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Voltage Balancing Control of Diode-Clamped Multilevel Converters With Passive Front-Ends

2008; Institute of Electrical and Electronics Engineers; Volume: 23; Issue: 4 Linguagem: Inglês

10.1109/tpel.2008.925182

1941-0107

Sergio Busquets‐Monge, Salvador Alepuz, J. Bordonau, J. Peracaula,

HVDC Systems and Fault Protection

In the previous literature, it has been reported that it is not possible to guarantee the balance of the DC-link capacitor voltages of multilevel three-phase diode-clamped DC-AC converters with passive front-ends for high modulation indices, especially for more than three levels. This paper proposes a novel closed-loop control approach capable of guaranteeing such balance for all operating conditions of the converters without the need for additional hardware. Three different phase duty-ratio perturbation schemes are proposed. They are compared through simulation for the case of a four-level three-phase diode-clamped DC-AC converter operated with a virtual-vector-based modulation. The most simple and effective perturbation scheme, only requiring the sensing of all DC-link capacitor voltages, is tested experimentally in the same four-level converter. The results demonstrate the feasibility of guaranteeing the dc-link capacitor voltage balance for all converter operating conditions.