Joseph Plastino, Process Control Engineer, GE Walid G. Morsi, Assistant Professor, UOIT

EPEC 2011

  Problem statement

  Describe system using single-line diagram

  Machine data input to AVR model

  MatLab output: AVR model

  Describe features of DVR

  MatLab output: DVR model

 Three back-up generators running in parallel must limit the voltage dip to 15% and recover to +/-3% of rated volts within 1.5 seconds after start of biggest motor.

 Generators are rated for 31500kVA, 0.8 PF, 13.8kV.

 Assume generators are initially loaded at 70% by a constant kVA 0.8 PF load.

 Large motor rated at 10500kW at 13.8kV with inrush = 3.8 x rated current at 0.15 PF. Efficiency = 0.97 and rated PF = 0.89.

Simplified model from text:

Real model implemented in Matlab:

 Exciter Control is a PID controller. Very similar to textbook examples in Chapter 12.

 Sensor is an standard IEEE model.

Simplified models show only 1/sƮE .

Model exciter saturation described by open circuit saturation curves.

The air gap line represents the relationship:

1 pu field current = 1 pu stator voltage

For real exciters saturation occurs. Thus, for an x pu increase of field current yields less than x pu increase of stator voltage.

Recall impedance network from SLD.

Find E’ by using phasor diagram for salient pole

synchronous generator.

For salient pole machines IaXs can be shown as the vector sum of IdXd and IqXq.

E’ (here shown as Ef) is the vector sum of VTcos(δ) + IdXd.

VT = IT * Ztotal, where IT = E’/[Ztotal*cos(δ) + X’d*sin(θ+δ)]

Ztotal = Zinitial + Zmotor, where Zinitial is modeled as a constant kVA 0.8 PF load.

Zinitial = VT2 / 0.7, where 0.7 is the per unit power consumed by the load.

Generator voltage VT.

Voltage at load. Line impedance

neglected.

Harmonic filter – passive LC components.

DC-to-AC power conversion.

Rechargeable Battery.

Reference voltage = 1pu.

Voltage Sag from Motor Start.

Load voltage.

Joseph Plastino Process Control Engineer

General Electric (GE), Canada Joseph.plastino@ge.com

Walid G. Morsi Assistant Professor

University of Ontario Institute of Technology (UOIT)

Oshawa, ON, Canada L1H7K4 Walidmorsi.ibrahim@uoit.ca