There are several methods to control power flow in power systems:
A simple generator in the system is represented by its Thevenin equivalent circuit, which represents its model operating under balanced steady-state conditions. The key parameters include the generator terminal voltage Vt, the excitation voltage Eg, the power angle δ, and the positive-sequence synchronous reactance Xg.
The generator current is:
and the complex power delivered is:
A shunt capacitor bank added to a power system bus increases the bus voltage magnitude and compensates for reactive power. This adjustment is modeled by connecting a capacitor, which absorbs negative reactive power, thereby reducing the overall reactive power demand from the system. Additionally, tap-changing transformers are used to regulate bus voltages and manage reactive power flows by adjusting the turns ratio, thereby influencing the voltage and reactive power profile in the network. This adjustment helps maintain system stability and efficiency, accommodating load variations and enhancing power delivery.
Power flow studies often use trial and error to adjust generation levels and control settings. These adjustments ensure the system meets desired equipment loadings and voltage profiles, preparing the network for load growth, new transmissions, transformers, and generation. The control of power flow is a dynamic process involving various methods and adjustments to maintain system stability, efficiency, and reliability.
Controlling power flow requires managing components like generators' prime mover and excitation control, shunt capacitor banks, reactors, static var systems, and regulating transformers.
A generator under steady-state conditions is represented by the Thévenin equivalent, including terminal voltage, excitation voltage, power angle, and synchronous reactance.
The generator's current, real, and reactive powers are then calculated.
Increasing the power angle boosts real power but decreases reactive power, while raising excitation voltage increases reactive power and slightly decreases the power angle.
Adding a shunt capacitor bank to a bus increases its voltage, whereas a shunt reactor decreases it.
Tap-changing and voltage-regulating transformers control bus voltages and reactive power flows. Phase-angle regulating transformers control bus angles and real power flows.
Alterations in tap settings or voltage regulation alters the transformer's turns ratio computed by the power flow program.
The program also evaluates the effects of switching lines, transformers, loads, and generators. It simulates changes to meet future load growth.
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