Effect of HVDC Harmonics on Synchronous Machin; Transient and Dynamic Behaviour

Abstract

During the last four decades, a number of DC transmission links have gone into commercial operation in various parts of the world. Several other DC links are now under construction or proposed. One of the problems associated with the DC transmission is the generation of harmonic currents on both AC and DC sides.

These harmonics affect the AC system adversely and interfere with its operation. Their presence results in extra losses, interference with control and communication systems, and over voltages

It is well known that the order and level of these harmonics can be influenced by the parameters of the system and converters as well as by the system operating conditions.

The main purpose of this thesis is :

(I) To simulate digitally a representative AC/DC system.

(II) To present comprehensive investigations on the effect of several parameters on the harmonic level . These are :

1. The MW proportion generated by the infinite and finite power systems. 2. The proportion of the power transferred to AC and DC loads. 3. The stiffness of the AC interconnected systems.

(III) To explore the impact ofHVDC converter station faults on the torsional torques induced in turbine-generator shafts. Faults considered are:

1. Firethrough 2. Misfire 3. Short circuit across inverter terminals

The results of these investigations are presented in the form of typical time responses as well as harmonic spectra of each variable.