Hydrogen-Based Hybrid Microgrid System: History
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Hydrogen is acknowledged as a potential and appealing energy carrier for decarbonizing the sectors that contribute to global warming, such as power generation, industries, and transportation. Many people are interested in employing low-carbon sources of energy to produce hydrogen by using water electrolysis. Additionally, the intermittency of renewable energy supplies, such as wind and solar, makes electricity generation less predictable, potentially leading to power network incompatibilities. Hence, hydrogen generation and storage can offer a solution by enhancing system flexibility. Hydrogen saved as compressed gas could be turned back into energy or utilized as a feedstock for manufacturing, building heating, and automobile fuel.

  • hybrid microgrid
  • bidirectional AC-DC converter
  • hydrogen energy
  • wind energy
  • energy management

1. Introduction

Due to the rapid development of power electronic technology, the energy storage systems (ESS) dependent on applying renewable energy sources (RESs) emerged as the best and most cutting-edge way to electrify remote locations while addressing the dangers associated with the depletion of fossil fuels and pertinent environmental concerns [1]. Wind energy generation increased rapidly during the last few decades. Wind energy utilization climbed from 0.2% to 4.8% of total power output between 2000 and 2018, and is anticipated to reach more than 12% by 2040 [2]. The wind industry’s advancements in technology contributed to this quick expansion. Additionally, the solar future research explored the contribution of solar energy to the development of a carbon-free power grid. The solar futures study investigates the contribution of solar energy to the development of a carbon-free electric grid [3].
The National Renewable Energy Laboratory (NREL) and the Solar Energy Technologies Office (SETO) of the U.S. Department of Energy conducted research and found that solar energy could supply up to 40% of the country’s power by 2035 and 45% by 2050 [3]. The microgrid applications in logistics, Singapore islands, and buildings are represented in [4,5,6]. More than 85% of all cargo traffic worldwide is moved by sea, which gives marine logistics a vital role as global trade expands. Between 2000 and 2015, the energy demand for international shipping, including seaports, expanded on average by 1.6% per year [4]. There are several ways to integrate RES and storage systems, including direct integration, and employing virtual power plants or microgrids [5]. Distributed energy storage raises demand elasticity, which improves grid balancing services via smart meters. Specifically, energy storage increases the income stream from distributed generation by enhancing energy supply methods [6]. However, regulating supply and demand in the power network is becoming increasingly difficult due to the growing amount of solar and wind-based electricity. Additionally, the changing wind speeds and unpredictable future weather patterns make relying on the offshore wind a problematic venture. These factors make it difficult to make forward energy supply agreements. Further research is needed to determine the optimal operation and reconfiguring of HMG systems using RESs without batteries due to the intermittency of solar irradiance and wind speed. Following that, the hydrogen storage system (HSS) presents itself as a green and cutting-edge method [7].
Since the earliest internal combustion engines were powered by hydrogen energy and manufactured over 200 years ago, these two became crucial components of the current stationery and automobile industries [8]. When energy is created from naturally occurring substances, hydrogen is the perfect component for storing or delivering it [9]. No fuel has more energy per mass than hydrogen. However, due to its low density at room temperature, it has a low volumetric energy content. As a result, various storage and production techniques can be taken into account to achieve greater target energy densities [10]. In fuel cell (FC), hydrogen can also be utilized to generate electricity without emitting any pollutants, especially if it is created using renewable energy. Utilizing hydrogen has significant advantages. It can be utilized in industry, public transportation, and indoor heating [11]. Due to system integration and improved use of renewable energy sources, hydrogen energy storage systems provide a chance to improve the flexibility and resilience of sustainable energy systems while also possibly lowering total energy prices. Climate change, energy security, and the negative effects of bad air quality on health are all motivating factors for a more sustainable energy future [12].
