High-Frequency Cycloconverter Suitable for Alternative Energy Systems

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High-Frequency Cycloconverter Suitable for
Alternative Energy Systems

• Robert S. Balog, PhD, PE

University of Illinois at Urbana Champaign
The Power Affiliates Program Annual Review, May
12, 2006
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Conventional Inverter Design
Transformer isolation for safety (high
frequency), battery for backup / transients,
traditional inverter for ac output
DC DC AC DC AC
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UIUC Proposed Inverter Design
Transformer isolation for safety (high
frequency), battery for backup / transients,
eliminate rectifier and filter
DC DC AC AC
but requires new control techniques for ac to ac
output converter
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Square-Wave Cycloconverter w/Multi-Carrier PWM
Control
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Switch Configurations
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HF Link Commutation
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Zero-Cross Commutation
Reverse Recovery Finite time to turn-off
switch (Cant turn on Q5 Q6 until Q1 Q2
recovers)
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Current-Limiting Reactor
Inter-group inductance limits short-circuit
current
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Dead Time
Break Before Make (requires logic)
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New Technique Patent Pending
Choose next switch pair that can support polarity
of the link voltage and allow current to cross
through zero
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Correct Switching Sequence
Split into 4 pairs of switches, depending on
polarity of HF Positive Converter Q1 Q2, Q3
Q4 Negative Converter Q7 Q8, Q5 Q6
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State Machine Implementation
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Experimental Hardware
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Experimental Results
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New Control Techniques for High-Frequency Link
Cycloconverter

• Multi-carrier PWM
• Overcomes historical difficulty in cycloconverter
  control
• Output waveforms are identical to traditional PWM
  
• Ripple is at twice the switching frequency
• Support bi-directional power flow
• Current commutation technique
• Manages output-bridge switching
• Solves not mitigates current zero-cross problem
• Applicable to other modulation schemes

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Intellectual Property
Patents R. S. Balog and P. T. Krein, "Commutation
technique for an AC-to-AC converter based on
state machine control," US Patent application no.
11/202,597, filed 8/11/2005. P. T. Krein,
"Systems and methods for pulse width modulation,"
U.S. Patent 6,700,803, March 2, 2004. Journal
Papers R. S. Balog and P. T. Krein, "Commutation
technique for high-frequency link
cycloconverter," IEEE Power Electronics Letters,
Sept. 2005. P. T. Krein, R. S. Balog, and X.
Geng, "High-frequency link inverter for fuel
cells based on multiple-carrier PWM," IEEE
Transactions on Power Electronics, Sept.
2004. Conference Papers P. T. Krein, X. Geng,
and R. Balog, "High-frequency link inverter based
on multiple-carrier PWM," in Proceedings, IEEE
Applied Power Electronics Conference, 2002. P. T.
Krein and R. Balog, "Low cost inverter suitable
for medium-power fuel cell sources, in Record,
IEEE Power Electronics Specialists Conference,
2002.