A Three-Phase Static Var Compensator (SVC) is a device used in power systems to control and regulate the reactive power (var) flow on transmission lines or within distribution networks. Reactive power is essential for maintaining voltage levels and stability in an electrical grid. An SVC is designed to quickly and dynamically control the reactive power output or absorption to help stabilize the system voltage and improve power quality.
Here's how a Three-Phase SVC works:
Basic Components: An SVC typically consists of the following main components:
Thyristor Valves: These are semiconductor devices (thyristors or insulated gate bipolar transistors) that can be turned on or off to control the flow of reactive power. They are used to switch capacitors or reactors in and out of the circuit.
Capacitor Banks: These are banks of capacitors connected in parallel. They provide reactive power support to the system when switched on. Capacitors generate leading reactive power (capacitive) which helps to counteract the lagging reactive power (inductive) generated by loads.
Reactor Banks: These are banks of reactors connected in series. They provide inductive reactive power support to the system when switched on. Reactors generate lagging reactive power which helps to counteract leading reactive power generated by overvoltages or excessive capacitive loads.
Control Strategy: The SVC's control system measures the system's voltage and current in real-time. It uses this information to determine the amount of reactive power that needs to be injected or absorbed to maintain stable voltage levels.
Switching Operation: Based on the control strategy, the thyristor valves are triggered to switch the capacitor banks and reactor banks in and out of the circuit. When the thyristors are conducting, the corresponding capacitors or reactors are connected to the system, injecting or absorbing reactive power as needed.
Dynamic Compensation: The SVC can respond rapidly to changes in system conditions. For example, if there is a sudden increase in load or a disturbance that causes a drop in voltage, the SVC can quickly inject capacitive reactive power to counteract the voltage drop and improve system stability. Similarly, during periods of high voltage, the SVC can absorb reactive power to prevent overvoltage conditions.
Harmonic Filtering: An SVC can also provide some level of harmonic filtering due to the presence of reactive components. The reactors and capacitors can help mitigate harmonics and improve power quality.
In summary, a Three-Phase Static Var Compensator (SVC) is a device that uses thyristor-controlled capacitors and reactors to provide dynamic and rapid control of reactive power in an electrical system. By injecting or absorbing reactive power as needed, the SVC helps to regulate voltage levels, stabilize the power grid, and improve overall power quality.