# Closed-loop DC-link Voltage Balancing Algorithm for a Four-level π-type Converter

Research output: Chapter in Book/Report/Conference proceedingConference Contribution (Conference Proceeding)

### Abstract

A four-level π-type converter is a Neutral Point Clamped (NPC) multilevel converter topology for low/medium voltage applications. As the inherent issue with this topology, the DC-link capacitor voltage balancing is challenging, especially when it operates as a single-end inverter/rectifier with unity power factor. This paper proposes a closed-loop DC-link voltage balancing algorithm of a π-type converter that is effective and simple to implement. In principle, this approach is based on Redundant Level Modulation (RLM). The RLM utilizes additional voltage levels in each switching window to gain extra controllability of the DC-link capacitor voltages without affecting the average output voltage. An algorithm based on mathematical and logical operations is developed to utilize RLM to achieve the closed-loop voltage balancing. The proposed control method is effective over the full modulation index ( $M=0\sim$ 1.15) and full power factor range $(cos\varphi=0\sim 1)$ . The algorithm is implemented in a test rig, and the experiment confirms its effectiveness.
Original language English IECON 2019 - 45th Annual Conference of the IEEE Industrial Electronics Society Institute of Electrical and Electronics Engineers (IEEE) 6 45 978-1-7281-4878-6 978-1-7281-4879-3 https://doi.org/10.1109/IECON.2019.8927147 Published - 9 Dec 2019 Annual Conference of the IEEE Industrial Electronics Society - Duration: 14 Oct 2019 → 17 Oct 2019https://iecon2019.org/

### Publication series

Name Proceedings of the Industrial Electronics Society Annual Conference IEEE 45 1553-572X 2577-1647

### Conference

Conference Annual Conference of the IEEE Industrial Electronics Society IECON 14/10/19 → 17/10/19 https://iecon2019.org/

### Keywords

• multilevel converter
• voltage balancing
• level-shifted carrier
• π-type

• ## Cite this

Wang, J., Yuan, X., Jin, B., & Laird, I. (2019). Closed-loop DC-link Voltage Balancing Algorithm for a Four-level π-type Converter. In IECON 2019 - 45th Annual Conference of the IEEE Industrial Electronics Society (Vol. 45). (Proceedings of the Industrial Electronics Society Annual Conference; Vol. 45). Institute of Electrical and Electronics Engineers (IEEE). https://doi.org/10.1109/IECON.2019.8927147