Ali Abdali was born in Zanjan, Iran, on October 31, 1991. He received the B.Sc. and M.Sc. degrees in electrical engineering from the University of Zanjan, Iran in 2014 and 2017, respectively. He is currently chief of the R&D department of Kooshkan Transformer Company. His research interests include condition monitoring and diagnostics of transformers, distribution transformers electrical design, power system and microgrids protection problems, renewable energies, and optimization methods. Supervisors: Kazem Mazlumi and Abbas Rabiee Phone: +989102030445 Address: Department of Electrical Engineering, Faculty of Engineering, University of Zanjan, P.O. Box 45371-38791, Zanjan, Iran
The use of large-scale electric vehicles (EVs), along with technological advances in battery ener... more The use of large-scale electric vehicles (EVs), along with technological advances in battery energy storage systems (BESS), offers numerous technical and economic benefits to the smart distribution system. Parking lots not only provide EV owners with the opportunity to charge their BESS but also contribute power to the grid via vehicle-to-grid (V2G) technology, which significantly improves the reliability of distribution systems. In addition, parking lots equipped with V2G capability can participate in the electricity market as a producer. In this study, the reliability of a smart radial distribution system in the presence of EVs is investigated. It should always be borne in mind that parking lots can improve system reliability if the charging and discharging strategies are optimally and correctly scheduled. On the contrary, the parking lot participates in sending power to the grid in a situation where the profit is appropriate. Accordingly, in this study, first, five optimal strategies for scheduling the process of EV charging and discharging in a parking lot equipped with V2G capability are proposed to maximize parking profits. The proposed strategies include constraints on the amount of power exchange between the parking lot and the distribution system and the random and stochastic nature of quantities, such as when EVs enter and exit the parking lot and their BESS charge amounts when entering the parking lot. The results demonstrate that using the proposed optimal charging and discharging strategies scheduling increases the parking profit by 31% and also improves the reliability of the understudy distribution system by 9%.
Distribution transformers (DTs) are deemed as one of the major and high-priced equipment of elect... more Distribution transformers (DTs) are deemed as one of the major and high-priced equipment of electrical grids and their destruction negatively affects the stability and security of the network. The insulation status of the transformer depends on the hotspot and oil temperatures. Accordingly, controlling and, if possible, reduction of transformer oil temperature will improve the insulation status. In this paper, the effect of using nano-oil on oil temperature and loading capacity increment (LCI) of DTs has been studied via the electro-thermal resistance model (E-TRM). The studied nanofluids are two volumetric concentrations of multi-walled carbon nanotubes (MWCNTs) and three volumetric concentrations of diamond nanoparticles dispersed in pure mineral oil (MO). First, the numerical results gained from the E-TRM method are compared and verified with the experiential results of a 500 kVA DT. As well as, the effect of using MWCNT, diamond and proposed ONF nanoparticles in the heat transfer capacity of the transformer are investigated and compared. The results demonstrate that the highest temperature reduction in comparison with MO among the studied nanofluids is about 1 • C and for nanofluid ODI2. While the use of hypothetical ONF nanofluid reduces the oil temperature by 2.7 • C. Finally, the LCI of DTs caused by the use of nanofluids is investigated by the proposed novel equation. The use of nanofluids, especially the proposed ONF nanofluid, leads to the LCI up to 5%.
In this paper, a robust scheduling model is proposed for combined heat and power (CHP)-based micr... more In this paper, a robust scheduling model is proposed for combined heat and power (CHP)-based microgrids using information gap decision theory (IGDT). The microgrid under study consists of conventional power generation as well as boiler units, fuel cells, CHPs, wind turbines, solar PVs, heat storage units, and battery energy storage systems (BESS) as the set of distributed energy resources (DERs). Additionally, a demand response program (DRP) model is considered which has a successful performance in the microgrid hourly scheduling. One of the goals of CHP-based microgrid scheduling is to provide both thermal and electrical energy demands of the consumers. Additionally, the other objective is to benefit from the revenues obtained by selling the surplus electricity to the main grid during the high energy price intervals or purchasing it from the grid when the price of electricity is low at the electric market. Hence, in this paper, a robust scheduling approach is developed with the aim of maximizing the total profit of different energy suppliers in the entire scheduling horizon. The employed IGDT technique aims to handle the impact of uncertainties in the power output of wind and solar PV units on the overall profit.
