SYNCHROPHASOR DEVELOPMENT OF A NEW ALGORITHM FOR VOLTAGE STABILITY ASSESSMENT
ABSTRACT
Increased demand for electricity has forced utility transmission systems to operate under stressed conditions that are close to breaking point.
Operating power systems under such conditions, combined with insufficient reactive power reserves, sets off a chain of voltage instability points that can eventually lead to system voltage collapse. Significant research has been focused on time-synchronized measurements of power systems, which can be used to determine the state of a power system on a regular basis and can lead to more robust protection, control, and operational performance.
This thesis examines the suitability of two voltage stability synchrophasor-based indices from the literature for analyzing power system stability. Using Power World Simulator, various load flow scenarios were tested on the BPA 10-Bus and IEEE 39-Bus systems.
The two indices were analyzed and compared to one another, as well as to other well-known methods. The results show that their performances are coherent in terms of system voltage stability; the indices can also predict voltage collapse and provide insight into other locations within the system that can contribute to instability.
Chapter One
1.1 Introduction
Because of recent increases in demand for electricity, utility transmission systems have been forced to operate under stressful conditions, frequently close to the limits of instability. Economic and environmental constraints limit efforts to build new transmission lines or expand networks.
According to the US Department of Energy, since 1982, annual growth in peak demand for electricity has outpaced annual transmission growth by nearly 25%. Increased bulk power across interconnected systems has resulted from the deregulation of the electricity market.
The amount of transactions previously purchased in a year is now managed in one day by some utilities. Operating power systems under such conditions, combined with insufficient reactive power reserves, sets off a chain of voltage instability points that can eventually lead to system voltage collapse.
Special emphasis is being placed on developing methods for assessing voltage stability in real time as well as strategies for mitigating instability issues once they have been identified. Synchronized phasor measurement technology, which is already available at most substation locations via protection relays, is capable of directly measuring power system variables (voltage and current phasors) in real time, to within a millisecond.
With advancements in high-speed communication infrastructure, it is now possible to construct wide-area measurement and protection systems to supplement traditional protection, applications, and to prevent cascading system level outages.
With this new direction in wide area measurement systems, new approaches for wide area protection and control functions, such as generating voltage collapse prevention indices, have emerged. Many studies on voltage stability indices have been conducted, including those based on phasor measurements. Some comparisons between these various indices can be found as we progress through this work.
1.2 Statement Of the problem
The primary goal of this seminar is to create a novel algorithm for assessing voltage stability using synchrophasor data. The analysis will consider voltage collapse proximity: “How close is the system to voltage instability?” and voltage instability mechanism: “What are the voltage-weak areas?”
In light of these concerns, the seminar will begin with a discussion of traditional and newer voltage stability methods presented in Chapter 2. Following that, an analysis and comparison of two indices based on synchrophasor data using static analysis will be conducted and discussed.
To demonstrate the use of indices in voltage stability analysis, various cases will be created, such as increasing system load/generation and/or N-1 contingency. The results will show their overall effectiveness in solving the voltage stability problem.
An application of these analyses is then briefly discussed in an investigation into the impact of wind generation on voltage stability, taking into account wind generation’s intermittent nature and penetration level. The investigated indices will be used in a scenario in which a simulated wind farm is placed on a bus. Indices will be created for each test case. Finally, a novel algorithm for measuring voltage stability will be developed.
1.3 Study’s Objectives
Using simulated synchrophasor data, this seminar investigated several key aspects of voltage stability. Two indices from VSI and VCPI were investigated to demonstrate how synchrophasor data can be used to determine how far the entire system is from its voltage collapse point, as well as the system’s weak points.
Power World Simulators were used for steady-state analysis, and the indices were generated in Matlab. The indices’ performance was evaluated in a 10-bus-3-generator system as well as a larger network with 39 buses and 10 generators. The results show that their performances are coherent in terms of system voltage stability.
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SYNCHROPHASOR DEVELOPMENT OF A NEW ALGORITHM FOR VOLTAGE STABILITY ASSESSMENT