The concept of smart grid has been introduced as a new vision of the conventional power grid to figure out an efficient way of integrating green and renewable energy technologies. In this way, ...Internet-connected smart grid, also called energy Internet, is also emerging as an innovative approach to ensure the energy from anywhere at any time. The ultimate goal of these developments is to build a sustainable society. However, integrating and coordinating a large number of growing connections can be a challenging issue for the traditional centralized grid system. Consequently, the smart grid is undergoing a transformation to the decentralized topology from its centralized form. On the other hand, blockchain has some excellent features which make it a promising application for smart grid paradigm. In this paper, we aim to provide a comprehensive survey on application of blockchain in smart grid. As such, we identify the significant security challenges of smart grid scenarios that can be addressed by blockchain. Then, we present a number of blockchain-based recent research works presented in different literatures addressing security issues in the area of smart grid. We also summarize several related practical projects, trials, and products that have been emerged recently. Finally, we discuss essential research challenges and future directions of applying blockchain to smart grid security issues.
This paper performs a sensitivity analysis for transient stability margin of power systems with random wind power variation. Through the sensitivity analysis, transient stability degree could be ...assessed potently and quickly for random wind power output. Extended Equal Area Criterion (EEAC) transient stability assessment approach is applied to obtain transient stability margin. In most existing studies, wind power variations are always compensated by slack generator. In this paper, four feasible strategies to compensate wind power changes are proposed and compared. The sensitivity analysis results for the above four strategies will provide deep insights into the quantitative impact of random wind power variation on power system's transient stability. The proposed method is tested on New England 10-machine 39-bus system by using commercial simulation software TSAT.
A novel control scheme to improve the performance of LLC resonant mode controller under light load operation and wide input-output voltage variations is presented in this paper. Poor light load ...voltage regulation in the LLC resonant converter necessitates the use of burst control mode, which results in performance degradation under light loading conditions. The proposed control scheme uses an adaptive deadband technique that avoids the burst control mode even at extremely light loads resulting in continuous operation and thereby lower output voltage and current ripple, lower noise and higher efficiency. Furthermore, a neural-network-based compensator is proposed in this paper for improving the dynamic performance of the converter under varied operating conditions. Theoretical and simulation results are provided to show the advantages of the proposed control algorithms. A 200W-LLC resonant converter is used for experimental verification of the proposed control scheme.
In the energy storage system, a DC/DC converter is usually deployed to ensure the wide range of voltage gain, to guarantee the life-span of battery, as well as to improve the efficiency, which puts a ...challenge on the seamless switch of charging modes. Therefore, a high-efficiency oriented control method is proposed for bidirectional resonant DC/DC converter based on the features of energy storage system. In the charging mode, the constant current (CC) and constant voltage (CV) schemes are combined together to properly adapt the changing equivalent inner resistance of battery. In the discharging mode, the output DC voltage of converter remains unchanged by regulating switching frequency to avoid the disturbance on the DC bus. The simulation using xx platform/software has been developed to verify the feasibility and superiority of the proposed method.
Designing DC Optimizer for EMC/EMI Compliance Ong, Hueh Chuah; Hai Koh, Leong; Nguyen, Bac Xuan ...
2019 IEEE 4th International Future Energy Electronics Conference (IFEEC),
2019-Nov.
Conference Proceeding
Design and fabricate new product for commercialization is the dream of every designer. However, it is an industry requirement to ensure the product pass EMC/EMI certification. This paper using the ...newly developed product DC Optimizer as an example develop the comprehensive EMC/EMI test plan for 3 rd party certification. During the design and development of DC Optimizer, we have also studied and implemented various EMC/EMI mitigation strategies before proceed to carry out the EMC/EMI certification according to the defined test plan. With successful EMC/EMI and other certification, we can then proceed to start the production and sell the products officially.
