Effective approximations suitable for the control algorithm of microprocessor-based cycloconvertor

Two approximation methods for simplifying the control algorithm of cycloconvertor control are obtained from studies in a phase plane called a `time process chart¿. One is a simple straight line approximation, in which only arithmetic operations are involved, and one can avoid the use of trigonometric or inverse trigonometric functions. The other is also a straightline approximation, but some function tables are used in combination, to improve the accuracy of approximation. To evaluate the accuracy, the theoretical output waveform obtained by each of the above approximations is analysed using the DFT method. Results of the analysis show that both approximations can be used effectively for the control algorithm, and that the second method, in particular, is highly accurate. Requiring only simple procedures in application, both of the two proposed methods can be used for microprocessor-based control with advantage.