Chawasak Rakpenthai

State Estimation of Power System Considering Network Parameter Uncertainty Based on Parametric Interval Linear Systems

This paper addresses the state estimation of a power system whose network parameters are known to be within certain tolerance bounds. The power system is assumed to be fully observable by having enough phasor measurement units installed. Using synchronized phasor measurement data and state variables expressed in rectangular forms, the state estimation under the transmission line parameter uncertainties is formulated based on the weight least square criterion as a parametric interval linear system of equations. The solutions are obtained as interval numbers representing the outer bound of state variables. The proposed method is also extended to a power system with mixed phasor and conventional power measurements. A technique based on affine arithmetic for converting state variable into polar form is also presented. The proposed method has been implemented using MATLAB and INTLAB toolbox and applied to some IEEE test systems. The numerical experiment results indicate that, in shorter computation time, the proposed algorithm can find the outer bounds that are close to those computed by performing Monte Carlo simulations or by solving constrained nonlinear optimization problems.

On Harmonic State Estimation of Power System With Uncertain Network Parameters

This paper addresses the problem of harmonic state estimation (HSE) of a power system whose network parameters are known to be within certain tolerance bounds. The harmonic voltage and current phasors at harmonics of interest are measured by using adequate numbers of phasor measurement units. The HSE is formulated based on the weighted least squares (WLS) criterion as a parametric interval linear system of equations. The solutions are obtained as interval numbers representing the outer bound of state variables. A method for adjusting the weight used in WLS which takes uncertain network parameters into consideration is also proposed. The proposed HSE algorithm is applied to the three-phase power systems and the results from numerical experiments show that the bounds of state variables obtained by the proposed method agree with those estimated by performing Monte Carlo simulations but with much shorter computation time.

Power System State and Transmission Line Conductor Temperature Estimation

This paper presents a state estimation technique for three-phase power systems where not only bus voltage phasors but also the temperature of transmission line conductors is considered as states. Transmission line admittance parameters depending on line conductor and ambient temperature are approximated from the pre-computed data based on polynomial interpolations. Weather environment and heat-balance equations have been also included in the measurement functions in order to estimate the temperature of conductors. The technique for segmenting transmission lines is also applied for handling temperature variations along the lines. The estimation problem is then formulated as a constrained nonlinear optimization based on the weighted least-squares criterion. A solution is obtained by applying a predictor–corrector interior point algorithm. Simulation results on some three-phase power systems indicate that the proposed method yields estimations with a better accuracy.

On harmonic state estimation of power system with uncertain network parameters

This paper addresses the problem of harmonic state estimation (HSE) of a power system whose network parameters are known to be within certain tolerance bounds. The harmonic voltage and current phasors at harmonics of interest are measured by using adequate numbers of phasor measurement units. The HSE is formulated based on the weighted least squares (WLS) criterion as a parametric interval linear system of equations. The solutions are obtained as interval numbers representing the outer bound of state variables. A method for adjusting the weight used in WLS which takes uncertain network parameters into consideration is also proposed. The proposed HSE algorithm is applied to the three-phase power systems and the results from numerical experiments show that the bounds of state variables obtained by the proposed method agree with those estimated by performing Monte Carlo simulations but with much shorter computation time.

State estimation of power system considering network parameter uncertainty based on parametric interval linear systems

This paper addresses the state estimation of a power system whose network parameters are known to be within certain tolerance bounds. The power system is assumed to be fully observable by having enough phasor measurement units installed. Using synchronized phasor measurement data and state variables expressed in rectangular forms, the state estimation under the transmission line parameter uncertainties is formulated based on the weight least square criterion as a parametric interval linear system of equations. The solutions are obtained as interval numbers representing the outer bound of state variables. The proposed method is also extended to a power system with mixed phasor and conventional power measurements. A technique based on affine arithmetic for converting state variable into polar form is also presented. The proposed method has been implemented using MATLAB and INTLAB toolbox and applied to some IEEE test systems. The numerical experiment results indicate that, in shorter computation time, the proposed algorithm can find the outer bounds that are close to those computed by performing Monte Carlo simulations or by solving constrained nonlinear optimization problems.

A new hybrid state estimation based on pseudo-voltage measurements: A NEW HYBRID STATE ESTIMATION

This paper presents a new hybrid state estimation method based on the concept of pseudo-voltage measurements for a power system containing both conventional and synchronizing phasor measurements. Actual measurement data is employed to calculate the magnitude and phase of the pseudo-voltage. In the proposed formulation, the measurement matrix describing the relations between the measured data and the state variables contains only 0 or 1. Then the state estimation problem is formulated based on the weighted least-squares criterion, and its solution can be obtained without using iterative procedures. Comparisons with previous hybrid state estimation methods have been performed on IEEE 14-bus, 57-bus, and 118-bus systems. Numerical experimental results indicate that the proposed approach yields solutions of comparable accuracy with other methods but with shorter computation times. Moreover, the proposed method also provides superior results in the presence of bad data.

A new hybrid state estimation based on pseudo‐voltage measurements

This paper presents a new hybrid state estimation method based on the concept of pseudo-voltage measurements for a power system containing both conventional and synchronizing phasor measurements. Actual measurement data is employed to calculate the magnitude and phase of the pseudo-voltage. In the proposed formulation, the measurement matrix describing the relations between the measured data and the state variables contains only 0 or 1. Then the state estimation problem is formulated based on the weighted least-squares criterion, and its solution can be obtained without using iterative procedures. Comparisons with previous hybrid state estimation methods have been performed on IEEE 14-bus, 57-bus, and 118-bus systems. Numerical experimental results indicate that the proposed approach yields solutions of comparable accuracy with other methods but with shorter computation times. Moreover, the proposed method also provides superior results in the presence of bad data.