Network reduction algorithm for developing distribution feeders for real-time simulators

Nagarajan, Adarsh; Nelson, Austin; Prabakar, Kumaraguru; Hoke, Andy; Asano, Marc; Ueda, Reid; Nepal, Shaili

doi:10.1109/pesgm.2017.8273938

Cited by 19 publications

(25 citation statements)

References 9 publications

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“…This section describes the process involved in the model conversion from Synergi to OpenDSS. A brief description about the characteristics of the selected feeders is provided prior to details about the model conversion [6].…”

Section: Discussionmentioning

confidence: 99%

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Studies on the Effects of High Renewable Penetrations on Driving Point Impedance and Voltage Regulator Performance: National Renewable Energy Laboratory/Sacramento Municipal Utility District Load Tap Changer Driving Point Impedance Project

Nagarajan

Coddington

Brown

et al. 2018

Self Cite

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This project explored the role of controllers-load tap changers (LTCs) and line regulators-on distribution feeders with increased distributed energy resources (DERs). Distribution feeders are facing a steep increase in DER penetration from specific classes of devices, including photovoltaic (PV) generators, energy storage systems, and demand response. Line regulators and LTCs represent a subset of control devices on distribution feeders used to regulate voltage delivered to customer locations. These devices operate in discrete steps, with each step changing the tap rate by 0.625% (hence a 10% change requires 16 steps). Before DERs were introduced, power flow in a distribution feeder was unidirectional, i.e., from the substation to loads. Additionally, a predictable loading pattern that peaks in the afternoons or evenings and dips during nighttime made the operation of voltage regulators easier and understandable. However, with increased penetration of renewable generation on distribution feeders, including homeowners installing solar panels on rooftop and additional utility-scale or commercial PV installations, a paradigm shift is occurring in the operational expectations of voltage regulators and LTCs. It has become very common to expect reverse power flows to the substation as a result of increased PV penetration. Voltage regulators perform as desired when regulating from the source to the load and when regulating from a strong source (utility) to a weak source (distributed generation). (See the glossary for definitions of a strong source and weak source.) Even when the control is provisioned for reverse operation, it has been observed that tap-changing voltage regulators do not perform as desired in reverse when attempting regulation from the weak source to the strong source. The region of performance that is not as well understood is the regulation between sources that are approaching equal strength. As part of this study, we explored all three scenarios: regulator control from a strong source to a weak source (classic case), control from a weak source to a strong source (during reverse power flow), and control between equivalent sources. In this report, we reassess the topic of existing LTC and line-regulator controls and on a realworld distribution feeder with renewable penetration, and we explore their benefits and disadvantages. This study makes use of metrics such as driving point impedance (DPI), the effectiveness of tap change (tap-delta), reactive power flow, and transformer efficiency to evaluate the performance of LTCs/line regulators on distribution feeders with substantial DER penetrations. These metrics were carefully chosen because they unmask the shortcomings of existing LTC/line regulator control practices on feeders with high DER penetrations. The first chapter takes a deeper dive into the description of these metrics and the reasons we choose them. This project was executed in three sequential tasks to help the Sacramento Municipal Utility District (SMUD) understand the role of existing LTC/...

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Section: Discussionmentioning

confidence: 99%

“…Because the PLECS transient simulation engine, which will be used for the power hardware-inthe-loop experiments, cannot solve the entire network model of a few thousand nodes, a reducedorder model was developed [6].…”

Section: Discussionmentioning

confidence: 99%

Studies on the Effects of High Renewable Penetrations on Driving Point Impedance and Voltage Regulator Performance: National Renewable Energy Laboratory/Sacramento Municipal Utility District Load Tap Changer Driving Point Impedance Project

Nagarajan

Coddington

Brown

et al. 2018

Self Cite

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“…The required new monitoring and control functionalities make available a very large amount of information [2], [3]; not all this information needs a detailed consideration, and a significant reduction in the related treatment burden can be achieved by considering only the strictly relevant one [4]. The need for a reduced representation of distribution grids is found also in real-time simulations useful to utilities to understand the operational behavior of physical devices without interfering with the actual grid [5].…”

Section: Introductionmentioning

confidence: 99%

“…In [4], unbalanced laterals are reduced to the three-phase main feeders, while in this study the reduction is not focused on feeders, whose representation can be further compacted, and unbalanced busses can be retained as representative busses if needed. Reference [5] proposes a Montecarlo approach to reduce the grid, while our approach is non-iterative thanks to the eigenvalue sensitivities [9], [10] the LA approach is based upon. Reference [11] proposes a general network reduction method that groups nodes based on congestions only, while the current study also considers voltage issues and is specialized for unbalanced radial distribution systems.…”

Section: Introductionmentioning

confidence: 99%

Reduced Modeling of Unbalanced Radial Distribution Grids in Load Area Framework

Casolino

Losi

2020

IEEE Access

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A simplified representation of a distribution network offers relevant advantages in limiting the amount of information processed and reducing the computational burden necessary for its treatment, in particular in planning studies, real-time simulations, monitoring and control. The identification of the relevant information for obtaining a correct reduced modeling of a distribution network results from the Load Area (LA) approach. It is based on the concept of groups of nodes/prosumers whose power injection has a similar impact on the operating conditions of distribution grids; the groups are identified through overload and voltage indexes. The paper presents a method for obtaining the reduced equivalent modeling of unbalanced radial grids in the LA framework, once the LAs have been identified. It is based on the backward-forward graph navigation technique for radial grids and a generalization of the modeling of singlephase and two-phase branches. The application and discussion of the method for five different size test cases highlight the computational issues related to the representation and solution of the reduced networks. The results show the feasibility of the proposed method and highlight the computational gains deriving from its adoption.

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“…In [5], a reduction method for real-time simulation of distribution grids is proposed. It eliminates all nodes that are not in a keep list, that are not topological nodes, nor have capacitors or regulators connected to it.…”

Section: Introductionmentioning

confidence: 99%

An Alternative Proposal for Quantification of Technical Losses Using a Reduced Equivalent Circuit

Brasil

Augusto

Filho

et al. 2020

Anais Do Simpósio Brasileiro De Sistemas Elétricos 2020

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Electrical grid technical losses affects the electricity tariff and the planning of new lines. Nonetheless, their assessment by means of time-series or real-time simulations is computationally burdensome for large grids. In order to achieve simplified equivalent circuits, reduction techniques have been developed. The only one that is applicable for unbalanced grids is the multiphase reduction, but it does not preserve the losses. This paper proposes an algorithm that allows indirect evaluation of total losses, thus extending the multiphase reduction technique. In the validation process, IEEE 34-bus and a Brazilian real feeder are evaluated. A daily time-series simulation, with hourly loadshapes, is performed in OpenDSS. Using this novel method, the losses errors obtained are lower than 2%. The proposed algorithm, therefore, may be applied to speed up the definition of electricity tariff and the planning process of unbalanced grids.

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Network reduction algorithm for developing distribution feeders for real-time simulators

Cited by 19 publications

References 9 publications

Studies on the Effects of High Renewable Penetrations on Driving Point Impedance and Voltage Regulator Performance: National Renewable Energy Laboratory/Sacramento Municipal Utility District Load Tap Changer Driving Point Impedance Project

Studies on the Effects of High Renewable Penetrations on Driving Point Impedance and Voltage Regulator Performance: National Renewable Energy Laboratory/Sacramento Municipal Utility District Load Tap Changer Driving Point Impedance Project

Reduced Modeling of Unbalanced Radial Distribution Grids in Load Area Framework

An Alternative Proposal for Quantification of Technical Losses Using a Reduced Equivalent Circuit

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