Introduction
Due to continuously growing energy consumption and the policy of decarbonization of most leading countries, based on the reduction of traditional fossil fuel-based generation, one of the main directions of development of the global energy sector is the large-scale penetration of new generation facilities based on renewable energy sources (RES) [1]. According to a report by the International Energy Agency [2], the increase in installed RES capacity in 2020 was almost 280GW, an increase of 45% compared to 2019. According to this report, the positive dynamics recorded in 2020 became the “new normal”: an additional 270GW of RES generation capacity were installed in 2021 and almost 280GW is expected in 2022.
Common to RES facilities is the use of power converters (PC) to connect to the grid, which leads to a lack of direct coupling to the grid and, consequently, a contribution to the overall mechanical inertia of the system [[3], [4], [5]]. The above features of devices based on power semiconductor technology significantly change the dynamic properties of electric power systems (EPS) due to the different dynamics of PC functioning, especially its automatic control system (ACS), compared to the traditional equipment of EPS. As a result, the continuous growth of the integration level of RES facilities, which will last until at least 2030 according to the Paris Agreement [6], leads to a significant decrease in the reliability of modern EPS functioning in normal and especially emergency modes, which is no longer ensured by the traditional paradigm of EPS control and protection [[7], [8], [9]]. One of the main problems identified by the academic and industrial community is frequency stability saving [[10], [11], [12]], which means the ability of the EPS not to allow consumers and equipment to increase or decrease frequency, leading to a blackout if an emergency imbalance of active power occurs in the EPS or in its isolated part. The emergence of this problem is associated with the penetration of inertia-free RES facilities, including by replacing conventional generation, which leads to a decrease in available rotating reserve and overall system inertia. This leads to an increase in the rate of voltage frequency change when unbalanced power occurs [13]. As a result, in power systems with low inertia the depth of frequency reduction is much greater for a similar disturbance compared to traditional EPS, which significantly increases the probability of undesirable triggering of load-shedding automatics and disconnection of consumers [14]. In order to ensure the reliable operation of EPS with low inertia and reduce the negative effects of the RES facilities, it is necessary to adapt their ACS to the requirements of conventional generation in the EPS [15]. In addition, when operating RES facilities, it is necessary to take into account the heterogeneity of the value of inertia, which leads to different rates of change and, accordingly, the values of frequency reduction in different parts of the network, which causes serious difficulties in setting up systems of over- and underfrequency protection [16]. To minimize this aspect of the problem in question, the frequency control function should be implemented at most of the installed RES facilities, which leads to a significant amount of research and proposed solutions in this direction. Among them are such major projects as Enhanced Frequency Control Capability (EFCC) and Massive InteGRATion of Power Electronic Devices (MIGRATE) projects led by UK National Grid and TenneT [17,18]. Similar projects are underway in Australia, China, and the USA.
All currently proposed approaches to frequency regulation can be divided into two large groups: provision of temporary and permanent power reserve for RES facilities. Their review, comparison, advantages and disadvantages are considered in the works of [11,19]. However, because of the necessary mass use of frequency control algorithms, the solutions developed must be simple and reliable. One such approach, which is applicable to all dominant types of RES, is synthetic inertia [20,21], which is considered in this article.
Most studies of synthetic inertia are reduced to determining the optimal value of the coefficients of amplification of additional channels of PC ACS [22]. However, the existing methods for calculating such coefficients are usually reduced to taking into account the capabilities and limitations of wind turbines to transfer the stored kinetic energy of the wind turbine through a DC circuit and PC into the grid [23], which is obviously unfeasible for the PV station, due to the lack of rotating parts in the latter. Despite this, the majority of researchers, when tuning PV station ACS, use the methods tested for wind turbines, and do not take into account the different nature of the functioning of these devices [24,25]. At the same time, the use of PV station for frequency regulation in the EPS, including in the emergency mode, can be provided in two ways: through the use of energy storage or deloading of PV station. Both of these methods are being investigated, but the latter is more economically advantageous [26] points out that the latter method is more cost-effective because the cost of installing auxiliary component is high. In this regard, this method is considered in the article in terms of maintaining a given level of frequency under load surges in the network, including at different levels of insolation and temperature of PV panels [27].
This article deals with this issue and is organized as follows. The basic principles of the combined application of RES and hydrogen ESS in a grid-connected mode is considered in Section The basic principles of a hybrid renewable energy system with a hydrogen storage. The second section describes the synthetic inertia algorithm under consideration and peculiarities of its application and tuning for different RES devices. The third section presents the used mathematical model of the RES object and the test scheme of the EPS. The fourth section presents the results of the experiments with the corresponding description. The fifth and sixth sections, respectively, present the algorithm for determining the optimal coefficients of the synthetic inertia block for frequency stability at different levels of insolation and temperature of PV panels, and the results of its testing. The conclusion of the research is presented in the end.
