most common sources are those that use energy contained in biomass, water, sun, and wind. When connected to a medium-voltage grid, individual wind power plants must meet specific conditions to maintain electricity quality. This article presents field study results on the impact of switching operations (turning the power plant on and off) at a 2 MW Vestas V90 wind turbine on the voltage parameters at the connection point of a farm located 450 m from the source. The analysis showed that the wind turbine under study significantly affects customers’ voltage near the source, causing it to increase by approximately 2.5%. Sudden cessation of generation during the afternoon peak causes a 3% voltage fluctuation, potentially affecting equipment sensitive to rapid voltage changes.

Voropay A.N., Vladimir E.D., Osetrov E.S., Usenko A.A., Deryabina E.O., Zueva V.V.

The development of vanadium redox flow batteries requires elaborating new materials to improve their performance. To date, the studies of electrode materials for these energy storage devices are focused on increasing their specific power and energy efficiency. It is known that the energy efficiency can be increased by reducing the electrode polarization, which hinders the transport of the ions that carry charge between half-elements. This can be achieved for an electrochemically active layer localized immediately near the membrane surface. For this purpose, it is proposed to use bilayer composite electrodes with the active layer localized immediately at the electrode/membrane boundary. For the active layer of carbon black CH210 and a PVDF binder with a loading of 20 mg/cm2, the energy efficiency stays and a level of 79.6% for the current density of 150 mA/cm2. However, an increase in the layer thickness reduces the discharge capacity to 1% of its initial value corresponding to the uncoated electrode at a current density of 25 mA/cm2. Thus, the development of an active layer on the surface of a commercially available GFD 4.6 EA material by airbrush spraying is a fairly simple way to increase the efficiency of the charge-discharge cycle for a cell in a vanadium redox flow battery.

Izadi M., Hajjar A., El Idi M.M., Lam Q.N., Alqurashi F., Mohamed M.H.

Chivenkov A.I., Sosnina E.N., Lipuzhin I.A., Trofimov I.M., Aleshin D.A.

This article presents the circuit design and research results of a prototype of low-voltage solid-state transformer based on a controlled semiconductor AC/DC/AC converter. The device allows two different AC and DC voltage sources to be connected to the network simultaneously, ensuring reliable power supply and improving the power quality of electricity delivered to the consumer. The article presents the structural and basic electrical circuit diagrams of the prototype and its design and technical characteristics, as well as the control system and the device operation algorithm, together with the operating principle of its main units: an active rectifier, dual-channel converter, autonomous voltage inverter, and DC link capacitive storage. The results of experimental research of a prototype of low-voltage solid-state transformer are shown, which makes it possible to determine the permissible range of the input voltage of power sources connected to the device, as well as the ability of the device to stabilize and balance the output voltage.

Belmesov Andrey A., Shmygleva Lyubov V., Baranov Alexander A., Levchenko Alexey O.

Over the last decade, the potential of proton exchange membrane fuel cells (PEMFCs) for use in a range of applications, including automotive transport, has attracted the attention of scientific groups and industry representatives worldwide. The active development of PEMFCs is already enabling them to compete with internal combustion engines and lithium-ion batteries in a number of applications. However, significant improvements in a number of PEMFCs characteristics are required to expand the scope of their applications. This review is intended to bridge the gap between existing reviews, which are either overly general or overly specific, and provide a comprehensive overview of the current state of the art and potential future applications of PEMFCs. It will focus on the main components of PEMFCs, including proton exchange membranes, catalytic and gas diffusion layers, bipolar plates, and cooling systems, and the factors affecting the PEMFC performance.The bibliography includes 428 references.

Madhav D., Wang J., Keloth R., Mus J., Buysschaert F., Vandeginste V.

Proton exchange membrane fuel cells (PEMFCs) have the potential to tackle major challenges associated with fossil fuel-sourced energy consumption. Nafion, a perfluorosulfonic acid (PFSA) membrane that has high proton conductivity and good chemical stability, is a standard proton exchange membrane (PEM) used in PEMFCs. However, PEM degradation is one of the significant issues in the long-term operation of PEMFCs. Membrane degradation can lead to a decrease in the performance and the lifespan of PEMFCs. The membrane can degrade through chemical, mechanical, and thermal pathways. This paper reviews the different causes of all three routes of PFSA degradation, underlying mechanisms, their effects, and mitigation strategies. A better understanding of different degradation pathways and mechanisms is valuable in producing robust fuel cell membranes. Hence, the progress in membrane fabrication for PEMFC application is also explored and summarized.

Loskutov A., Dar'enkov A., Lipuzhin I., Shalukho A., Bedretdinov R., Vanyaev V., Shakhov A.