International Journal of Emerging Electric Power Systems (De Gruyter), 2021
Photovoltaic is one of the renewable energies in generating electricity. The MPPT as effective te... more Photovoltaic is one of the renewable energies in generating electricity. The MPPT as effective technique can improve the performance of photovoltaic cells. Key problem in photovoltaic systems is that it does not achieve much power since the various weather conditions effects on photovoltaic power cells in working such as solar radiation or rainy and cloudy weather. Therefore, the MPPT in PV cells runs and leads to change during the day and seasons. On the other hand, providing an appropriate controller for the MPPT is too important. Here, main purpose is applying the robust controller, which is tuned by firefly algorithm to optimize MPPT in photovoltaic systems. The main reason to propose this method is some defects in previous controllers such as low stability, low battery lifetime, inability to combine AC/DC and low efficiency. The suggested model is performed by MATLAB/Simulink software. Finally, the FLFA model has higher efficiency and best dynamic response than other methods.
Engineering Science and Technology, an International Journal (Elsevier), 2021
The importance of the distribution network is not overlooked by anyone. The transformer is one of... more The importance of the distribution network is not overlooked by anyone. The transformer is one of the key equipment in this network. Therefore, great care and attention are needed in its design, maintenance and operation. Most of the oil-immersed distribution transformers are operated under solar radiation conditions. However, increasing the oil temperature due to solar radiation is not considered in their design. This increases the oil temperature above the design temperature value and thus reduces the life of the transformer. In this paper, due to the lack of specified equations for solar energy absorption by the fins and tank of the transformer, a novel method and equation are proposed for the calculation of the transformer solar radiation absorption amount. As well as, the effect of orientation on the corrugated tank distribution transformers oil temperature is investigated using the Electro-Thermal Resistance Model (E-TRM). For this purpose, two identical transformers with different orientations are tested experimentally and the results are compared and verified with the numerical results. The transformer tank color is one of the effective factors of solar radiation absorption. Depending on the absorption and emission rates, the effect of the different colors of the transformer tank on the oil temperature in different loading is investigated in this paper. The results show that the use of bright colors in comparison with dark colors can lower the oil temperature by about 3°C on the rated loading of the transformer. In order to consider the effect of solar radiation on the transformer, the modified ambient temperature is introduced for the design of the transformer. Finally, the effect of transformer operation under solar radiation and with different colors is investigated and transformer loading de-rating is proposed by a novel equation. Ó 2020 Karabuk University. Publishing services by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Direct current (dc) microgrids have gained significant interest in research due to dc generation/... more Direct current (dc) microgrids have gained significant interest in research due to dc generation/storage technologies-such as photovoltaics (PV) and batteries-increasing performance and reducing in cost. However, proper protection and control systems are critical in order to make dc microgrids feasible. This paper aims to propose a novel integrated control and protection scheme by using the state-dependent Riccati equation (SDRE) method for PV-battery based islanded dc microgrids. The dc microgrid under study consists of photovoltaic (PV) generation, a battery energy storage system (BESS), a capacitor bank and a dc load. The aims of this study are fast fault detection and voltage control of the dc load bus. To do so, the SDRE observer-controller-a nonlinear mathematical model-is employed to model the operation of the dc microgrid. Simulation results show that the proposed SDRE method is effective for fault detection and robust against external disturbances, resulting in it being capable of controlling the dc load bus voltage during disturbances. Finally, the dc microgrid and its proposed protection scheme are implemented in an experimental testbed prototype to verify the fault detection algorithm feasibility. The experimental results indicate that the SDRE scheme can effectively detect faults in a few milliseconds.
