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.
Industrial Electronics Society, Annual Conference of, 2012, p. 585-589
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I E E E Industrial Electronics Society. Annual Conference. Proceedings
the 38th Annual Conference of the IEEE Industrial Electronics Society, IECON 2012