Publication Detail

Advanced Numerical Methods for Simulating Nonlinear Multirate Lumped Parameter Models

Norbert H. Doerry
331 pp.

Naval shipboard electric power systems are transitioning from the relatively simple distribution of ship service electric power to extremely complex integrated electric drive (IED) systems. The optimal design of warships employing lED is presently hampered by the lack of existing simulation computer tools for analyzing the highly coupled and controlled electro-mechanical systems characteristic of IED. As a first step in the development of a viable computer simulation tool, the numerical algorithm testing program WAVESIM was created.)

The key contributions of WAVESIM are the systematic treatment of waveforms as an abstract data type, the development of the terminal description of devices, and the use of
structural jacobians in system reduction.

WAVESIM represents variables by waveforms consisting of a vector of coefficients and a waveform type code indicating how the coefficients should be interpreted. The
principal advantage of using waveforms over conventional discrete point methods is the
avoidance of unstable integration techniques since for most waveform types, integration and
differentiation are linear matrix operations.

Devices are described in WAVESIM by relationships between terminal interface
variables. WAVESIM recognizes two types of terminals: normal terminals having both
potential and flow variables, and information terminals having only a potential variable. In
this manner, WAVESIM can simulate processes involving both energy transfer and control

WAVESIM extends the structural jacobian matrix concept to reflect the properties of the dependence of system equations on system variables. The system structural jacobian matrix is constructed from the constitutive device structural jacobian matrices and is used to identify a sequence of smaller blocks when can be solved consecutively for all the system variables.

To demonstrate and verify the capabilities of WAVESIM, several simulations were conducted. In all simulations, WAVESIM provide results matching data generated by other simulation methods.

type: Full theses / dissertations

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