Energies

Research

15 pages, 5583 KiB

Open AccessArticle

The Development of Bi-LSTM Based on Fault Diagnosis Scheme in MVDC System

by Jae-Sung Lim, Haesong Cho, Dohoon Kwon and Junho Hong

Energies 2024, 17(18), 4689; https://doi.org/10.3390/en17184689 - 20 Sep 2024

Viewed by 762

Diagnosing faults is crucial for ensuring the safety and reliability of medium-voltage direct current (MVDC) systems. In this study, we propose a bidirectional long short-term memory (Bi-LSTM)-based fault diagnosis scheme for the accurate classification of faults occurring in MVDC systems. First, to ensure [...] Read more.

Diagnosing faults is crucial for ensuring the safety and reliability of medium-voltage direct current (MVDC) systems. In this study, we propose a bidirectional long short-term memory (Bi-LSTM)-based fault diagnosis scheme for the accurate classification of faults occurring in MVDC systems. First, to ensure stability in case a fault occurs, we modeled an MVDC system that included a resistor-based fault current limiter (R-FCL) and a direct current circuit breaker (DCCB). A discrete wavelet transform (DWT) extracted the transient voltages and currents measured using DC lines and AC grids in the frequency–time domain. Based on the digital signal normalized by the DWT, using the measurement data, the Bi-LSTM algorithm was used to classify and learn the types and locations of faults, such as DC line (PTP, P-PTG, and N-PTG) and internal inverter faults. The effectiveness of the proposed fault diagnosis scheme was validated through comparative analysis within the four-terminal MVDC system, demonstrating superior accuracy and a faster diagnosis time compared to those of the existing schemes that utilize other AI algorithms, such as the CNN and LSTM. According to the test results, the proposed fault diagnosis scheme detects MVDC faults and shows a high recognition accuracy of 97.7%. Additionally, when applying the Bi-LSTM-based fault diagnosis scheme, it was confirmed that not only the training diagnosis time (TraDT) but also the average diagnosis time (AvgDT) were 0.03 ms and 0.05 ms faster than LSTM and CNN, respectively. The results validate the superior fault clarification and fast diagnosis performance of the proposed scheme over those of the other methods. Full article

(This article belongs to the Special Issue Advances in Research and Practice of Smart Electric Power Systems)

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15 pages, 4345 KiB

Open AccessArticle

Policy Evaluation and Enhanced Operational Strategies for PV-Linked ESS in Korea: Practical Applications and Insights from Real-World Data

by Seungha Kim, Siyoung Lee and Sungsoo Kim

Energies 2024, 17(16), 3893; https://doi.org/10.3390/en17163893 - 7 Aug 2024

Viewed by 796

Abstract

With the intensification of the global commitment to renewable energy, South Korea’s rapid expansion in renewable capacity necessitates efficient operational strategies to address the inherent variability of these energy sources. Despite the implementation of policies aimed at integrating energy storage systems (ESS) with [...] Read more.

With the intensification of the global commitment to renewable energy, South Korea’s rapid expansion in renewable capacity necessitates efficient operational strategies to address the inherent variability of these energy sources. Despite the implementation of policies aimed at integrating energy storage systems (ESS) with renewable generation, such as providing additional renewable energy certificates (RECs), the measures undertaken remain relatively ineffective. Thus, this study evaluates the shortcomings of existing policies and proposes an innovative operational strategy tailored to Korea’s energy landscape. The strategy is implementable immediately using existing facilities, without requiring any new equipment, and facilitates profits of up to 12.45% greater compared with those generated using the original approach. Moreover, the results are nearly as effective as an ideal scenario wherein the PV generation and system marginal price are accurately known. Additionally, the decreased economic feasibility of ESS owing to the discontinuation of subsidies is highlighted and solutions are proposed to mitigate the problem. This underscores the urgent need for improved regulatory measures and enhanced operational strategies. The proposed approach highlights the potential to considerably reduce inefficiencies and operational costs, thereby contributing to more sustainable energy management practices within Korea. Full article

