Simple Carrier Based Capacitor Voltage Balancing Technique for Three-Level Voltage Source Inverters

This paper presents a simple carrier-based dc-link capacitor voltage balancing technique for three-level voltage source inverters. It modifies the amplitudes of the two carrier signals based on the dc-link capacitor voltage deviations to regulate the charging and discharging of the dc-link capacitors. This capacitor voltage balancing method is simple and suitable for implementation in low power microcontrollers. Compared to the conventional dc-link capacitor voltage balancing method based on Space Vector Modulation (SVM) strategy, the proposed voltage balancing method reduces both code size and execution time by 40 percent. In addition, it provides tight neutral-point potential regulations for a wide range of modulation indices and load power factor values. The only drawback of the proposed voltage balancing method is its slightly higher switching loss and output current ripple compared to the conventional SVM based dc-link capacitor voltage balancing method. The validity of the proposed dc-link voltage balancing method is verified using experimental test.