A Modular Multilevel Converter With Filter Capacitor for Long-Cable-Fed Drive Application

This paper proposes a modular multilevel converter (MMC) with a filter capacitor for medium-voltage long-cable-fed drive applications. Arm inductors that are inherent components in each phase of MMC are tuned with a filter capacitor to behave like a low-pass LC filter at the MMC output terminal. As a result, the output voltage of the converter is highly sinusoidal with negligible switching frequency harmonics. The overvoltage phenomenon that occurs at motor terminal due to cable resonance and voltage reflection is almost eliminated, and hence, with the proposed concept, the motor can be installed at very long distances from the converter. The voltage amplification at the motor terminal is negligible for different cable lengths with the proposed filter. Additionally, the output voltage quality of the converter is not degraded due to internal fault and subsequent bypass in power cells. The validity of the proposed concept is supported by simulation and experimental results.