م.م علي عماد القيم
الملخص: اليوم، مع التوسع في تقنيات إنتاج الطاقة، وزيادة الاهتمام بالقضايا البيئية والاهتمام بتحسين موثوقية الشبكات الكهربائية، أصبحت الإمكانية والدافع لتغيير شبكات التوزيع من السلبية إلى الإيجابية والرغبة في إنتاج الطاقة المتجددة على مستوى تم توفير نظام التوزيع. ومن ناحية أخرى، فإن ربط موارد الإنتاج المتفرقة بشبكات التوزيع الحالية لم يلبي الاحتياجات الفنية والاقتصادية للمستثمرين. وبينما كان من المتوقع أن تتحسن جودة الطاقة من خلال زيادة معدل تغلغل مصادر التوليد الموزعة، فقد تم الحصول على نتائج عكسية بسبب تقلبات الطاقة الناتجة عن اختلاف الجهد والتردد لمصادر الطاقة المتجددة المختلفة. على الرغم من أن استخدام موارد التوليد الموزعة يمكن أن يقلل من الحاجة إلى توسيع الشبكات الكهربائية التقليدية، إلا أن التحكم في عدد كبير منها إلى جانب الأحمال التي يمكن التحكم فيها قد خلق تحديًا جديدًا في التحكم وتشغيل شبكة موثوقة واقتصادية. يتم تقليل هذا التحدي بنفس القدر من خلال الشبكة الذكية من خلال تقليل مسؤولية التحكم في الشبكة وإتاحة الحصول على أقصى قدر من الكفاءة الاقتصادية. ولذلك فإن الحل الصحيح هو بناء شبكات صغيرة مستقلة عن الشبكة الرئيسية. لذا تناولت هذه الدراسة الشبكة الذكية ومكوناتها.استجابة للحاجة إلى إجراء تغييرات في شبكات الطاقة واستخدام التقنيات الجديدة. لذلك من المتوقع أن تقلل هذه الشبكات بشكل كبير من مشاكل شبكة الطاقة وتوفر ميزات وإمكانيات جديدة لها. بدأت فكرة الشبكة الذكية بتركيب أدوات القياس المتقدمة (AMI) لتحسين إدارة جانب الطلب، وزيادة كفاءة الطاقة، وإنشاء شبكة كهربائية ذاتية الإصلاح، لتحسين موثوقية الموارد والاستجابة للكوارث الطبيعية أو التخريب المتعمد. تم اقتراح مفهوم الشبكة الذكية بهدف حل مشاكل شبكات الطاقة وإدارة أفضل وأكثر كفاءة لنظام الطاقة. تعمل الشبكات على تحسين التحكم في نظام الطاقة وتشغيله وتوفر إمكانية الاستخدام الواسع النطاق للإنتاج الموزع. في حالة حدوث خطأ على مستوى نظام الطاقة، يجب أن تكون الشبكة الذكية قادرة على إصلاح نفسها والعودة بسرعة إلى الظروف المثلى. أيضًا، شبكة المشغلين الذكية كرس نفسك لإيجاد طرق جديدة لإجراء التبادلات، وسوف يساعد Eddie Energy في نظام الطاقة
Introducing The Smart Energy Network and Its Components
Ali Imad Naji*,
*Department of Electrical Engineering, techniques University of MUS
Abstract: Today, with the expansion of energy production technologies, increasing attention to environmental issues and interest in improving the reliability of electrical networks, the possibility and motivation to change distribution networks from passive to active and the desire to produce renewable energy at the level of the distribution system has been provided. On the other hand, connecting scattered production resources to current distribution networks has not met the technical and economic needs of investors. While it was expected that the power quality would be improved by increasing the penetration rate of distributed generation sources, the opposite results have been obtained due to power fluctuations caused by the difference in voltage and frequency of different renewable energy sources. Although the use of distributed generation resources can potentially reduce the need to expand traditional electrical networks, controlling a large number of them along with controllable loads has created a new challenge in the control and operation of a reliable and economical network. This challenge is reduced to the same extent by smart network by reducing the control responsibility of the network and makes it possible to obtain the maximum economic efficiency. Therefore, the right solution is to build small networks independent of the main network. So this study introduces smart network and its components.
