Power Factor is a measure of how efficiently electrical power is consumed. In the ideal world Power Factor would be unity (or 1). Unfortunately in the real world Power Factor is reduced by highly inductive loads to 0.7 or less. This induction is caused by equipment such as lightly loaded electric motors and fluorescent lighting ballasts and welding sets, etc. Three phase power factor can be corrected using different approaches like sine wave control, vector control, single cycle control or Vienne Bridge Rectifier.

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Three Phase PFC system

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Topologies and control approaches
• 3 phase 6 controlled switch - sine wave control
• 3 phase 6 controlled switch - vector control
• Single cycle control
• Vienna bridge

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Sine wave control
• 6 controlled switches (MOSFETS, IGBTs ) are used
• Current shape may be made to track the voltage shape
OR
• Current shape may be made to track a sine wave
• 10 KHz switching frequency and 50-60 Hz no problem (higher
frequency may pose challenge)

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Sine wave control.
• Bi-directional operation possible
• SVM allows smaller DC voltages to be achieved (15 % lesser)
• 3 input voltage sensing (potential divider)
• 2 phase current sensing (hall effect based or shunt + diff
amplifier based) required
• 3 extra inductors

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Vector control
• 6 controlled switches (MOSFETS, IGBTs) are used
• Complicated control (modified motor drive system fig. below)

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Vector control
• Current shape only tracks a sine wave
• 10 KHz switching frequency and 50-60 Hz no problem (higher
frequency may pose challenge)
• Bi directional operation possible
• Harmonics in input voltage leads to problems
• Complicated code

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Vector control.
• Required when higher frequency sine wave input is used 3
extra inductors
• 2 phase current sensing (hall effect based or shunt + diff
amplifier based) required
• Voltage Zero cross detection
• Phase lock loop for electrical phase angle tracking
• Best dynamic performance under rapidly fluctuating source

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Single cycle control
• Unidirectional operation (AC to DC conversion) only
• Simple code structure
• Simple operation
• Currents automatically track the voltages
• 6 switch inverter topology

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Single cycle control
• PF degrades at lower load in single phase.
(stays near ~ 0.99 for 3 phase systems)
• 3 extra inductors
• 3 input voltage sensing (potential divider)
• 2 phase current sensing (hall effect based or shunt + diff
amplifier based) required

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Vienna Bridge Rectifier

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Vienna Bridge Rectifier.
• Three phase, three level, three switch PWM rectifier with
controlled output voltage
• Three-wire input, no connection to neutral
• Ohmic mains behavior
• Boost system (continuous input current).
• Unidirectional power flow only !
• High power density

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Vienna Bridge Rectifier..
• Low conducted common-mode EMI emissions
• Low switching losses
• Higher diode conduction losses
• Reliable behavior (guaranteeing ohmic mains behavior) under
heavily unbalanced mains voltages and in case of mains failure.
• Need 2 DC , 3 ac voltage feedback and 2 ac current feedback
• Telecom application (where space is at a premium)

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How we can contribute
• Proprietary algorithms for MIPS optimized implementation
• Simulation and analysis
• Implementation on MCHV board or other custom hardware
• Performance Testing (test case generation and result analysis)
• Hardware design consulting
• Research and development
• Guaranteed Best possible performance and support
• Competitive prices
• Proto development using 3rd party EMS/EDS

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Desired Specs
• Input 380 V +/-20 V , 50 /60 Hz
• Unbalance can be upto 10 percent
• Output 600 V +/- 10 %
likely outcome( @400 ~ 660V, @360 V ~ 600V )
• THD < 5 %
• PF > 0.99
• Switching frequency ~20 Khz
• Power ~ 1-12 KW
• Telecom application

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TBD
• Currents are required to be balanced ?
(or track unbalanced voltages)?
• (usually currents are to be balanced)
• Bidirectional required or unidirectional requirement?
• Space and power density constraints
• DC side neutral point balancing

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Thank You
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