Earticle

Remote communities are typically isolated from large power systems (off-grid) and use diesel generation in conjunction with a dump load to feed the local grid. Inherent high operation costs and emissions can be reduced with the integration of renewable energy (RE) sources at a high penetration level. These renewable sources such as wind and solar (PV) energies have been proposed due to their economical and environmental advantages.planning and operation of power systems with medium to high penetration levels of RE implies some difficulties due to the stochastic and intermittent characteristics of the sources. Furthermore, isolated grids with fossil-fuel based power generation that have been integrated with RE (primarily wind farms) require the additional use of dump loads or generation curtailment.The implementation of energy storage systems (ESS) with large storage capacity for several hours, offers a good solution for avoiding the energy wasted from intermittent sources and increases the penetration of RE

Renewable energy policy have had a great influence on power industry in terms of energy mix and energy market environment. However, due to its output variability and uncertainty, power system operation has become more complicated. Specifically, Microgrid that procures its generation capacity mostly from renewable energy resources faces the financial and operational volatility. Thus, this paper suggests a contract between main-grid and Microgrid and the optimal scheduling of Microgrid resources based on the contract. Numerical simulations on a test Microgrid exhibit the effectiveness of the proposed methodology.

This paper illustrates the vulnerability of local energy trading to false data injection attacks in a smart residential microgrid and demonstrates the impact of such attacks on the financial benefits earned by the participants. In a local energy market, the attacker can overhear the energy generation and consumption patterns of legitimate participants and based on this, optimize its attack signal to achieve maximum benefits either as a buyer/seller, while balancing the supply?demand to remain undetected. For such a system, we have formulated an optimization problem at the attacker, to extract the maximum possible benefits from legitimate participants. The numerical results show that the false data injection from the attacker causes significant losses in the benefits of legitimate participants, up to a reduction of 94% in certain hours.

Seismic disasters can cause systemic urban paralysis by destroying critical land-based power infrastructure. The catastrophic risk of such collapses was certainly demonstrated by the Great East Japan Earthquake of 2011. The loss of emergency cooling power, caused by the destruction of both external grids and backup generators, led to the Fukushima nuclear disaster. Furthermore, the 2024 Noto Peninsula earthquake revealed a significant vulnerability in transport systems. Rapid ground displacement and road destruction physically blocked the supply of generators, resulting in prolonged blackouts in isolated coastal areas. To overcome these vulnerabilities, this study proposes the use of semisubmersible Floating Energy Storage Systems(FESS). The FESS ensures high survivability by isolating the energy module from earthquake-induced destruction. Also, the semisubmersible structure has physical stability at sea due to its deep-draft. As modern smart cities increasingly pursue the construction of microgrids for energy independence, FESS will facilitate recovery from earthquakes. The FESS is connected to a pre-installed coastal emergency connection point. It can function as a starting point of Black Start, providing the essential reference voltage to restart Distributed Energy Resources(DERs) that have shut down. Through Grid-Forming Control, FESS establishes a stable voltage standard and synchronises the DERs, gradually restoring the smart city's microgrids. This enables critical infrastructure, such as nuclear power plant cooling systems and medical facilities, to be restored as a priority, even in the event of a power grid collapse. In conclusion, this study presents a practical framework for enhancing the resilience of smart cities by utilising FESS as an energy hub for rapid recovery.

본 논문은 현재 진행 중인 대한민국 남부지역에 위치한 대학 내 스마트에너지캠퍼스 마이크로그리드에서 대학 내 빌딩에 설치될 수소전기분해 이용 연료전지 시스템 운용을 위한 선행 연구로써 고분자전해질막 전기분해 (PEMWE)과 고분자전해질막 연료전지(PEMFC) 장치에서 동시에 온도변화 효과를 연구하고자 한다. 전반적으로 실험실에서 50W 고분자전해질막 연료전지(PEMFC)을 사용하여 수행하였다. 모니터링 프로세스는 무선 로라 노 드와 게이트웨이 네트워크를 구성하여 실행하였다. 그리고 PEMWE와 PEMFC에 대한 수학적 모델링과 운전 알 고리즘을 제안하였으며 제안한 모델에서 PEMWE는 낮은 발열 기준에서 효율이 더 높음을, 반면에 PEMFC는 높 은 발열기준에서 효율이 더 높음을 을 알 수 있었다. 향후 대학 구내 빌딩에 설치될 실증시스템 성능을 높이기 위해 PEMWE와 PEMFC의 온도와 압력을 모니터링, 통신 및 제어 등 연구개발을 통하여 구현할 예정이다.