(This article belongs to the Special Issue Advances in Research and Practice of Smart Electric Power Systems)

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20 pages, 8590 KiB

Open AccessFeature PaperArticle

Evaluating Frequency Stability with a Generic Model for IBR Penetration and the Implementation of Grid-Forming Control Strategies

by Adji Prastiantono, Umar Fitra Ramadhan, Donghwi Kim, Don Hur and Minhan Yoon

Energies 2024, 17(11), 2779; https://doi.org/10.3390/en17112779 - 6 Jun 2024

Viewed by 1371

Abstract

In recent years, there has been a significant uptick in the integration of Inverter-Based Resources (IBRs) into the power grid, driven by the global shift toward renewable energy sources. The Western Electricity Coordinating Council (WECC) has developed standardized models for these inverters to [...] Read more.

In recent years, there has been a significant uptick in the integration of Inverter-Based Resources (IBRs) into the power grid, driven by the global shift toward renewable energy sources. The Western Electricity Coordinating Council (WECC) has developed standardized models for these inverters to facilitate their representation in system studies, playing a crucial role in evaluating IBRs, especially those modeled as grid-following inverters (GFLs). However, with the increasing prevalence of IBRs, the adjustment of grid interaction between grid-forming inverters (GFMs) and GFLs should be considered in terms of frequency stability assessment. This study investigates the optimization of synchronous generators and IBR operations in more detail. The IBR operation is evaluated with considerations for ratio and penetration. The findings suggest that with over 50% IBR penetration, GFL capacity should be reduced, and GFM capacity should be over 35% of IBR to maintain grid frequency stability. Moreover, this study also explains advanced prediction of frequency nadir, particularly the optimal ratio of WECC generic and GFM through the least squares method. Furthermore, the small-signal dynamic characteristics of WECC are studied at various gain values to investigate frequency droop control. Full article

(This article belongs to the Special Issue Advances in Research and Practice of Smart Electric Power Systems)

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14 pages, 1742 KiB

Open AccessArticle

Online Optimization of Vehicle-to-Grid Scheduling to Mitigate Battery Aging

by Qingguang Zhang, Mubasher Ikram and Kun Xu

Energies 2024, 17(7), 1681; https://doi.org/10.3390/en17071681 - 1 Apr 2024

Cited by 1 | Viewed by 1140

Abstract

The penetration of electric vehicles (EVs) in vehicle-to-grid (V2G) interaction can effectively assist the grid in achieving frequency regulation and peak load balancing. However, the customer perceives that participating in V2G services would result in the additional cycling of the battery and the [...] Read more.

The penetration of electric vehicles (EVs) in vehicle-to-grid (V2G) interaction can effectively assist the grid in achieving frequency regulation and peak load balancing. However, the customer perceives that participating in V2G services would result in the additional cycling of the battery and the accelerated aging of the EVs’ power battery, which has become a major obstacle to the widespread adoption of V2G services. Most existing methods require long-term cycling data and battery parameters to quantify battery aging, which is not suitable for the V2G scenario with large-scale and short-time intervals. Consequently, the real-time and accurate quantification of battery aging for optimization remains a challenge. This study proposes a charging scheduling method for EVs that can accurately and online quantify battery aging. Firstly, V2G scheduling is formulated as an optimization problem by defining an online sliding window to collect real-time vehicle information on the grid, enabling online optimization. Secondly, battery aging is more accurately quantified by proposing a novel amplitude-based rain-flow cycle counting (MRCC) method, which utilizes the charging information of the battery within a shorter time period. Lastly, an intelligent optimization algorithm is employed to optimize the charging and discharging power of EVs, aiming to minimize grid fluctuations and battery aging. The proposed method is validated using a V2G scenario with 50 EVs with randomly generated behaviors, and the results demonstrate that the proposed online scheduling method not only reduces the EFCC of the battery by 8.4%, but also achieves results close to global optimization. Full article