Hydrogen storage technologies (HSTs) are major obstacles to the growth of the hydrogen economy. More sophisticated storage techniques based on carbon-based polymers and metal-organic frameworks hydrides are being explored as possible alternatives [13]. In order to provide a better energy density, improved HSTs must be developed [14]. These systems cover both material- and physically based storage. First, hydrogen could be kept in liquid or gas form. In order to store hydrogen as a vapor, adequate high-pressure tanks (between 350 and 700 bars) are often needed [15]. Although hydrogen has such a critical temperature of −252.8 °C, freezing temperatures are needed to keep it in a liquid [16]. Second, hydrogen may be held within solids, such as in metal hydride compounds on the edges of solids through adsorption. Liquid hydrogen has an energy density per volume of roughly 8 MJL-1, which is greater than hydrogen storage based on high-pressure tanks. However, gasoline and kerosene have energy densities per volume of 32 MJL-1 and 35 MJL-1, respectively.
The integrated power system of HMG will search for prospective advantages of HSS as well as the growth in wind and solar farms’ technological and economic efficiency [17]. In a future civilization that is carbon neutral, such facilities that concurrently run HSS, wind, and solar power production are expected to play a key role [18]. Profitability can be increased by jointly running an HSS and participating in the electricity market while making the greatest use of the circumstances of the electricity market and hydrogen gas-based use cases. As a consequence, the behavior of the Hydrogen based HMG that arises is complicated, and in order to revolutionize the global energy sector. The National Thermal Power Corporation (NTPC) supports the need for such an examination in Andrapradesh, India [19].
A schematic illustration of hydrogen applications taking into account nuclear and RES is shown in Figure 1. Distributed energy (DG) is quickly integrated into the grid as an HMG, as a result of breakthroughs in power electronic devices and the assistance of advancements on both the power source and load side. Additionally, BAC is required for HMGs to guarantee voltage stability and power equilibration between the DC and AC grids [20]. The coordinated control scheme allows for efficient power transfer across AC and DC connections, as well as reliable system performance under a variety of load and generating situations. In [21], an assessment and mitigation solutions for system-level dynamic interaction with control power converters in HMG are examined. To increase system stability, an efficient control strategy to modify the DC side admittance is performed. Hydrogen is a viable choice for energy storage, since it can be used for a variety of purposes, including power generation and the management of renewable hydrogen production [22].
Figure 1. Applications of hydrogen energy [1].
Incorporating renewable energy sources, such as photovoltaic (PV), wind, diesel production, or a mix of these sources, HMGs are pushed to address a variety of electrical and energy-related concerns. Clean energy, improved grid stability, and decreased congestion are just a few advantages of using microgrids in the production of electric power. Despite these benefits, cost issues prevent the widespread adoption of microgrids. In order to deal with these financial issues, it is required to investigate the best microgrid configurations based on the number, quality, and accessibility of RES utilized to establish the microgrid as well as the best layout of microgrid elements.
The expense of initial management and operating energy is significantly impacted by the development of HSS as a possible kind of ESSs. It is often added to HMG as energy buffer area to stabilize power fluctuation and achieve autonomous operation [23]. If all distributed sources, together with the grid-connected operating mode’s peak load, cannot be met, inadequate electricity is supplied by the utility grid. If not, extra electricity is added to the electrical system [24]. Due to power assistance, the effect of ESS on the balance of power is not highlighted in this operating condition. Considerations such as operation costs, economy, serviceability, and power response time should be made while choosing an appropriate ESS. As an illustration, battery ESS has high efficiency but high power consumption. Large-scale applications of pumped hydro systems are possible, but utility grid deployment locations have some unique needs. Because it transforms chemical energy into electrical energy, an HSS is classified as a chemical storage system. Contrast to battery ESS, this power transmission method uses a fuel cell, an electrolyzer, and a hydrogen storage tank, and is therefore applicable to both power and energy.
The operating strategy and power management plan are crucial for delivering reliable operation in both grid-connected and standalone operating modes. The phrases “energy management” and “power management” have various meanings in microgrids when controlling activities and time scales. The ultimate aim of long-term energy management methods would be to optimally adapt the total generating capacity to the demand [25,26].