In this paper we are trying to explain the effect of temperature on polymer membrane exchange water electrolysis (PEMWE) and polymer membrane exchange fuel cell (PEMFC) simultaneously. A comprehensive studying approach is proposed and applied to a 50Watt PEM fuel cell system in the laboratory. The monitoring process is carried out through wireless LoRa node and gateway network concept. In this experiment, temperature sensor measure the temperature level of electrolyzer, fuel cell stack and H2 storage tank and transmitted the measured value of data to the management control unit (MCU) through the individual node and gateway of each PEMWE and PEMFC. In MCU we can monitor the temperature and its effect on the performance of the fuel cell system and control it to keep the lower heating value to increase the efficiency of the fuel cell system. And we also proposed a mathematical model and operation algorithm for PEMWE and PEMFC. In this model, PEMWE gives higher efficiency at lower heating level where as PEMFC gives higher efficiency at higher heating value. In order to increase the performance of the fuel cell system, we are going to monitor, communicate and control the temperature and pressure of PEMWE and PEMFC by installing these systems in a building of university which is located in the southern part of Korea.

This study presents an improved doubly fed induction generator (DFIG) that is integrated with a battery energy storage system (BESS) for microgrid control. The proposed DFIG can generate independently the power output of the rotor-side converter (RSC), grid-side converter (GSC), and battery-side converter. The maximum power point tracking (MPPT) is included in the RSC to maximize the generated power of DFIGURE. The power of the GSC is used to smooth total wind power of DFIG and to maintain stably AC voltage and frequency in the island mode. The battery-side converter is used to keep the dc link voltage of a back-to-back converter. The effective of the proposed DFIG is validated by simulations on Matlab / Simulink environment.

The operation of microgrid is an important research topic due to its high efficiency of energy consumption and various types of energy source. Demand response (DR) programs can be applied to operate microgrid efficiently and economically. This paper deals with an optimal operation a microgrid in grid-connected operation mode. DR programs based on time of use (TOU) program and emergency demand response program (EDRP) are applied in this paper. Mixed integer linear programming is used to the end of simulation. Through the simulation results, the effectiveness of the DR programs based on TOU and EDRP to the microgrid operation are shown.

Roles of energy storage systems (ESSs) in microgrid control are very important because a microgrid has uncontrollable energy sources such as the wind turbine and power trade with the utility grid. Especially, the ESSs have different characteristics – power density and energy density. The characteristics show a trade-off. For this reason, the coordinated control among ESSs considering their characteristics is required. In this paper, a coordinated control of SMES and BESS is tested with high reliability using the hardware-in-the-loop simulation (HILS) system in two grid-connected and islanded modes.

The distributed generation sources (DGS) offer more economic and environmental energy than traditional centralized generation. However, the loads demand for electricity can not be met simultaneously owing to the limitation of the capabilities of DGS when the microgrid is isolated from main power grid. In this paper, the method of the current power supply capacity calculating for some common micro power sources is given firstly. Thereafter, a multi-agent system based coordinated control strategy for distributed loads in microgrid is developed. When consumers need electricity, the load agent (LD Agent) is used to negotiate with distributed generation resources agent (DG Agent) whether the load can be connected to grid. When loads’ power exceeds the power supply capability, the microgrid central controller (MGCC) is used to request corresponding LD Agent to disconnect the lower grade loads according to the priorities of loads. The simulation results show that the effectiveness of the presented Multi-Agent based coordinated control strategy.

Islanding detection is one of the essential features for photovoltaic grid-connected systems; detection performance is directly related to safe operation of the equipment. Summarize existing islanding detection, then an active method based on frequency – reactive power feedback islanding detection is proposed. Once an islanding condition occurs, the method introducing a load frequency - reactive power characteristics associated component as input of reactive power perturbation, breaks the existing islands of stability point in the case of the power balance. Then it detects the system frequency deviation by real time, and draws into the function of reactive perturbation to form a positive feedback loop. So the frequency drifting is accelerated and the frequency of the output voltage of the photovoltaic grid-connected inverter exceeds a preset threshold value, and then the islanding will be detected. Simulation shows that the proposed method has no detection dead zone and it is fast and has little influence on power quality.

This paper presents a novel approach for dynamic economic dispatch in a MicroGrid by using the improved ant colony optimization (ACO). In order to satisfy the power balance and load demand, the mathematical model of economic dispatch is given to support the MicroGrid in both grid-connected and islanded mode. By means of ACO, the dynamic economic dispatch solution is proposed in combination with sequential quadratic programming (SQP), and the essential procedure is introduced. Simulation results demonstrate the feasibility and benefits of the proposed scheme.

