Reynaldo Nuqui

AC Grid with Embedded VSC-HVDC for Secure and Efficient Power Delivery

Increased bulk power transactions in competitive energy markets together with large scale integration of renewable energy sources are posing challenges to high-voltage transmission systems. Environmental constraints and energy efficiency requirements also have significant effects on future transmission infrastructure development. This paper reviews the recent development in HVDC technologies and discusses the needs of the hybrid AC/DC grid structure for future power systems with focus on VSC-HVDC applications in meshed AC grid. It has also been recognized that hybrid AC/DC transmission system together with the wide area measurement system (WAMS) could effectively manage the overall power grid operation security and efficiency under uncertain supply and demand conditions.

Eastern Interconnection model reduction based on phasor measurements

This paper presents a procedure for constructing the dynamic equivalent of large power system based on the Frequency Monitoring Network (FNET) measurements. It consists of determination of coherent regions, generator and load aggregation, and network reduction. The coherent regions are determined from FNET voltage angle responses using a divisive hierarchical k-means clustering algorithm. Generator and load aggregation based on the detailed model is performed. This procedure is applied to the US Eastern Interconnection (EI) system by building its dynamic equivalent model in PSS/E. Preliminary simulation results are provided. The dynamic equivalent of the EI system can be further developed for possible use as a decision aid for system operators.

The impact of optical current and voltage sensors on phasor measurements and applications

The increased penetration of phasor measurements units (PMUs) in electric power grids have put to forefront issues related to quality of phasor data. Phasor measurements, because of their perceived inherent accuracies, are oftentimes used to benchmark the results of critical system monitoring functions such as state estimators. However, instrument transformers significantly impact the final accuracies of phasor data. This paper will quantify the impact of optical current and voltage sensors on the accuracies of phasor data and wide area control. By comparing these results with those of traditional instrument transformer we demonstrate the benefits of using optical measurement units to better the performance of PMUs and their wide area applications.

A Wide-Area Loss-Index based method for voltage instability protection

This paper discusses a novel method for protection of a bulk power system against voltage instability. In the discussed approach, a region of interest is defined and the system is protected against voltage collapse using synchronized wide-area power-flow measurements. As will be explained, synchronized measurements of Intelligent Electronic Devices can be used for creation of a Wide-Area Loss-Index which shows proximity of a system to voltage collapse. It will be shown that the required measurements for protection of a system need to be taken from critical points, including bulk generations and loads inside a region of interest, as well as its borders.