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Frequency dynamics, occurring due to the high penetration of the renewable energy in the microgrid (MG) are of great concern to the system dynamic stability. The battery energy storage systems are reported to have a good frequency regulating ability in the off-grid microgrid systems. However, to compensate the power irregularities, the battery is needed to charge and discharge at a high frequency, which degrades its lifetime significantly. In addition, in the primary frequency control (PFC) the battery needs to deal with the abrupt power changes, which will also accelerate the battery degradation process. In this regard, this paper presents a new concept of primary frequency control by integrating the superconducting magnetic energy storage (SMES) with battery, thus achieving the ability of not only performing a good frequency regulating function but also extending the battery service time. A novel power sharing method using the dynamic droop factors to control charge/discharge prioritization between the SMES and the battery is proposed and has been proved to have a better operation than the preceding droop control. A microgrid system based on the case of Uligam Island of Maldives is developed in the PSCAD, verifying the performance of PFC with the hybrid energy storage system (HESS) using the dynamic droop control. The results show that the HESSs have a better frequency regulating ability and the proposed dynamic droop control is capable of exploiting the different characteristics of both SMES and battery, forming a kind of complementary hybrid energy storage system. Moreover, the battery in the new control scheme is better protected from the short-term frequent cycles and abrupt currents, hence has been proved to have a longer lifetime extension.

Frequency dynamics, occurring due to the high penetration of the renewable energy in the microgrid (MG) are of great concern to the system dynamic stability. The battery energy storage systems are reported to have a good frequency regulating ability in the off-grid microgrid systems. However, to compensate the power irregularities, the battery is needed to charge and discharge at a high frequency, which degrades its lifetime significantly. In addition, in the primary frequency control (PFC) the battery needs to deal with the abrupt power changes, which will also accelerate the battery degradation process. In this regard, this paper presents a new concept of primary frequency control by integrating the superconducting magnetic energy storage (SMES) with battery, thus achieving the ability of not only performing a good frequency regulating function but also extending the battery service time. A novel power sharing method using the dynamic droop factors to control charge/discharge prioritization between the SMES and the battery is proposed and has been proved to have a better operation than the preceding droop control. A microgrid system based on the case of Uligam Island of Maldives is developed in the PSCAD, verifying the performance of PFC with the hybrid energy storage system (HESS) using the dynamic droop control. The results show that the HESSs have a better frequency regulating ability and the proposed dynamic droop control is capable of exploiting the different characteristics of both SMES and battery, forming a kind of complementary hybrid energy storage system. Moreover, the battery in the new control scheme is better protected from the short-term frequent cycles and abrupt currents, hence has been proved to have a longer lifetime extension.

Abstract Electric Vehicles (EVs) have been suggested as alternatives to conventional vehicles for reducing petrol consumption and carbon dioxide (CO 2 ) emissions. When a large number of EVs connect to the grid, they can cause a large amount of power loss. Where to install multiple charge stations in the grid, so as to mitigate losses caused by EVs when providing energy to those EVs, is becoming vitally important. In this paper, a distribution test-network model is described. A new analytical method is proposed, using the stations’ cooperation in terms of optimal active and reactive power dispatch as well as power flow analysis for locating the optimal placement of charge stations, so as to reduce power losses. This method is compared with the previously developed current density method for single charge stations using system simulation results. It was demonstrated that the methods proposed in this paper are more accurate than the current density method, and that 17% of the average active power loss can be saved for three different types of load profile. In addition, 27% of the average active power loss was saved by installing two charge stations rather than no charge stations in the test-line. It is shown that this could represent a 2.6% annual yield above inflation for investing in installing and running such charge stations.

Abstract Electric Vehicles (EVs) have been suggested as alternatives to conventional vehicles for reducing petrol consumption and carbon dioxide (CO 2 ) emissions. When a large number of EVs connect to the grid, they can cause a large amount of power loss. Where to install multiple charge stations in the grid, so as to mitigate losses caused by EVs when providing energy to those EVs, is becoming vitally important. In this paper, a distribution test-network model is described. A new analytical method is proposed, using the stations’ cooperation in terms of optimal active and reactive power dispatch as well as power flow analysis for locating the optimal placement of charge stations, so as to reduce power losses. This method is compared with the previously developed current density method for single charge stations using system simulation results. It was demonstrated that the methods proposed in this paper are more accurate than the current density method, and that 17% of the average active power loss can be saved for three different types of load profile. In addition, 27% of the average active power loss was saved by installing two charge stations rather than no charge stations in the test-line. It is shown that this could represent a 2.6% annual yield above inflation for investing in installing and running such charge stations.

A high temperature superconducting magnetic energy storage system (HT-SMES) is constructed using YBCO coated conductor and is integrated with a cryogenic system using sub-cooled LN2. A closed loop control algorithm, based on the digital signal processor (DSP) TMS320F2812, is proposed using the 2G HT-SMES to compensate dynamic voltage sag in power systems. A dynamic simulation experiment for compensation of instantaneous voltage sag is achieved. The experiment circuit is built using a signal conditioning circuit, a DSP controlling circuit, a power conversion circuit and a SMES unit. Analysis of the voltage waveforms before and after compensation validates that this SMES system is able to compensate instantaneous voltage sag.

A high temperature superconducting magnetic energy storage system (HT-SMES) is constructed using YBCO coated conductor and is integrated with a cryogenic system using sub-cooled LN2. A closed loop control algorithm, based on the digital signal processor (DSP) TMS320F2812, is proposed using the 2G HT-SMES to compensate dynamic voltage sag in power systems. A dynamic simulation experiment for compensation of instantaneous voltage sag is achieved. The experiment circuit is built using a signal conditioning circuit, a DSP controlling circuit, a power conversion circuit and a SMES unit. Analysis of the voltage waveforms before and after compensation validates that this SMES system is able to compensate instantaneous voltage sag.

This paper proposes a novel use of superconducting magnetic energy storage (SMES) hybridized with the battery into the electric bus (EB) with the benefit of extending battery lifetime. A new power control algorithm, which integrates a power grading strategy with the filtration control method, is introduced in this paper, achieving further improvement of battery lifetime. To demonstrate the performance of the SMES/battery hybrid energy storage system (HESS), a dynamic EB system is described with the advantage of considering more factors into the driving patterns. Simulation results show that the proposed HESS has successfully combined the SMES with the battery forming an optimal system that has the advantages of primary energy storage systems while complementing the disadvantages of each system. This paper also does the quantitative analysis of battery lifetime extension in the battery-only system, the filtration-based HESS, and the novel control-based HESS.