The ever increasing trend of renewable energy sources (RES) into the power system has increased the uncertainty in the operation and control of power system. The vulnerability of RES towards the unforeseeable variation of meteorological conditions demands additional resources to support. In such instance, energy storage systems (ESS) are inevitable as they are one among the various resources to support RES penetration. However, ESS has limited ability to fulfil all the requirements of a certain application. So, hybridization of multiple ESS to form a composite ESS is a potential solution. While integrating these different ESS, their power sharing control plays a crucial role to exploit the complementary characteristics of each other. Therefore, this article attempts to bring the numerous control strategies proposed in the literature at one place. Various control techniques implemented for HESS are critically reviewed and the notable observations are tabulated for better insights. Furthermore, the control techniques are classified into broad categories and they are briefly discussed with their limitations. From the carried-out analysis, the challenges faced towards the implementation of HESS for standalone and grid connected microgrid systems are presented. Finally, the future directions are laid out for the researchers to carry out the research and implementation of HESS technologies. Overall, this article would serve as a thorough guide on various control techniques implemented for HESS including their features, limitations and real-time applications.

The increase in the penetration of renewable energy sources (RES) has reduced the effective inertia of the power system dominated by synchronous machines. The reduction in inertia has paved the way to the development of inertia emulation techniques, which complements the increased penetration of RES. The synchronverter technology is one among the virtual inertia emulation techniques which resembles close to the synchronous machine. The advancements in control and adaptations of synchronverter for various applications demand a comprehensive yet critical review. Thus, the main objective of this paper is to present a critical review of synchronverter technology which could increase the inertial response of RES. A critical analysis of modifications made to original synchronverter and the stability assessment techniques is presented. The effect of parameter variation on stability and dynamic performance is brought out as a decision matrix by analysing the movement of eigenvalues presented in various works. Towards the end, a synoptic overview is presented to depict the research trend and emphasize the domain which requires further attention. Furthermore, a brief discussion of the research gaps perceived during the phase of review is presented to leverage future research in the field.

Autonomous microgrids are potential alternative to grid connectivity for powering remote communities around the globe. A sustainable microgrid with renewables and energy storage having minimum operation and maintenance routines is the most sought option. Batteries are predominantly used to support the stochastic behavior of renewables in such microgrids. However, they are prone to frequent failure and require periodic maintenance, which demands an alternative. Thus, in this article, the renewable powered irrigation system in India was configured to form sustainable pico hydel energy storage (PHES). To enhance the inertia of the microgrid with static sources, virtual inertia capability was induced into PHES by modified synchronverter technology. First, the small-signal modeling approach was presented to derive the closed-loop transfer function of the system. Subsequently, the effect of control parameter variation on system stability and the interaction between the governor and the synchronverter was investigated using eigenvalue analysis. Next, the performance of synchronverter was compared with the established vector control through time-domain simulations in MATLAB/Simulink. The simulation results revealed that the proposed strategy improved the inertial response of PHES and outperformed vector control by reducing peak overshoot, settling time, and steady-state error.

Frequency regulation of autonomous microgrids with intermittent renewables is a tedious task, which requires additional support from energy storage systems (ESS). Ideally, the system requires a faster‐acting ESS to arrest the initial frequency deviation and high energy capacity ESS to restore the frequency to its nominal value. Pico hydel energy storage (PHES) is one such high energy capacity ESS developed from the agricultural pumping systems. However, PHES has a slower response and cannot switch rapidly between pumping and generation modes. Hence, this paper incorporates a battery with PHES to achieve a faster dynamic response and absorb high‐frequency power dynamics. Additionally, a frequency regulation strategy with synchronverter control is proposed to mimic synchronous machines, especially to reduce the rate of change of frequency (ROCOF) and frequency nadir. Firstly, a small‐signal modelling approach is proposed, and it was utilized to assess the system stability through eigenvalue analysis. Subsequently, transient simulations were carried out to gauge the performance of the synchronverter strategy with vector control for frequency regulation. As a result, the frequency nadir and ROCOF were substantially reduced with the synchronverter strategy compared to the vector control based on the simulation results.