Multilevel Fixed Pulse Pattern Control for Medium-Voltage High-Frequency Inverter

抄録

To satisfy the demand for more compact medium-voltage motor drive systems, it is desirable to increase the frequencies of cascaded H-bridge inverters used in high-speed motor systems. However, in asynchronous pulse-width modulation (PWM) systems, as the output frequency increases, the command voltage and triangular wave carrier frequencies become closer, making it impossible to output the command voltage accurately. This manifests in the form of increased current harmonics, increased surge voltage at the motor terminals, and increased low-frequency ripple current owing to the asynchronous nature of the system. In this study, we adopt a fixed pulse pattern modulation method to address these problems. In our method, a low-distortion output voltage without multiple simultaneous changes is compiled into a table in advance, and subsequently output in synchronization with the fundamental voltage phase. We were able to confirm the effectiveness of the proposed method via simulations and mini-model experiments at fundamental wave frequencies of 700Hz and 1000Hz.