(This article belongs to the Special Issue Advances in Research and Practice of Smart Electric Power Systems)

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21 pages, 4189 KiB

Open AccessFeature PaperArticle

Integrated Active and Reactive Power Control Methods for Distributed Energy Resources in Distribution Systems for Enhancing Hosting Capacity

by Phi-Hai Trinh and Il-Yop Chung

Energies 2024, 17(7), 1642; https://doi.org/10.3390/en17071642 - 29 Mar 2024

Cited by 2 | Viewed by 1181

Abstract

Recently, there has been a significant increase in the integration of distributed energy resources (DERs) such as small-scale photovoltaic systems and wind turbines in power distribution systems. When the aggregated outputs of DERs are combined, excessive reverse current may occur in distribution lines, [...] Read more.

Recently, there has been a significant increase in the integration of distributed energy resources (DERs) such as small-scale photovoltaic systems and wind turbines in power distribution systems. When the aggregated outputs of DERs are combined, excessive reverse current may occur in distribution lines, leading to overvoltage issues and exceeding thermal limits of the distribution lines. To address these issues, it is necessary to limit the output of DERs to a certain level, which results in constraining the hosting capacity of DERs in the distribution system. In this paper, coordination control methodologies of DERs are developed and executed to mitigate the overvoltage and overcurrent induced by DERs, thereby increasing the hosting capacity for DERs of the distribution system. This paper proposes three coordinated approaches of active and reactive power control of DERs, namely Var Precedence, Watt Precedence, and Integrated Watt and Var Control. The Var and Watt Precedence prioritizes reactive power for voltage (Q–V) and active power for current (P–I) to address network congestion, thereby enhancing hosting capacity. Conversely, the Integrated Var and Watt Precedence propose a novel algorithm that combines four control indices (Q–V, P–V, Q–I, and P–I) to solve network problems while maximizing hosting capacity. The three proposed methods are based on the sensitivity analysis of voltage and current to the active and reactive power outputs at the DER installation locations on the distribution lines, aiming to minimize DER active power curtailment. Each sensitivity is derived from linearized power equations at the operating points of the distribution system. To minimize the computation burden of iterative computation, each proposed method decouples active and reactive power and proceeds with sequential control in its own unique way, iteratively determining the precise output control of distributed power sources to reduce linearization errors. The three proposed algorithms are verified via case studies, evaluating their performance compared to conventional approaches. The case studies exhibit superior control effectiveness of the proposed DER power control methods compared to conventional methods when issues such as overvoltage and overcurrent occur simultaneously in the distribution line so that the DER hosting capacity of the system can be improved. Full article

(This article belongs to the Special Issue Advances in Research and Practice of Smart Electric Power Systems)

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20 pages, 5454 KiB

Open AccessArticle

Optimal Trading Volume of Electricity and Capacity of Energy Storage System for Electric Vehicle Charging Station Integrated with Photovoltaic Generator

by Yong Woo Jeong, Kyung-Chang Lee, Chunghun Kim and Woo Young Choi

Energies 2024, 17(4), 936; https://doi.org/10.3390/en17040936 - 17 Feb 2024

Viewed by 1064

Abstract

As penetration of EVs in the transportation sector is increasing, the demand for the mandatory installation of charging infrastructure also is increasing. In addition, renewable energy and energy storage systems (ESSs) are being reviewed for use in electric vehicle charging stations (EVCSs). In [...] Read more.

