Harnessing wind energy is the most rapidly growing amongst renewable energy sources. However, because of its intermittency in nature, wind power results in unfavorable influences on power system control, operation and stability. The voltage sag and flicker and grid frequency fluctuation are significant in this regard. To minimize the effect of wind power fluctuations and other contingencies on the grid frequency and AC-bus voltage, this paper presents a droop-fed vector control strategy based variable speed pumped storage (VSPS) system comprising the doubly fed induction machine. Modelling of the system is undertaken based on a phasor model technique. The case study is made by considering the droop-controlled VSPS plant in a grid containing conventional synchronous machines for hydropower and thermal power plants and an induction machine wind farm. The performance is validated and analyzed using a MATLAB/Simulink platform. The proposed droop-fed control model is compared with the conventional control strategy (without being droop-fed) and tested to wind power fluctuations, start-up transients, load variations and three-phase fault. The results show that the droop-fed vector control strategy of the VSPS plant achieves better dynamic and steady state controlling responses for grid frequency and AC-bus voltage in the power system than the conventional vector control scheme during wind power fluctuations and contingencies.

Pumped‐storage hydropower plants can contribute to a better integration of intermittent renewable energy and to balance generation and demand in real time by providing rapid response generation. The utilisation of variable‐speed pump‐turbine units with a doubly fed induction machine is being progressively applied due to its overall efficiency and high level of operating flexibility. This study presents state‐of‐the‐art pumped energy storage system technology and its AC–DC interface topology, modelling, simulation and control analysis. It also provides information on the existing global capacities, technological development, topologies and control strategies of the pumped‐storage system. This report also outlines the analysis of dynamic performances of the system. It also attempts to recommend the future works in this area. This study concludes that pumped storage is the most suitable technology for small autonomous island grids and massive energy storage, where the energy efficiency of pumped storage varies in practice. Around the world, the size of the pumped‐storage plant mostly lies in the range of a small size to 3060 MW. The back‐to‐back voltage source converter topology is mostly conducted due to its significant features. Due to its imperative features, the vector control strategy is widely used. The pumped‐storage plant is dedicated to power management and stability regulation of grid and isolated power systems.

This paper presents stability and control of a grid integrated doubly-fed induction machine (DFIM) based variable speed pumped storage (VSPS) system. The paper aims to verify whether the VSPS unit can support the grid frequency stability. Models of the converters with control units and the mechanical and electrical machines for the VSPS are developed based on phasor representation technique. Based on the dq-frame control theory, the direct power control strategy is designed. Steady-state and transient stability responses of the proposed system are analyzed in MATLAB/Simulink platform. Frequency stability responses are particularly evaluated by comparing between a grid with VSPS and without it. Frequency droop control is also proposed and validated. The results show that the VSPS improves the steady state operations and dynamic stability of the power system. The droop controller ensures that the frequency dynamic stability is highly improved. Hence, the VSPS system is effective in supporting the frequency stability, and adopting droop control in the power grid.

Harnessing wind energy is the most rapidly growing amongst the renewable energy sources. However, because of its intermittency nature, wind power results in unfavorable influences on power system operations and stability. The voltage flicker and grid frequency fluctuation are significant in this regard. To minimize the effect of wind power fluctuations on the grid frequency and AC bus voltage, this paper presents direct power control strategy-based variable speed pumped storage system. Modeling of the system is undertaken based on phasor model technique. The case study is made by considering conventional synchronous machines for hydropower and thermal power plans in the grid and induction machines for the VSPS and wind turbines. The performance is analyzed using MATLAB/Simulink platform. The results show that the proposed VSPS control strategy achieves well-regulated and stable grid frequency and AC voltage in the power system.

The voltage source converters (VSC) medium‐voltage DC (MVDC) is the future distribution network for integrating renewable energy sources. The doubly fed induction generator (DFIG) wind turbine is the most efficient option for wind farm application. The intermittency of wind power is challenging in grid integration at the AC distribution system level. This study presents a ±10 kV VSC MVDC network with DFIG wind farm integrated to mitigate these effect. Key MVDC network components and controllers are modelled including the control strategy for the MVDC grid. The proposed system is validated in MATLAB/SIMULINK for steady state and transient conditions. The results show that the MVDC can work as firewall that absorbs the fluctuating wind power to a stable system with good power flow and balance as well as constant DC voltage. Therefore, the MVDC network is a stable system with fast dynamic response.