In the energy distribution networks, the most important and valuable equipment is oil-immersed di... more In the energy distribution networks, the most important and valuable equipment is oil-immersed distribution transformers. Besides, due to the key role of these transformers and their multiplicity, their lifetime monitoring is inevitable. The life of a transformer depends on the weakest solid insulation material (i.e. paper insulation). On the other hand, monitoring the transformer insulation status requires accurate information to be available about the oil temperature at every moment. Therefore, it is important to control and predict the oil temperature rise in the transformer. In this study, a new model based on fundamental heat transfer theory is proposed for thermal behaviour prediction of top oil of indoor distribution transformers using the concept of thermal resistance, namely electro-thermal resistance model (E-TRM). In E-TRM, the thermal resistance network is formed by following three-dimensional heat transfer path and assigning thermal resistance to each path. To evaluate the proposed E-TRM, the results of this model are verified with experimental results. Moreover, the E-TRM is used to predict the thermal behaviour of the indoor transformer in the overloading condition. At the end, the transformer loss of life is estimated based on the oil temperature and a normal cyclic overloading strategy is presented for overloading management.
Monitoring the insulation status of a transformer requires the availability of accurate informati... more Monitoring the insulation status of a transformer requires the availability of accurate information of the oil temperature at any moment. Considering the importance of oil temperature prediction in oil-immersed transformers and its direct relation with the life of transformer, a novel model is presented in this paper using the concept of thermal resistance with consideration of solar radiation for expressing the heat transfer in distribution transformers. The results of the proposed model are compared and validated with experimental results. These results show that in the studied transformer and rated loading, solar radiation can increase the oil temperature by about 3.7°C. In this paper, the thermal resistance model with solar radiation is used to predict the thermal behavior of the transformer in overloading condition. Finally, the transformer operation with/without consideration of solar radiation effect is studied and its impact on the transformer's loss of life due to the increase in oil temperature is investigated. In order to consider the effect of solar radiation on oil temperature, new equations using the concept of thermal resistance are presented to calculate the shadow surface created on the fin-folded transformers, and a novel equation is proposed for permissible loading of distribution transformers.
International Journal of Electrical Power & Energy Systems (Elsevier), 2019
This paper proposes a novel simultaneous control interface and protection scheme for DC microgrid... more This paper proposes a novel simultaneous control interface and protection scheme for DC microgrids (DCµG) interconnected systems, although the interconnections could be possible via two power electronic systems such as DC/DC converter. Each DCµG presented in this paper is supplied by AC grid as well as battery bank unit, distributed generation (DG) unit and AC load unit. The proposed control interface is based on a developed suitable small signal model for each DCµG that provides proper power flow control and cancellation of interactions between DCµG. Also, the presented protection scheme for fast fault detection in DC link is based on fuzzy inference system (FIS), so that faults could be detected as quickly as possible in few milliseconds. In fact, the aim of this paper is simultaneous protection and control interface for DC multi microgrids, so that the performance of the controller and protection system is separate, yet integrated together. As such, DC multi microgrid performance under different events, such as change in active power of DGs and short circuit is not in trouble and disorder. Simulation results indicate the remarkable effectiveness of the proposed control interface and protection scheme for DCµG interconnected systems. For validation of the capability and feasibility of FIS fault detection scheme, simulated network and protection algorithm are implemented in laboratory-scale. The implementation results demonstrate that FIS protection scheme can swiftly detect faults within a few milliseconds.
