Case Study 1: Dynamic Load Balancing with 2-Level UPFC in a Transmission Corridor

Client: Confidential

Location: Southeastern USA

System Configuration: Single-machine to infinite bus system with parallel lines

Objective: Prevent line overload during rapid generation shifts

Background:

A power plant in the southeastern U.S. experienced overloading on its secondary transmission line (Line 1B) whenever active generation ramped up beyond 120 MW due to seasonal peak demand. The primary line (Line 1) was underutilized due to a lack of dynamic flow control.



This scenario highlights the importance of unified power flow controller (UPFC) solutions for effective power flow control in transmission lines under dynamic operating conditions.

Solution Implemented:

Keentel Engineering deployed a 2-level Unified Power Flow Controller (UPFC) on Line 1, as modeled in the referenced IEEE study. The UPFC’s series compensator regulated active power while the shunt branch maintained DC bus and voltage stability.

The implementation enabled dynamic load balancing in the power system by actively controlling line loading and redistributing power flow.

Technical Highlights:

• Initial Generation: 75 MW (25 MW via Line 1, 50 MW via Line 1B)
• Ramped Generation: 140 MW post 100ms demand spike
• Power Re-routing: UPFC dynamically rerouted power to Line 1, reducing Line 1B stress
• Control Strategy: Block diagram-based d-q rotating frame control as shown on page 2, Fig. 3

Results:

• Maintained power flow within the 80 MW thermal limit of Line 1B
• Enabled flexible generation ramping without reconfiguration
• Improved system stability and minimized reactive power losses

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Case Study 2: Voltage Support in Urban Substation Using Shunt Compensation

Client: Confidential

Location: Midwest USA

System Configuration: 400 kV ring bus with dual supply and dynamic RL load

Objective: Mitigate voltage sag at critical urban bus under fluctuating load

Background:

A major metropolitan area in the Midwest observed voltage dips at a distribution bus (Bus 2) when reactive-heavy RL industrial loads were introduced. The instability risked tripping protection relays and violating utility voltage criteria.

Voltage stability in power systems becomes critical under reactive load conditions, especially in urban substations with fluctuating demand.

Solution Implemented:

Keentel Engineering integrated a 2-level UPFC at Bus 2 using the configuration described in page 3, Fig. 9. The shunt branch regulated reactive power injection, while the series branch maintained power flow balance across Line 1.

The UPFC provided fast voltage support by injecting reactive power, helping maintain stable bus voltage during transient disturbances.

System Parameters:

• Base Load: 80 MW
• Disturbance Load: 5 MW + 75 MVAr RL load added at 0.02 sec
• Control Mechanism: Reactive power control via d-q frame (equation 9, page 2)

Results:

• Voltage sag was reduced by 12% compared to the non-UPFC case (Fig. 10, page 3)
• Reactive power injected adaptively, peaking at 0.8 pu during maximum load
• Voltage restored to nominal value within 50ms of disturbance