DIRECT DIGITAL SIMULATION OF POWER SEMICONDUCTOR-CONTROLLED ELECTRICAL MACHINES.

摘要

Generalized computer programming techniques for simulating power semiconductor-controlled electric machines in coil-variable representation are developed. These techniques are developed primarily for implementation in large scale general purpose computer-aided design and analysis (CADA) circuit programs.; The machine model is represented by a set of mutually coupled "static" circuits. The voltages induced by the rotation of the rotating member of the machine, or "speed voltages", are taken into account as dependent voltage sources. These voltages are usually ignored by CADA circuit programs, and therefore, representation of their effect is necessary for machine simulation.; The CADA programs have built-in solid state device models (diode, thyristor) with very small time-constants compared to those of the machine. Therefore, in order to avoid the "wide-spread" time-constant problem, the buildt-in solid-state device models are replaced with the conventional two-valued resistance piecewise-linear model for practical applications. The switching conditions are programmed and stored as subroutines; the switching operation is achieved entirely by these subroutines. In addition, the firing pulses of an SCR, and their sequence, can be generated by a set of logic equations which are interfaced with the above subroutines to control the switching of an SCR.; Most of the systems which control the performance of the electrical machines can be implemented easily in CADA circuit programs as long as they can be represented by their transfer function block diagram model. The interface between the machine coil-variable model and the control system models is done internally by the program itself.; The effect of magnetic saturation on the machine inductances is accounted for instant by instant during the transients by updating the magnetic reluctance of the flux paths with the saturation level. This permits a rigorous treatment of the effect of saturation on the machine dynamic performance.; To demonstrate the validity and the usefulness of the developed techniques, a coil-variable model of a brushless synchronous generator with an A.C. exciter and rotating rectifiers is constructed from its basic component models. The performance of the control system (thyristor voltage regulator) is represented by a transfer function block diagram model. The CADA circuit program used is the recently developed SUPER*SCEPTRE program. The model is validated using the design data and test results of a 60 KVA brushless generator. Numerous computer simulation cases are presented including the steady state and transient conditions. Brushless generator performance under diode failure faults (opened-diode, shorted-diode) is simulated. The effects of the external faults, at the main generator terminals, on the main generator, as well as its excitation system currents, are simulated.; The modeling techniques developed need no transformation, i.e., the identity of the system variables is preserved. Furthermore, the simplicity and flexibility of the programming achieved by the user oriented language and supported by the virtually unlimited capabilities of modern CADA circuit programs, make the developed techniques very useful to the design engineer. Computation time in most of the simulation cases is found to be reasonable. Successful application of these techniques might also help substitute for the lack of specialized programs in the A.C. drive (generation) field of applications.