This paper presents a new protection method for LVDC ring-bus microgrid systems based on Multi-Cr... more This paper presents a new protection method for LVDC ring-bus microgrid systems based on Multi-Criterion System (MCS) and Neural Network (NN). The proposed method aimed at high-speed detecting line-to-ground (LG) and line-to-line (LL) low impedance faults without using a definite threshold of differential current by using specific rules and multi-criterion system. MCS protection showed speed and accuracy compared to differential protection. Also, NN estimated fault location in percent of line length acceptably as a secondary controller. In order to evaluate the reliability and the enforceability of fault detection and location schemes, simulated network and protection algorithms are implemented and tested in laboratory-scale. The implementation results indicate that the MCS and NN protection scheme can consistently detect and estimate fault locations in the order of a few milliseconds. To reach this goal, a loop type LVDC microgrid with proper power electronic equipment like solid-state bidirectional breakers and the multi-level inverter is fulfilled.
Sigma Journal of Engineering and Natural Sciences, 2018
Nowadays, microgrids have attracted much attention in developed countries. The protection of DC s... more Nowadays, microgrids have attracted much attention in developed countries. The protection of DC systems, unlike conventional AC systems, is a highly challenging task. The acquaintance on fault location in distribution network causes for quick restoration, maintenance and decrease unnecessary power outage period. Neural Networks (NNs) are among the powerful, reliable approaches and are used in many different engineering applications. Also, Multi-Layer Perceptron (MLP) NNs are used for different estimating problems. This paper presents an accurate protection method for Low-Voltage DC (LVDC) ring-bus microgrid systems based on MLP NN. The aim of the proposed method is precise fault location estimation in microgrids, irrespective of the type and magnitude of fault, current, and the power supply quantity, by instantaneous current monitoring of each segment of the microgrid. Simulation results demonstrate the NN fault location estimation in percent of line length are in a suitable range. The results show that the estimation error is small and is within the permissible range. According to the results, efficiency and accuracy of MLP NN are confirmed. To do so, an LVDC ring-bus microgrid is used that utilizes solid-state bidirectional switches along with master and slave controllers
Sigma Journal of Engineering and Natural Sciences, 2019
Power system is getting complex due to a boost in the number of new power plants and the expansio... more Power system is getting complex due to a boost in the number of new power plants and the expansion of the transmission system in order to meet the growing for electricity. This scenario results in a large number of short circuits in the system, which may exceed the rating of existing circuit breakers (CBs) and may severely destroy system equipment. Installing fault current limiters (FCLs) into the power system is one of the most cost-effective ways to degrade fault current levels. This paper presents a method to specify the optimal numbers and locations for FCLs placement in terms of installing the smallest FCL parameters to restrain short-circuit currents below the interrupting currents of circuit breakers, to minimize transmission loss. Due to a lack of genetic, PSO and other optimization algorithms, an Elitist Gravitational Search Algorithm (EGSA) for more accurate and better results is used. This algorithm is employed to search for the location and parameter of FCLs to meet the specific requirements. The proposed method is applied to the IEEE 30-bus test system. Simulation results indicated the adequacy and precision of the proposed method.
IEEE (5th Iranian Joint Congress on Fuzzy and Intelligent Systems), 2017
Contrary to conventional AC systems, protection has been challenging for DC systems. In this pape... more Contrary to conventional AC systems, protection has been challenging for DC systems. In this paper, a novel fault detection method using a fuzzy logic is proposed for Low-Voltage DC (LVDC) microgrid. A fuzzy system makes the best and most appropriate decision on the basis of a number of specific rules and conditions for any state of the grid. The aim of this paper is fast fault detection in microgrids, regardless of the faults type and current magnitude as well as power supply's feeding capacity, by instantaneous current monitoring that faulted segment is isolated and the remaining system stays online. To do so, an LVDC ring-bus microgrid is proposed that utilizes solid-state bidirectional switches with master and slave controllers.
11th International Conference on Protection & Automation in Power System, 2017
Despite AC classical systems, protection of DC system is a real challenging task. The method of h... more Despite AC classical systems, protection of DC system is a real challenging task. The method of high and low fault detection for LVDC microgrids using fuzzy interface systems is presented in this paper. Based on specific rules and conditions, fuzzy inference systems try to make the most appropriate decision for each system state as quickly as possible. The aim of this paper is the fast detection of low and high impedance faults in LVDC microgrids, regardless of the type and amplitude of fault current and the power supply capacity, by instantaneous current monitoring. So, that the entire system would not experience an outage, while the faulted segment is isolated. To do so, an LVDC ring-bus microgrid is used that utilizes solid-state bidirectional switches along with master and slave controllers.
