Search

Knowledge of the process noise covariance matrix Q is essential for the application of Kalman filtering. However, it is usually a difficult task to obtain an explicit expression of Q for large time varying systems. This paper looks at an adaptive Kalman filter method for dynamic harmonic state estimation and harmonic injection tracking. The method models the system as a linear frequency independent state model and does not require an exact knowledge of the noise covariance matrix Q. As an alter- native, the proposed adaptive Kalman filter switches between the two basic Q models for steady-state and transient estimation. Its adaptive function allows for the resetting of the Kalman gain to avoid Kalman filter divergence problems under steady-state and allow fast tracking of system variations in transient conditions. Simulation results on the 220 kV network of the lower South Island of New Zealand are presented to validate this approach. [ABSTRACT FROM AUTHOR]

A new STATCOM configuration is described in this paper that combines the advantages of the diode clamped, dc. voltage reinjection VSC and soft switching concepts. The new scheme uses asymmetrical switches instead of diodes in a common clamping switching circuit for the three-phases of the converter bridges. Detailed analysis is provided of the steady state output voltage and current waveforms. It is shown that this configuration provides very low distortion levels with greatly simplified auxiliary switching arrangements and reduced switching losses. [ABSTRACT FROM AUTHOR]

Electromagnetic transient simulation can be used to model complex non-linearities that are very difficult to represent adequately in the frequency domain. After reaching the steady state the voltage and current waveforms, represented by sets of discrete values at equally spaced intervals (corresponding with the integration steps), are subjected to fast Fourier transform processing to derive the harmonic spectra. However, the accuracy of the EMTP approach is limited by the restricted frequency dependence representation of the AC system components. It is shown that this problem is greatly reduced with the use of frequency-dependent network equivalents for the linear part of the system. [ABSTRACT FROM AUTHOR]