Derivative-Free Power Flow Solution for Bipolar DC Networks with Multiple Constant Power Terminals

Area of Science:

• Electrical Engineering
• Power Systems Analysis
• Direct Current (DC) Networks

Background:

• Bipolar DC networks with radial structures are increasingly used.
• Non-grounded reference poles in these networks lead to neutral currents and voltage imbalances.
• Accurate power flow solutions are crucial for stable operation.

Purpose of the Study:

• To analyze the power flow solution in bipolar DC networks with radial structures.
• To investigate the impact of multiple monopolar and bipolar constant power loads.
• To evaluate the effect of the neutral cable's grounding on voltage profiles and power losses.

Main Methods:

• Formulation of the power flow problem using a triangular-based representation of grid topology.
• Development of a recursive formulation for iterative voltage determination at demand nodes.
• Testing the linear convergence of the triangular-based power flow method under various load conditions.

Main Results:

• The triangular-based method demonstrates linear convergence for power flow solutions.
• Numerical results on 21- and 85-bus grids show significant variations in voltage profiles.
• Total grid power losses are notably affected by whether the neutral cable is solidly grounded or not.

Conclusions:

• The proposed power flow method is effective for analyzing bipolar DC networks.
• Ungrounded neutral configurations in bipolar DC grids introduce significant voltage imbalances.
• Grounding strategy for the neutral cable is a critical factor influencing power system efficiency and stability.