The use of large-scale electric vehicles (EVs), along with technological advances in battery ener... more The use of large-scale electric vehicles (EVs), along with technological advances in battery energy storage systems (BESS), offers numerous technical and economic benefits to the smart distribution system. Parking lots not only provide EV owners with the opportunity to charge their BESS but also contribute power to the grid via vehicle-to-grid (V2G) technology, which significantly improves the reliability of distribution systems. In addition, parking lots equipped with V2G capability can participate in the electricity market as a producer. In this study, the reliability of a smart radial distribution system in the presence of EVs is investigated. It should always be borne in mind that parking lots can improve system reliability if the charging and discharging strategies are optimally and correctly scheduled. On the contrary, the parking lot participates in sending power to the grid in a situation where the profit is appropriate. Accordingly, in this study, first, five optimal strategies for scheduling the process of EV charging and discharging in a parking lot equipped with V2G capability are proposed to maximize parking profits. The proposed strategies include constraints on the amount of power exchange between the parking lot and the distribution system and the random and stochastic nature of quantities, such as when EVs enter and exit the parking lot and their BESS charge amounts when entering the parking lot. The results demonstrate that using the proposed optimal charging and discharging strategies scheduling increases the parking profit by 31% and also improves the reliability of the understudy distribution system by 9%.
Distribution transformers (DTs) are deemed as one of the major and high-priced equipment of elect... more Distribution transformers (DTs) are deemed as one of the major and high-priced equipment of electrical grids and their destruction negatively affects the stability and security of the network. The insulation status of the transformer depends on the hotspot and oil temperatures. Accordingly, controlling and, if possible, reduction of transformer oil temperature will improve the insulation status. In this paper, the effect of using nano-oil on oil temperature and loading capacity increment (LCI) of DTs has been studied via the electro-thermal resistance model (E-TRM). The studied nanofluids are two volumetric concentrations of multi-walled carbon nanotubes (MWCNTs) and three volumetric concentrations of diamond nanoparticles dispersed in pure mineral oil (MO). First, the numerical results gained from the E-TRM method are compared and verified with the experiential results of a 500 kVA DT. As well as, the effect of using MWCNT, diamond and proposed ONF nanoparticles in the heat transfer capacity of the transformer are investigated and compared. The results demonstrate that the highest temperature reduction in comparison with MO among the studied nanofluids is about 1 • C and for nanofluid ODI2. While the use of hypothetical ONF nanofluid reduces the oil temperature by 2.7 • C. Finally, the LCI of DTs caused by the use of nanofluids is investigated by the proposed novel equation. The use of nanofluids, especially the proposed ONF nanofluid, leads to the LCI up to 5%.
In this paper, a robust scheduling model is proposed for combined heat and power (CHP)-based micr... more In this paper, a robust scheduling model is proposed for combined heat and power (CHP)-based microgrids using information gap decision theory (IGDT). The microgrid under study consists of conventional power generation as well as boiler units, fuel cells, CHPs, wind turbines, solar PVs, heat storage units, and battery energy storage systems (BESS) as the set of distributed energy resources (DERs). Additionally, a demand response program (DRP) model is considered which has a successful performance in the microgrid hourly scheduling. One of the goals of CHP-based microgrid scheduling is to provide both thermal and electrical energy demands of the consumers. Additionally, the other objective is to benefit from the revenues obtained by selling the surplus electricity to the main grid during the high energy price intervals or purchasing it from the grid when the price of electricity is low at the electric market. Hence, in this paper, a robust scheduling approach is developed with the aim of maximizing the total profit of different energy suppliers in the entire scheduling horizon. The employed IGDT technique aims to handle the impact of uncertainties in the power output of wind and solar PV units on the overall profit.
