SHE-PWM Control for A Four-level Hybrid-Clamped Inverter

In this paper, a control strategy for a four-level hybrid-clamped inverter using SHE-PWM is introduced. An algebraic method combining Groebner bases and symmetric polynomials is implemented to obtain the seven switching angles of SHE-PWM. Compared with the widely-used numerical and intelligent methods, it does not need to choose initial values and is able to obtain all the solutions. Moreover, the calculation efficiency is much higher than the existing algebraic methods. The voltage balancing of the DC-link capacitors and flying capacitors can be achieved by selecting proper redundant switching states. Simulation results are presented to confirm the harmonic elimination effect and the validity of this voltage control strategy.