Section snippets
The basic principles of a hybrid renewable energy system with a hydrogen storage
The use of hydrogen as an energy source is developing worldwide because it is one of the cleanest, lightest, and most efficient fuels [28]. Hydrogen can be produced, stored, and consumed using an electrolyzer (EL), a hydrogen tank (HT), and a fuel cell (FC) unit (Fig.1). At the same time, the most environmentally friendly and cost-effective way to produce hydrogen is electrolysis of water using electricity from RES [29]. The hydrogen produced can be stored in a HT as a high-pressure liquid or
Approaches to the formation of virtual inertia
In EPSs with reduced inertia, all transients are faster (in particular, the rate of frequency change) and the probability of their stable operation is increased. Therefore, frequency control of RES units should be performed using special algorithms, necessary to introduce an artificial slowdown of their response to the transient process in the external power system. Currently, many approaches have been developed to solve this problem and provide the formation of the so-called virtual inertia.
PV station model
For the study, we use the conventional PV station model described in [45] and allowing for active and reactive power control at the level of PV station. The deloading of PV station is realized by adjusting the ACS of the DC/DC converter connected to the PV panels (Fig.3), namely, by controlling the MPPT according to the dependence shown in Fig.4.
The MPPT control normally changes the DC voltage of the PV units to achieve maximum efficiency (point 1 in Fig.4). The maximum power point and the
Study of the effect of the synthetic inertia block adjustment on the frequency stability of the EPS
For the presented EPS model (Fig.6), a load surge of 1.4MW in bus 4at different levels of insolation and PV panels temperature was carried out. The load surge allows to estimate the influence of the synthetic inertia block on the frequency response of the PV panels. Initially, the PV station operates independently of the insolation level with a constant power reserve value of 2.5MW (Fig.7), which is 10% of its installed power. When the PV station is deloaded, part of the available power
Algorithm for determining the optimal coefficients of the synthetic inertia block for frequency stability at different levels of insolation and temperature of pv panels
The integration of the selected coefficients into the ACS of PV station can be implemented by any microcontroller. However, for this purpose, it is necessary to form the functional dependences on the obtained values of the coefficients. Thus, based on the obtained results, the graphical dependences for the coefficients Kin and Kd (presented in Table 2) on the insolation level (Fig.12, Fig.13), and Kin (presented in Table 4) on the PV panel temperature level (Fig.14) were plotted.
The
Checking the algorithm
The synthetic inertia block coefficients selected in the previous section make it possible to maintain frequency stability in the EPS using the PV station at different levels of insolation and temperature of PV panels for the selected topology and the level of power generated by the PV station. However, in the case of increasing the installed capacity of the PV station or changing the generation at other power plants of the scheme under consideration, a different development of the situation is
Conclusion
The results presented in the article prove the possibility of effective use of the synthetic inertia formation block of the ACS of PV station to maintain the frequency stability in the EPS, regardless of the level of insolation and temperature of the PV panels. It is experimentally confirmed that by varying the coefficients of the control channels of the synthetic inertia block, it is possible to achieve the formation of almost identical course of the transient process under different lighting
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
The reported study was funded by the Russian Science Foundation, project number 22-79-00204.
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FAQs
What is the effect of energy storage in improving the frequency regulation of the power system? ›
Energy storage can reduce the cost to provide frequency regulation and spinning reserve services, as well as offset the costs to consumers by storing low-cost energy and using it later, during peak periods at higher electricity rates.
How can hydrogen storage systems be used as energy storage and energy carrier? ›Hydrogen energy storage is another form of chemical energy storage in which electrical power is converted into hydrogen. This energy can then be released again by using the gas as fuel in a combustion engine or a fuel cell.
What are the potential uses of hydrogen and its connection to energy storage options? ›Once produced, hydrogen can be used in stationary fuel cells for power generation or stored as a compressed gas, cryogenic liquid or wide variety of loosely bonded hydride compounds for longer-term use.
How do you store solar energy in hydrogen? ›The basic idea is that the electricity generated by solar PV systems during daytime can be used to run electrolyzers to split water into hydrogen and oxygen gases. Hydrogen is collected and stored in one or another form.
How is the frequency controlled in a power system? ›Primary frequency control is provided by generators that measure and respond to the frequency changes at their local connection points. These generators have some room to ramp up or down as required and will act in response to these large disturbance events to try and correct the frequency.
