A three-phase voltage sag compensator, also known as a voltage sag mitigator or voltage sag corrector, is a device used to address voltage sags in a three-phase electrical power system. Voltage sags, also referred to as voltage dips or momentary voltage reductions, occur when the voltage level of the power supply drops below its nominal value for a short duration. Voltage sags can be caused by various factors such as faults, starting of large motors, or sudden changes in load.
The operation of a three-phase voltage sag compensator involves the following key components and steps:
Voltage Sensing: The compensator continuously monitors the incoming voltage waveform of all three phases using voltage sensors. These sensors measure the instantaneous voltage levels and provide feedback to the compensator's control system.
Detection and Analysis: When a voltage sag is detected, the compensator's control system analyzes the severity and duration of the sag. It determines whether the sag requires compensation and how much correction is needed.
Energy Storage: To mitigate the voltage sag, the compensator employs energy storage elements such as capacitors or batteries. These storage elements are connected to the system and can rapidly discharge energy to compensate for the voltage drop during a sag.
Voltage Injection: When a voltage sag is detected, the compensator's control system triggers the release of stored energy from the energy storage elements. This injected energy is added to the system voltage, effectively raising it back to the nominal level.
Phase Synchronization: The compensator ensures that the injected voltage is synchronized with the phase of the original power supply. This synchronization is crucial to prevent phase mismatches or imbalances that could disrupt the connected equipment.
Voltage Restoration: As the compensator injects the stored energy into the system, the voltage levels of all three phases gradually rise back to their nominal values. The compensation process typically takes a fraction of a second to a few seconds, depending on the design and capabilities of the compensator.
Monitoring and Feedback: Throughout the compensation process, the control system continues to monitor the system voltage and the effectiveness of the compensation. Once the voltage has been restored to its nominal value, the compensator's operation is halted until another voltage sag occurs.
Protection and Safety: The compensator is designed with protective mechanisms to prevent overcompensation or unintended disturbances to the power system. It also includes safety features to ensure proper functioning and prevent any hazardous situations.
Overall, a three-phase voltage sag compensator plays a crucial role in maintaining the stability and reliability of three-phase electrical systems by swiftly addressing voltage sags and ensuring that sensitive equipment and processes are not disrupted by these transient events.