John B. Schneider

The electromagnetic interference (EMI) generated by switching operations within high-voltage DC (HVDC) converter stations is an issue that has been addressed by CIGRE, and methods to manage EMI should be considered in the design phase using electromagnetic modeling techniques. It is shown that the methods of the moments-based techniques that have been used in many previous studies may not be sufficient. Here, a finite-difference time-domain method is used to study the properties of single switching events using a realistic model of an HVDC converter station with a special emphasis on determining the impact of the valve hall on shielding EMI. It is shown that the valve hall does not confine high-frequency electromagnetic fields to the valve hall; rather, it delays them from exiting through bushings in the wall and spreads them out in time. Further, it is shown that incorporating electromagnetic absorbing material into the valve hall’s design can significantly reduce EMI outside the converter station.

Electromagnetic interference (EMI) generated by switching operations within high voltage DC (HVDC) converter stations is an issue that has been addressed by CIGRE and methods to manage EMI should be considered in the design phase using electromagnetic modeling techniques. It is shown that method of moments-based techniques that have been used in many previous studies may not be sufficient. Here, the finite-difference time-domain method is used to study the properties of single switching events using a realistic model of an HVDC converter station with special emphasis on determining the impact of the valve hall on shielding EMI. It is shown that the valve hall does not confine high frequency electromagnetic fields to the valve hall; rather it delays them from exiting through bushings in the wall. Further, it is shown that incorporating electromagnetic absorbing material into the valve hall design can significantly reduce EMI outside the converter station.

Open region FDTD simulation requires terminating the computational domain with an operator or with an absorbing material that simulates the effect of an unbounded medium. Two techniques for mesh termination have emerged that succeed in bringing the artificial reflections generated from the terminal boundaries of FDTD space to unprecedented low levels. These two techniques are the perfectly matched layer (PML) introduced by Berenger (1994) and the complementary operators method (COM) introduced by Ramahi (1995). No direct comparison between the two techniques has yet been published. In this paper, an evaluation and comparison of these two techniques is presented that is based on a numerical experiment which has been discussed in the literature (Ramahi). Here, the primary factors in the comparison are: accuracy, memory overhead and operations count. Although this example gives numerical data, it is still intended to give primarily a qualitative perspective on the relative performance of the two techniques. The example demonstrates that COM provides comparable accuracy to that obtained by an 18-layer PML, while requiring less memory and fewer operations.

The long-term goal is to develop exact numerical methods and visualization techniques for the study of propagation of acoustic energy in shallow water in the time domain. Exact in this context means the methods place no restrictions on the underlying physics of the environment.

The long-term goal is to develop exact numerical methods and visualization techniques that can be used to study the propagation of acoustic energy in shallow water in the time domain. Exact in this contexts means the methods place no restrictions on the underlying physics of the environment. The objectives are to: develop new, and enhance existing, numerical methods; to establish the accuracy, robustness, flexibility, and tractability of these methods; and to apply these methods to meaningful practical problems. To create a robust software suite for the application of the methods and to develop techniques for visualizing the propagation of scalar and vector fields in complex environments.