What happens if frequency increases in power system? ›If the frequency rises, the turbine reduces its steam flow. If it falls it will increase, changing the electrical output – a change that needs to happen in seconds.
What is the best method of hydrogen storage and why? ›Hydrogen can be stored physically as either a gas or a liquid. Storage of hydrogen as a gas typically requires high-pressure tanks (350–700 bar [5,000–10,000 psi] tank pressure). Storage of hydrogen as a liquid requires cryogenic temperatures because the boiling point of hydrogen at one atmosphere pressure is −252.8°C.
What are the major problems for using hydrogen for energy storage? ›Fuel Storage
Hydrogen's energy content by volume is low. This makes storing hydrogen a challenge because it requires high pressures, low temperatures, or chemical processes to be stored compactly.
- Renewable and Readily Available. ...
- Hydrogen is a Clean and Flexible Energy Source to support Zero-Carbon Energy Strategies. ...
- More Powerful and Energy Efficient than Fossil Fuels. ...
- Highly Efficient when Compared to Other Energy Sources. ...
- Almost Zero Emissions.
In order to produce hydrogen (with zero emissions) a process called, electrolysis. 20 - 30% of energy is lost in the process of creating hydrogen. The hydrogen must then be compressed and stored, losing another 10%. Finally, another 30% is lost when converting the hydrogen into electricity.
What is the efficiency of electricity to hydrogen to electricity? ›
Hydrogen Re-Electrification
Hydrogen can be re-electrified in fuel cells with efficiencies up to 50%, or alternatively burned in combined cycle gas power plants (efficiencies as high as 60%).
Hydrogen fuel cells
Pros: No vehicle emissions other than water vapor. Fuel economy equivalent to about twice that of gasoline vehicles. Hydrogen is abundant, and can be made from renewable energy. Cons: This space-age technology is expensive.
- Geological hydrogen storage. One of the world's largest renewable energy storage hubs, the Advanced Clean Energy Storage Hub, is currently under construction in Utah in the US. ...
- Liquified hydrogen. ...
- Compressed hydrogen storage. ...
- Materials-based storage.
These two energy storage methods are either treated as complementary or substitute technologies depending on the energy storage application. Batteries require lower maintenance, are easy to operate, and possess higher energy capacity, while hydrogen storage systems have better gravimetric and volumetric densities.
Why is it difficult to store hydrogen? ›Hydrogen is difficult to store due to its low volumetric energy density. It is the lightest of and simplest of all elements, being lighter than helium, and so is easily lost into the atmosphere.
How do you change the frequency of a power? ›There are three primary methods to convert power frequency: varying engine speed, using a frequency converter, or employing a variable speed generator.
What is frequency control system? ›Frequency control is a process of maintaining the stability of a power system. In the power system, the frequency of the loop gets deviate from the steady-state value under the action of load perturbation.
How do we control frequency and voltage? ›Hence, a power system control is required to maintain a continuous balance between power generation and load demand. Load Frequency Controller and Automatic Voltage Regulator play an important role in maintaining constant frequency and voltage in order to ensure the reliability of electric power.
Does a higher frequency mean more energy electricity? ›The amount of energy they carry is related to their frequency and their amplitude. The higher the frequency, the more energy, and the higher the amplitude, the more energy.
What causes high frequency on a power system? ›High frequency disturbances are caused by the sparks generated in the AC commutator motors, the “corona effect” on the high voltage lines, the igniters of luminous signs and burners, and by the magnetic fields irradiated by radio and TV stations.
What causes over frequency in a power system? ›
Over-frequency is most often the result of an instantaneous load reduction when the generator is synchronized to the system, or from excessive turbine torque when the generator is in the open-circuit condition before synchronization with the grid.
What are three methods of hydrogen storage? ›- As a compressed gas in high-pressure tanks.
- As a liquid in dewars or tanks (stored at -253°C).
- As a solid by either absorbing or reacting with metals or chemical compounds or storing in an alternative chemical form.
Hydrogen gas is highly flammable and can easily escape containment. If hydrogen gas escapes containment, it can corrode metals. This, in turn, can make these contaminated metals brittle and prone to breaking.
What is the best material for hydrogen storage? ›Formic acid. Formic acid is a highly effective hydrogen storage material, although its H2density is low. Carbon monoxide free hydrogen has been generated in a very wide pressure range (1–600 bar).
Why is Elon Musk against hydrogen? ›“It's important to understand that if you want a means of energy storage, hydrogen is a bad choice.” Expanding on his argument, Musk went on to state that “gigantic tanks” would be required to hold hydrogen in liquid form. If it were to be stored in gaseous form, “even bigger” tanks would be needed, he said.
