In this paper, a deep reinforcement learning (DRL)-based electric vehicles (EVs) management strategy is proposed to achieve peak shaving and regulate the voltage violations in distribution networks. ...We present a new approach for modeling the EV user willingness considering the effect of multi-attribute attitudes and price incentives on user' behaviors. The real-time optimal regulation problem is modeled as a bi-level optimization and then formulated as a constrained Markov decision process. To solve the problem, we first define an EV energy availability criterion for K-means clustering method to assess the EV scheduling potential for hierarchical dispatching, which facilitates meeting the user charging demand constraint. Then we present a bi-level safe soft actor critic algorithm with optimal convergence guarantee to solve the optimal sequential gaming problem between distribution system operator and charging stations aggregator. For each constraint, we employ individual neural networks to compute the cost Q-function and update independent Lagrange multiplier, which contributes to the setting of expected cost thresholds for practical application. In addition, we develop a data-enhanced method using Gaussian mixture model with a two-stage training process to improve the data efficiency and model robustness, as well as avoiding the constraint violations in the start-up process. Test results on the modified IEEE 33-bus and 118-bus systems with the real-world data are presented to validate the effectiveness of the proposed approach.
This paper presents a measurement-based method to calculate distribution locational marginal prices (DLMPs) toward establishing real-time electricity markets that help to support reliable and ...efficient operation of distribution systems. The calculation of DLMPs typically relies on an accurate and up-to-date distribution network model, but this may not be available in practice. Instead, central to the proposed method is the online estimation of linear sensitivity models that map bus voltages to power injections and to line power flows using only synchrophasor measurements collected at buses interfacing market participants and in lines of interest. The estimated linear models replace the nonlinear power flow constraints in a multi-period look-ahead optimal power flow (OPF) problem, thus obviating the need for an offline distribution network model in obtaining DLMPs as the optimal Lagrange multipliers of the linear sensitivity constraints. Moreover, the modified OPF problem with linear constraints is a convex quadratic programming problem, for which computationally efficient solvers are readily available. The resulting DLMPs also embed costs due to potential congestion in certain lines monitored by synchrophasor measurements. Numerical simulations demonstrate the effectiveness, adaptability, and scalability of the proposed measurement-based method to establish a real-time market for distributed generation, energy storage devices, and flexible loads.
To solve the problem of difficult location (especially high grounding resistances) for single‐phase grounding faults in distribution networks, a fault location method based on equivalent admittance ...distortion rate is proposed in this paper. The equivalent admittance distortion rates are first obtained by measuring the pre‐fault and post‐fault equivalent admittances of each phase, each feeder and each section. Then the phase with the largest equivalent admittance distortion rate in each phase is determined as the fault phase, the feeder with the largest equivalent admittance distortion rate in each feeder is determined as the fault feeder, and the section with the largest equivalent admittance distortion rate in each section is determined as the fault section. Moreover, a fault identification strategy for single‐phase grounding faults is proposed to improve the robustness of this method. By measuring bus voltages and currents before and after faults, the fault type with only one‐phase in which voltage decreased and current increased is identified as single‐phase grounding faults. Compared with the existing methods, simulation results show that the proposed method is simple to implement and has strong robustness to high grounding resistances, long grounding distances and interference harmonics.
Increasing penetration of photovoltaic (PV), as well as increasing peak load demand, has resulted in poor voltage profile for some residential distribution networks. This paper proposes coordinated ...use of PV and battery energy storage (BES) to address voltage rise and/or dip problems. The reactive capability of PV inverter combined with droop-based BES system is evaluated for rural and urban scenarios (having different \mbi R/X ratios). Results show that reactive compensation from PV inverters alone is sufficient to maintain acceptable voltage profile in an urban scenario (low-resistance feeder), whereas coordinated PV and BES support is required for the rural scenario (high-resistance feeder). Constant, as well as variable, droop-based BES schemes are analyzed. The required BES sizing and associated cost to maintain the acceptable voltage profile under both schemes are presented. Uncertainties in PV generation and load are considered, with probabilistic estimation of PV generation and randomness in load modeled to characterize the effective utilization of BES. Actual PV generation data and distribution system network data are used to verify the efficacy of the proposed method.
In this study, a three-phase power flow solution method using graph theory, injection current, and sparse matrix techniques for large-scale unbalanced distribution networks is proposed. In the bus ...frame of reference, a direct iterative method is adopted. To integrate the electric characteristics of transformers and step voltage regulators into the proposed method, the existing component models are modified by equivalent injected currents. To validate the performance and effectiveness of the proposed method, four three-phase IEEE test systems and random test systems are used for comparison purposes. As the size of the network increases, the proposed direct ZBUS method drastically shows its superiority over the other methods. The results reveal that the proposed method has good potential for improving the computational efficiency of optimal planning and design as well as real-time power dispatch applications in large-scale distribution systems.
•Bibliometric analysis and systematic literature review for resilience of water distribution networks between 2000 and 2021.•Specifying and visualizing influential authors, publications, and citation ...patterns.•Identification of scientific collaboration, thematic clusters, and current trends.•Analysing resilience metrics, dimensions, and capacities of water distribution networks.•Discussion of limitations, challenges, and future directions.
Infrastructure resilience is quite an emerging topic that has captured tremendous interest among researchers and practitioners. Resilience of water distribution networks (WDNs) established itself as one of the most promising and growing hotspots in the realm of sustainable management against extreme hazards. This study aims to delve into the manifestation, genesis, progression, and gaps of the resilience research related to WDNs. The study comprises a meticulous quantitative and qualitative delineation of 184 articles between 2000 and 2021 utilizing a combination of bibliometric analysis and systematic review. Network analysis (co-word, co-citation, co-author, and clustering) was employed to determine and visualize the prominent topics, influential publications, citation patterns, and productive authors and countries along with their interconnections. Subsequently, text mining tools and critical content analysis were adopted to explore extant research characteristics and gaps. Three thematic clusters were identified 1) hydraulic simulation for resilience assessment, 2) surrogate measures and comparative studies, and 3) connectivity and topological metrics. A bias in the research literature towards classical resilience assessment overlooking organizational, adaptive, and interdependency aspects was reported. The in-depth understanding provided in this study is expected to unlock new research and investment opportunities in the domain of WDNs resilience.
Reliability improvement is a fundamental issue in electric distribution network (EDN) operation. In this regard, providing the most efficient maintenance policy can dramatically assist the electric ...utility companies in reducing the failure rate of EDN components. In the present study, a novel probabilistic reliability‐centred maintenance (RCM) approach is proposed in which the reliability level of the EDN components are evaluated according to the three‐state Markov model (MM). Using the MM, this study presents a trade‐off between the corrective maintenance and the preventive maintenance (PM) actions and finally determines the precedence of EDN components in PM financial resource allocation. Through the method presented in this study, the financial resources of the PM are economically allocated with regards to economic parameters such as customer outage costs and budget constraints. The efficacy of the proposed RCM approach is evaluated through the implementation of the RCM approach on bus number four of the well‐known Roy Billinton test system.
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