A Dipolar PWM Algorithm for Direct Power Control of Dual-Input Three-Level Inverters

This article proposes a new dipolar pulse width modulation (PWM) algorithm for direct power control of each dc source of a dual-input three-level inverter. This capability, which is required for dual maximum power point tracking (MPPT) in photovoltaic (PV) applications and power distribution control of mixed or hybrid dc-sources, cannot be achieved easily with the conventional control methods. In the proposed algorithm, the upper and lower dc-bus powers are controlled directly by simply decomposing the output voltage command into upper and lower reference voltages of the dipolar PWM using two coefficients that are proportional to the commanded dc-bus powers. Implementation of the proposed dipolar PWM algorithm is simple because it uses a carrier-based PWM method and the complexity of the algorithm is much lower than that of the conventional methods. The limitation of dc-bus power distribution under the dipolar PWM is also analyzed. The effectiveness of the proposed algorithm is verified by simulation and experiment.