Ioni T. Fernando

Support Vector Machine-Based Algorithm for Post-Fault Transient Stability Status Prediction Using Synchronized Measurements

The paper first shows that the transient stability status of a power system following a large disturbance such as a fault can be early predicted based on the measured post-fault values of the generator voltages, speeds, or rotor angles. Synchronously sampled values provided by phasor measurement units (PMUs) of the generator voltages, frequencies, or rotor angles collected immediately after clearing a fault are used as inputs to a support vector machines (SVM) classifier which predicts the transient stability status. Studies with the New England 39-bus test system and the Venezuelan power network indicated that faster and more accurate predictions can be made by using the post-fault recovery voltage magnitude measurements as inputs. The accuracy and robustness of the transient stability prediction algorithm with the voltage magnitude measurements was extensively tested under both balanced and unbalanced fault conditions, as well as under different operating conditions, presence of measurement errors, voltage sensitive loads, and changes in the network topology. During the various tests carried out using the New England 39-bus test system, the proposed algorithm could always predict when the power system is approaching a transient instability with over 95% success rate.

Commutation Failure Analysis in Multi-Infeed HVDC Systems

The commutation failure vulnerability of multi-infeed HVDC converters to ac side faults is analyzed. Faults in multi-infeed systems can cause commutation failure events in the nearby local converter or concurrently in both converters. The immunity of the system to both these events is investigated and suitably parameterized. “Commutation Failure Immunity Index” is calculated for multi-infeed systems with different ratings. Anomalous failure in valve current commutation due to voltage distortion has been investigated.

Hybrid HVDC converters and their impact on power system dynamic performance

Hybrid converter HVDC transmission is a new hybrid transmission system for connecting two AC systems. Because it uses different converters, this new configuration offers several advantages over conventional HVDC systems. This paper demonstrates the superior performance of hybrid converter based HVDC transmission systems with respect to increased stability and terminal AC voltage control. A control system is developed for the hybrid system and its dynamic performance is investigated. The hybrid system performance with emphasis on commutation failure during severe disturbances and its results is also compared with a conventional HVDC scheme.

HYBRID HVDC CONVERTERS AND THEIR IMPACT ON POWER SYSTEM DYNAMIC PERFORMANCE

Hybrid converter HVDC transmission is a new hybrid transmission system for connecting two AC systems. Because it uses different converters, this new configuration offers several advantages over conventional HVDC systems. This paper demonstrates the superior performance of hybrid converter based HVDC transmission systems with respect to increased stability and terminal AC voltage control. A control system is developed for the hybrid system and its dynamic performance is investigated. The hybrid system performance with emphasis on commutation failure during severe disturbances and its results is also compared with a conventional HVDC scheme

Improving the accuracy of normal form analysis

In second-order normal form (NF) analysis, the nonlinear dynamical system being analyzed is modeled with nonlinearities up to second order. Due to the presence of nonlinearities in the model, the results of second order NF analysis are initial condition dependent , . There are two assumptions in the theory of NF analysis and in this paper it has been shown that if the initial condition chosen do not satisfy these two main assumptions, then NF analysis is inaccurate. This paper also proposes three criteria to identify whether the initial condition satisfies one of the assumptions or not. This paper proposes to use a snap shot of state variables at an instant subsequent to the clearing of disturbance in situations where the state variables immediately after clearing the disturbance is not suitable for NF analysis. The time-domain simulations are presented to support the analysis.

Support vector machine-based algorithm for post-fault transient stability status prediction using synchronized measurements

The paper first shows that the transient stability status of a power system following a large disturbance such as a fault can be early predicted based on the measured post-fault values of the generator voltages, speeds, or rotor angles. Synchronously sampled values provided by phasor measurement units(PMUs) of the generator voltages, frequencies, or rotor angles collected immediately after clearing a fault are used as inputs to a support vector machines (SVM) classifier which predicts the transient stability status. Studies with the New England 39-bus test system and the Venezuelan power network indicated that faster and more accurate predictions can be made by using the post-fault recovery voltage magnitude measurements as inputs. The accuracy and robustness of the transient stability prediction algorithm with the voltage magnitude measurements was extensively tested under both balanced and unbalanced fault conditions, as well as under different operating conditions, presence of measurement errors, voltage sensitive loads, and changes in the network topology. During the various tests carried out using the New England 39-bus test system, the proposed algorithm could always predict when the power system is approaching a transient instability with over 95% success rate.

Commutation failure analysis in multi-infeed HVDC systems

The commutation failure vulnerability of multi-infeed HVDC converters to ac side faults is analyzed. Faults in multi-infeed systems can cause commutation failure events in the nearby local converter or concurrently in both converters. The immunity of the system to both these events is investigated and suitably parameterized. “Commutation Failure Immunity Index” is calculated for multi-infeed systems with different ratings. Anomalous failure in valve current commutation due to voltage distortion has been investigated.