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Ratnesh Sharma worked at NEC Laboratories America, Inc.

Posts

Battery Degradation Temporal Modeling Using LSTM Networks

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Accurate modeling of battery capacity degradation is an important component for both battery manufacturers and energy management systems. In this paper, we develop a battery degradation model using deep learning algorithms. The model is trained with the real data collected from battery storage solutions installed and operated for behind-the-meter customers. In the dataset, battery operation data are recorded at a small scale (five minutes) and battery capacity is measured at every six months. In order to improve the training performance, we apply two preprocessing techniques, namely subsampling and feature extraction on operation data, and also interpolating between capacity measurements at times for which battery operation features are available. We integrate both cyclic and calendar aging processes in a unified framework by extracting the corresponding features from operation data. The proposed model uses LSTM units followed by a fully-connected network to process weekly battery operation features and predicts the capacity degradation. The experimental results show that our method can accurately predict the capacity fading and significantly outperforms baseline models including persistence and autoregressive (AR) models.

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Conditioning Neural Networks: A Case Study of Electrical Load Forecasting

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Machine learning tasks typically involve minimizing a loss function that measures the distance of the model output and the ground-truth. In some applications, in addition to the usual loss function, the output must also satisfy certain requirements for further processing. We call such requirements model conditioning. We investigate cases where the conditioner is not differentiable or cannot be expressed in closed form and, hence, cannot be directly included in the loss function of the machine learning model. We propose to replace the conditioner with a learned dummy model which is applied on the output of the main model. The entire model, composed of the main and dummy models, is trained end-to-end. Throughout training, the dummy model learns to approximate the conditioner and, thus, forces the main model to generate outputs that satisfy the specified requirements. We demonstrate our approach on a use-case of demand charge-aware electricity load forecasting. We show that jointly minimizing the error in forecast load and its demand charge threshold results in significant improvement to existing load forecast methods.

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Demand Charge and Response with Energy Storage

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Commercial and industry (C& I) customers incur two types of electricity charges on their bills: one for the amount of energy usage and another one for the maximum demand during certain billing periods. The second charge type is known as Demand Charge (DC), which could account for over half of a customers’ electricity bill. Those C& I customers often sign up for Demand Response (DR) programs to contribute to peak demand reduction as well as to receive incentives and rewards from participating in the programs. The critical factor of achieving both DR and DC reduction is to recognize the nature of these two types of problems and create an effective strategy that can handle them at the same time by which the benefits from DR incentives and DC reduction are maximized. This paper discusses the possible DR scenarios with DC reduction framework for C& I customers who use a Behind-the-Meter (BTM) energy storage and proposes a consistent real-time procedure of deciding battery’s charging and discharging set points to solve the problem of maximizing the rewards by conducting DRs as well as the savings by reducing DC costs.

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Battery Optimal Approach to Demand Charge Reduction in Behind-The-Meter Energy Management Systems

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Large monthly demand charge of commercial and industrial entities is a major problem for their economical business. Utilizing a battery by behind-the-meter Energy Management Systems (EMS) has been seen as a solution to demand charge reduction. In state-of-the-art approaches, the EMS maintains sufficient energy for the unexpected large demands and uses the battery to meet them. However, large amount of energy stored in the battery may increase the average battery State-of-Charge (SoC) and cause degradation in battery capacity. Therefore, the current approaches of demand charge reduction significantly shortens the battery lifetime which is not economical. In this paper, we propose a novel battery optimal approach to reduce the monthly demand charges. In our approach, load profile of the previous month is used by daily optimizations to shave daily power demands while considering the battery lifetime model. Evaluated daily demand thresholds and load profile are statistically analyzed to cluster different types of day. Hence, it helps the EMS to find the typical daily load profile and appropriate monthly demand threshold for the entity. The performance of our approach has been analyzed and compared to the state-of-the-arts by experimenting on multiple real-life load profiles and battery configurations. The results show significant reduction of 16% in annual average battery SoC that increases the battery lifetime from 4.1 to 5.6 years while achieving up to 13.4% demand charge reduction.

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Adaptive and Integared PV Output control with Battery Energy Storage

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An adaptive control system for battery integrated PV generation is designed to reduce the fluctuating in PV power production. The core component of the system is a four-layer power control system (PCS) for Battery Energy Storage (BES). BES responds to the power dispatch commands from PCS and charges/discharges to mitigate variations in PV power output. As a core part of the system, a novel PV power smoothing algorithm is proposed to reduce battery capacity requirements and reduce battery life losses by adaptively adjusting control parameter settings based on real-time system characteristics. Extensive simulation results based on real PV generation data have been presented to justify the effectiveness of the proposed approach and to show how several key parameters affect its performance.

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Optimal Sizing and Operation of Energy Storage for Demand Charge Management and PV Utilization

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This paper presents a method to determine optimal energy and power capacity of distributed Energy Storage Systems (ESS) in behind-the-meter applications to maximize local Photovoltaic (PV) utilization or minimize Demand Charge (DC) cost. The problem is solved as a multi-objective optimization model to obtain a set of Pareto optimal solutions for each scenario in each month. An approach is then presented to map the monthly Pareto fronts into a single yearly Pareto front. A cost benefit analysis has also been carried out to show the compromise between PV utilization, DC cost, and ESS cost.

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illiad: InteLLigent Invariant and Anomaly Detection in Cyber-Physical Systems

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Cyber-physical systems (CPSs) are today ubiquitous in urban environments. Such systems now serve as the backbone to numerous critical infrastructure applications, from smart grids to IoT installations. Scalable and seamless operation of such CPSs requires sophisticated tools for monitoring the time series progression of the system, dynamically tracking relationships, and issuing alerts about anomalies to operators. We present an online monitoring system (illiad) that models the state of the CPS as a function of its relationships between constituent components, using a combination of model-based and data-driven strategies. In addition to accurate inference for state estimation and anomaly tracking, illiad also exploits the underlying network structure of the CPS (wired or wireless) for state estimation purposes. We demonstrate the application of illiad to two diverse settings: a wireless sensor motes application and an IEEE 33-bus microgrid.

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