Keywords: Distributed generation, Energy storage, Smart network
1. Introduction
The existing energy networks are very complex networks that consist of centralized power plants, transmission lines and distribution networks. These networks have the ability to supply and transmit a large amount of electrical power. The existing network covers system uncertainties including load changes and as a result provides the required energy with a high level of reliability. Currently, the operation of the power grid is hierarchical. In this structure, the power plant at the top of the chain delivers power to customers at the bottom of the chain. These systems have one-way communication, which means that the information transmission path is only from the power company to the consumer, and the power companies do not have any real-time information from the endpoints. These networks must able to provide the maximum load of the system with a suitable level of reliability. Smart power networks were proposed in
response to the need to make changes in power networks and use new technologies. Therefore, it is expected that these networks will greatly reduce the problems of the power network and provide new features and capabilities to it. The idea of a smart grid began with the installation of Advanced Metering Instruments (AMI) to improve demand-side management, increase energy efficiency, and create a self-healing electrical grid, to improve resource reliability and response to natural disasters or intentional sabotage. The concept of smart grid has been proposed with the aim of solving the problems of power grids and better and more efficient management of the power system. Networks improve the control and operation of the power system and provide the possibility of widespread use of distributed production. In the event of an error at the level of the power system, the smart network must be able to repair itself and quickly return to optimal conditions. Also, the smart network of operators Devote yourself to finding new ways to make exchanges Eddie Energy will help in the power system.
2. Smart Energy Network Components
The smart grid consists of elements that together add many capabilities to the current power system. Some of the capabilities of the smart grid are introduced separately below.
2.1 Distributed Generation (DG)
In power systems, from the beginning until now, the electrical energy needed by consumers is produced in large volumes and in centralized power plants, and then it is transferred to the place of the consumer through energy transmission and distribution lines. This huge complex of power plants is usually close to They are installed at the place of primary energy (such as gas, coal, water, etc.). Therefore, in these systems, electric energy must travel a long way to be transferred from the place of production to consumption, which causes the loss of part of the electric energy. It is produced in energy transmission lines. On the other hand, with the passage of time and the increase in the demand for electric energy, the need to install huge
power plants and the installation of energy transmission lines increases, both of which require spending a lot of money and time. Some of these problems The hand made governments and researchers think of finding a solution for these problems. The use of distributed sources of electrical energy production was proposed as one of the solutions to the mentioned problem. So far, there are different definitions for distributed production in terms of capacity and level. The voltage of these electrical energy sources is presented. According to the definition of the International Energy Agency (IEA), the production of Para Log refers to the production units that supply the energy needed by the consumers at the place of consumption or are connected to the distribution network as backup, usually the capacity of these production units is considered to be maximum 50 MW.
2.1.1. DG advantages
The use of DGs in the distribution system has many environmental, economic, and technical advantages. These advantages can be realized if the DGs have the right size and on the other hand, are installed in the right place.
In general, the use of power plants with distributed generation has the following advantages:
1- Emergency power supply: these resources provide power as an auxiliary source and largely prevent the distribution company from creating new transmission and distribution systems.
2- Reduction of energy transmission losses: the use of scattered production sources reduces the amount of current in the lines from the generator to the distribution transformer.
3- The possibility of heat recovery using these sources: in the method of simultaneous production of electricity and heat (CHP), steam or hot water needed for various processes can be supplied.
4- Balanced load distribution: Using DG improves load distribution in the network. Engineering research shows that the logical implementation of the installation of scattered production units at the substations can change the flow direction and load distribution and improve the load distribution imbalance.
5- Correcting the voltage profile: the use of distributed generation in distribution stations reduces the load seen from the producer's point of view. This load reduction will reduce the voltage drop in the transmission lines.
6- Increasing the life of system equipment: One of the benefits of distributed generation is reducing the peak load values in the network. The equipment used in the electricity industry all have thermal application limits and the allowed range of current or voltage. In other words, the performance of power components in excess modes. The load, which will also bring thermal problems, will cause them to age and wear out prematurely.
7- Freeing the capacity of transmission and distribution systems: by installing the power generation system at or near the point of consumption, the effective length of the
transmission and distribution network increases and the network capacity is freed to respond to other subscribers.
8- Power quality and reliability: Distributed generation can reduce network outages, which in turn reduces outage time and also reduces concerns in the field of safety, and can also provide high-quality power and energy to subscribers. deliver and therefore this will reduce or eliminate existing concerns in the field of network voltage fluctuations and harmonics that affect the sensitive loads of subscribers.
2.1.2. DG challenges
In spite of all the benefits of distributed generation sources, we must pay special attention to its possible negative effects on the distribution network, which may be the most important of these effects related to voltage level and protection coordination issues. Some of these problems are:
1- High initial cost
2- Complication of network operation and control
3- Frequency deviation of the system
4- System voltage deviation
5- Low selection power in choosing the type of primary fuel
6- Change in load distribution
7- Providing low reactive power
8- Creating harmonics in the network
2.1.3. DG technologies
DG includes various technologies, some types of these technologies are explained below.
