ABSTRACT
This
paper presents two topologies of three-phase semicontrolled rectifiers suitable
for open-end ac power sources. The rectifiers are composed by a combination of
two-level three phase bridges (controlled, semicontrolled or uncontrolled), and
three single-phase floating capacitor h-bridges (controlled). These topologies
generate two powered dc-links, each one belonging to a three-phase bridge. They
present a reduced number of controlled power switches if compared to other
open-end configurations of similar complexity found in the literature. It is
also proposed a space-vector pulse width modulation (SV-PWM) approach and a
method of floating capacitor voltage control dedicated to the topologies, with
an equivalent approach based on the level-shifted PWM (LS-PWM). The proposed
SV-PWM solving method is based on a redundant state selection (RSS) technique,
which allows the floating capacitors voltage regulation. On the other hand, the
LS-PWM solving method is based on the neutral voltage selection, which is shown
to be equivalent to the SVPWM RSS technique seen from the control system. Simulation
results are shown to validate proposed topologies, as well as the SV-PWM and
LS-PWM techniques, and the control strategy. Experimental results are shown to
demonstrate proposed configurations feasibility.
KEYWORDS
1. Power
electronics
2. Ac-dc
power conversion
3. Unidirectional
converters
4. Cascade
systems
5. Multilevel
systems
6. Pulse
width modulated power converters
7. Space
vector pwm
8. Level
shifted pwm
9. Floating
capacitor control
10. Redundant
state selection
SOFTWARE: MATLAB/SIMULINK
BLOCK DIAGRAM:
Fig.
1: Proposed configurations with open-end power source and cascaded floating
h-bridges. (a) Configuration 1, where converter A is a three-phase diode
bridge. (b) Configuration 2, where converters A and B have semi-controlled
legs.
EXPECTED SIMULATION
RESULTS
Fig.
2: Simulation graphics for the conventional configuration 0. (a) Currents ik.
(b) Voltages vk, vrk and v0s0. (c) Mean voltages vk, vrk and v0s0.
Fig.
3: Currents ik from simulation results for both proposed configurations with
the LS-PWM. (a) For configuration 1. (b) For configuration 2.
Fig.
4: Voltages v1, vr1 and v0b0a from simulation results for both proposed
configurations. (a) For configuration 1 with SV-PWM. (b) For configuration 1
with LS-PWM. (c) For configuration 2 with SV-PWM. (d) For configuration 2 with
LS-PWM.
Fig.
5: Mean voltages v1, vr1 and v0b0a for both proposed configurations. (a) For
configuration 1 with SV-PWM. (b) For configuration 1
with
LS-PWM. (c) For configuration 2 with SV-PWM. (d) For configuration 2 with LS-PWM.
Fig.
6: DC capacitors voltages vCck from simulation results for both proposed
configurations with the LS-PWM. (a) For configuration 1. (b) For configuration
2.
Fig.
7: Pole voltages va10a, vb10b, vcp10c1 and vcn10c1 for both proposed configurations.
(a) For configuration 1 with SV-PWM. (b) For configuration 1 with LS-PWM. (c)
For configuration 2 with SV-PWM. (d) For configuration 2 with LS-PWM.
CONCLUSION
In
this paper, two configurations of unidirectional rectifiers were proposed. They
were based on the cascaded connection of two three-phase bridges with three
floating capacitor h bridges (one per-phase), which was allowed by the open-end
configuration of the three-phase power source. The voltage regulation of the
floating capacitor h-bridges was realized by two proposed PWM solving
techniques. The first was applied to the SV-PWM, where methods for redundancy
selection and state switching minimization were also proposed. The second was
proposed for the LS-PWM as an alternative to the SVPWM. In this case, the
floating capacitors voltage regulation was based in solving the PWM for
appropriately selected neutral voltage references. Simulation results were
provided to supply evidence that proposed topologies are viable and that
proposed SV-PWM redundancy selection technique is effective within the control
system. It was also shown that the control based on the LS-PWM was effective
and equivalent to the SV-PWM. It could be concluded that the proposed configurations
could present lower current THD and voltage WTHD with fixed switching
frequency, as well as lower semiconductor losses with matched current THD, if
compared to the conventional three-phase IBGT rectifier bridge. Experimental results
were also provided to show the feasibility of proposed topologies and control
strategy.
REFERENCES
[1]
S. Debnath, J. Qin, B. Bahrani, M. Saeedifard, and P. Barbosa, “Operation, control,
and applications of the modular multilevel converter: A review,” IEEE
Transactions on Power Electronics, vol. 30, no. 1, pp. 37–53, Jan 2015.
[2]
R. A. Krishna and L. P. Suresh, “A brief review on multi level inverter topologies,”
in 2016 International Conference on Circuit, Power and Computing Technologies
(ICCPCT), March 2016, pp. 1–6.
[3]
F. Z. Peng, W. Qian, and D. Cao, “Recent advances in multilevel converter inverter
topologies and applications,” in Power Electronics Conference (IPEC), 2010
International, June 2010, pp. 492–501.
[4]
J. Rodriguez, J.-S. Lai, and F. Z. Peng, “Multilevel inverters: a survey of
topologies, controls, and applications,” Industrial Electronics, IEEE Transactions
on, vol. 49, no. 4, pp. 724–738, Aug 2002.
[5]
M. Diaz, R. Cardenas, M. Espinoza, F. Rojas, A. Mora, J. C. Clare, and P.
Wheeler, “Control of wind energy conversion systems based on the modular
multilevel matrix converter,” IEEE Transactions on Industrial Electronics, vol.
64, no. 11, pp. 8799–8810, Nov 2017.
