Fast-Processing Modulation Strategy for the Neutral-Point-Clamped Converter with Total Elimination of Low-Frequency Voltage Oscillations in the Neutral Point
Location: USA
Publication date: 2007-08-01
Published in: IEEE Transactions on Industrial Electronics, August 2007
ref. DOI: 10.1109/TIE.2007.894788

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External members

Pou, J. , Zaragoza, J. , Ceballos, S. , Sala, V.M. , Burgos, R.P. , Boroyevich, D.



This paper presents a novel modulation strategy for a neutral-point-clamped converter. Thisstrategy overcomes one of the main problems of this converter, which is the low-frequencyvoltage oscillation that appears in the neutral point under some operating conditions. The proposed modulation strategy can completely remove this oscillation for all the operating points and for any kind of loads, even unbalanced and nonlinear loads. The algorithm is based on a carrier-based pulsewidth modulation. Nevertheless, it can generate the maximum output-voltageamplitudes that are attainable under linear modulation, such as space-vector modulation. Furthermore, this technique can be implemented with a very simple algorithm and, hence, can be processed very quickly. The only drawback of this strategy is that the switching frequencies of the devices are one third higher than those of standard sinusoidal pulsewidth modulation. A control loop for balancing the voltages on the dc-link capacitors is also proposed. This balancingstrategy is designed, so that it does not further increase the switching frequencies of the devices when it is applied to the converter. The proposed modulation technique is verified by simulation and experiment.



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