Seven-level inverter with switched capacitors

Abstract

The seven-level (7L) inverter with a nearly sinusoidal output voltage is suitable for renewable energy conversion applications. A novel 7L inverter topology with switched capacitors is proposed here. The topology is composed of an active clamping inverter and a switched-capacitor part in series connection. The switched-capacitor part, consisting of three switches and two clamped capacitors, can provide 1/3 or 2/3 level of output voltage. By connecting switched-capacitor part in forward or backward series to the inverter output, a 7L output voltage waveform can be obtained with enough redundancy switching states to balance the voltage of switching capacitors. A modified modulation method is also proposed to make the topology operating properly. The voltage of switched-capacitor part can be sustained E and 2E alternately by adjusting a modulation index according to the capacitor voltage and load current. The effectiveness of the proposed topology is validated by both simulative and experimental results. Comparing with conventional 7L inverter topology, less number of devices were adopted in the proposed topology with a simple and practicable modulation method.

Keywords

• voltage control
• switched capacitor networks
• switching convertors
• PWM invertors
• capacitors
• switches
• invertors
• power capacitors
• seven-level inverter
• sinusoidal output voltage
• novel 7L inverter topology
• switched capacitors
• active clamping inverter
• switched-capacitor part
• switches
• clamped capacitors
• inverter output
• switching capacitors
• capacitor voltage
• conventional 7L inverter topology