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AC-DC-AC Three-Phase Converter Based on Three
Three-Leg Converters Connected in Series
Abstract:
An unidirectional three-phase to three-phase dc link converter is proposed in this
paper. It is composed of three unidirectional ac-dc-ac three-leg converters. The
three-leg converter is composed of a non-controlled leg, two controlled legs and a
dc-link. A suitable model and control strategy of the system, including a
synchronization method, are proposed. The synchronization method, associated
with the PWM strategy, imposes the grid currents and load voltages have the same
phase angle of the converter voltages. This method ensures sinusoidal grid currents
and mitigate the zero-crossing distortions normally caused by the use of diodes.
Simulation and experimental results are also presented for validation purposes.
Existing system:
 With the continuous progress of human civilization, greater amounts of
energy are required. Thus, the development of new types of power
converters for processing energy has became very important. In this context,
further studies of single-phase and three-phase inverters in series and in
parallel are being widely discussed in literature.
 The association of single-phase inverters in series to form three-phase
converters is discussed in and. Such series and parallel converters can be
used in the chemical and oil industries, power generation and power
transmission.
Proposed system:
The proposed system presents an unidirectional three-phase ac-dc ac converter that
combines three unidirectional single-phase three-leg ac-dc-ac converters in series.
The converter uses six diodes and twelve controlled switches (each controlled
switch is formed by an IGBT and a diode), The advantages of this configuration
are: i) lower dc-link voltage, reducing the voltage stress across the devices and ii)
multilevel input and output voltages with lower harmonic distortion in the grid
currents and load voltages when compared to the conventional converter.
Block diagram:
Reference:
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