International Journal of Emerging Electric Power Systems (De Gruyter), 2021
Photovoltaic is one of the renewable energies in generating electricity. The MPPT as effective te... more Photovoltaic is one of the renewable energies in generating electricity. The MPPT as effective technique can improve the performance of photovoltaic cells. Key problem in photovoltaic systems is that it does not achieve much power since the various weather conditions effects on photovoltaic power cells in working such as solar radiation or rainy and cloudy weather. Therefore, the MPPT in PV cells runs and leads to change during the day and seasons. On the other hand, providing an appropriate controller for the MPPT is too important. Here, main purpose is applying the robust controller, which is tuned by firefly algorithm to optimize MPPT in photovoltaic systems. The main reason to propose this method is some defects in previous controllers such as low stability, low battery lifetime, inability to combine AC/DC and low efficiency. The suggested model is performed by MATLAB/Simulink software. Finally, the FLFA model has higher efficiency and best dynamic response than other methods.
Engineering Science and Technology, an International Journal (Elsevier), 2021
The importance of the distribution network is not overlooked by anyone. The transformer is one of... more The importance of the distribution network is not overlooked by anyone. The transformer is one of the key equipment in this network. Therefore, great care and attention are needed in its design, maintenance and operation. Most of the oil-immersed distribution transformers are operated under solar radiation conditions. However, increasing the oil temperature due to solar radiation is not considered in their design. This increases the oil temperature above the design temperature value and thus reduces the life of the transformer. In this paper, due to the lack of specified equations for solar energy absorption by the fins and tank of the transformer, a novel method and equation are proposed for the calculation of the transformer solar radiation absorption amount. As well as, the effect of orientation on the corrugated tank distribution transformers oil temperature is investigated using the Electro-Thermal Resistance Model (E-TRM). For this purpose, two identical transformers with different orientations are tested experimentally and the results are compared and verified with the numerical results. The transformer tank color is one of the effective factors of solar radiation absorption. Depending on the absorption and emission rates, the effect of the different colors of the transformer tank on the oil temperature in different loading is investigated in this paper. The results show that the use of bright colors in comparison with dark colors can lower the oil temperature by about 3°C on the rated loading of the transformer. In order to consider the effect of solar radiation on the transformer, the modified ambient temperature is introduced for the design of the transformer. Finally, the effect of transformer operation under solar radiation and with different colors is investigated and transformer loading de-rating is proposed by a novel equation. Ó 2020 Karabuk University. Publishing services by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Direct current (dc) microgrids have gained significant interest in research due to dc generation/... more Direct current (dc) microgrids have gained significant interest in research due to dc generation/storage technologies-such as photovoltaics (PV) and batteries-increasing performance and reducing in cost. However, proper protection and control systems are critical in order to make dc microgrids feasible. This paper aims to propose a novel integrated control and protection scheme by using the state-dependent Riccati equation (SDRE) method for PV-battery based islanded dc microgrids. The dc microgrid under study consists of photovoltaic (PV) generation, a battery energy storage system (BESS), a capacitor bank and a dc load. The aims of this study are fast fault detection and voltage control of the dc load bus. To do so, the SDRE observer-controller-a nonlinear mathematical model-is employed to model the operation of the dc microgrid. Simulation results show that the proposed SDRE method is effective for fault detection and robust against external disturbances, resulting in it being capable of controlling the dc load bus voltage during disturbances. Finally, the dc microgrid and its proposed protection scheme are implemented in an experimental testbed prototype to verify the fault detection algorithm feasibility. The experimental results indicate that the SDRE scheme can effectively detect faults in a few milliseconds.
