Study of State Estimation Using Weighted Least Squares Method

Majdoub Meriem, Sabri Omar, Cheddadi Bouchra, Belfqih Abdelaziz, Boukherouaa Jamal, El Mariami Faissal, Cherkaoui Nazha

Level of noise, Measurement type, Measurement weight, Number of measurements, Voltage measurement, weighted least squares state estimation method.

Power state estimation constitutes the core of the on-line security analysis function. The challenge number one of a state estimator is to provide the optimal estimates of system state with minimum of measurement data. This paper describes weighted least squares state estimation method and investigates how the efficiency of WLS state estimation changes according to 4 parameters: number of measurements, measurement type, measurement weight and level of noise. Different simulation cases are tested on 3-bus system and IEEE 14-bus system. The results show that accurate estimates of system state can be obtained with minimum of measurement data on condition to choose a good combination of accurate measurements with a minimum of voltage measurements and power injection measurements and these data should be properly distributed throughout the system. For best results, the two factors (weight and noise) must be combined to obtain the best estimation. Indeed, the most accurate measurements (lower level of noise) should have greater weight compared to bad measurements (higher level of noise), specially voltage measurements due to their big impact.