What are 3 disadvantages of hydrogen? ›- If it is “grey”, it pollutes. If it is not produced using renewable sources, hydrogen pollutes. ...
- It is a gas that is difficult to handle. ...
- It is less advantageous than electric power for cars.
But when emitted into the atmosphere, hydrogen contributes to climate change by increasing the amounts of other greenhouse gases such as methane, ozone and water vapor, resulting in indirect warming. That's a problem because hydrogen's small molecule is difficult to contain.
How much does a gallon of hydrogen fuel cost? ›Hydrogen fuel is much more efficient than gasoline, but it's also four times more expensive, roughly equivalent to about $16 a gallon.
Why hydrogen is not used as a fuel? ›But it is not used as domestic fuel, due to several reasons : Hydrogen is not easily available and cost of production is high Unlike other gases, hydrogen is not readily available in the atmosphere. It requires processes like electrolysis of water for its production. This is a very costly process and time consuming.
Why isn't hydrogen used in cars? ›The vast majority of car companies have turned away from hydrogen because of the high density of energy consumed in its production, as well as poor funding and backing from governments, which is stopping the hydrogen revolution from expanding ever more.
Are hydrogen fuel cells better than batteries? ›
Hydrogen is significantly more energy dense than batteries, which means a fuel-cell pushed powertrain will weigh less. To illustrate, for a 800 kms range truck, the difference can be as much as 2 tons. Consequently, fuel cell technology allows for longer driving ranges and heavier payloads.
Is hydrogen cheaper than electric? ›Hydrogen vehicles are more expensive than electric vehicles, with no budget options on the market currently, the price tag for a new hydrogen vehicle is comparative to that of a top end electric vehicle.
Why is hydrogen power better than electric? ›As with electric cars, hydrogen cars produce zero harmful emissions on the road, but unlike electric cars, which take a fair amount of time to recharge, hydrogen cars can be refilled about as quickly as a petrol or diesel car.
How much electricity is needed for hydrogen? ›At present, the overall efficiency is around 50– 60% depending on the use of cell technology. To produce 1 kg of hydrogen, about 9 liters of water and about 50 kWh of electricity is required. There are other methods of hydrogen production that can be found in the literature.
How efficient is solar to hydrogen energy conversion? ›The highest efficiency of 24.4% for the solar-to-hydrogen (STH) energy conversion was obtained in an outdoor field test by combining concentrator photovoltaic (CPV) modules with InGaP/GaAs/Ge three-junction cells and polymer-electrolyte electrochemical (EC) cells.
How much electricity does it take to separate hydrogen from water? ›As of 2022, commercial electrolysis requires around 53 kWh of electricity to produce one kg of hydrogen, which holds 33.6 kWh of energy.
Is burning hydrogen bad for the environment? ›Hydrogen interferes with the breakdown of heat-trapping methane in the atmosphere. It has other warming effects, too. Here, hydrogen increases high-altitude water vapor. Hydrogen increases ozone levels here, a greenhouse gas and key component of smog.
What are 3 advantages of hydrogen power? ›Hydrogen is an optimal energy solution in areas that are difficult to decarbonize. Hydrogen advantages include eliminating emissions to improve regional air quality while reducing greenhouse gas emissions; hydrogen reduces CO2, particulates, and NOx emissions as compared to internal combustion engines.
How much does hydrogen cost compared to natural gas? ›Hydrogen produced by steam reformation costs approximately three times the cost of natural gas per unit of energy produced. This means that if natural gas costs $6/million BTU, then hydrogen will be $18/million BTU.
Can you fill a hydrogen car at home? ›No plugging, just pumping. Hydrogen-powered vehicles don't need charging like an electric vehicle. You refuel them with hydrogen gas, pumped in the same safe and convenient way you would a conventional petrol or diesel car. Filling up takes the same amount of time too, between 3-5 minutes for a full tank.
How much does hydrogen storage cost? ›
Storing this hydrogen underground will add about another $0.30/kg, thus the hydrogen costs $2/kg. If this hydrogen is used to generate power, the resulting cost is $100 to $200/MWh.
Can you store hydrogen fuel at home? ›Typically, hydrogen is stored as gas and requires very large storage tanks operated at high pressure up to 300 bars. Using metal powder as a medium to store hydrogen has some obvious benefits: the same amount of hydrogen gas can be stored in a tank not even half the size compared to gas.
Will hydrogen overtake batteries? ›A new study published in the peer-reviewed journal Nature has confirmed what common sense has made clear for years: Hydrogen fuel cell vehicles aren't likely to catch up to battery-electric vehicles – even for commercial trucks.
