Search

This paper presents the analysis and design for a quasi-proportional-resonant (quasi-PR) controller used in a voltage balancing control technique for the flying capacitors of a grid-connected five-level nested neutral point clamped (NNPC) converter. This voltage balancing control technique entails using the quasi-PR controller to obtain the deviation of the flying capacitor voltage from its rated value and using the output signal from the controller to adjust the duty cycle of the switching power semiconductor devices of the converter. The parameters of the quasi-proportional-resonant controller are obtained by the derived mathematical formulae presented in this paper. The design of the quasi-PR controller is analysed using a bode-plot with the aid of MATLAB/Simulink. In addition, a three phase prototype of the grid-connected five-level NNPC has been developed to verify the theoretical and simulation analysis.

Further growth in renewable energy integration would be dependent on reliability and cost-effectiveness. These two factors can be achieved through power converter topologies that enable transformer-less connection of renewable energy based technology to the grid. This paper presents a three phase five level dual tapped inductor quasi impedance source (qZS)-nested neutral point clamped (NNPC) topology for medium voltage, renewable energy applications. This topology is based on the high boosting factor of the dual tapped inductor quasi source network with minimal shoot-through period and the multilevel feature of the nested neutral-point clamped (NNPC) converter. The steady-state analysis of the proposed topology is presented to illustrate the performance of the converter at continuous conduction mode (CCM). The theoretical analysis has been verified.