Modeling of Five-Level Converter Used in a Synchronous Rectifier Application

In this paper it is presented a modeling process of a five-level neutral point clamped converter used in a synchronous rectifier application and the resulting model that describes the dynamics for such converter. The highly nonlinear model, originally in abc-coordinates, is also expressed in its alphabetagamma-coordinates. Special attention is given to the gamma-component of the control input, which represents a degree of freedom that can be used for the balancing of the capacitors voltages. It is shown that the sum of capacitors voltages is a natural state of the system since it is necessary to control the total voltage on the DC side and, indeed, it reduce considerably the model expression which describes the dynamics of that voltage. It is also shown that the controller gamma-component has a minimum influence on the sum of the capacitors voltages, but it has a strong influence on the difference, hence its importance in the capacitors voltages balance. Simulations are presented to validate the proposed model. This new modeling approach and resulting model it is expected to stimulate new control proposals in the future