2. Literature Work

The fundamental issue of combining hydrogen energy storage devices with solar and wind power generation is the subject of a very small number of studies. Herein, the operational issues with hydrogen energy systems are described. The linkages between research on hydrogen system operation and the related electrical markets, agreements, renewable energy resources, storage, energy management in HMG, and the possibilities of hydrogen energy globally can be evaluated.
Yue et al. [31] provided a summary of current advancements in hydrogen technologies and their utilization in power systems for the creation, storage, and re-electrification of hydrogen. Dawood et al. [32] evaluated these pathways as well in order to evaluate how different pathways for producing hydrogen interacted with one other and with other phases of the hydrogen square. Najjar [33] assessed the safety of hydrogen during its production, transfer, and use, but did not examine the many drawbacks of the various methods used to produce hydrogen. Their analysis indicates that safety concerns about the usage of hydrogen are mostly highlighted in reference to its ignition and burning characteristics, including its lower ionization energy, quick diffusion, relatively high flame velocities, and wide combustibility range explosions. Parra et al. [34] provided the cost-based evaluation of the evolution of hydrogen generation, but lacked a thorough analysis of the numerous trends in the advancement of the various technologies. Recently, Mengdi and Wang [35] provided a summary of the technologies used to produce hydrogen, which covers both sustainable and non-renewable resources. Additionally, they contrasted the environmental effect assessments for each technology’s life cycle. Lane et al. [36] discussed the prediction for renewable hydrogen technologies production shareholdings. This work indicates that in the early markets, biomass gasifiers are the dominant technology.
The chemical energy of a fuel and oxidizer agent is turned into electrical energy through electrochemical reaction FCs, which are electromechanical devices. The reagents are continually supplied, unlike batteries. Transportation, portable, and stationary industries can all benefit from the utilization of FCs [37]. The main technical obstacles of this technology are still the price, performance, and endurance. Platinum is the most expensive component in terms of the potential cost. One of the key obstacles to overcoming the technical hurdles and improving FC’s effectiveness, durability, and price is the development of materials that reduce the degradation mechanisms in FCs [38]. Furthermore, the cost of hydrogen must be equivalent to that of current fuels and technology.
Edathil et al. [39] looked at the best fuel alternatives while analyzing the practicality of HMG systems. An ant colony algorithm was used in the study to design multi-objective economic operations for three separate Egyptian island communities. Abo-Elyousr et al. [40] used several optimization strategies to find the hybrid PV/wind/diesel microgrid system’s ideal size while taking the battery banks into account as energy storage systems. The techno-economic viability of preserving energy in biomass-fired industrial boilers was examined by Diab et al. [41]. The cycle tempo program was used to determine how ecofriendly rice husk is as a fuel. Arévalo et al. [42], used HOMER software to examine the effects of five various storage technologies incorporated into hydrokinetics, a diesel generator, PV, and hybrid RES.
Mahani et al. [43] presented the HSS-based integrated transport network. The authors established HSS’s viability and its potential in Germany. Using HOMER software, Cai et al. [44] studied the techno-economic analysis of fuel cells for a vehicle system, hydrogen generation, and wind energy limitation. The excess wind power restriction was, however, best stored by the hydrogen fuel cell generator. El-Taweel et al. [45] planned privately owned hydrogen storage facilities and topologies. The PV battery hydrogen systems had an identity of higher than 54%, according to Coppitters et al. [46], who looked into the optimal design and stochastic performance of an on-grid PV system. These findings indicate that the generated system was less vulnerable to real-world uncertainties.
A proposed interface converter-based adaptive virtual inertia control approach for HMG is discussed by Luo et al. [47]. By reducing the rate of variation in AC frequency and DC voltage and increasing the variation in AC frequency and DC voltage, this control strategy dynamically modifies the system’s virtual momentum when the performance differs from the nominal voltage. Xia et al., [23] proposed an HMG configuration for a grid-connected microgrid with a DC link at back-to-back converters. An additional DC bus connection can make it easier to use the DC microsources than a back-to-back connection between two AC systems, which might provide a dependable, isolated, and effective coupling. In order to guarantee voltage stability and power equilibration between the AC and DC grids, a BAC is required for HMGs.
Majumder [48] created a flexible detection method that validates reaction time while taking into account detection performance. However, the grid voltage magnitude was impacted by the effectiveness of the detecting system. The identification impact is highly consistent, there are no complex matrix modifications needed. Based on the study of harmonic identification, the appropriate control method is required to perform the power transfer between the AC and DC sub microgrid [49]. Toghani et al. [50] implies a more effective droop control (DRC) strategy that puts BAC in a shutdown state and stops power electrical device activities. The DRC methods mentioned above are predicated on perfect conditions. NL loads in a grid are not taken into account. A NL load can generate further power outages and conflicts with equipment linked to the grid when it alters the current.
A harmonic rectification system of integrated converters is described by Tian et al. [51] using the NL control approach. The instantaneous depiction of the harmonic component on the PWM signal greatly reduces the influence of bandwidth management on harmonic voltage minimization. The above approach does not have a high compensating harmonic accuracy. Liu et al. [52] present the parallel functioning transformer with a mutual filter. This method provides a high attenuation capacity, a reduced resonance risk, and enhanced filtering performance. The aim of the multi-mode control scheme for combining interface converters is to address unbalanced power quality (PQ) problems in a targeted manner and within a limited area of application, as stated by Senthil Kumar et al. [53].
When a microgrid is cut off from the main grid and running autonomously with small sources and loads, it is referred to as being in island mode [54]. Power to the PCC is abruptly interrupted while switching from grid-connected mode to islanded mode. If this electricity goes to the microgrid before the changeover, there will be a power shortage in the microgrid after the system switches to island mode. The island mode HMG system is shown in Figure 2, where the DC bus is interconnected to the PV, wind turbine, and HSS. A hydrogen storage tank, an electrolyzer, and a FC make up the HSS. It is being examined if the HMG system can optimize each power source in accordance with the levelized cost of energy. Therefore, a load profile is a tool to aid in pointing the direction of HSS growth. Active and reactive power changes are effectively suppressed while current distortion is decreased when a percentage resonant controller is integrated with the BAC.
Figure 2. Schematic layout of islanding mode of HMG with HSS.
In recent times, meta-heuristic optimizing techniques were applied to identify the best structure, scale, and energy management for hydrogen-based HMG systems. Mohseni et al. [55] evaluated the economics of designing hydrogen-based HMG using several meta heuristic-driven algorithms. Abdelshafy et al. [56] presented a non-sorting genetic algorithm (GA)-based optimum energy management technique for on-grid dual storage systems powered by PV and wind systems. There are several nature swarm techniques to address problems with HMG systems. Edathi et al. [57] used ant colony and cuckoo search-based metaheuristic optimization approaches to predict the best possible economic operation for HSS. Using multi-objective heuristic optimization techniques, Li et al. [58] investigated how energy storage may be integrated into isolated microgrids. According to the analysis of the aforementioned investigations, virtually a single evolutionary algorithm was tested, exposing the answer for local optima. Additionally, testing two hybridized meta-heuristic algorithms is a viable option with plenty of room for further study to address these issues.
In summary, this research makes significant contributions to the literature by providing an in-depth analysis of the energy storage techniques used in hydrogen-based HMG, developing the BAC for reactive power consumption, and outlining strategies for integrated solar, wind, and hydrogen systems that work in concert with the HMG’s electricity and energy management systems.

