PARAMETRIC AVERAGE-VALUE MODELING, SIMULATION, AND CHARACTERIZATION OF MACHINE-RECTIFIER SYSTEMS
Year of Publication
Doctor of Philosophy (PhD)
Electrical and Computer Engineering
Dr. Aaron Cramer
There are many techniques for modeling and simulation of synchronous machine-rectifier systems. The more common approaches are the detailed and average-value modeling techniques. The detailed simulation technique takes into account the details of the diode switching and is both very accurate and very expensive in terms of computational resources. To alleviate this disadvantage, the average-value modeling technique is often utilized. In this approach, the details of diode switching are neglected or averaged. In that light, the work presented herein proposes a unique saliency-sensitive parametric average-value model (SSPAVM) of the synchronous machine-rectifier system. This model extends existing parametric average-value models to account for machine saliency by includng the angle of the machine's ac current as an input to the parameterized rectifier relationships. The performance of the proposed SSPAVM is compared with both detailed simulation and prior AVM in steady and transient state scenarios. The proposed SSPAVM more accurately predicts the detailed model waveforms in comparison to the existing AVM, while retaining the extensive computational cost savings associated with average-value models.
In addition, parametric average-value models~(PAVMs) of synchronous machine-rectifier systems have proven to be very useful in studying the behavior of these systems. PAVMS are able to represent the system's dynamic characteristics in a computationally efficient manner. They require characterization using the detailed model simulation. Hence, to develop a PAVM of the synchronous machine-rectifier system, the essential parametric functions are extracted once from the detailed model of the system. Herein, it is shown that the rectifier parametric functions can be represented as functions of both the dynamic loading condition of the rectifier and the current angle of the synchronous machine's ac currents, and a method of extracting these two-dimensional relationships is proposed. It is also shown that previous PAVMs are unable to represent the rectifier parametric functions during transient events, particularly for more salient synchronous machines.
Furthermore, the characterization method is extended to a fast procedure, wherein instead of multiple steady state simulations with a single value of the load resistance and machine's ac current angle at each simulation loop, the method adopted in this study involves a single transient exponential load increase for each current angle at each simulation loop. This multidimensional fast procedure greatly improves simulation times; and computational overhead associated with the multidimensional steady state approach.
Finally, an exact detailed model of the rectifier, in which all modes of operation/switching are accounted for is developed using stateflow-simulink hybrid state variable simulation environments. To achieve this, the exact differential equations with their appropriate state variable governing each state is utilized.
Digital Object Identifier (DOI)
US Office of Naval Research N00014-20-1-2816
Ojo, Isuje, "PARAMETRIC AVERAGE-VALUE MODELING, SIMULATION, AND CHARACTERIZATION OF MACHINE-RECTIFIER SYSTEMS" (2022). Theses and Dissertations--Electrical and Computer Engineering. 182.