This study presents a method of estimating the effective inertia of a power system from ambient frequency and active power signals measured by PMUs. Most importantly, we demonstrate that inertia can be estimated from ambient measurement data, not only from disturbances. This leads to the possibility of monitoring inertia in a close to continuous manner in the time scale of minutes or tens of minutes. The method allows the system to be divided into a number of areas and the effective inertia of each area to be estimated as a separate quantity. In principle, inertia is estimated by observing the dynamics between changes in active power and resulting frequency deviations during normal operation of the system. The method is based on applying system identification on these measurements and extracting inertia values from identified models. Efficacy of the method is demonstrated on results of real measurements from the Icelandic power system.

The objective of this paper is to develop and analyse a variable speed hydropower (VSHP) model that can aid the design of controllers that maximize the utilization of power plant for the provision of ancillary services, considering the limitations given by the hydraulic system. The model is tested and analysed with more or less conventional controllers to identify critical modes, adverse interactions or other limitations that must be taken into account in the future design of potentially multivariable or more advanced controllers for VSHP. Dynamic tests are performed by simulating step responses in power demand and by comparing responses of the model with the VSHP and with a conventional hydropower plant. A participation factor-based interaction analysis shows that there are no strong dynamic couplings between the hydraulic system of the VSHP and the rest of the grid. This simplifies the tuning of the control system. However, the analysis concludes that some oscillatory modes associated with the hydraulic system become significantly more excited when operating at variable speed; which is due to the larger deviation in turbine rotational speed. Extra awareness when designing the control system is therefore needed to keep the hydraulic system variables within their limits.

The main purpose of this article is to demonstrate the grid support capability of variable speed hydropower (VSHP). The hypothesis is that active power control of VSHP plants can improve both the frequency stability and the transient rotor angle stability by contributing to virtual inertia (VI), fast frequency reserves and power oscillation damping. Fast active power control is made possible by power electronic converters obtaining the energy from the rotating masses of the turbine and generator while the rotational speed is restored by control of the guide vane opening of the hydro turbine. A detailed dynamic simulation model is developed to simulate the VSHP within the Nordic 44-bus grid model. The VSHP controller includes a moving horizon estimator (MHE), model predictive control (MPC) with inertia emulation realised by the frequency converter of the VSHP plant. The results show that VSHP can contribute significantly to reduce the maximum frequency deviation following a sudden loss of generation. In addition, the amplitudes of power oscillations are reduced and the critical fault clearing times are generally improved. The VSHP should, therefore, be regarded as one of the technically viable options for provision of fast balancing system services.

The cost of peak power for end-users subject to a demand charge may be substantial, expecting to increase further with the vast growth of power-demanding devices. In cases where load-shifting is not a viable option for cost reduction, battery storage systems used for peak shaving purposes are emerging as a promising solution. In this paper, the economic benefits of implementing battery storage into an existing grid-connected photovoltaic system for a medium-scale swimming facility is studied. The objective is to minimize the total cost of electricity for the facility, including the cost of energy and peak power demand, while ensuring the longevity of the battery. An optimization model based on multi-integer linear programming is built, and simulated using a one-year time horizon in GAMS and Matlab. The main results reveal that installing a battery storage system is economically attractive today, with net savings on the total system cost of 0.64% yearly. The cost of peak power is reduced by 13.9%, and the savings from peak shaving operation alone is enough to compensate for the yearly cost of the battery. Moreover, the battery ensures additional revenue by performing price arbitrage operations. When simulating the system for an assumed 2030 scenario, the battery is found to be more profitable with a yearly net savings of 4.15%.

Microgrids are in demonstration phase for rural electrification in Nepal. There are different viable options of forming rural microgrids by the interconnection of distributed energy resources like micro-hydropower plant (MHP), Wind Turbines (WT) and photovoltaic (PV) systems. The rural microgrid under study includes three renewable energy sources MHP, WT and PV system, and battery bank for energy storage. The paper presents the current socio-economic status of rural community fulfilling its electrical need from the rural microgrid. The socio-economic challenges for the sustainability of the rural microgrid are also discussed.

Wide-area monitoring, protection, and control (WAMPAC) systems are expected to support the transmission system operators in maintaining stability and security of supply in the future power systems. The WAMPAC solutions heavily rely on deployment and use of phasor measurement units (PMU) and related communication technologies. Laboratory testing in a realistic environment utilizing hardware in the loop (HIL) approaches can be successfully used to evaluate WAMPAC functionalities algorithms and to accelerate proofs of concept. However, different implementations of the HIL testing can be adopted and their inherent characteristics affect both the accuracy of the results and the overall testing capabilities. The objective of this paper is to provide a comparative assessment of three HIL approaches for laboratory testing of WAMPAC systems and devices. These testing approaches have been implemented in a laboratory configuration and applied to characterize WAMPAC devices. Moreover, methodologies to quantify the error introduced by these testing approaches in static and dynamic conditions are presented and applied to this laboratory configuration.