The virtual synchronous generator (VSG) improves the robustness of the inverter-interfaced distributed generator (IIDG) against instability by introducing a virtual inertia. However, the transient response of the active power and the angular frequency conflict with each other for the IIDG with fixed inertia control. It is necessary to adopt adaptive control to improve overall performances of power and frequency as the operating condition changes. This paper analyzes the impact of the inertia on power and angular frequency. A dual-adaptivity inertia control strategy is proposed to offer a responsive and stable frequency support and also achieve the balance between power regulation and frequency regulation according to different operating conditions. The principle of parameter design is given to obtain the range of adaptivity. Quantitative assessment considering the cumulative effect of the output deviation and its duration is also presented to evaluate the proposed strategy intuitively. The strategy is further verified based on PSCAD/EMTDC and a hardware-in-loop experiment platform based on RTDS. Results confirm that the proposed strategy not only achieves rapid frequency response with slight dynamic deviations under disturbances but also strikes a balance between the frequency and power and leads to improved overall control.

Ports are major energy consumers and carbon emission producers. Developing integrated port energy systems (IPES) is the key to solve this problem. The energy forms in an IPES include electricity, hydrogen, heat and natural gas. Hydrogen can be generated from surplus renewable energies via water electrolysis, and thus power the previously oil-fueled equipment. Meanwhile, the remaining hydrogen can be converted to natural gas by the methanation reaction. By using fuel cells, gas turbine, hydrogen boiler and gas boiler, hydrogen and natural gas can supply the electrical and heat loads in the port area, forming a closed-loop of energy flow. Based on the above energy coupling structure, a day-ahead optimal economic dispatching model for IPES is established. The model takes the energy conversion loss and carbon dioxide emissions into account. The second-order conic relaxation is used to deal with the nonlinear part of power flow calculation. The linearization model for connecting heat source and heat load is built. Numerical results demonstrate that the proposed economic dispatching model effectively reduces the total energy cost and carbon dioxide emissions of IPES.

The DC microgrid has become a typical distribution network due to its excellent performance. However, a well-designed protection scheme still remains a challenge for DC microgrids. At present, researches on DC microgrids primarily focus on the topology structure, control method and energy control, while researches on fault analysis, detection and isolation have not drawn enough attention. Therefore, this paper intends to depict the current research status in different relative areas and review the proposed protection strategies in order to help researchers to have a clear understanding on DC microgrid protection. Meanwhile, to solve the protection issues and promote the development of the DC microgrid, this paper points out the key areas of future research. The future protection research directions lie in the development of novel protection devices, which are based on electronic technology to provide loose protection constraints and the improvement of suitable protection schemes. In addition, the novel concept of coordinated strategy of control and protection of the DC microgrids is explained.

Wind power is the fastest growing and environmentally sustainable source of energy among all available renewable energy resources. The primary objective of this paper is to analyze the wind characteristics and power potential at Hyderabad, Southeastern province in Pakistan. Two years of wind speed data measured at 10 m above ground level (AGL) have been considered in this study. The annually, monthly, and seasonal variations in wind speed were analyzed, and minimum, maximum, and average values of recorded wind speeds are presented in this paper. Weibull and Rayleigh distribution functions have been applied to analyze the wind characteristics and evaluate the wind power potential of the proposed site. The Weibull shape k and scale c parameters have been estimated using the Weibull function. The higher values of k showed that the wind speed is steady at the site. The average wind speed was found above 6 m/s throughout the year. The most probable wind speed (V_mp) and maximum carrying energy (V_maxE) wind speed were also calculated using Weibull parameters. Root mean square error (RMSE), the coefficient of determination (R²), and mean bias error (MBE) were computed to ensure the good fit of Weibull distribution function. The annual average wind power and energy densities were estimated at more than 255 W/m² and 2245 kWh/m², respectively. The power density calculated by Weibull and Rayleigh functions was compared with that calculated by using measured wind data. The energy output and capacity factor of different commercially available wind turbines (WTs), i.e., power ratings from 0.33 to 2.75 MW, have been calculated. The cost of energy was estimated and ranged from $19.27 to $32.80 per MWh. Wind power potential and economic analysis of the collected data reveals that the site is suitable for developing wind power generation projects to power the local communities.

The interconnected converter (IC) links the ac and dc microgrids (MGs) and exchanges powers to maintain the hybrid system stability. However, inertia stored in the ac or dc side cannot be transferred through IC to support each other flexibly according to demand. This paper proposes a novel bidirectional virtual inertia (BVI) control strategy for the IC with an inertia transferring mechanism. IC actively transfers the inertial power to balance the transient performance of both sides of the interconnected MGs. The adaptive strategy is proposed for coefficients of the BVI control to change the inertial power flexibly according to the inertia gap caused by disturbances. Experimental results demonstrate that the proposed strategy of transferring inertia strikes a transient balance between the dc voltage and ac frequency and hence, enhance the transient stability of the hybrid system.

Accurate fault location reduces operating cost and outage time. This paper proposes a time-domain method to accurately locate faults in transmission lines, which only requires a very short data window (several milliseconds) during faults. First, the voltage distribution through the line during faults is accurately obtained by solving the matrix form partial differential equations using the proposed numerical scheme. The proposed numerical scheme is mathematically validated for the transmission line fault location problem, with the optimal selection of time and distance intervals to ensure stability and minimum solution error. Afterwards, the fault location is obtained via the extremum value of the voltage distribution. The method fully considers distributed parameters as well as asymmetry of the line. Extensive numerical experiments validated that (a) the proposed numerical scheme demonstrates advantages towards other numerical schemes; (b) the proposed method presents higher fault location accuracy compared to the existing method, independent of fault types, locations and impedances; and (c) the fault location accuracy is not sensitive towards fault inception angles, loading conditions, measurement errors and parameter errors. The proposed method works with relatively low sampling rates (80 samples per cycle) and is compatible with IEC 61850 standard in present digital substations.