To guarantee the security and stability of islanded microgrid, transmission congestion problem is considered during the frequency control so as to efficiently make use of power available without violating system constraints. A novel strategy was proposed, which combines distributed frequency control and congestion management and makes the distributive frequency control reasonable at the request of line congestion. It effectively solve multi-objective problem with multi-linear equality and inequality constraints. To testify the proposed strategy, an islanded microgrid with five-machines is provided in Matlab/Simulink. The results demonstrate that fast frequency regulation and effective settlement of transmission congestion are obtained by this approach.

Hybrid microgrid consists of AC and DC grids, in which the interlinking converter is used to connect AC and DC microgrids. The droop control scheme is widely applied to hybrid microgrid control including interlinking converter because it can be used to control power in hybrid microgrid without communication. However, the existing steady-state error in conventional droop control might affect to the power quality of sensitive load. Therefore, the improved droop control scheme is proposed in this study, in which the steady-stated error is removed by using an additional PI regulator. Various simulation scenarios in term of load variations are performed in the MATLAB/Simulink environment to verify the control performance of proposed control scheme. Simulation results show that the frequency and DC voltage are controlled stably by using improved droop control scheme.

This paper deals with the real-time scheduling of a microgrid considering uncertainties of renewable energy sources (RESs). A two-step mathematical model based on real-time scheduling and demand responses (DRs) is proposed. DR programs, time of use (TOU) and emergency demand response programs (EDRP), are used to minimize the operation cost of microgrid. The proposed real-time scheduling is based on spinning and load reserves to deal with uncertainties of RESs. In the first step, the day-ahead scheduling is run for 24 hours with forecasted RESs. The second step deals with the actual RESs and the microgrid operation is rescheduled in the real time. The effectiveness of DR programs on the electrical demand for each interval is also shown in this study. The mixed-integer linear programming (MILP) method using CPLEX optimization program is used to solve the proposed two-step mathematical model.

The renewable energy sources penetration has increased nowadays. Numerous techniques are developed for grid connected photovoltaic system for intensive penetration of photovoltaic (PV) production into the grid from various research papers. Several researches have been carried out in the field of PV design, but few work for grid connected multi-junction solar cell. Cascaded multilevel inverter provides many advantages over conventional inverters to improve the overall efficiency and reduce harmonics with the grid integration of renewable energy sources. The paper proposes a design of multi-junction photovoltaic solar cell with maximum power point tracking and a novel topology of cascaded multilevel inverters to improve power quality delivered to grid in terms of harmonics, by minimizing total harmonic distortion of microgrid (MJSC) interface. A model was developed and the system was tested for performance. The results found were encouraging as compared to the traditional methods. MATLAB/Simulink platform is used to model and simulate the entire system.

This paper proposes an operation strategy to optimize the day-ahead scheduling of hybrid AC/DC microgrid (MG). The strategy schedules its resources, such as distributed generators, AC/DC battery energy storage systems to minimize the operation cost while increasing the system reliability. Moreover, an energy management system (EMS) is developed based on centralized optimization framework, which is used to optimize the MG operation in grid-connected mode. On the other hand, the EMS aims to minimize the load shedding amount in both AC and DC sides in islanded mode. In this study, the operation of hybrid MG under different connection failure scenarios is also represented. The results illustrate the effectiveness of the strategy for different operation modes of hybrid AC/DC MG.

In order to solve the problem of transient oscillation of microgrid during process switching between grid-connected operation and islanded operation, the basic principle of traditional control strategy is analyzed, a novel control structure of smooth switchover for microgrid based on the double negative feedback controller is proposed. Also, to avoid the risk of voltage oscillation caused by the mutual interference of the two controllers in the traditional quasi-synchronization method, an improved quasi-synchronization controller is proposed, which is simpler and easier to implement. Finally, the simulation results verify the validity of the proposed structure. Research results show that the busbar voltage and current oscillation can be solved better with the novel structure, and lay the foundation for smooth switchover.

The microgrid systems play a vital role in reducing the impact of renewable generation effect on the main grid. Microgrid systems can achieve grid-tied operation and isolated operation modes with fast switching and isolation functions. The reliability of power supply can be further achieved through the microgrid by reforming a mesh configuration. However, the protection of the network is a challenging task due to the bi-directional power flow and the change of the network structure. In this paper, an adaptive -model and simulation of the solar photovoltaic microgrid differential current protection scheme -are presented. Differential scheme denotes a very credible method to secure the protection zone. The protection system that is under consideration behaves the most important part of the power system. Current protection relay scheme plays an important role in the protection of transmission lines, because it is sufficient and reliable. This paper discusses (dual slope) differential relay parameters of the system with various fault situation states. Therefore, the protection scheme must identify the fault zone for rapid separation to reduce the damage of equipment. Our simulation results show that the proposed method is effective and can reduce the percentage of errors.