How AECOM Uses ETAP Modeling and Analysis of a Microgrid for a Wastewater Treatment Plant

Power system modelling is just a representation of the power system electrical network in the form of a simulation model. Power system analysis is the calculation and simulation to verify that the electrical system, including its components, is correctly specified to perform and operate as intended. It should protect itself well in case of disturbances and short circuit faults.
By Abinet Tesfaye Eseye, Microgrid Power Systems Lead, AECOM

This case study presents ETAP-based power system studies of a microgrid designed for a mission-critical wastewater treatment plant (WWTP) facility. Engineering and operation objectives of mission-critical facilities require a reliable and secure power supply system. Microgrids are the leading technological solution for a resilient and sustainable electricity supply for critical infrastructures. The microgrid consists of a behind-the-meter (BTM) solar photovoltaic (PV) system, a battery energy storage system (BESS), a combined heat and power (CHP) generator, and standby diesel generators. Several scenarios were created based on different loading conditions and power source combinations, which are utilized to validate the power system studies in grid-connected and islanded modes. We will discuss the model of the power system investigated, operational strategy, and sequences of operation, findings, challenges, lessons learned, and future works.

AECOM is an American multinational infrastructure consulting firm headquartered in Dallas, Texas. Across the globe, their teams push the limits of what’s possible and build legacies for generations to come – the world’s longest cable-stayed bridge, record-breaking sports events, the largest greenfield port development mega project, life-sustaining disaster recovery programs, and the tallest tower in the Western Hemisphere. By harnessing the power of digital technology and the innovation of their technical experts worldwide, they deliver tailored solutions and transformative outcomes for their clients and the communities they serve. AECOM has more than 50,000 employees.

Location: Dallas, Texas, United States

Year: 2022

To create a microgrid model for emission critical facility and to provide calculations and validations of the power system

Challenges

  • To ensure and confirm the resiliency of the microgrid designed for a mission-critical facility: wastewater treatment Plant.
  • To create a flexible electric power system model with all electrical equipment like transformers, circuit breakers, buses, lines, motors, distributed energy sources, especially renewable energy sources. The model should include heat and power generators, diesel generators, a battery energy storage system, and behind-the-meter solar sources. 
  • To find modeling software that enables simulation of grid-connected mode, islanded mode, black start, and transitions between different modes of operation on a single central line diagram.
  • To create relevant scenarios for the designed electrical network, enabling power load flow and short circuit analyses in many sequences of connection.
  • To provide analyses according to the customer's needs and confirm the system's stability.

Which solutions did they choose?

Selected applications

They chose ETAP Digital-Twin version 20.6 for modeling the microgrid and performing power system studies. ETAP iSLD, an intelligent electrical single-line diagram, was the base of a multi-layered one-line view of the digital twin they used.

They use ETAP Predictive Simulation Software for simulation, which allows the prediction of system behavior in response to events or operator actions and Unbalanced Network Short Circuits for calculations. 

Why do they use ETAP?

Main Customer Benefits

  • The Electrical Network model was created using ETAP Digital Modeling with the iSLD solution. The microgrid model, which is a One-Line Diagram, consists of two utilities connections, the buses, three batteries (PV1, PV2, PV3), six switchgear, four fuses, four transformers, thirteen circuit breakers, two diesel generators, one battery storage system, one cogeneration source (CHP), and other equipment symbols needed to reflect the analyzed situations. 
  • The transition logical model was created according to the IEEE 1547 standard for Distributed Energy Resources Interconnection and Interoperability with the Electricity Grid.
  • The Strategy and Sequence of Operations were created to understand and analyze transitions such as steady state connected and islanded, unplanned and planned islanding, black start, and reconnection.
  • To perform power system studies, consultants have considered several scenarios created in ETAP based on different loading conditions and power source combinations. They established nine scenarios, five in grid-connected operation mode and four in islanded operation mode.
  • Simulation results showed that the tap position adjustments of the SCE-1-side tie transformer T12 are required to maintain the bus voltages within 5% of the nominal voltage. It was found thanks to scenario number one. The same situation was found thanks to simulation, according to scenario nine. The information was provided to the customer.
  • Scenario two (Grid-connected mode with PV, CHP, and Bess) showed problems with generating reactive power. Scenario 6 (Islanded mode with PV, CHP, and Bess without utility grid) showed that islanded work is possible enough to power the system.
  • Short circuit studies were performed for the symmetrical three-phase current to determine the short circuit interrupting capacity of the protection devices, such as circuit breakers and fuses, and the short circuit withstand capability of the switchgears and the motor control centers.
  • The study results were provided in relevant tables, using data and colors to show that the analyzed electrical system would work well and that the design is acceptable.
  • The main benefit is the conclusion that the electrical network of the surveyed company can operate with and without the utility grid and serve the maximum load for grid-connected and islanded modes.

What do they think about ETAP?

Opinions

We modelled this microgrid by leveraging ETAP version 20.6 and performed power system studies for both grid-connected and islanded operation modes. So, in the next power system study results, we'll show the results for all these scenarios based on the ETAP analysis and modelling.
By Abinet Tesfaye Eseye, Microgrid Power Systems Lead, AECOM

So, based on this analysis, we observed that ETAP is a useful tool to model and analyze microgrid steady and transient/dynamic behaviors. There are still a lot of capabilities in the ETAP to explore to perform several microgrid studies. So of course, we have conducted a number of power system studies, but for this presentation, two major studies, load flow and short circuit are presented.
By Abinet Tesfaye Eseye, Microgrid Power Systems Lead, AECOM


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Modeling and Analysis of a Microgrid for a Wastewater Treatment Plant - AECOM

Engineering and operation objectives of mission-critical facilities require a reliable and secure power supply system. Microgrids have become the leading technological solution for a resilient and sustainable supply of electricity for critical infrastructures. This paper presents ETAP-based power system studies of a microgrid designed for a mission-critical facility, a wastewater treatment plant (WWTP). The microgrid consists of a behind-the-meter (BTM) solar photovoltaic (PV) system, a battery energy storage system (BESS), a combined heat and power (CHP) generator, and standby diesel generators. We modeled this microgrid by leveraging the ETAP software and performed power system studies for both grid-connected and islanded modes of operation. Several scenarios were created based on different loading conditions and power source combinations, which are utilized to validate the power system studies. We will discuss the model of the power system investigated, operational strategy and sequences of operation, findings, challenges, lessons learned, and future works.


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