ABSTRACT:
Boundary Conduction Modulation (BCM)
featuring zero voltage switching has caught researchers’ eyes recently. In single-phase
full-bridge inverter with one leg operating in high switching frequency and one
leg in line frequency, it is easy to achieve high conversion efficiency for low
power applications. However, severe distortion will be introduced during zero
voltage crossing area due to too low switching frequency around this area, and
reactive power generation is not allowed under this modulation scheme due to
zero voltage crossing issue. This paper proposes a hybrid BCM strategy for a
single-phase full-bridge inverter to both alleviate voltage zero-crossing
distortion and enable reactive power generation by reshaping the triangular waveform
of inductor current into quadrangle waveform through rearranging the driving
signals during voltage zero crossing area. This alleviates zero-crossing
distortion by avoiding too low switching frequency and enables reactive power generation
by employing the hybrid BCM around voltage zero crossing area. High efficiency
can be maintained by combining the proposed hybrid BCM employed only for a
small portion of zero crossing area and the conventional BCM for the rest. The principle
of operation, theoretical analysis and simulation results are presented in this
paper. A 300W microinverter prototype was built to verify the feasibility and
effectiveness of the proposed hybrid BCM scheme.
KEYWORDS:
1.
Microinverter
2.
BCM operation
3.
Hybrid
modulation strategy
4.
High
efficiency
SOFTWARE: MATLAB/SIMULINK
CIRCUIT DIAGRAM:
Fig. 1. The control diagram of the
prototype proposed.
Fig. 2. The simulated wave forms of
inverter operated in the proposed
control scheme (a) full load (b) half load.
Fig. 3. The simulated waveforms of BCM
inverter when output reactive
power. (a)output current leads grid voltage
30o phase. (b)output current lags
grid voltage 30o phase.
Fig. 4. The detailed wave forms of hybrid
BCM when output reactive power.
CONCLUSION:
This
paper proposes a hybrid BCM for single-phase full bridge inverters to both overcome
the current distortion at voltage zero-crossing region and have capability of
reactive power generation. By combining the proposed hybrid BCM and unipolar
BCM, the inverter will alleviate the current distortion without lowering efficiency.
The hybrid modulation scheme is explained in details and the design
considerations are also given for selecting control parameters and driving signal
arrangement. To verify the proposed control scheme, a two-stage 300W microinverter
prototype has been built. Simulation and experimental results verify the
feasibility and effectiveness of the proposed control scheme.
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