The article presents a developing of a 3 kW prototype of hybrid power system based on proton exchange membrane fuel cell and lithium iron phosphate batteries to energy supply remote consumers of the railway industry. The purpose is to develop an energy management system (EMS) that provides high efficiency of a fuel cell/battery hybrid power system (FCBHPS) operation as well as reduces hydrogen consumption. A FCBHPS prototype structure and characteristics of its major units are described. The choice of the required battery capacity is considered. Experimental tests of the fuel cell as a part of FCBHPS were carried out in order to determine EMS optimal settings. FCBHPS control algorithm based on finite-state machine concepts was developed with consideration of the results obtained. The article shows research results of the FCBHPS prototype in various operation modes which prove the correctness of the control algorithm and EMS settings selection, system efficiency while maintain power quality within acceptable limits. In addition, hydrogen storage technologies for stationary consumers are considered.

Puleston T., Serra M., Costa-Castelló R.

Electrolyte imbalance is the main cause of capacity loss in vanadium redox flow batteries. It has been widely reported that imbalance caused by vanadium crossover can be readily recovered by remixing the electrolytes, while imbalance caused by a net oxidation of the electrolyte can only be reverted by means of more complex chemical or electrochemical methods. At the moment, however, the joint effect of both types of imbalances on the battery capacity is still not well understood. To overcome this limitation, generalised State of Charge and State of Health indicators that consider both types of imbalances are derived in this work. Subsequently, a thorough analysis on how the battery capacity depends on electrolyte imbalance is performed. As a result of this analysis, two specific outcomes are highlighted. Firstly, it is shown that standard electrolyte remixing may be counterproductive under certain imbalance conditions, further reducing the battery capacity instead of augmenting it. Secondly, it is demonstrated that most of the capacity loss caused by oxidation can be mitigated by inducing an optimal mass imbalance in the system. Consequently, a systematic procedure to track this optimum is proposed and validated through computer simulation.

Khalatbarisoltani A., Zhou H., Tang X., Kandidayeni M., Boulon L., Hu X.

Chivenkov A.I., Sosnina E.N., Lipuzhin I.A.

Wi J., Jon S., Bae G., Kim Y., Jon S.

It is important to analyze concentrations of vanadium species with different valences in the electrolyte for vanadium redox flow battery (VRFB) for production of electrolytes and stable operation of the batteries. Herein, we proposed an analytical method by digital imaging to determine the vanadium species (V(IV)/V(III)) concentrations in the vanadium electrolyte manufacturing process. Standard electrolytes with different V(IV):V(III) ratios underwent digital imaging and the RGB values were extracted from the obtained images, and then the calibration curve was plotted based on these values. The data obtained from the blue channel were used as the analytical signal because it showed the best sensitivity and linearity (R2 = 0.9836, 0.9909). Precisions were determined using electrolyte samples with 50% and 100% V(III), respectively, and their RSDs were 2.18% and 1.01%, respectively. The accuracy of the digital imaging analysis method was evaluated by comparison with potentiometric titration, and the agreement was well made within the error limit. The results showed that this simple analytical method might be very suitable for real-time analysis of vanadium electrolyte.

Sosnina E., Chivenkov A., Lipuzhin I., Aleshin D., Trofimov I.

Rashitov I., Voropay A., Tsepilov G., Kuzmin I., Loskutov A., Kurkin A., Osetrov E., Lipuzhin I.

Vanadium redox flow batteries are gaining great popularity in the world due to their long service life, simple (from a technological point of view) capacity increase and overload resistance, which hardly affects the service life. However, these batteries have technical problems, namely in balancing stacks with each other in terms of volumetric flow rate of electrolyte. Stack power depends on the speed of the electrolyte flow through the stack. Stacks are connected in parallel by electrolytes to increase battery power. If one of the stacks has a lower hydrodynamic resistance, the volume of electrolytes passing through it increases, which leads to a decrease in the efficiency of the remaining stacks in the system. This experimental study was conducted on a 10 kW uninterruptible power supply system based on two 5 kW stacks of all-vanadium redox flow batteries. It was demonstrated that forced flow attenuation in a circuit with low hydrodynamic resistance leads to an overall improvement in the system operation.

Do T.D., Nguyen H.T., Al-Sumaiti A.S., Hosani K.A., Nguyen D.

Olabi A.G., Allam M.A., Abdelkareem M.A., Deepa T.D., Alami A.H., Abbas Q., Alkhalidi A., Sayed E.T.

Redox flow batteries represent a captivating class of electrochemical energy systems that are gaining prominence in large-scale storage applications. These batteries offer remarkable scalability, flexible operation, extended cycling life, and moderate maintenance costs. The fundamental operation and structure of these batteries revolve around the flow of an electrolyte, which facilitates energy conversion and storage. Notably, the power and energy capacities can be independently designed, allowing for the conversion of chemical energy from input fuel into electricity at working electrodes, resembling the functioning of fuel cells. This work provides a comprehensive overview of the components, advantages, disadvantages, and challenges of redox flow batteries (RFBs). Moreover, it explores various diagnostic techniques employed in analyzing flow batteries. The discussion encompasses the utilization of RFBs for large-scale energy storage applications and summarizes the engineering design aspects related to these batteries. Additionally, this study delves into emerging technologies, applications, and challenges in the realm of redox flow batteries.

Hossain M.B., Islam M.R., Muttaqi K.M., Sutanto D., Agalgaonkar A.P.

