How can power system operators use FACTS controllers to optimize voltage and reactive power profiles?

1 What are FACTS controllers?

FACTS controllers are power electronic devices that can modify the electrical parameters of transmission lines, such as impedance, voltage, and phase angle. They can be classified into four categories based on their functions: series controllers, shunt controllers, combined series-shunt controllers, and coordinated controllers. Series controllers insert a voltage in series with the line to control the power flow and the line impedance. Shunt controllers inject or absorb reactive power at the line terminals to control the voltage and the reactive power flow. Combined series-shunt controllers perform both functions simultaneously or selectively. Coordinated controllers coordinate the actions of multiple FACTS controllers to achieve a global objective.

2 How can FACTS controllers optimize voltage profiles?

Voltage profiles are affected by the balance between reactive power generation and consumption in the system. When there is a surplus of reactive power, the voltage rises. When there is a deficit of reactive power, the voltage drops. FACTS controllers can optimize voltage profiles by adjusting the reactive power balance at different points of the system. Shunt controllers can inject or absorb reactive power locally to regulate the voltage at the point of connection. Series controllers can regulate the voltage drop across the line by changing the line impedance. Combined series-shunt controllers can perform both functions and also compensate for voltage unbalance and harmonics. Coordinated controllers can optimize the voltage profile of the entire system or a specific area by coordinating the actions of multiple FACTS controllers.

3 How can FACTS controllers optimize reactive power profiles?

Reactive power profiles are affected by the power flow patterns and the line impedances in the system. When the power flow is high, the reactive power losses increase. When the line impedance is high, the reactive power flow is limited. FACTS controllers can optimize reactive power profiles by modifying the power flow patterns and the line impedances in the system. Series controllers can control the power flow and the line impedance by inserting a voltage in series with the line. They can also transfer reactive power from one line to another to balance the reactive power distribution. Shunt controllers can control the reactive power flow and the line impedance by injecting or absorbing reactive power at the line terminals. They can also provide dynamic reactive power support to improve the system stability and security. Combined series-shunt controllers can perform both functions and also provide voltage and reactive power compensation for multi-terminal systems. Coordinated controllers can optimize the reactive power profile of the entire system or a specific area by coordinating the actions of multiple FACTS controllers.

4 What are the benefits of using FACTS controllers?

The use of FACTS controllers to optimize voltage and reactive power profiles can bring a range of advantages to power system operators. These include improving the stability and security of the system, increasing its efficiency and reliability, enhancing the quality and flexibility of the system, and reducing the cost and environmental impact of the system. Specifically, FACTS controllers can enhance voltage and reactive power margins, damp oscillations, prevent cascading failures, reduce losses, congestion, and outages, increase utilization and availability of transmission lines, mitigate voltage sags, swells, unbalance, and harmonics, facilitate the integration of renewable energy sources and distributed generation, minimize the need for additional generation, transmission, and compensation equipment, and enable the use of cleaner and cheaper energy sources.