Real-time selective harmonic minimization using hybrid analog/digital computing

This paper presents a hybrid analog/digital computing circuit that solves a form of the selective harmonic minimization problem in a fast and scalable manner. Voltages in the circuit represent variables in the optimization problem, and, in steady state, converge to the optimal solution of the problem. A digital microcontroller sets voltages at particular nodes in the circuit as to program the cost function and other inputs to the optimization. We present a specific realization of the computing circuit that solves for eight independent switching angles for a quarter-wave symmetric PWM driven two-level single-phase inverter. This realization minimizes seven undesired harmonics while also maintaining control of the modulation index. The simulation results demonstrate that the proposed circuit can converge to the optimal solution in less than 5.0 ms. Our survey of prior methods indicates that this is substantially faster than existing published methods in the literature.