Is Tesla going to hydrogen? ›The next Tesla hydrogen vehicle hasn't been given any official information, but experts believe it will be built on the Model S or Model X platform and will have the company's renowned modern styling and cutting-edge technology.
Which has the best hydrogen storage capacity? ›Borohydrides. The borohydrides have the highest theoretical gravimetric hydrogen storage capacities of the complex hydrides; up to 18.5% (wt) for lithium borohydride (LiBH4) [94].
What is the biggest problem with hydrogen? ›Also, hydrogen gas is nontoxic. Yet hydrogen has its own major safety issues. It is highly flammable, with an ignition energy that is 20 times smaller than that of natural gas or gasoline.
What pressure is hydrogen stored at? ›How Hydrogen Storage Works. Hydrogen can be stored physically as either a gas or a liquid. Storage of hydrogen as a gas typically requires high-pressure tanks (350–700 bar [5,000–10,000 psi] tank pressure).
Can hydrogen pass through glass? ›Hydrogen molecules are so small that they will pass through glass, drywall, wood and most metals. Hydrogen is 14 times lighter than air. If it escapes from a container, it will always move up.
How energy storage affects the electrical power system? ›Electrical energy storage (EES) plays three main roles—lowering the electricity supply costs by storing energy at off-peak rates, improve reliability at times of unexpected failures or disasters, and maintain and improve power quality (frequency and voltage).
What is the impact factor of energy storage applications in power systems? ›The 2022-2023 Journal's Impact IF of Journal of Energy Storage is 8.907, which is just updated in 2023.
What is the role of energy storage in power system? ›
Energy storage can reduce high demand, and those cost savings could be passed on to customers. Community resiliency is essential in both rural and urban settings. Energy storage can help meet peak energy demands in densely populated cities, reducing strain on the grid and minimizing spikes in electricity costs.
What is frequency regulation energy storage? ›Frequency Regulation (or just “regulation”) ensures the balance of electricity supply and demand at all times, particularly over time frames from seconds to minutes. When supply exceeds demand the electric grid frequency increases and vice versa.
What are the methods of energy storage in solar system? ›Types of Energy Storage
The most common type of energy storage in the power grid is pumped hydropower. But the storage technologies most frequently coupled with solar power plants are electrochemical storage (batteries) with PV plants and thermal storage (fluids) with CSP plants.
The energy conversion goes from chemical energy stored in the fuels, to heat energy as it burns which is converted to kinetic energy as it drives large turbines and finally this is converted to electrical energy.
What is the most efficient form of energy storage? ›Energy storage in lithium-ion batteries is considered one of the most efficient.
What are main disadvantages of energy storage? ›- Shorter service life. While a flywheel storage device has around the same service life as the UPS, batteries generally need to be replaced several times over the same period.
- Higher maintenance requirement.
- Energy Storage Problems.
- Battery storage at the residential level.
- connection to the grid is also extremely costly.
- telecom tower power system market.
- Low capacity factor.
Lack of standardization in storage systems.
This often creates a challenge for projects that evolve over time as storage systems do not always fit the needs of the project and sometimes batteries need to be replaced.
Storage options include batteries, thermal, or mechanical systems. All of these technologies can be paired with software that controls the charge and discharge of energy.
What are the methods of storing hydrogen? ›Hydrogen can be stored physically as either a gas or a liquid. Storage of hydrogen as a gas typically requires high-pressure tanks (350–700 bar [5,000–10,000 psi] tank pressure). Storage of hydrogen as a liquid requires cryogenic temperatures because the boiling point of hydrogen at one atmosphere pressure is −252.8°C.
What is the best way to store electricity? ›
Electricity can be stored in electrical batteries, or it can be converted into heat and stored in a heat battery. Heat can also be stored in heat batteries or in thermal storage, such as a hot water cylinder.
How do you control frequency? ›Frequency variations in a power system occur because of an imbalance between generation and load. When the frequency value of a power system reaches the emergency condition, the control strategy is initiated. The frequency control is divided in three levels: primary, secondary and tertiary controls.
What are the types of frequency regulation used in power system? ›Different methods available for “frequency regulation” include generator inertia, adding and subtracting generation assets, dedicated demand response and electricity storage. Each of these methods has pros and cons, and the implementation of these methods takes from a millisecond to 20 minutes.
What are frequency control products? ›CTS Frequency Control products provide timing and synchronization solutions for applications such as wireless infrastructure, wireline core networking, synchronous Ethernet, optical networking, avionics, military, oil & gas exploration, and test & measurement.