3. Hydrogen Production

Numerous feedstocks, including fossil and sustainable energy, can be used to create hydrogen. Hydrogen can be produced using a variety of process methods, including catalytic, biologic, electrochemical, photochemical, and thermo-chemical [59]. A thorough overview of several hydrogen generating processes is provided in [60]

3.1. Coal and Other Hydrocarbon Gasification

The “gasification” method makes hydrogen from a diversity of hydrocarbon fuels, including lignite, heavy residue lubricants, and limited refining output [61]. Hydrogen generation is handled mostly by the condensing of fossil fuels and heavy oil, as well as the burning of coal, petroleum, and diesel oil [62].

3.2. Steam Reforming

The chemical method of making hydrogen from a combination of water and a hydrocarbon substrate, typically a fossil fuel, is known as steam reforming. Natural gas, usually methane, is the most prevalent substrate [63]. A chemical reaction takes place when steam and propane are mixed at a higher temperature and pressure, converting them to carbon monoxide and hydrogen. The calorific value of the hydrogen generated is really larger than that of the natural gas used, but because the reformer requires a significant amount of energy to function, the net conversion efficiency is often only approximately 65–70%. The environmental factor is also a key problem, since converting natural gas to hydrogen creates the same number of pollutants and CO2 as immediately burning natural gas. The technique of producing hydrogen from natural gas is well developed [64].