As penetration of EVs in the transportation sector is increasing, the demand for the mandatory installation of charging infrastructure also is increasing. In addition, renewable energy and energy storage systems (ESSs) are being reviewed for use in electric vehicle charging stations (EVCSs). In this paper, we present an optimal electricity trading volume and an optimal installation capacity of ESSs to maximize the daily profit of the EVCSs equipped with solar power generation when the EVCSs are licensed to sell energy to the power supplier during a specific time period. By formulating and solving the optimization problem of the EVCSs, this paper analyzes validation results for the different useful lives of ESSs, the peak power of a PV generator, and weather conditions at the Yangjae Solar Station and the Suseo Station public parking lot, Seoul, Republic of Korea. Furthermore, this paper validates that the daily expected profit of EVCSs with the proposed method outperforms the profit of conventional EVCSs which do not utilize ESSs. Full article

(This article belongs to the Special Issue Advances in Research and Practice of Smart Electric Power Systems)

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17 pages, 3348 KiB

Open AccessArticle

Automatic Generation Control Ancillary Service Cost-Allocation Methods Based on Causer-Pays Principle in Electricity Market

by Sunkyo Kim, Pyeong-Ik Hwang and Jaewan Suh

Energies 2024, 17(1), 11; https://doi.org/10.3390/en17010011 - 19 Dec 2023

Cited by 2 | Viewed by 1429

Abstract

The electric power system is rapidly transforming to address the urgent need for decarbonization and combat climate change. Integration of renewable energy sources into the power grid is accelerating, creating new challenges such as intermittency and uncertainty. To address these challenges, this paper [...] Read more.

The electric power system is rapidly transforming to address the urgent need for decarbonization and combat climate change. Integration of renewable energy sources into the power grid is accelerating, creating new challenges such as intermittency and uncertainty. To address these challenges, this paper proposes a new design of automatic generation control (AGC) ancillary service cost allocation based on the causer-pays rule. The proposed design treats reserves as inventory and aims to minimize them by allocating costs among consumers based on the causative factors for AGC operation. Two cost-allocation methods based on the causer-pays principle are introduced. The first method distributes costs according to the changes in loads causing ancillary service operation, while the second method considers opportunity costs. The case study on the IEEE 39 Bus System demonstrates that the proposed methods incentivize consumers to minimize volatility, resulting in reduced reserve requirements for system operation. In particular, the opportunity cost-based approach encourages loads and variable renewable energy (VRE) to actively reduce volatility, resulting in more efficient power system operation. In conclusion, the novel AGC ancillary service cost allocation methods offer a promising strategy for minimizing spinning reserves, increasing the power system’s efficiency, and incentivizing consumers to actively participate in frequency regulation for a more sustainable and reliable electricity market. Full article

(This article belongs to the Special Issue Advances in Research and Practice of Smart Electric Power Systems)

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27 pages, 2011 KiB

Open AccessArticle

A Robust Optimization Model of Aggregated Resources Considering Serving Ratio for Providing Reserve Power in the Joint Electricity Market

by Seong-Hyeon Cha, Sun-Hyeok Kwak and Woong Ko

Energies 2023, 16(20), 7061; https://doi.org/10.3390/en16207061 - 12 Oct 2023

Cited by 1 | Viewed by 1078

Abstract

As the share of distributed generation increases, so do the opportunities for aggregators to participate in the electricity market. In particular, aggregators participating in both the day-ahead and real-time markets contribute to improving the reliability of the power system. In addition, aggregators seeking [...] Read more.

As the share of distributed generation increases, so do the opportunities for aggregators to participate in the electricity market. In particular, aggregators participating in both the day-ahead and real-time markets contribute to improving the reliability of the power system. In addition, aggregators seeking additional revenue can benefit from providing reserves in a joint electricity market environment. However, aggregated resources with uncertainty are limited because of the uncertain nature of both reserve provision and the amount of reserves they can provide. Therefore, this study proposes a robust optimization model for an aggregator to formulate a strategy for participation in the day-ahead markets and deploys energy control in the real-time operation. The serving ratio reflects the availability of the aggregator’s reserve participation. Both the deployed up/down power and renewable energy in the real-time operation are considered as uncertain parameters to reflect the uncertainty. In the case study, we analyze the profit-maximization strategy of an aggregator that owns renewable energy resources and energy-storage systems under the variation interval for uncertain parameters and the serving ratio. The bidding strategies vary by the variation interval and the serving ratio. Full article

(This article belongs to the Special Issue Advances in Research and Practice of Smart Electric Power Systems)

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