Implementation of real-time selective harmonic elimination using microcontrollers

The paper presents an analytical approach to find switching angles for an optimal PWM signal and its implementation using an ordinary microcontroller. The solution is in closed form that eliminates the need for numerical solution to find the transition angles. The disadvantage in iterative computation is overhead in computational effort as it requires a PC with expensive software and solution time can be a problem in real-time operation. Such an approach is prohibitive in low cost applications. In the proposed work, the equations can be programmed into a microcontroller and the PWM is generated by the micro with a digital control of the fundamental. The approach has been illustrated for two switching angles to avoid complexity although it is applicable to more transition angles. The paper also focuses on three phase systems where it is not necessary to eliminate the triplen harmonics. The analysis provides an insight for multiple solutions that exist in triplen system. The modulation depth can be altered digitally and this feature makes the approach attractive for MPPT integrated inverter. Simulation and microcontroller implementation results are included.