Name: voltage and reactive power control
Uploaded: 2024-11-21T14:54:26.000Z
Duration: 1 min 30 s
Channel: JoVE

Controlling power flow requires managing components like generators&#39; 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 Th&#233;venin equivalent, including terminal voltage, excitation voltage, power angle, and synchronous reactance.
The generator&#39;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&#39;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.

control of power flow

There are several methods to control power flow in power systems:
<ol style="list-style-type: circle;">
	<li>Prime mover and excitation control of generators</li>
	<li>Switching of shunt capacitor banks, shunt reactors, and static var systems</li>
	<li>Control of tap-changing and regulating transformers</li>
</ol>
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 &#948;, and the positive-sequence synchronous reactance Xg.
<img alt="AC voltage equation diagram for electrical circuit analysis, showing complex power relationships." src="/files/ftp_upload/16150/16150_PT_Image_1.svg" style="height: 36px;" data-altupdatedat="1762173717000" data-alt="Figure1" />
The generator current is:
<img alt="LC circuit diagram, illustrating inductance, showing AC source, coil, current flow analysis." src="/files/ftp_upload/16150/16150_PT_equation_1.svg" style="height: 160px;" data-altupdatedat="1762173717000" data-alt="Equation1" />
and the complex power delivered is:
<img alt="Electrical power equations; complex power formula; mathematical analysis; phasor representation." src="/files/ftp_upload/16150/16150_PT_equation_2.svg" style="height: 36px;" data-altupdatedat="1762173717000" data-alt="Equation2" />
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.

Control of Power Flow

Controlling power flow requires managing components like generators&#39; prime mover and excitation control, shunt capacitor banks, reactors, static var ...

Education

JoVE Core

Electrical Engineering

Unit 1

Steady-State Transmission Lines and Power Flows

steady-state-transmission-lines-and-power-flows

KEY TERMS AND CONCEPTS

voltage and reactive power control

Voltage and reactive power control help keep a power system stable and efficient. In this topic, generator settings, switched equipment, and transformer taps work together to guide how power moves through the network.

A generator can be modeled with a Thevenin equivalent circuit under balanced steady-state conditions. The main terms are terminal voltage Vt, excitation voltage Eg, power angle δ, and positive-sequence synchronous reactance Xg. From this model, the generator current and the complex power delivered can be determined.

One way to adjust power flow is through generator control. The prime mover and the excitation system can be changed to influence generation and voltage behavior. Power flow studies often use trial and error to set these values and other controls.

Shunt capacitor banks, shunt reactors, and static var systems are also used to manage reactive power. A shunt capacitor bank connected to a bus raises the bus voltage magnitude. It also compensates for reactive power by absorbing negative reactive power, which lowers the system’s overall reactive power demand.

Tap-changing and regulating transformers provide another way to control bus voltage and reactive power flow. By changing the turns ratio, these transformers alter the voltage profile across the network. This helps the system handle load changes and support efficient power delivery.

These control steps are used to meet equipment loading limits and desired voltage profiles. They also prepare the network for load growth, new transmission lines, transformers, and added generation. In this way, power flow control remains a dynamic process that supports stability, efficiency, and reliability.

Voltage and Reactive Power Control

transmission-line differential equations

Modeling Voltage and Current on Transmission Lines

Transmission lines carry electric power, and their resistance, inductance, and capacitance are spread out along the line. Because these properties are distributed per unit length, voltage and current change as they move from one end of the line to the other. Differential equations are used to describe that variation. A line-section model helps show how this works. In the model, a small length, Δx, is used to represent the line. Voltage V(x) and current i(x) are measured from the receiving end.

lossless lines

Lossless Lines and Voltage Behavior

Lossless transmission lines in electrical engineering are described by a purely imaginary propagation constant and a resistive characteristic impedance. Their ABCD parameters show an equivalent pi circuit with an imaginary series impedance and a shunt admittance. When the product of beta and line length is less than pi, the line has inductive series impedance and capacitive shunt admittance, which keeps it lossless. Wavelength is the physical length over which voltage or current phase changes...

maximum power flow and line loadability

Transmission Line Power Limits and Loadability

Transmission line power limits and loadability depend on voltage, angle, and line impedance. For lossy transmission lines, ABCD parameters in phasor form are used to relate sending-end and receiving-end voltages and currents. This matrix relation makes it possible to find the receiving-end current and then calculate the complex power delivered to the load. From the complex power, the real and reactive power components can be determined. For a lossless line, the equations become simpler, and...

the power flow problem and solution

Power Flow Analysis in Electric Networks

Power flow analysis helps determine how real and reactive power move through an electric network. It uses the system’s single-line diagram, which shows the buses, transmission lines, transformers, and loads. The analysis focuses on balanced three-phase steady-state operation. Each bus in the system has four key variables: voltage magnitude V k, phase angle δ k, real power P k, and reactive power Q k. Two of these four variables are treated as inputs. The power flow program solves for the...

Voltage and reactive power control help keep a power system stable and efficient. In this topic, generator settings, switched equipment, and transformer taps work together to guide how power moves through the network. A generator can be modeled with a Thevenin equivalent circuit under balanced steady-state conditions. The main terms are terminal voltage Vt, excitation voltage Eg, power angle δ, and positive-sequence synchronous reactance Xg. From this model, the generator current and the...

fast decoupled and dc powerflow

Power Flow Shortcuts for Grid Contingencies

Fast decoupled power flow and DC power flow give engineers faster ways to study a power system during contingencies such as generator outages or transmission line failures. These methods help operators get quick power flow solutions, which is important for real-time system adjustments. Fast decoupled power flow simplifies the Jacobian matrix, the set of equations used in power flow calculations, by neglecting some elements. The method drops J2 and J3 and assumes voltage magnitudes stay close...

key terms and concepts

Learn how generator settings, shunt capacitors, reactors, and tap-changing transformers help control voltage, reactive power, and power flow in power systems.

Voltage and Reactive Power Control | JoVE K12

JoVE Core Electrical Engineering offers easy-to-understand animated videos that cover fundamental concepts of electric circuits along with circuit analysis techniques. It incorporates first-order and second-order circuits using operational amplifiers and circuit transformation concepts. The inclusion of practical design examples and real-world applications through scientist-in-action videos adds significant educational value, making complex concepts accessible.

electrical engineering

Voltage and Reactive Power Control

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