Jae Woong Shim

Synergistic Control of SMES and Battery Energy Storage for Enabling Dispatchability of Renewable Energy Sources

The use of renewable energy source can reduce greenhouse gas emission and fossil fuel pollution. Compared with fossil fuel energy, renewable energy is not stable and cannot supply firm electrical output (i.e., it is nondispatchable). Fluctuating power from renewables may result in grid power oscillation. To reduce grid swing, energy storage is necessary to smooth output from renewable energy. Energy storage with high energy density and fast response time or high power capacity is desired for compensation of fluctuating output. Generally, superconducting magnetic energy storage (SMES) has higher power capacity than battery energy storage, while battery provides higher energy density. Thus, this research proposes a hybrid energy storage system (HESS) composed of an SMES and battery. Novel and practical synergistic control is presented for firming power fluctuation by exploiting the strong power and energy capabilities of the SMES and the battery while within the efficient operating range of (i.e., state of charges of) HESS. Comprehensive case studies demonstrate the efficacy of the proposed HESS topology and control algorithm using PSCAD/EMTDC.

Enhanced frequency regulation service using Hybrid Energy Storage System against increasing power-load variability

Increasing penetration of wind energy resource raises concerns about system frequency regulation because wind turbines lack in control capability necessary to provide regulation in compensating generation-load imbalance. Inherent variability on every time scale, in fact contributes to a need for more sophisticated regulation; existing load-following spinning reserves may be too slow or limited in responding to the imbalance. One feasible solution for enhancing regulation capability is the use of Hybrid Energy Storage System (HESS) as proposed in this paper. In this research, the HESS is designed to be composed of a Li-ion battery and supercapacitor (SC), exploiting their respective high energy and power capabilities to fully handle long-term and short-term changes. This paper demonstrates the effectiveness of HESS for frequency regulation in meeting the grid code while smoothing the net variability (load-wind) for an isolated power system modeled using an electromagnetic transient program.

Towards a Self-Healing Electric Grid With Superconducting Fault Current Controllers

Uncertainty and complexity due to expanded adoption of renewable energy resources, distributed energy resources as well as expanded electric transportation and dynamic demand response technologies in the power industry present significant challenges in grid operations. It is thus required to develop smart protection and control actions for ensuring highly reliable and healthy electric power infrastructure by increasing resiliency against component failures or natural disasters, i.e. self-healing ability. This paper, in particular focuses on the self-healing in the context of grid protection using smart superconducting fault current controller (Smart FCC). A systematic framework and technological requirements are presented for realizing the envisioned self-healing protection capability using Smart FCC while minimizing the electric loss near zero through superconducting coil. Illustrative examples, modeling and simulation studies demonstrate the validity and efficacy of the proposed framework and envisioned technology.

Design and Operation of Double SMES Coils for Variable Power System Through VSC-HVDC Connections

In this paper, a new topology incorporating double superconducting magnetic energy storage (SMES) coils is proposed, and control strategies for effectively delivering power to a grid via high-voltage direct current (HVDC) are developed. Power grids have become increasingly complex due to the use of renewable energy and dynamic loads. As such, it is important to design a power transmission system that satisfies power supply and demand requirements. HVDC is especially attractive for particular power transmission technologies, because the fast control characteristics of HVDC contribute to the stabilization of connected power grids. SMES has also received attention as a promising method to overcome the aforementioned issues. In the proposed scheme, one SMES coil in series with the dc line is specifically designed for use as a fault current limiter, while the other coil in parallel with the line is employed for energy storage. This study describes the effectiveness of combining these two schemes to mitigate the dynamic power fluctuation of generator and load, reinforcing controllability, and dependability of the power delivery. Case studies demonstrate the improved performance and robustness of voltage sourced converter-HVDC linked with double SMES coils for dc fault.

A Novel and Smart Design of Superconducting Fault Current Controller: Implementation and Verification for Various Fault Condition

By the advent of the Smart Grid and integration of distributed generators, electrical networks are facing uncountable challenges. The existing protection schemes that simply limit the fault current to the predetermined set values may not perform optimally, and even the existing protection coordination schemes fail and lead to catastrophic failures in the increasingly complex and unpredictable grid operation. This paper proposes a novel and smart design of fault current controller constituting a full-bridge thyristor rectifier embedding a superconducting coil. When a fault occurs and the resulting current through the superconducting coil exceeds a certain preset value based on the current operating conditions of the grid to maintain the grid integrity, the magnitude of the fault current is regulated to a desired value by automatic controlling of the thyristor. This research also implements a lab-scale Smart FCC with smart current control capability and demonstrates the desired functionality and efficacy of design by changing the fault conditions. This proposed Smart FCC design will make the Smart Power Grid capable of self-healing against current faults.

Assessment of Improved Power Quality Due to Fault Current Limiting HTS Cable

Fault current limiting high-temperature superconductor (FCL-HTS) cable not only provides effective power transmission, but also reduces the negative impact of fault current. As the demand grows rapidly, distributed generation (DG) is being implemented into the power grids. The integration of DG into the existing power grid causes an increase in short circuit current. In order to facilitate reliable planning and operation of future power systems, power system planners and operators will need to avoid the potential threat of increased fault current. The superconductor cable is considered as an enabling technology because it can raise power transmission capability and effectiveness with minimal loss. However, high fault current through the superconductor cable may seriously damage the power system. However, FCL-HTS cables can reduce the impact from unexpected high fault current. The FCL-HTS cable helps avoid interruption and voltage sag without harming existing coordination of protection devices. This study addresses the power quality issues for increased fault current that will be caused by the DG. We also analyze the response of FCL-HTS cable in perspective of power quality, when the fault occurs with DG.

Three control options for integrating wind power system using Hybrid Energy Storage System

This paper compares three control options of a Hybrid Energy Storage System (HESS) consisting of Li-ion battery and Super Capacitor (SC). The compared control options are the constant reference, first-order filter reference, and step average reference control. For the constant reference, HESS makes the fluctuating wind power a constant level. Both first-order filter reference and step average help smooth wind power fluctuation by mitigating the intermittence of wind power. Role allocating control assigns different roles to Li-ion and Super-capacitor, in order to make the most of their strength. The feasibility of these control options has been demonstrated with 10 MW wind power source, using PSCAD/EMTDC and MATLAB.

On the Reclose Operation of Superconducting Fault Current Controller for Smart Power Grid With Increasing DG

At present, the operation of protection coordination in a complex and uncertain power distribution system is satisfied through the use of a recloser and fuse. Due to the increased adoption of renewable energy resources, distributed energy resources as well as expanded electric transportation and dynamic demand response technologies in the power industry confront significant challenges during grid operations. As a result, protection coordination may be broken due to an increase in the current level in a power system. In general, once the protection is well coordinated by a fault current controller (FCC), the previously installed recloser on the existing power distribution system becomes useless because the FCC plays the role of the recloser. In this work, we propose an operating strategy of protection coordination for the FCC, which is capable of replacing the recloser in an environment where various types of distributed generation are introduced simultaneously due to the proliferating demand of renewable energy sources. Specifically, the suggested method based on PSCAD/EMTDC is investigated.