As renewables are being integrated into the power grids, new challenges are introduced, such as the impacts on the grid due to sudden variations in weather conditions and load demands. Green hydrogen energy (GHE) storage, using electrolyzers (EL) and fuel cells (FC), has been identified as one of the potential solutions. As the world transitions to a zero-carbon economy, the production and storage of hydrogen using EL from surplus renewable is receiving global interest. Whenever electricity is required, the stored hydrogen gas can be used to produce electrical energy using an FC to supply to the loads/grid. To make the renewable energy sources (RESs) and FC/EL integrated power systems optimal, efficient, reliable, and cost-effective, an adaptive energy conversion system and power management control strategy (PMCS) that includes advanced control algorithms need to be formulated to utilize the surplus of renewable energy. Despite many review studies on FCs/ELs integrated power systems, a detailed review of FCs/ELs technologies for utilizing the renewable energy surplus is still limited in terms of different types of grids (AC or DC) integrated topologies, multiple types of FCs/ELs models, and a variety of power electronic interfaces with appropriate PMCS. This paper presents a comprehensive review with a more specific assessment of FC/EL comprised GHE storage technologies for the widespread interconnection of RESs. It is expected that this in-depth review will help in advancing the relevant technologies and eventually support the transition to a zero-carbon economy and meet Goal 7 of the United Nation Sustainable Development.

Ding C., Shen Z., Zhu Y., Cheng Y.

The vanadium redox flow battery (VRFB) has been regarded as one of the best potential stationary electrochemical storage systems for its design flexibility, long cycle life, high efficiency, and high safety; it is usually utilized to resolve the fluctuations and intermittent nature of renewable energy sources. As one of the critical components of VRFBs to provide the reaction sites for redox couples, an ideal electrode should possess excellent chemical and electrochemical stability, conductivity, and a low price, as well as good reaction kinetics, hydrophilicity, and electrochemical activity, in order to satisfy the requirements for high-performance VRFBs. However, the most commonly used electrode material, a carbonous felt electrode, such as graphite felt (GF) or carbon felt (CF), suffers from relatively inferior kinetic reversibility and poor catalytic activity toward the V2+/V3+ and VO2+/VO2+ redox couples, limiting the operation of VRFBs at low current density. Therefore, modified carbon substrates have been extensively investigated to improve vanadium redox reactions. Here, we give a brief review of recent progress in the modification methods of carbonous felt electrodes, such as surface treatment, the deposition of low-cost metal oxides, the doping of nonmetal elements, and complexation with nanostructured carbon materials. Thus, we give new insights into the relationships between the structure and the electrochemical performance, and provide some perspectives for the future development of VRFBs. Through a comprehensive analysis, it is found that the increase in the surface area and active sites are two decisive factors that enhance the performance of carbonous felt electrodes. Based on the varied structural and electrochemical characterizations, the relationship between the surface nature and electrochemical activity, as well as the mechanism of the modified carbon felt electrodes, is also discussed.

Hossain M.H., Abdullah N., Tan K.H., Saidur R., Mohd Radzi M.A., Shafie S.

AbstractThe vanadium redox flow battery (VRFB) is a highly regarded technology for large‐scale energy storage due to its outstanding features, such as scalability, efficiency, long lifespan, and site independence. This paper provides a comprehensive analysis of its performance in carbon‐based electrodes, along with a comprehensive review of the system‘s principles and mechanisms. It discusses potential applications, recent industrial involvement, and economic factors associated with VRFB technology. The study also covers the latest advancements in VRFB electrodes, including electrode surface modification and electrocatalyst materials, and highlights their effects on the VRFB system‘s performance. Additionally, the potential of two‐dimensional material MXene to enhance electrode performance is evaluated, and the author concludes that MXenes offer significant advantages for use in high‐power VRFB at a low cost. Finally, the paper reviews the challenges and future development of VRFB technology.

Bineshaq A., Hossain M.I., Binqadhi H., Salem A., Abido M.A.

The critical challenges with integrating renewable energy into the grid are smooth power flow control, isolation between the high-voltage and low-voltage networks, voltage regulation, harmonic isolation, and power quality regulation. This paper considers the design and construction of a two-stage DC-AC solid-state transformer based on wide bandgap (WBG) semiconductor technologies, an optimized medium-frequency transformer, and PI and dq controllers for supplying urban area electric drive systems and microgrid applications. The designed SST consists of a dual active bridge (DAB) DC-DC converter followed by a DC-AC three-phase inverter. Each stage of the SST was simulated with independent controllers. The proposed system was initially developed in MATLAB/Simulink and a laboratory prototype was constructed to verify the results experimentally. Resistive and inductive load were used to test the load disturbance to evaluate the voltage regulation performance. This work has comprehensively provided the performance of a double stage (DC-DC and DC-AC converter) by taking into consideration input voltage, load disturbance, and voltage tracking both in simulation and experiment. The dual active bridge with its controller is able to maintain the desired output reference voltage with minimal voltage ripples under input voltage fluctuations and load variations. Similarly, the three-phase DC-AC converter’s controller exhibits better performance in tracking the desired reference voltage and producing well-regulated AC voltage with low harmonic distortion.