Regarding the access of a micro-grid with multiple distributed generation (DG) units into the power distribution network, superconducting fault current limiters (SFCLs) may be used to improve the ...micro-grid's robustness against short-circuit faults. In this paper, the flux-coupling-type SFCL is selected to play the role, and the optimal allocation of the SFCLs for protection of a micro-grid with wind-PV hybrid generation and battery energy storage is performed. The SFCL's structural principle is conducted first. Further, those candidate allocation scenarios of the SFCLs used in the micro-grid are enumerated, and each of them includes installation number, mounting location and impedance parameter. Besides, a matching optimal objective function is proposed, and herein the each SFCL's current-limiting performance and the micro-grid's frequency stability are considered as two key optimization criterions. Time-domain simulation is done, and the results imply that the SFCL should be located on the direct path of current flowing from the DG and the main network. Through the optimal utilization of the fluxcoupling-type SFCLs, it can be obtained that reduce of the fault current, inhibition of the frequency fluctuation and acceleration of the system restoration. Thus, the micro-grid system's transient stability is enhanced well.
A bipolar dc microgrid features three voltage levels and is capable of transmitting power more efficiently than a unipolar system. This paper proposes a droop control to achieve load sharing and ...voltage balancing in such a microgrid system. Droop control is adopted to ensure that autonomous sharing of load power can be realized without communication. Moreover, the positive and negative pole voltages in the bipolar dc microgrid can be well regulated regardless of load changes and input voltage mismatch. Two battery energy storage systems are incorporated for balancing load and generation, and the lifetime of batteries can be improved through proper coordination control. Simulation results in the PLECS environment and experimental results obtained from an OPAL-RT system are presented to verify the effectiveness of load sharing and voltage balancing of droop control.
This paper presents a coordination secondary control strategy for autonomous hybrid AC/DC microgrids with global power sharing operation. In the previous work, primary control with droop control ...method was applied to distributed generators to ensure local power sharing without communication links in either ac or dc microgrid. An extension of local power sharing for individual microgrid is the global power sharing for hybrid microgrids. With global power sharing control, all distributed generators throughout the hybrid system are capable of sharing the entire ac and dc loads without any information exchange. The coexistence of local power sharing and global power sharing in hybrid system is thereafter defined as generalized primary control, which is usually employed for fully decentralized power management throughout the whole hybrid system. To eliminate the inherent voltage/frequency deviations caused by the generalized primary control, the secondary control is usually applied to each distribution generator for voltage/frequency restoration. This however will degrade the performance of global power sharing operation because of its characteristics of voltage/frequency deviation dependence. To achieve voltage/frequency restoration while maintaining the global power sharing operation, a coordination secondary control was proposed and the effectiveness of the proposed method has been verified by the simulation results.
To enhance the interaction between the thermal and electrical, a hybrid AC/DC microgrid (MG) embedded energy hub (EH) is proposed. In EH, electrical, thermal, i.e. heat and cooling are supplied and ...managed to increase the operational efficiency while meeting the energy demand. It formulates a two-stage stochastic optimization problem. In the first stage, i.e. day-ahead operation, the hourly generation, conversion, and storage are optimized to minimize the fuel cost. In the second stage, considering the stochastic nature of photovoltaic and demand, the heat and cooling supply are adjusted to realize the power balancing in the electrical system, while meeting the thermal energy demand. The two-stage optimization problem is reformulated to a deterministic optimization problem, using sample average approximation. Simulations have been carried out on the test system. Results have verified the effectiveness of the proposed method, collecting the flexibility of the thermal system to the electrical networks via EH.
Hybrid AC/DC microgrid exhibits better compatibility with renewable energy sources, energy storages and various loads. The conventional smart grid system are building based and require customized ...system design, which is costly and time-consuming. In this paper, smart energy hub, which is the modularized microgrid system design, is proposed to simplify system deployment. In order to realize the three-level hierarchical control to ensure both speed of response and system control accuracy, different sub-systems have been designed and developed. Multi-mode operation of the power electronic converters is enabled to cater for system operation in different scenarios. Resource manager serves as a super smart meter + relay controller to simplify the SCADA system design and enhance the speed of response. Microgrid operating system is designed to coordinate all the function blocks to realize hierarchical control in robust manner. Prototype of the proposed energy hub has been designed and developed to integrate all the sub-systems (both hardware and software).