Gas turbines: These types of turbines were initially used for jet engines, currently gas turbines of various sizes are used in the power industry. This technology is used in the combined heat and electricity (CHP). and can be designed in such a way that it brings high thermal efficiency. Currently, small MW12 gas turbines are used in CHP.
Micro-turbines: Micro-turbines are actually smaller gas turbines. Each unit of these turbines alone can produce about 30-200 KW, but a combination of several units can be used as a power generation source. Due to the low combustion temperature, the amount of NOX emissions in them is low. Also, the noise pollution of these micro turbines is also low. Currently, the main disadvantage of micro turbines is their high cost compared to gas engines.
Fuel cell: A fuel cell uses hydrogen and oxygen to produce electrical energy. Compared to traditional technologies, a fuel cell produces electrical energy with high efficiency (about 35-60%). Due to the high efficiency of this type The production and non- combustion process in these energy generators, the emission of pollutants in these generators is low. Fuel cells have high reliability and as a result, they can be considered as a supplement or even a substitute for supplying the required electrical energy from the power grid. Fuel cells need a hydrogen source as their primary fuel. Most fuel cells use hydrogen from natural gas as a
hydrogen source, but other hydrogen sources can also be used for this purpose. Bringing hydrogen will result in low emissions of NOX and carbon dioxide.
Photovoltaic systems: This technology is one of the scattered productions from the set of renewable energy technologies and uses the energy from the sun's radiation to produce electricity. The initial investment cost of these systems is relatively significant, but the cost of their operation is The reason is that they do not have the cost of primary fuel, they are low. These sources of electrical energy production are inherently small and do not produce extra heat to produce electrical energy. They are small and suitable. The output of this type of generator changes with the change of weather conditions. Photovoltaic systems are used for a variety of applications, including household, communication, lighting, small business centers, agriculture, and treatment.
Some photovoltaic systems are not connected to the power grid and work individually, but others are connected to the grid and are considered part of distributed production. Generally, solar energy is used in both thermal and photovoltaic systems.
Wind energy production: according to the definition of the International Energy Agency (IEA), wind power plants are not considered as distributed production because they are not connected to distribution systems and are at the transmission level. But if these productions are somehow Installed at a lower voltage level and with smaller capacities and connected to the distribution network, they can be placed in the category of distributed production. Wind energy is also a type of renewable energy that is used to drive wind turbines. These energy generators also have a low operating cost and are considered in the clean energy group because they do not emit polluting gases.
2.2 Energy Storages (ES)
The use of renewable energies in the production of electrical energy, sudden changes in load and the occurrence of errors in energy transmission lines, cause a drop in the system voltage and create a challenge in the reliability of the system. One of the solutions to compensate for the changing nature of renewable energies in a short period of time. Without the need to cut loads or turn on another power plant unit, using energy storage devices. In general, energy storage devices are used at different voltage levels, from power plant units to distribution voltage levels. The use of energy storage devices improves Electrical stability, power quality and improvement of load power supply peak. In general, the use of energy storage devices brings technical and economic benefits.
2.2.1. ES advantages
The technical advantages of storage devices can be divided into the following two categories:
Providing a part of the system reserve: The system reserve is defined as the amount of standby capacity of the power plant units that can start producing power in the event of an error and an imbalance between production and consumption. System reserves are defined in terms of time which is needed to be able to be injected into the network in the form of power, are categorized. The rotating storage can be considered the fastest type of storage; this type of storage is provided through the capacity of the open units. Energy storage devices can be used in providing storage system needs to replace the use of thermal units. In this way, the use of fossil fuels is also saved and as a result, the emission of air polluting fuels is also prevented (to keep the rotating storage ready for use, It is clear that providing the required reserve of the system will have a significant impact on improving the reliability of the system.
Improving energy supply during peak load: the energy stored in the storage resources during the low load period should be supplied through the excess energy of wind and solar production or production units with low pollution production during the hours when the system load is low and during the peak hours instead of using production units with a high pollution production rate, it is also possible to store the electrical energy of cheaper units (which have low emission of polluting gases) in non-peak consumption periods in storage sources and used it during peak hours. Therefore, the use of energy storage resources reduces the need to use fossil fuels and, as a result, reduces the emission of greenhouse gases. In addition to what was said, the use of energy storage resources improves Control voltage, frequency and improve power quality.
2.1.2. ES technologies
Currently, the technology that can store AC electrical energy is not available. Therefore, in order to store energy, it is necessary to store electrical energy in the form of DC or through conversion to other types of energy. Energy storage devices actually store electrical energy in They convert and store another type of energy that can be stored, then when needed, they convert the stored energy back into electrical energy. Energy storage systems are different in terms of the type of technology. Currently, they are built and used, on a large scale, pumped storage power plants and on a small scale, batteries. Although other technologies of these storage devices are being developed and developed.
