Browsing by Author "Pineda Fornerod, Cristian Andres"

Now showing 1 - 3 of 3
  • No Thumbnail Available
    Item
    Optimal ZCS Modulation for BidirectionalHigh-Step-Ratio Modular Multilevel dc-dc Converter
    (2021) Pineda Fornerod, Cristian Andres; Pereda Torres, Javier Eduardo; Rojas, Félix; Droguett Olea, Gabriel; Burgos Mellado, Claudio; Watson, Alan J.
    Recent developments in dc powered technologies have increased interest in highly efficient dc-dc converters, especially at high voltage and high-step voltage ratios. Modular multilevel converters (MMCs) are an attractive alternative approach to this demand because they can manage medium and high dc voltages while using standard semiconductor devices with high efficiency if they employ soft-switching techniques. However, the latest soft-switching techniques require resonant circuits, limiting their operation. This paper proposes an optimal modulation technique for a high-step-ratio dc-dc MMC, which achieves minimal rms current and zero-current switching. The proposed optimization generates trapezoidal or triangular current to operate the converter over a wide output voltage and power range, while using a simple control scheme to regulate the output voltage and the voltage balance among the floating cell capacitors. The theoretical analysis has been verified with a laboratory-scaled prototype, demonstrating the effectiveness of the approach and excellent dynamical response.
  • Thumbnail Image
    Item
    Trapezoidal Current Mode for Bidirectional High Step Ratio Modular Multilevel dc-dc Converter
    (IEEE, 2019) Pineda Fornerod, Cristian Andres; Pereda Torres, Javier Eduardo; Neira Castillo, Sebastian Felipe; Bravo, P.; Rodríguez, J.; Garcí­a, C.
    High voltage direct current (HVDC) transmission systems and low voltage direct current (LVDC) networks are becoming popular due to their advantages and present feasibility, mainly pushed by the advance in power electronics. However, one of the main drawbacks of dc networks is the lack of a dc-dc converter that performs as the ac transformer in terms of efficiency, reliability and high-step voltage ratio, specially in medium and high voltage. Modular multilevel converters are an attractive alternative because they can manage medium and high dc voltages with standard semiconductor devices, and they can achieve high efficiency with soft switching modulation, such as resonant, trapezoidal or triangular currents usually used in double active bridges (DAB). This paper proposes a novel generalized trapezoidal current mode applied to high step ratio Modular Multilevel dc-dc Converters. The proposed modulation increases the efficiency and achieves bidirectional control of the power, soft-switching and a natural balance of the voltage in the capacitors. The simulation results show the bidirectional operation and the capacitor voltage balance of the converter under different operating conditions with high efficiency (98.2%).
  • No Thumbnail Available
    Item
    Triangular Current Mode for High Step Ratio Modular Multilevel DC-DC Converter
    (IEEE, 2018) Pineda Fornerod, Cristian Andres; Pereda Torres, Javier Eduardo; Zhang, Xiaotang; Rojas, Félix
    DC networks have generated much interest in recent years, from transmission in high voltage to their use in distribution systems. One of the major challenges is to replace the high efficient and reliable ac transformer, especially at high voltage and step ratio. New resonant modular multilevel topologies have arisen as an alternative, mainly because of advantages such as optional use of transformers, natural voltage balance, simple control and soft-switching. However, this type of operation generates a high peak current, does not allow control of power flow in all power range and has a limited range of voltage variation. This paper proposes an asymmetrical triangular current mode applied in high step ratio Modular Multilevel dc-dc Converters that achieves bidirectional control of the power, soft-switching and a natural balance of the voltage in the capacitors. The simulation results show the bidirectional operation and the capacitor voltage balance of the converter under different operating conditions with high efficiency and low peak current compared to resonant mode. The proposal was tested in a down-scale prototype, confirming the operation principle.