Chapter 18 Utility Interface • Power quality has become an important issue 18-1 Various Loads Supplied by the Utility Source • PCC is the point of common coupling Chapter 18 Utility Interface 18-2 Diode-Rectifier Bridge • Bock diagram Chapter 18 Utility Interface 18-3 Typical Harmonics in the Input Current • Single-phase diode-rectifier bridge Chapter 18 Utility Interface 18-4 Harmonic Guidelines: IEEE 519 • commonly used for specifying limits on the input current distortion Chapter 18 Utility Interface 18-5 Harmonic Guidelines: IEEE 519 • Limits on distortion in the input voltage supplied by the utility Chapter 18 Utility Interface 18-6 Reducing the Input Current Distortion • use of passive filters Chapter 18 Utility Interface 18-7 Power-Factor-Correction (PFC) Circuit • For meeting the harmonic guidelines Chapter 18 Utility Interface 18-8 Dc current • No losses and current sinusoidal in input side pin 2U s sin t 2 I s sin t U s I s U s I s cos 2t • Dc voltage ud can be assumed constant pd U d id • Large switching frequency – Ld can be assumed small – Instantaneous powers are equal, pin = pd Us Is Us Is id I d iC cos 2t Ud Ud 18-9 Voltage ripple Us Is Us Is id I d iC cos 2t Ud Ud I d I load Us Is Ud • Capacitor current Us Is iC cos 2t I d cos 2t Ud • Capacitor voltage ripple ud ,ripple Id 1 iC dt cos 2t Cd 2Cd 18-10 Power-Factor-Correction (PFC) Circuit Control • generating the switch on/off signals Chapter 18 Utility Interface 18-11 Power-Factor-Correction (PFC) Circuit • Operation during each half-cycle Chapter 18 Utility Interface 18-12 Current ripple • Both dc voltage Ud and supply voltage assumed constant during switch conduction – times ton Ld I hys us toff Ld I hys U d us U d us us 1 fs ton toff Ld I hysU d • Switching frequency • Switching frequency is constant, current ripple and its maximum value I hys U d us us f s LdU d I hys,max Ud 4 f s Ld kun U us d 2 18-13 Thyristor Converters for 4-Quadrant Operation • Two back-to-back connected 2-quadrant converters Chapter 18 Utility Interface 18-14 Switch-Mode Converter Interface • Bi-directional power flow; unity PF is possible Chapter 18 Utility Interface 18-15 Switch-Mode Converter Interface • Rectifier and Inverter modes based on the direction of power flow Chapter 18 Utility Interface 18-16 Switch-Mode Converter Control • DC bus voltage is maintained at the reference value Chapter 18 Utility Interface 18-17 Switch-Mode Converter Interface • Waveforms in the rectifier mode Chapter 18 Utility Interface 18-18 3-Phase Switch-Mode Converter Interface • Rectifier and Inverter modes based on the direction of power flow Chapter 18 Utility Interface 18-19 EMI: Conducted Interefence • Common and differential modes Chapter 18 Utility Interface 18-20 Switching Waveforms • Typical rise and fall times Chapter 18 Utility Interface 18-21 Conducted EMI • Various Standards Chapter 18 Utility Interface 18-22 Conducted EMI • Filter arrangement Chapter 18 Utility Interface 18-23