Control of a four-level active neutral point clamped converter with neutral point voltage balance

IECON 2019 - 45th Annual Conference of the IEEE Industrial Electronics Society

Jin

et al. 2019

Self Cite

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 ~ 1.15) and full power factor range (cos φ = 0 ~ 1). The algorithm is implemented in a test rig, and the experiment confirms its effectiveness.

Section: B Limitations Of the Existing Voltage-balancing Methodsmentioning

confidence: 99%

Section: B Limitations Of the Existing Voltage-balancing Methodsmentioning

confidence: 99%

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

Wang

IECON 2019 - 45th Annual Conference of the IEEE Industrial Electronics Society

Jin

et al. 2019

Self Cite

“…However, the dc-link neutral point voltages of this structure cannot be balanced with a single inverter or rectifier. The balance of dc-link neutral point voltages can only be achieved with a back-to-back structure [29,30]. Another advantage to obtain the topology through the derivation process is that it is easy to understand in some topologies why certain devices need to block higher voltages, e.g.…”

Section: A Generalized Topology and Derivation Methods Imentioning

confidence: 99%

Derivation of Voltage Source Multilevel Converter Topologies

IEEE Trans. Ind. Electron.

2017

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Multilevel converters have gained popularity in both medium voltage and low voltage applications. To find out the connections between various multilevel voltage source converter topologies and to reveal how to obtain new topologies, this paper has presented four methods to derive multilevel converter topologies. Many existing topologies as well as new topologies can be derived with the methods presented in this paper. The fundamental characteristics of the multilevel converters which determine their usability such as dc-link neutral point voltage balancing and flying capacitor voltage control are also investigated in the paper with a mathematical model and an example. It is expected that more new topologies will be invented based on the work in the paper for emerging applications.

“…Some converters, especially with reduced devices, cannot realize capacitor voltage balance over the full range of modulation index and power factor, which limits their application areas. To address this issue, researchers utilize additional hardware balancing circuits [13]- [15] or back-to-back topology to balance capacitor voltages [16], [17]. However, additional hardware not only increases the cost, but also hinders the power density.…”

Section: Introductionmentioning

confidence: 99%

Two Variations of Five-Level Hybrid-Clamped Converters and Their Voltage Balancing Control Using Three Degrees of Freedom

Wang

IECON 2022 – 48th Annual Conference of the IEEE Industrial Electronics Society

et al. 2022

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This paper comprehensively utilizes three control freedoms, i.e., switching state selection, zero sequence injection(ZSI) and redundant level modulation(RLM), to maintain capacitor voltage balance in two five-level three-phase converters over the full range of modulation index and power factor. The calculation process of the proposed control method is explained in detail. This method is easy to implement and can be used in other multilevel converters. The first topology is proposed for the first time in this paper. The capacitor voltage controllable region of the second topology has been extended to full operation range without extra circuits. Voltage jumps are found during the deadtime. The performance of the proposed topology and control method is verified by simulation and experiment.