In the energy distribution networks, the most important and valuable equipment is oil-immersed di... more In the energy distribution networks, the most important and valuable equipment is oil-immersed distribution transformers. Besides, due to the key role of these transformers and their multiplicity, their lifetime monitoring is inevitable. The life of a transformer depends on the weakest solid insulation material (i.e. paper insulation). On the other hand, monitoring the transformer insulation status requires accurate information to be available about the oil temperature at every moment. Therefore, it is important to control and predict the oil temperature rise in the transformer. In this study, a new model based on fundamental heat transfer theory is proposed for thermal behaviour prediction of top oil of indoor distribution transformers using the concept of thermal resistance, namely electro-thermal resistance model (E-TRM). In E-TRM, the thermal resistance network is formed by following three-dimensional heat transfer path and assigning thermal resistance to each path. To evaluate the proposed E-TRM, the results of this model are verified with experimental results. Moreover, the E-TRM is used to predict the thermal behaviour of the indoor transformer in the overloading condition. At the end, the transformer loss of life is estimated based on the oil temperature and a normal cyclic overloading strategy is presented for overloading management.
Monitoring the insulation status of a transformer requires the availability of accurate informati... more Monitoring the insulation status of a transformer requires the availability of accurate information of the oil temperature at any moment. Considering the importance of oil temperature prediction in oil-immersed transformers and its direct relation with the life of transformer, a novel model is presented in this paper using the concept of thermal resistance with consideration of solar radiation for expressing the heat transfer in distribution transformers. The results of the proposed model are compared and validated with experimental results. These results show that in the studied transformer and rated loading, solar radiation can increase the oil temperature by about 3.7°C. In this paper, the thermal resistance model with solar radiation is used to predict the thermal behavior of the transformer in overloading condition. Finally, the transformer operation with/without consideration of solar radiation effect is studied and its impact on the transformer's loss of life due to the increase in oil temperature is investigated. In order to consider the effect of solar radiation on oil temperature, new equations using the concept of thermal resistance are presented to calculate the shadow surface created on the fin-folded transformers, and a novel equation is proposed for permissible loading of distribution transformers.
International Journal of Electrical Power & Energy Systems (Elsevier), 2019
This paper proposes a novel simultaneous control interface and protection scheme for DC microgrid... more This paper proposes a novel simultaneous control interface and protection scheme for DC microgrids (DCµG) interconnected systems, although the interconnections could be possible via two power electronic systems such as DC/DC converter. Each DCµG presented in this paper is supplied by AC grid as well as battery bank unit, distributed generation (DG) unit and AC load unit. The proposed control interface is based on a developed suitable small signal model for each DCµG that provides proper power flow control and cancellation of interactions between DCµG. Also, the presented protection scheme for fast fault detection in DC link is based on fuzzy inference system (FIS), so that faults could be detected as quickly as possible in few milliseconds. In fact, the aim of this paper is simultaneous protection and control interface for DC multi microgrids, so that the performance of the controller and protection system is separate, yet integrated together. As such, DC multi microgrid performance under different events, such as change in active power of DGs and short circuit is not in trouble and disorder. Simulation results indicate the remarkable effectiveness of the proposed control interface and protection scheme for DCµG interconnected systems. For validation of the capability and feasibility of FIS fault detection scheme, simulated network and protection algorithm are implemented in laboratory-scale. The implementation results demonstrate that FIS protection scheme can swiftly detect faults within a few milliseconds.
This paper presents a new protection method for LVDC ring-bus microgrid systems based on Multi-Cr... more This paper presents a new protection method for LVDC ring-bus microgrid systems based on Multi-Criterion System (MCS) and Neural Network (NN). The proposed method aimed at high-speed detecting line-to-ground (LG) and line-to-line (LL) low impedance faults without using a definite threshold of differential current by using specific rules and multi-criterion system. MCS protection showed speed and accuracy compared to differential protection. Also, NN estimated fault location in percent of line length acceptably as a secondary controller. In order to evaluate the reliability and the enforceability of fault detection and location schemes, simulated network and protection algorithms are implemented and tested in laboratory-scale. The implementation results indicate that the MCS and NN protection scheme can consistently detect and estimate fault locations in the order of a few milliseconds. To reach this goal, a loop type LVDC microgrid with proper power electronic equipment like solid-state bidirectional breakers and the multi-level inverter is fulfilled.