3.3. Electrolysis

Electrolysis is the process of sending a current over water to separate specific molecules into oxygen and hydrogen [65]. As it is a precise method and water is available, electrolysis garnered great interest while accounting for just a small proportion of modern hydrogen generation. However, at the moment, the process is only employed in small facilities at a cost of 2.40–3.60 USD/kg of gases produced. Electrolysis is now conducted at rates ranging from several kW to 2000 kW of each electrolysis cell. As a consequence of the electrolysis procedure, molecular oxygen and pure hydrogen are produced [66]. Although the benefits of generating highly pure hydrocarbons via electrolysis of water were known for nearly two centuries [67], its implementations are still restricted to simple scale and unique situations. A massive scale hydrocarbon processing facility is not feasible or cost-effective, such as for marine, rockets, spaceships, industrial application, farming industry, and healthcare. Water electrolysis now accounts for just 4% of global producing hydrogen [68].

3.4. Solar Hydrogen

The solar hydrogen paradigm proposes creating electricity directly from sunlight utilizing PVs, electrolyzing water to create hydrogen, and replacing this hydrogen for petrol as well as other fossil fuels now in usage [69]. The terminology is increasingly used much more generally to cover electrolysis relying on various renewable energy sources, such as wind. This concept is attracting a lot of interest, owing to the ecological benefits of using hydrogen rather than fossil fuels. It also tackles two impediments to the eventual realization of massive solar power use. Solar electricity cannot be immediately used for quasi purposes, such as internal combustion, and electricity is complicated and expensive to retain.

3.5. Thermochemical Process

Heat is used to divide hydrogen from water. The most basic type of such a process is thermal transformation, which involves boiling water to extreme temperatures, approximately 3400 K. Direct heat conversions, though, are still impracticable beyond the study due to the extreme heat necessary [70]. Chemical processes can be used to minimize the needed temperature. Several alternatives were investigated, generally including intricate multistep procedures.

3.6. Nuclear Energy

Hydrogen may well be generated using a variety of nuclear energy-based systems. This includes nuclear heat conversion of water utilizing specific chemical techniques, including the sodium-iodine cycle and nuclear power hydrolysis of water. Moreover, high-temperature electrolytic employs nuclear excess heat to reduce the amount of power needed for electrolysis [71]. Though the use of nuclear energy for hydrogen generation is appealing from a carbon reduction standpoint, it poses additional severe environmental and health problems connected to uranium extraction and smelting, the possibility of accidents, and the administration and disposal of hazardous waste.

3.7. Biomass

There are two types of conversion of biomass techniques: thermochemical and biological processes. Thermochemical operations are less costly because they can be run at higher temperatures and therefore produce quicker response rates. Biomass combustion is recognized as a potential technique for producing renewable hydrogen. It is advantageous to leverage biomass resources in order to build an extremely efficient clean method for massive production of hydrogen. Adhesives, carbon black, activated charcoal, polymers, fertilizers, ethanol, different acids, Friedel diesel, paraffin, and methanol can all be produced using many of the techniques available to produce hydrogen from biomass [72].

3.8. Off-Gas Cleanup

After steam generation, the cleaning of commercial off-gases is currently the most prevalent source of hydrogen. Many industries emit significant levels of hydrogen in their solid waste, including refineries, steel plants, and some chemical facilities. Most off-gas hydrogen is utilized by the industry that generates it [73]. However, it is doubtful that off-gas cleaning could be extended sufficiently to meet the increasing demand that would come from the extensive utilization of hydrogen as a fuel.
During the early stages of infrastructure development, biomass combustion is used in small, decentralized facilities, and later in larger centralized units. Steam reformation and electrolyzers can also be downscaled and installed on site at fueling stations, but coal gasification or nuclear energy is only for large-scale, centralized production and is hence limited to later stages with significant hydrogen consumption [74]. Natural gas combustion, coal liquefaction, and water electrolysis are established methods for hydrogen generation that are already used on a large scale across the world. Natural gas hydrogen production is the most widely utilized method in the petrochemical and chemical sectors. It is now the least expensive technique of generation and emits the least CO2 of any fossil fuel-producing route. Electrolysis, on the other hand, is more costly and only viable if high-purity hydrogen is desired. With natural gas prices predicted to rise, coal gasification is expected to become the most cost-effective alternative around 2030 [75]. A comparison of various hydrogen production methods and observations is shown in Table 1. It shows the possible ways to produce hydrogen, and the steam reforming method is a simple way to produce hydrogen.
Table 1. Comparison of various hydrogen production methods.

