Technical Presentations

Evaluation of 3rd Order Harmonics in Microgrids894

Abstract
The implementation of distributed generation sources with islanding microgrid capabilities can introduce new challenges for engineers integrating new large generators to existing power systems. The ge... see morenerator interconnection transformer winding configuration and the generator winding pitch greatly impacts the flow of circulating currents and can result in unexpected generator heating, as well as high grounding resistor operating temperatures. This presentation presents a case study of the flow of 3rd order harmonic currents in a microgrid power system, and how EMTP was used to design equipment modifications necessary to reduce the current. A review of generators and how they can lead to 3rd order harmonic current generatio, along with additional options for correcting this condition will be presented.

Tag(s): Distributed Generation, Harmonic Currents, EMTP Simulations

Time-Domain Protection Scheme for Microgrids with Aggregated Inverter-Based Distributed Energy Resources897

Abstract
This paper proposes a time-domain-based protection scheme for radial and loop microgrid systems with inverter-based resources (IBRs), such as solar photovoltaic (PV) systems and type-4 wind turbines. ... see moreThe protection scheme is designed to function during both grid-interconnected and grid-isolated modes. The proposed scheme provides an ultra-high-speed sub-cycle directional element aided with low bandwidth communication between relays. Like directional comparison schemes, relays identify whether faults are in-zone or out-zone. The directional element is based on time-domain superimposed quantities and Park`s transformation algorithms. Specifically, the element calculates the superimposed positive-sequence direct component of transient energy during faults. Superimposed voltage and current quantities are calculated using delta filters and decoupled double synchronous reference frame (DDSRF) filters. The proposed filtering method improves the reliability of the superimposed directional element when IBRs are the main source of fault current. The protection scheme is evaluated on a modified IEEE 34-bus distribution system simulated using an electromagnetic transients program (EMTP).

Tag(s): Microgrid, Protection Scheme, Inverter-Based Resources (IBRs)

Data driven and machine learning based approach for microgrid protection using EMTP873

Abstract
Modern intelligent digital relays embedded with phasor measurement units have facilitated easy access and collection of electrical signals in a microgrid. ? In this work, a model for detection, locati... see moreon and isolation of faults in AC microgrids is presented. The real time voltage, frequency and current data are processed via simple formulations to detect the fault. The tripping command is promptly communicated to the incumbent line relays within fault tolerance time, after fault detection. The proposed scheme assures reliable protection in grid connected and islanded mode of operation with added security in case of primary protection failure. Post tripping, the exact location of fault in any distribution line from the utility grid is predicted using a fault locator module. This module is designed and developed by gaussian process regression technique. Further, various machine learning techniques used for fault location has been explored and compared to establish the superiority of GPR method over others. Also the features extracted for model training is quite simpler, which imposes less computational burden on central protection computer. An IEEE 15 bus distribution system with synchronous and solar photovoltaic based DG is simulated in EMTP platform to generate the electrical data. Further the required calculations are performed in MATLAB 2020a.

Tag(s): Machine Learning, Protection Schemes, Fault Detection, Fault Isolation, Real-Time Implementation

Frequency and Voltage Data Processing789

Abstract
The complexity of an active distribution system with distributed generation (DG) is increasing day-by-day. Therefore, a reliable protection system is very necessary to satisfy customer demand. Apart f... see morerom main grid supply, active sources are also available near load centers due to which traditional protection schemes fails to function properly.

The magnitude of fault current during grid connected mode of microgrid, is much higher than islanded operation. Therefore, in most of the previous works, overcurrent protection crashes if its pickup current value is not changed when microgrid is shifted to islanded mode. In this work, the current, voltage and frequency data sampled through PMU is processed to protect the system in both the operating modes. A centralized protection scheme is employed that takes frequency data and voltage phasor to differentiate between islanding and fault condition. Further, it detects the faulted feeder and sends trip command to respective relays within a tolerant time.

This method is devised to work as backup protection when main utility grid is available. However, it can work as a primary protection during islanded mode, when local overcurrent relay fails to operate due to settings based on grid connected mode. A standard IEEE 15 bus system modeled in EMTP is taken as test system for every analysis.