A Dynamic Voltage Restorer (DVR) is a power quality device used to mitigate voltage sags, swells, and other voltage disturbances in electrical power systems. When combined with supercapacitor storage, it enhances its performance by providing rapid energy storage and release capabilities. A three-phase DVR with supercapacitor storage operates as follows:
Sensing: The DVR continuously monitors the voltage at the point of connection to the power grid. It detects voltage disturbances such as sags (temporary reductions) or swells (temporary increases) in the voltage level. These disturbances can be caused by various factors, including faults, switching operations, and load changes.
Detection and Decision-Making: When a voltage disturbance is detected, the DVR's control system analyzes the severity and duration of the disturbance. Based on this analysis, the control system decides whether to inject compensating voltage to mitigate the disturbance.
Supercapacitor Storage: Supercapacitors are used to store and release electrical energy rapidly. Unlike conventional batteries, they can charge and discharge quickly, making them suitable for applications where rapid response is required. In a DVR, supercapacitors are connected to the grid via power electronic converters.
Energy Injection: If a voltage sag is detected, the DVR control system triggers the power electronic converters to discharge energy from the supercapacitors into the grid. This injection of energy compensates for the reduced voltage level during the sag, helping to restore the voltage to the desired level.
Energy Absorption: Conversely, if a voltage swell occurs, the DVR can absorb excess energy from the grid and store it in the supercapacitors. This action helps prevent equipment damage and stabilize the voltage level.
Control Strategies: The control strategies used in a three-phase DVR with supercapacitor storage are designed to respond quickly to voltage disturbances while maintaining stable and balanced operation of the system. These strategies involve regulating the voltage amplitude, frequency, and phase angles of the injected compensating voltage to match the grid's nominal conditions.
Transitioning: After the disturbance has passed and the grid voltage returns to normal, the control system gradually reduces the compensation provided by the DVR. This transition prevents sudden changes in voltage levels that could potentially impact connected equipment.
By integrating supercapacitor storage into a three-phase DVR, the device can provide rapid and high-power energy injection or absorption, making it more effective at mitigating voltage disturbances compared to traditional DVRs without energy storage. This combination enhances power quality, minimizes equipment damage, and improves the overall reliability of the electrical power system.