4. Hydrogen Storage Technologies

Storage and transmission of hydrogen energy are ongoing and evolving concerns. Operations involving transportation and storage are at minimum as crucial as those involving manufacturing [76]. The hydrogen economy benefits greatly from these processes. The objective of conserving hydrogen energy is to make it safe, effective, and available at all times. Hydrogen has a lower volume power density and a large specific gravity energy density when it is purified [77].
There are two techniques for storing hydrogen. Physical storage methods include pressurized storage, and material-based hydrogen storage [78]. The various storage methods and their categorizations are shown in Figure 3. The most popular strategies are pressurized gas and liquid hydrogen preservation. The solid-state storage technology is in progress and anticipates increased application in the next decades. Hydrogen can be compressed to 700 bar in appropriate buildings and kept as a gas in cylinders, containers, and subterranean cavities.
Figure 3. Types of HSTs [79].

5. Hydrogen Based HMG

Integration of storage energy systems into grid-connected and standalone energy systems emerged as a promising research area. For both static and mobile applications, the use of hydrogen as a fuel for fuel cell technologies presents a significant difficulty [96]. Numerous studies concentrated on identifying the ideal size and design of HMG systems for practical energy management purposes, as well as conducting techno-economic analyzes in these areas. Utilizing renewable energy efficiently may be achieved by combining local load, hydrogen energy storage, PV, wind power generation, and HMG. The HMG may, however, also include alternative energy sources. Even still, the power’s properties are greatly worsened by its high reactive power under non-linear loads.
Figure 4 depicts the HMG, which comprises a DC grid, an AC grid, and an AC/DC power flow regulator, as well as stores hydrogen and batteries [97]. An AC/DC hybrid microgrid with hydrogen storage and battery storage was used to clarify the control approach. Both the AC sub grid and the DC sub grid consist of five components: PV, WT, HSS, battery ESS, and loads. Bidirectional converters are used to transfer power between the DC and AC sub grids and ensure steady operation of two sub grids. A DC/DC boost converter connects PV panels to the DC bus. A capacitor is used to reduce the high frequency voltage ripples from solar panels. In order to replicate AC sources, an AC bus is linked to a permanent magnet synchronous generator in a wind turbine. DC/DC converters are used to connect hydrogen tanks and fuel cells to both DC and AC buses. In order to ensure excellent PQ, HMG should offer voltage stability and power balancing. PQ is substantially impacted by harmonics and unbalanced load currents that arise when NL loads are present in the system. The identification and rectification of harmonic currents must be effective as a consequence [98].
Figure 4. Multi energy storage system in HMG [94].

6. Hydrogen Energy Integration in HMG

The establishment of an HSS to modernize separate HMG systems with a bidirectional converter for smooth integration of renewable energy, power transmission, and harmonic current reduction is the focus of this research. For this research, the modelling of HMG for lagging and NL load is taken into account. The solar energy system, wind energy, hydrogen energy, batteries, and ultracapacitors with linear and NL demands are included in the DC power grid. The BAC functions as an inverting form and a rectifying phase to supply a grid system with consistent, uninterrupted electricity. The following standards can be followed when developing this structure. The non-saturated linear inductance is only kept in the filter part on the AC side, and the grid voltage is always kept in a steady state with three phases. Additionally, the optimal power electronic controls offered by the bidirectional converter unit eliminate the switching losses [121].

This entry is adapted from the peer-reviewed paper 10.3390/en15217979

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