A three-level neutral-point-clamped inverter needs a controller for the neutral-point voltage. Typically, the controller design is based on a dynamic model. The dynamic model of the neutral-point voltage depends on the pulse width modulation technique used for the inverter. A pulse width modulation strategy which allows modeling the neutral-point voltage as a first-order continuous function is proposed in this paper. The new model shows that the neutral-point current is proportional to the reactive power drawn from the inverter. Since the model is a first-order model, a simple proportional controller is used in this paper to control the neutral-point voltage. Experimental results verifying the proposed modulation strategy and the controller are also presented in this paper.
Proceedings of the Annual Conference of the Ieee Industrial Electronics Society, 2012, p. 585-589
the 38th Annual Conference of the IEEE Industrial Electronics Society, IECON 2012