A Static Synchronous Compensator (STATCOM) is a power electronic device used for voltage control and reactive power compensation in electrical power systems. It is typically connected to the grid and is capable of injecting or absorbing reactive power to regulate the system voltage.

The control of voltage by a STATCOM is primarily achieved by manipulating its reactive power output. Here's a basic overview of how STATCOM controls voltage:

Voltage Sensing:

The STATCOM measures the voltage at its point of connection to the grid using voltage sensors or potential transformers.

Voltage Reference:

A desired or reference voltage level is set, which represents the desired voltage at the point of connection. This reference can be manually set or determined by an automatic voltage control system.

Error Detection:

The measured voltage is compared to the reference voltage to determine the voltage deviation or error. The error represents the difference between the actual voltage and the desired voltage.

Control Algorithm:

The control algorithm, usually implemented in a microprocessor-based controller, calculates the control signal based on the voltage error. The control algorithm determines the amount of reactive power that needs to be injected or absorbed by the STATCOM.

Modulation and Pulse Width Modulation (PWM):

The control signal is converted into switching signals that control the power electronic devices inside the STATCOM. These devices, such as insulated gate bipolar transistors (IGBTs), are used to create the required voltage waveform.

Injecting or Absorbing Reactive Power:

Based on the modulation and PWM signals, the STATCOM generates the necessary reactive power by switching its power devices. The injected or absorbed reactive power interacts with the grid, compensating for voltage fluctuations and regulating the voltage at the point of connection.

Feedback and Iteration:

The voltage sensing process is continuous, and the control algorithm adjusts the reactive power output of the STATCOM based on the feedback of the measured voltage. This feedback loop ensures that the voltage is continuously regulated.

By dynamically adjusting the reactive power output, the STATCOM can maintain the grid voltage at the desired level, mitigate voltage fluctuations, and improve the stability and performance of the electrical power system.

Here, we usually call Statcom as high voltage Static Var Generator(SVG).