A Predictive Capacitor Voltage Control of a Hybrid Cascaded Multilevel Inverter With a Single DC-Link and Reduced Common-Mode Voltage Operation

For cascaded multilevel inverter topologies with a single dc supply, closed-loop capacitor voltage control is necessary for proper operation. This paper presents zero and reduced common-mode voltage (CMV) operation of a hybrid cascaded multilevel inverter with predictive capacitor voltage control. Each phase of the inverter is realized by cascading two-three-level flying capacitor inverters with a half-bridge module in between. For the presented inverter topology, there are redundant switching states for each inverter voltage levels. By using these switching state redundancies, for every sampling instant, a cost function is evaluated based on the predicted capacitor voltages for each phase. The switching state that minimizes cost function is treated as the best and is switched for that sampling instant. The inverter operates with zero CMV for a modulation index upto 86%. For modulation indices from 86% to 96%, the inverter can operate with reduced CMV magnitude (V-dc/18) and reduced CMV switching frequency using the new space-vector pulsewidth modulation (SVPWM) presented herein. As a result, the linear modulation range is increased to 96% as compared to 86% for zero CMV operation. Simulation and experimental results are presented for the inverter topology for various steady state and transient operating conditions by running an induction motor drive with open loop V/f control scheme

A Seventeen-level Inverter With a Single DC-link For Motor Drives

In the present paper, a novel topology for generating a 17-level inverter using three-level flying capacitor inverter and cascaded H-bridge modules with floating capacitors. The proposed circuit is analyzed and various aspects of it are presented in the paper. This circuit is experimentally verified and the results are shown. The stability of the capacitor balancing algorithm has been verified during sudden acceleration. This circuit has many pole voltage redundancies. This circuit has an advantage of balancing all the capacitor voltages instantaneously by switching through the redundancies. Another advantage of this topology is its ability to generate all the 17 pole voltages from a single DC link which enables back to back converter operation. Also, the proposed inverter can be operated at all load power factors and modulation indices. Another advantage is, if one of the H-bridges fail, the inverter can still be operated at full load with reduced number of levels

Seventeen-Level Inverter Formed by Cascading Flying Capacitor and Floating Capacitor H-Bridges

A multilevel inverter for generating 17 voltage levels using a three-level flying capacitor inverter and cascaded H-bridge modules with floating capacitors has been proposed. Various aspects of the proposed inverter like capacitor voltage balancing have been presented in the present paper. Experimental results are presented to study the performance of the proposed converter. The stability of the capacitor balancing algorithm has been verified both during transients and steady-state operation. All the capacitors in this circuit can be balanced instantaneously by using one of the pole voltage combinations. Another advantage of this topology is its ability to generate all the voltages from a single dc-link power supply which enables back-to-back operation of converter. Also, the proposed inverter can be operated at all load power factors and modulation indices. Additional advantage is, if one of the H-bridges fail, the inverter can still be operated at full load with reduced number of levels. This configuration has very low dv/dt and common-mode voltage variation

A Hybrid Multilevel Inverter scheme for Induction Motor Drives and Grid-Tied Applications using a Single DC-link

This paper proposes a hybrid seventeen-level induction motor drive with a single DC-link fed from a five-level active front-end converter connected to the utility grid. The five-level active front-end draws power from the grid at unity power factor and feeds a seventeen level induction motor drive. Both the grid side inverter (five-level) and the load side inverter (seventeen-level) are realized by cascading a three-level flying capacitor inverter with floating capacitor H-bridges. The voltages of the floating capacitors are controlled by switching through the redundant states. The capacitor voltage is regulated for all power factors irrespective of current direction. The main advantage of the proposed scheme is that, both front-end converter and the induction motor drive use a single DC-bus which enables multiple sources to interact easily with the proposed system. In addition to that, the proposed system can be operated in all four quadrants which enables bi-directional power flow. As an advantage, this system can operate at full power with reduced number of levels even when some devices of the H-bridges fail. This improves performance of the system without compromising on the reliability of the overall system. The performance of the drive for various operations has been verified experimentally