Inverter harmonic reduction using Walsh function harmonic elimination method

The Walsh function harmonic elimination method provides a simple method to optimize the switching angles by solving linear algebraic equations instead of non-linear transcendental equations. However, the method becomes impractical when a large number of switching angles are computed since a high degree of freedom is involved in the computations. An appropriate hypothesis is required to obtain the correct solution under the constraints of the initial conditions.; The modified algorithm of the Walsh function harmonic elimination method devised by this research allows the computer to calculate the coefficients in the linear algebraic equations to obtain the correct solution. Several switching patterns are optimized by using the modified algorithm. The results show that the modified algorithm accurately eliminates selected harmonics. The new algorithm solves the linear algebraic equations off-line. Thus, fewer computations are required and a smaller memory is needed for the hardware implementation. By using the curve fitting method, the switching angles can be expressed as a fundamental amplitude and fundamental frequency. The voltage and frequency control for the inverter is simplified by using the curve fitting method.