Sigma Journal of Engineering and Natural Sciences, 2018
Nowadays, microgrids have attracted much attention in developed countries. The protection of DC s... more Nowadays, microgrids have attracted much attention in developed countries. The protection of DC systems, unlike conventional AC systems, is a highly challenging task. The acquaintance on fault location in distribution network causes for quick restoration, maintenance and decrease unnecessary power outage period. Neural Networks (NNs) are among the powerful, reliable approaches and are used in many different engineering applications. Also, Multi-Layer Perceptron (MLP) NNs are used for different estimating problems. This paper presents an accurate protection method for Low-Voltage DC (LVDC) ring-bus microgrid systems based on MLP NN. The aim of the proposed method is precise fault location estimation in microgrids, irrespective of the type and magnitude of fault, current, and the power supply quantity, by instantaneous current monitoring of each segment of the microgrid. Simulation results demonstrate the NN fault location estimation in percent of line length are in a suitable range. The results show that the estimation error is small and is within the permissible range. According to the results, efficiency and accuracy of MLP NN are confirmed. To do so, an LVDC ring-bus microgrid is used that utilizes solid-state bidirectional switches along with master and slave controllers
Sigma Journal of Engineering and Natural Sciences, 2019
Power system is getting complex due to a boost in the number of new power plants and the expansio... more Power system is getting complex due to a boost in the number of new power plants and the expansion of the transmission system in order to meet the growing for electricity. This scenario results in a large number of short circuits in the system, which may exceed the rating of existing circuit breakers (CBs) and may severely destroy system equipment. Installing fault current limiters (FCLs) into the power system is one of the most cost-effective ways to degrade fault current levels. This paper presents a method to specify the optimal numbers and locations for FCLs placement in terms of installing the smallest FCL parameters to restrain short-circuit currents below the interrupting currents of circuit breakers, to minimize transmission loss. Due to a lack of genetic, PSO and other optimization algorithms, an Elitist Gravitational Search Algorithm (EGSA) for more accurate and better results is used. This algorithm is employed to search for the location and parameter of FCLs to meet the specific requirements. The proposed method is applied to the IEEE 30-bus test system. Simulation results indicated the adequacy and precision of the proposed method.
IEEE (5th Iranian Joint Congress on Fuzzy and Intelligent Systems), 2017
Contrary to conventional AC systems, protection has been challenging for DC systems. In this pape... more Contrary to conventional AC systems, protection has been challenging for DC systems. In this paper, a novel fault detection method using a fuzzy logic is proposed for Low-Voltage DC (LVDC) microgrid. A fuzzy system makes the best and most appropriate decision on the basis of a number of specific rules and conditions for any state of the grid. The aim of this paper is fast fault detection in microgrids, regardless of the faults type and current magnitude as well as power supply's feeding capacity, by instantaneous current monitoring that faulted segment is isolated and the remaining system stays online. To do so, an LVDC ring-bus microgrid is proposed that utilizes solid-state bidirectional switches with master and slave controllers.
11th International Conference on Protection & Automation in Power System, 2017
Despite AC classical systems, protection of DC system is a real challenging task. The method of h... more Despite AC classical systems, protection of DC system is a real challenging task. The method of high and low fault detection for LVDC microgrids using fuzzy interface systems is presented in this paper. Based on specific rules and conditions, fuzzy inference systems try to make the most appropriate decision for each system state as quickly as possible. The aim of this paper is the fast detection of low and high impedance faults in LVDC microgrids, regardless of the type and amplitude of fault current and the power supply capacity, by instantaneous current monitoring. So, that the entire system would not experience an outage, while the faulted segment is isolated. To do so, an LVDC ring-bus microgrid is used that utilizes solid-state bidirectional switches along with master and slave controllers.
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