A Seven-Level Boost Inverter for Medium Power PV Applications

Conventional multilevel inverters typically utilize high component count and cannot step up the input voltage. This paper presents an improved multilevel boost-type inverter with low component count. The proposed inverter is able to generate a seven-level ac output voltage (0, 0.5V
_dc
, V
_dc
, 1.5V
_dc
, -0.5V
_dc
, -V
_dc
, - 1.5V
_dc
), while only eight switches and three capacitors are employed. The charge pump principle helps to boost the output voltage to 1.5 times of the input voltage. A level-shift pulse-width-modulation mechanism is introduced to drive the switches. The switch pattern is designed to balance the capacitors' voltages and to control the charge/discharge of the filtering capacitor. In order to verify and validate the proper operation of the developed circuit configuration, the system is simulated in MATLAB/Simulink and are experimentally evaluated using a hardware set-up. Obtained results agree well with the theoretical analysis. A low total-harmonic-distortion is achieved with low filter requirement and the capacitor voltages are well balanced with the level-shift pulse-width-modulation pattern.