Krishnanjan Gubba Ravikumar

Synchrophasor-based power system protection and control applications

Synchrophasor data consist of analog and digital values with an associated precise time stamp. With precise time, these quantities are collected from various locations, time-aligned, and then processed as a coherent data set. Synchrophasors have generally been used for visualization and post-event analysis. However, new technologies allow synchrophasors to be processed in real time. Synchrophasor systems are now being used for realtime wide-area protection and control. This paper examines several ways synchrophasors are being used: · Voltage stability detection and correction · Load/generator shedding · Islanding control · Intermittent generation source control and grid interconnection Each application includes a discussion of how synchrophasors provided a unique solution and benefit over traditional solutions. Application performance, speed, data requirements, and equipment are also reviewed. We also discuss a future time-synchronized control solution.

Solar generation control with time-synchronized phasors

Solar-energy-based photovoltaic (PV) systems are a quickly growing source of distributed generation (DG) and connect to the power distribution system. PV-based DG poses challenges to grid reliability and power quality. One critical challenge is islanding control. Research is underway to devise best practice methods for anti-islanding for all power mismatch conditions. Synchrophasors provide an accurate means to detect islanding conditions by enabling precise, time-synchronized wide-area measurements. This paper presents an islanding detection system for PV-based DG. The system utilizes synchrophasor data collected from local and remote locations to detect the islanded condition. The paper shows how synchrophasors are used to control the DG during such conditions. It also discusses the power system modeling using a Real Time Digital Simulator (RTDS®) and closed-loop testing of the synchrophasor-based islanding detection system, which includes the PV-based inverter and the power distribution system. The effectiveness of the system was experimentally tested on a live power system.

Interconnection control of distributed generation with time-synchronized phasors

Distributed generation (DG), such as solar-energy-based photovoltaic (PV) systems, wind generation, and other renewable resources, is a quickly growing source of energy for todays power system. These assets pose challenges to grid reliability and power quality. One critical challenge is islanding (inadvertent system separation) detection, separation, and eventual resynchronizing. Research is underway to devise best practice methods for appropriate islanding control for all load and generation conditions. Wide-area measurements such as synchrophasors provide an accurate means to detect islanding conditions by enabling precise time-synchronized measurements at diverse locations. This paper presents a real-time islanding detection system for PV-based generation that is representative of many types of DG. The system utilizes synchrophasor data collected at the PV location and elsewhere in the system to detect the islanded condition. The paper shows how synchrophasors are used to isolate the DG during such conditions. It also discusses the real-time modeling and closed-loop testing of the synchrophasor-based islanding detection system, which includes the PV-based inverter and the power distribution system. The effectiveness of the system was experimentally tested on a live power system. An evaluation is also presented for using synchrophasors to resynchronize the islanded system.

Distributed simulation of power systems using real-time digital simulator

The simulation of power system behavior, especially transient behavior, helps in the analysis and planning of various power systems phenomenon. However, power systems are usually highly complex and distributed, thus system partitioning has to be used to allow for sharing resources in simulation. At Mississippi State University, researchers are developing distributed simulations of power system models using an electromagnetic transient simulator, namely RTDS. The goal is to demonstrate and assess the feasibility of both non-real-time and real-time simulations using the RTDS in a geographically distributed scenario. RTDS has the capability of sending and receiving digital data in a local area network using a special interface known as GTNET. In this work the RTDS is used in a wide area network for sending and receiving data. The different protocols and options used in the RTDS communication between power system models will be studied and analyzed.

A statistically-based method of control of distributed photovoltaics using synchrophasors

Despite many years of effort in the distributed energy resources (DER) industry, there remains a need for an islanding detection method that a) facilitates, rather than conflicts with, DER participation in grid support functions; b) does not degrade power quality; and c) reliably detects a loss of mains without nuisance trips. This paper describes a method that can meet this challenge. The method is a communications-based method that uses statistical analysis on synchrophasor data measured in two locations, an upstream reference point and at the DER bus. Simulation results, and laboratory and field test results are presented for one very simple implementation of the method. It is shown that the method works very well, even in its simplest form.

Real Time Modeling and Control of Smart Grid Systems

The real time modeling and simulation of smart grid behavior under the disturbance helps in the analysis and planning of system in order to minimize the possible damage. Real time modeling and simulations with hardware in the loop capabilities allows testing the smart grid control algorithms and new equipments.

Analysis of fault-induced delayed voltage recovery using EMTP simulations

This paper focuses on testing the dynamic behavior of single-phase air conditioner motors on distribution power networks. The primary goal is to study the phenomenon of delayed voltage recovery by applying multiple instances of a custom-built single-phase induction motor model on a given distribution feeder. This model was developed in an Electromagnetic Transients Program (EMTP) simulation environment. The motors were subjected to voltage disturbances seen in feeders experiencing the fault-induced delayed voltage recovery (FIDVR) phenomenon. To study the FIDVR phenomenon, a range of voltage depressions were simulated for predetermined system conditions. This paper describes a point-on-wave model development and simulation study that supports a broader investigation of the effect of air conditioning and similar loads on the recovery of electric utility voltage after faults.