Online Measurements and Monitoring of Power System Impedance and Load Model Parameters.

摘要

In power system studies, some parameters cannot be measured directly by using the currently existing power meters. These power system parameters include the power system Thevenin impedance, harmonic impedances, zero sequence impedance, and the load model parameters.;The knowledge of power system harmonic impedances is necessary for harmonic mitigation, determination of harmonic limit compliance, prediction of system resonance, and harmonic propagation studies. Moreover, real-time monitoring of the system's harmonic impedances provides significant improvements to the design and operation of active filters. The system's zero sequence impedance at the substation bus is also important information for power system studies. It is used to calculate the different ground fault levels at substations.;Furthermore, the loads in power systems play a significant role in power system planning, control, and stability analysis. Having reliable and accurate models of the loads is essential for designing automatic control systems and optimizing their configuration. Obtaining such models has been a challenging problem for power system engineers for decades, especially in the current deregulated market environment.;This thesis presents newly developed and verified algorithms for online measurement and monitoring of these power system parameters. The algorithm proposed for monitoring the system's Thevenin, harmonic, and zero sequence impedance parameters, uses the natural variations of the loads connected to the substations. The proposed algorithm for monitoring of load model parameters uses the voltage and current waveforms captured during the operation of the Under Load Tap Change (ULTC) transformers installed in the distribution substations.;The power system's Thevenin impedance at a load bus is an important parameter for power system planning and operation. The effects of changing the system operation conditions on voltages at the load buses can be easily determined if the power system impedance parameters are known. Moreover, by knowing the Thevenin equivalent parameters, one can calculate the system's voltage stability margin and maximum loadability.;The proposed algorithms are applied to several field measurements from different substations. The results show that the algorithms fulfill the requirements for the online measurement and monitoring of power system Thevenin, harmonic and zero sequence impedances as well as the load model parameters.