Small-scale energy storage devices will be used in the smart energy grid. In the following, various storage device technologies will be briefly reviewed.
Pump storage devices: this type of storage devices are the oldest and largest type of storage devices. The capacity of this type of storage device is about 1000 MW. Pump units are an old storage of two large water basins, one of which is at a low altitude and the other one is located at a high altitude. In non-peak consumption periods, water is transferred from the lower basin to the
upper basin by a pump and stored there. The valve of the upper basin is opened during peak electricity consumption hours and the water stored in It flows down to the lower pond, as a result of the water hitting the blades of the water turbine located in this path, electrical energy is produced.
Compressed Air Energy Storage (CAES): These storages use electrical energy to compress air in an underground tank during off-peak periods and release this compressed air to generate electrical energy during peak periods. Apart from the storage pump storage, CAES are the only type of large storage available with high capacity (each unit of these storages alone has the ability to store more than 100 MW). This type of small scale storage that They store air with high pressure in cylinders and are under construction.
Regenerative fuel cells: the capability and release of energy in these storage devices are through the electrochemical activity between two electrolytes. For this purpose, different types of electrolytes such as ZnBr and NaBr are used. Electric storage devices convert the electrical energy of the grid into Chemical energy takes place. The conversion of this chemical energy into electrical energy results from ion exchange between electrochemical cells. The size of these energy storage devices depends on the size of the electrolyte used.
Batteries: There are different technologies for using batteries as energy storage devices. But all batteries are electrochemical cells. These batteries consist of two electrodes separated by an electrolyte. In the discharge state, the ions are released from the anode (the first electrode) and move towards the second electrode, which is called the cathode. In the charge state, the chemical operation is reversed. Currently, batteries are the best The available options for electric energy storage are small and medium levels.
Superconducting Magnetic Energy Storage (SMES): In this storage technology, energy is stored in a magnetic field created by passing direct current through a superconducting coil. The response speed of this type of storage is very low. less than 100 ms). Therefore, these storage devices are suitable for regulating the stability of the network. These equipments are up to the size of MW3 and are used in order to maintain the stability of the distribution network or provide power quality in the construction of sensitive equipment.
Flywheel: Flywheel energy storage systems store and maintain electric energy by accelerating the rotor to a very high speed. In order to increase the speed of the rotor as much as possible, lightweight materials are used in the construction of the rotor. The weight of the rotor is reduced and its speed is increased as much as possible. The energy stored in the rotor is proportional to the second power of the speed. to be by reducing the energy stored in the rotor, the speed of the rotor decreases and it is completely discharged. This system is compact and has a lower maintenance cost than batteries.
Large capacitors: These storage devices have the characteristics of capacitors and electrochemical batteries, with the difference that chemical activity is not performed in them. Energy storage in these super capacitors is in the form of electric fields between two electrodes.
Electric vehicles: the finiteness of energy stored in fossil fuels and the emission of polluting gases due to the combustion of these energy sources have become one of the concerns of governments and officials. The electricity industry is one of the largest producers of polluting gases; approximately 40 % of the amount of CO2 gas and 24% of it is produced by transportation. As it was said before; The high emission of greenhouse gases and the resulting climate change have made communities and governments interested in finding a solution to prevent the increase of these gases and use less fossil fuels. Reducing and preventing the emission of air pollutants produced by the biggest producers of these pollutants seems to be a logical solution for this problem. The use of renewable energy sources and the use of electric vehicles with the ability to connect to the grid (in order to charge the batteries of these cars or inject the excess energy stored in the batteries of these vehicles into the network) have been proposed as a way to reduce the emission of pollutants. Vehicles include PHEVs and EVs that have the ability to connect to the grid (V2G).
3. Conclusion
Today, with the expansion of energy production technologies, increasing attention to environmental issues and interest in improving the reliability of electrical networks, the possibility and motivation to change distribution networks from passive to active and the desire to produce renewable energy at the level of the distribution system has been provided. On the other hand, connecting scattered production resources to current distribution networks has not met the technical and economic needs of investors. While it was expected that the power quality would be improved by increasing the penetration rate of distributed generation sources, the opposite results have been obtained due to power fluctuations caused by the difference in voltage and frequency of different renewable energy sources. Although the use of distributed generation resources can potentially reduce the need to expand traditional electrical networks, controlling a large number of them along with controllable loads has created a new challenge in the control and operation of a reliable and economical network. This challenge is reduced to the same extent by smart network by reducing the control responsibility of the network and makes it possible to obtain the maximum economic efficiency. Therefore, the right solution is to build small networks independent of the main network. So this study introduces smart network and its components.
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