The aim of this research work is to develop a load shedding methodology to improve the frequency response of low inertia grids by attaining satisfactory voltage stability. In recent times, wind energy integration has considerably increased in many power grids. Consequently, conventional synchronous machines are being replaced from dispatch. Unlike traditional synchronous machines, variable speed wind turbine generators usually do not take part in frequency regulation without supplementary control mechanism. During substantial wind penetration, a power system may have a small number of online synchronous machines. As a result, synchronous inertia and governor responsive reserve significantly reduce. Under such situation, a system has to rely on load shedding as a last line of defense to rescue the system frequency following a large contingency. However, the conventional Under-Frequency Load Shedding (UFLS) strategy may lead to larger frequency deviation and higher amount of load cut in certain cases. A new load shedding methodology is presented in this paper to overcome this challenge. Unlike conventional UFLS technique, higher proportion of load shedding is applied to relatively weaker buses in terms of voltage stability in the proposed mechanism. Based on reactive power margin, which is an index to specify voltage stability, a general expression to quantify load shedding is derived. Also, the adaptability of the proposed strategy to various load levels is ensured. Later on, performances of the developed strategy are explored in a low inertia wind dominated test network. Simulations are executed considering various penetration levels of wind power and for two severe contingencies – loss of 550 MW interconnection and loss of 650 MW interconnection. Investigations reveal that the proposed load shedding methodology ensures satisfactory frequency response in all simulation cases. Also, the developed technique yields less frequency deviation and load cut compared to the conventional UFLS mechanism. Therefore, the reported load shedding scheme is found to be more competent to concurrently maintain frequency and voltage stabilities in renewable dominated power systems.

The utilization of Energy Storage Systems (ESS) for improving the frequency response of a low inertia power system is investigated in this article. Substantial wind power penetration is causing the replacement of conventional synchronous generators in several power systems. Variable speed wind machines traditionally do not contribute to frequency regulation without additional control strategy. As a result, a wind dominated power grid may have inadequate inertia and governor responsive reserve. In such situation, a large contingency may yield undesirable Rate of Change of Frequency (ROCOF) and frequency deviation. To overcome this problem, deployment of ESS, namely, Superconducting Magnetic Energy Storage (SMES) and Battery Energy Storage System (BESS) can be a worthwhile solution. Since these devices are costly, their appropriate sizing and operational approach are crucial. Therefore, in this paper, analytical expressions are derived to find the minimum ratings of SMES and BESS. To this end, system frequency deviation, ROCOF, inertial response and governor response are taken into account. Also, a coordinated operational strategy is proposed to retain frequency response adequacy and minimize under frequency load shedding where SMES is triggered when system ROCOF supersedes a certain limit and BESS is activated due to system frequency surpassing a preset threshold. The performance of the proposed strategy is explored in a low inertia network under substantial wind penetration considering several different wind penetration levels. Also, the results are validated against two existing approaches. Simulation results reveal that the proposed methodology considerably enhances the frequency response in various operating conditions.

The primary objective of this paper is to alleviate the over-frequency problem in low-inertia power systems through optimal allocation of a Battery Energy Storage System (BESS). With prolific integration of wind power, conventional fossil-fuel driven synchronous generators are being replaced in the generation fleet. Variable speed wind machines are connected to the grid via power electronics converters. As such, these machines usually do not participate in frequency regulation. During high wind penetration, a generation-rich zone of an interconnected power system may face significant over-frequency following the loss of interconnection. If the frequency goes above a certain threshold, an Over-Frequency Generator Shedding (OFGS) scheme is activated. This may cause considerable amount of generation cut in a low-inertia power system. To address this challenge, this paper develops a siting and sizing methodology of frequency-responsive BESS to simultaneously maintain frequency and voltage stabilities. As such, BESS is placed at the most voltage-sensitive bus, determined by an index called reactive power margin. Furthermore, an optimization model is formulated to determine the BESS size to avoid generation shedding. The proposed technique is applied to a low-inertia power system, which resembles the equivalent high-voltage transmission network of South Australia. The simulation results reveal that the developed methodology successfully mitigates the over-frequency phenomenon. In addition, the proposed technique is found to be more effective than its counterpart (i.e., without BESS) to enhance the frequency resilience of a low-inertia grid.

Methylammonium lead halide ( M A P b I 3 ) is widely used as perovskite absorber material in thin-film solar cell technology because of its eminent cell performance. Recently, formamidinium lead iodide perovskite ( F A P b I 3 ) has received great attention because of its optimum bandgap value closer to the infrared single junction range. In this paper, a suitable combination of hole transporting material (HTM) and electron transporting material (ETM) is determined to achieve higher efficiency compared to existing structures utilizing an F A P b I 3 absorber. The proposed structure uses two stable metal oxides as HTM ( N i O X ) and ETM ( S n O 2 ). A comparative numerical analysis of solar cell performance is shown among four different HTM materials using the Solar Cell Capacitor Simulator (SCAPS-1D). Performance evaluation is also carried out for three different compositions of F A P b I 3 having different band gaps with respect to absorber thickness. Optimized absorber thickness, HTM and ETM doping density, and absorber defect density are enumerated using numerical simulation. By deploying the optimized parameters, maximum power conversion efficiency is found to be 26.23%. Later on, effects of R s e r i e s and R s h u n t on ideal solar cell performance are analyzed using numerical simulation.

In this article, we present a comprehensive end-to-end evaluation platform for various front-end-of-line (FEOL) and back-end-of-line (BEOL) technology options at the 3-nm technology node. Based on TCAD modeling of FE and BE, we have developed a 3-nm GAAFET-based process design kit (PDK). We have developed a 6-track standard cell library including 65 cells with a library height of 144 nm. Based on TCAD modeling of interconnects, we have evaluated the resistance of the entire BEOL stack using ruthenium for lower metal levels (M0–M3) and copper for higher metal levels (M4–M13). Based on place and route (PnR) studies using our PDK, we have analyzed the impact of high aspect ratio (AR) Ru interconnects at M2 and M3 in terms of performance using benchmark designs. Our results show that using Ru interconnects improves the circuit performance by up to 10.4% compared with Cu interconnects and that increasing the AR generally results in performance degradation due to the increase in capacitance and via resistances. We have observed a 5.9% and 4% degradation in performance for AES and LDPC, respectively, when moving from AR2 to AR6 local interconnects. However, adding an airgap can improve the higher AR Ru interconnect cases and AR4 with airgap case shows the most performance improvement with an overall 19.7% improvement compared with Cu. This case study also serves as an example that shows the importance of an end-to-end evaluation platform.