ABSTRACT:
In
this paper, a single-phase buck-boost matrix converter is proposed which can
both buck and boost the input voltage with step-changed frequency. It consists
of only six unidirectional current flowing bidirectional voltage blocking
switches, two input and output filter capacitors, and one inductor. It has
following advantages over the existing single-phase matrix converters: 1) it
can both buck and boost input voltage solving the limited voltage transfer
ratio (only boost or buck) problem; 2) it also has enhanced reliability as it
is immune from shoot-through problem of voltage source when all switches are
turned-on simultaneously, and therefore, it has no need of PWM dead times and
RC snubbers or dedicated soft-commutation strategies to solve the commutation
problem; 3) it can also use high speed power MOSFETs as their body diodes never
conduct, which eliminate their poor reverse recovery problem. The operation
principle of the proposed converter is given, and switching strategies are
developed to obtain various multiples and submultiples of input frequency. To
verify its performance, a laboratory prototype is fabricated and experiments
are performed to produce step-down and step-up voltage with three different
frequencies of 120, 60 and 30 Hz.
KEYWORDS:
1. Buck-boost operation
2. Commutation problem
3. Single-phase matrix converter
4. Step-changed frequency
5. Z-source
SOFTWARE: MATLAB/SIMULINK
CIRCUIT DIAGRAM:
Fig.
1. Circuit topology of the proposed single-phase buck-boost MC.
Fig.
2. Experimental results of the proposed ac-ac converter under non-inverting
buck-boost mode operations for and . (a) Boost operation when, . (b)
Buck operation when , . (c) Components stresses. (d) Zoom-in waveforms
of (c).
Fig.
3. Experimental results of the proposed ac-ac converter under inverting buck-boost
mode operations for and . (a) Boost operation when . (b) Buck operation when . (c) Components stresses. (d)
Zoom-in waveforms
of
(c).
Fig.
4. Experimental results of the proposed ac-ac converter under buck-boost mode
operations for and step-down frequency operation
when . (a) Boost operation when . (b) Buck operation when . (c) Switch voltage and inductor current
stresses (d) Zoom-in waveforms of (c).
Fig.
5. Experimental results of the proposed ac-ac converter under buck-boost mode
operations for and step-up frequency
operation when . (a) Boost operation when. (b) Buck operation when . (c) Switch voltage and
inductor current stresses (d) Zoom-in waveforms of (c).
Fig.
8. Efficiency of the proposed single-phase buck-boost matrix converter.
CONCLUSION:
In
this paper, a single-phase buck-boost MC is proposed which consists of one
inductor, two filter capacitors, and six unidirectional current conducting
bidirectional voltage blocking switches. It can step-changed the output
frequency with both voltage buck and boost operation, therefore, solves the
limited gain (only buck or boost) ability of the existing single-phase MCs. The
proposed single-phase MC is more reliable than the existing MCs as it can turn
on all switches simultaneously without current overshoot problem caused by
short-circuit of voltage source. Therefore, it does not have commutation
problem and eliminates the need for PWM dead times and lossy RC snubbers or
dedicated soft-commutation strategies, which is a significant advantage.
A detailed analysis of the proposed topology and
switching strategies are given for buck-boost operation with step-down, same
and step-up frequency. A scaled down laboratory prototype of the proposed MC
with output voltage of 70 Vrms was fabricated based on TMS320F28335 DPS-kit to
generate the control signals, and experimental results under buck and boost
modes were given for output frequencies of 30 Hz (step-down frequency), 60 Hz
(same frequency) and 120 Hz (step-up frequency). The proposed MC can be used in
applications which require voltage regulation along with frequency variation
such as to control the speed of a fan or a pump, to drive induction motor, for
induction heating, and to implement a high boost AC-DC MC based on
Cockcroft-Walton voltage multiplier, etc.
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