ET2105 Electrical Power System Essentials

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Energy Management Systems

• ET2105 Electrical Power System Essentials

Prof. Lou van der Sluis
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Introduction (1)

• Energy Management Systems (EMS)
• Supervisory Control and Data Acquisition System
  (SCADA)
• State estimator
• Loadflow or power flow
• Optimal power flow

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Introduction (2)

• Controlled switching
• Contingency analysis
• Short circuit computations
• Stability analysis
• Reliability analysis

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Loadflow Computations
Input data and results
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Network Node Types
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The Admittance Matrix Y
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Example
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Loadflow Equations (1)

• Elements of the Y matrix
• Voltages of network nodes
• Injected current at node i

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Loadflow Equations (2)
Injected complex power
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Loadflow Equations (3)
Injected active and reactive power
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Loadflow Equations (4)

• To be solved

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Example
iter. ?V2 pu V2 pu ??2 rad ?2 rad
0 1.0000 0.0000
1 -0.0900 0.9100 -0.1425 -0.1425
2 -0.0237 0.8863 -0.0185 -0.1610
3 -0.0009 0.8853 -0.0007 -0.1617
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Iterative Loadflow Computation

• Construct the Jacobiaan J

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Flowchart of the Newton-Raphson loadflow
computation
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Decoupled Loadflow (1)

• Resistance of the overhead lines much smaller
  than the reactance
• Small differences between the voltage angles
• Elements of submatrices J12 and J21 are rather
  small
• Decoupling between active and reactive power

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Decoupled Loadflow (2)
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DC Loadflow

• The non linear equations are linearized
• Speeds up the computation
• Not an acurate solution
• Decoupled loadflow gives an accurate solution

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State Estimator
Input data and results