Ittiphong Leevongwat

Steady state voltage stability enhancement using shunt and series FACTS devices

Power systems consist of generation, transmission, and distribution of power to customers. To meet the ever increasing population demand, the power industry has also grown by increasing the number of devices and incorporating highly complex as well as expensive components into the power system. It becomes specifically important to focus on voltage stability analysis of the power system to avoid worst-case scenarios, such as voltage collapse, which may result in huge losses. One of the main causes of voltage collapse is the insufficient availability of reactive power in the system. This can be overcome by adding reactive power sources such as FACTS devices into it. An attempt on enhancing the steady-state voltage stability using FACTS devices has been made in this work. An IEEE 39-bus test system is built using MATLAB and PSAT. FACTS devices such as Static VAR Compensator (SVC), Static Synchronous Compensator (STATCOM), and Thyristor Controlled Series Capacitor (TCSC), are included into the test system as three separate test cases. Continuation power flow analysis is performed on the system with no FACTS included in it and on the three test cases with different FACTS included in it. The output is displayed in the form of P-V curves, loading margin curves, and active and reactive power losses curves. The results obtained are all compared with each other to draw conclusions on the effectiveness of the each of the FACTS devices in improving the static voltage stability of the power system.

Forecasting Locational Marginal Pricing in deregulated power markets

This investigation focuses on development of new methodologies for implementing power systems optimization for forecasting Location Marginal Prices (LMP) in deregulated electricity markets. The proposed approach uses the LMP method [1–3] to show relationships between generator bids, power system constraints, and electricity demand. The proposed approach uses Unit Commitment, Economic Dispatch, and Optimal Power Flow to perform load flow analysis that includes LMP calculation to determine price of electricity.

A practical method for power systems transient stability and security analysis

The purpose of this paper is to provide a summary of an investigation of transient stability analysis using a combination of step-by-step integration and direct methods. The proposed method is based on extension of equal area criterion to transient stability analysis of multi-machine power systems. The proposed method first calculates the potential and kinetic energies of all machines in a power system before and after occurrence of faults. It then calculates two numbers based on energies of two groups of generators. It finally compares the largest group of kinetic energy to the smallest group of potential energy to determine the systems transient stability. A decision on stability of the system is made when the smallest group of potential energy is larger than the largest group of kinetic energy. The proposed method is used in analysis of the New England IEEE 39-bus system and the accuracy of the result is performed by comparison to the results obtained by pure numerical methods. Determination of stability using the proposed method is conservative and may be appropriate for power system operation as well as planning purposes.

Status of Deregulation and Locational Marginal Pricing in Power Markets

In this paper, we present the status of electricity deregulation in the United States. Furthermore, we describe the use and advantages and disadvantages of locational marginal pricing (LMP) in deregulated power markets. Finally, we present the use of LMP in analyzing electricity pricing in a deregulated electric utility environment. Using LMP, our proposed methodology for determining electricity prices in deregulated power markets is presented as an optimization problem that aims to minimize the total system production cost subject to physical and operational power system constraints. As building blocks in our modeling and analysis, we consider NERC guidelines for regional generation and transmission planning. We show an application of LMP in analyzing a six-bus test system. The details of the test system are included in this paper.

Angle and magnitude stability using Real-Time Simulation

The purpose of this investigation is to determine and to detect signs and patterns of power system dynamic behaviors that lead to voltage instability long before approaching the point of system voltage collapse. In this study, we use EMTP- RV to study the system and the dynamic behavior of both time and frequency domain to determine patterns of voltage stable and unstable cases. We will report the results of a 10-bus system using the Real Time Simulation capability in the University of New Orleans.

A fast search algorithm for Critical Clearing Time for power systems transient stability analysis

The purpose of this investigation is to extend a previously documented work by introducing an algorithm that automatically determines groups of generators that participate in system separation and hence transient instability. The algorithm is based on measuring the accelerating power of a specific power system and determining maximum accelerating power in response to numerous simulated contingency scenarios. By analyzing maximum accelerating power of the simulated power system, a threshold for separating accelerated generators from stationary generators is determined. The threshold is then used to identify groups of generators that participate in system separation. This paper includes a summary of the proposed algorithm for determining generator grouping that causes system separation in a flow chart. The blocks of the flow chart further include the actions taken in each step of the algorithm. Utilization and success of the proposed algorithm are documented using results from the IEEE 39-Bus test system.

Comparative analysis of fault discrimination algorithms on sensitivity to high impedance busbar faults

Presently there is not one differential protection characteristic which is self-sufficient to detect all possible busbar faults accurately. Particularly, during close-in external fault, current transformer (CT) saturation creates high operating current which can cause mal-operation of differential relays. As a result, a fault discriminator is necessary to supervise the differential schemes to prevent undesired tripping operation. Most of the existing fault discrimination algorithms have been proven as an efficient external fault detector; however, they suffer from lack of sensitivity to high impedance internal faults. This paper presents a comparative analysis on sensitivity of three existing fault discrimination algorithms including Phase Angle Comparison Algorithm (PACA), Rate of Change of Differential Algorithm (ROCODA), and Alienation Coefficient Algorithm (ACA). Fault simulations were performed using a three-bus test system. The results documented in this paper show that the degree of sensitivity of ROCODA and ACA are similar and much higher than PACA. The comparative analysis presented in this paper can be employed as a useful guideline for selection of an appropriate protection scheme for busbar systems.

Automatic determination of fault current breakpoint locations for personnel protective grounding of distribution and transmission lines

Personnel protective grounding of overhead distribution and transmission lines is a required safety practice involving field personnel using grounding wires to de-energize lines prior to working on the lines. The purpose of this investigation is to create an automatic process that determines the possible fault currents at all locations of transmission lines to help guide field personnel through selection of grounding wires that are appropriate for the level of the fault currents at corresponding locations. When the power system topology changes, the fault currents at different locations of the lines change. The automation updates the information and contributes to safer environment for field personnel. ASPEN OneLiner, a short-circuit analysis program, was used to perform sliding fault analysis - a series of short circuits placed at incremental distances between the two endpoints of a transmission line resulting in a current profile that shows the fault current level as a function of distance along the line. The paper includes a case study that demonstrates practicality of the method for simulation and analysis of power systems.

Predicting voltage abnormality using power systems dynamic response

The purpose of this paper is to analyze dynamic behavior of a stressed power system and to correlate the dynamic responses to the future system voltage abnormality. A pattern recognition method called Regularized Least Square Classification (RLSC) was used to correlate dynamic behavior to system voltage abnormality. This research utilizes PSSE dynamic simulation tool to simulate the stressed cases for dynamic response and uses RLSC method to predict system voltage abnormality in future time after the occurrence of specific contingencies. Dynamics of a stressed IEEE 39 Bus test system is captured by introducing numerous contingencies and by driving the system to the point of abnormal operation and by identifying those simulated contingencies that cause system voltage abnormality. This research will determine the prominent features and parameters in the process of classification of voltage normal and voltage abnormal cases from dynamic simulation data.