A Real-Time Solution to the Harmonic Elimination Equations for Three-Level Inverter

The output voltage of the inverter must meet some THD limitation. This paper presents a real-time approach to eliminate harmonics in NPC 3-level inverter using the theory of multivariable polynomial. First, taking the fifth, seventh, and 11th harmonics eliminated for instance, it is shown that the elementary symmetric polynomials can be exploited to reduce the degrees of the polynomials and the resultant theory can be utilized to eliminate variables. Then, the explicit algorithm implemented to compute the switching angles is described. The process of solution indicates that the method has many merits, such as obtaining all solutions, computing the solutions fast enough for real-time with mathematical software, and so on. Finally, the simulation results are presented to confirm the validity of the technique