Nowadays, smart grid online monitoring systems are widely used in high voltage (HV) power transmission networks, leading to the requirement of reliable power supply units for the monitoring equipment. In this paper, we present a novel solution to harvest energy from the magnetic field around a 110 kV transmission line and transmit the energy to the online monitoring equipment on the transmission tower over 1.1 meter insulation distance. Printed circuit board (PCB) resonators are covered by the composite insulation material forming the first HV insulator with wireless power transfer (WPT) capability. The prototype of the HV insulator has passed the rigorous HV tests at 550 kV. The WPT characteristic of the HV insulator including the effects of corona rings is analyzed and verified by practical measurement.

Battery energy storage systems are often adopted to buffer the difference between the intermittent solar power and the load demand in power grids. The costs of such photovoltaic (PV) battery systems increase as the required energy storage increases. In this paper, a new configuration comprising the PV panels, a series dc electric spring (series ES) and a noncritical load is proposed to reduce the battery storage capacity of dc microgrids that have substantial PV installations. This arrangement forms a PV-embedded series dc ES (PVES). An optimization method considering the minimization of electricity bills of the dc microgrids is included to size the storage capacity and to determine the rating of the PV that are connected to the series ES. Experiments on a 48-V isolated dc grid and simulations on a 400-kVA grid-connected dc microgrid have been conducted to verify the storage reduction feature of the PVES. Both sets of results show that the PVES can tackle the intermittency of the solar power with a smaller storage capacity than that typically required in dc grids with PV installations.

The expanding functions of the emerging smart grid have posed new technical challenges on the power supplies for online monitoring systems in the transmission and distribution networks. A recent study has suggested that magnetic energy around the transmission line can be harvested and delivered wirelessly to the monitoring equipment through printed circuit board (PCB) resonators embedded inside an insulation rod. This article presents a rigorous analysis, modeling, and optimization of such PCB resonators. A new closed-form quasi-static model of the PCB resonators is derived. A fully automated simulation-driven optimization framework is constructed to enhance the quality factor of the resonator. Practical measurements show that the optimal design improves the quality factor ( $Q$ factor) from 52 to 132 as compared to the existing trial-and-error design. The corresponding wireless power transfer efficiency in a 20-W prototype across a 1.14-m distance improves significantly from 11 to 46%.

Increasing use of renewable energy sources to combat climate change comes with the challenge of power imbalance and instability issues in emerging power grids. To mitigate power fluctuation arising from the intermittent nature of renewables, electric spring has been proposed as a fast demand-side management technology. Since its original conceptualization in 2011, many versions and variants of electric springs have emerged and industrial evaluations have begun. This paper provides an update of existing electric spring topologies, their associated control methodologies, and studies from the device level to the power system level. Future trends of electric springs in large-scale infrastructures are also addressed.

This paper describes how a large-scale ice-thermal storage can be turned into a smart load for fast voltage control and demand-side management in power systems with intermittent renewable power, while maintaining its existing function of load shaving. The possibility of modifying a conventional thermal load has been practically demonstrated in a refrigerator using power electronics technology. With the help of an electric spring, the modified thermal load can reduce power imbalance in buildings while providing active and reactive power compensation for the power grid. Based on practical data, a building energy model incorporating a large-scale ice-thermal storage system has been successfully used to demonstrate the advantageous demand-response features using computer simulation of both grid connected and isolated power systems. The results indicate the potential of using ice-thermal storage in tall buildings in reducing voltage and frequency fluctuations in weak power grids.

Electric springs (ES) have been proposed as a demand-response technology for improving the stability and power quality of emerging power systems with high penetration of intermittent renewable energy sources (RES). Existing ES applications mainly involve the regulations of grid voltage and utility frequency. This paper reports a power control and balancing technique for a new integrated configuration of ES and photovoltaic (PV) system, and discusses its possible use to achieve dynamic supply-demand balance in power distribution networks. The proposed system enables delivery of maximally-harvested PV power to the grid via the ES, and concurrently controls the active power consumption of its ES-associated smart load so as to achieve supply-demand power balance of the overall system in real time. Importantly, battery storage is not necessary in the proposed design because the ES-associated smart-load power follows an appropriate consumption profile to compensate potential prediction errors of the PV power generation. Both simulation and experimental results are included to validate the proposed ES system.