SVC is a set of electrical devices for adjusting reactive power fast and effectively in high-voltage power grid, which can regulate voltage and power factor, keeping voltage stable and improving power quality. It is widely used in power transmission, HVDC converter station, industrial field and wind farm, and so on.
The PCS-9580 SVC system mainly consists of the following components:
The static var compensator is normally installed at low voltage side of main transformer, otherwise a step-down transformer is needed to reduce the voltage.
Medium Voltage Switchgear
The medium voltage switchgear typically includes isolating switches, grounding switches and transformers. It can be installed indoors or outdoors.
Linear (Air-core) Reactor
The air-core reactor in static var compensator has high stability and high linearity. It is used to absorb reactive power under the control of thyristors. Usually the air-core reactor is connected in series to the thyristor valve in delta-connection, and then connected to the power grid.
The thyristor valve is the main control part in a SVC system. It is composed of several series/paralleled connected thyristors and its auxiliary components. The thyristors are triggered by photoelectric triggering system and it adopts water cooling as the main cooling method.
The capacitor/filter banks can supply sufficient capacitive reactive power to power grid and filter the harmful harmonics. The filter is composed of capacitors, reactors and resistors, providing capacitive reactive power to the entire system.
In practical, the capacitor/filter banks are divided into several sub-banks which can be switched by mechanical breakers or other electrical switches according to the actual situation.
The heat produced by thyristor valve will be harmful to thyristors if the heat is not dissipated in time. The water cooling system is sufficient for the thyristor valves which have a high operating voltage. The cooling system uses the de-ionized pure water for internal cooling and airwind for outdoor cooling.
SVC Control and Protection System
The key functions of SVC control and protection system are:
Generating the control pulses to the valve at suitable time to fire the thyristors
Monitoring the SVC system to provide operation condition, fault record or self checking information
Switching the FCs in order
Protecting each component to ensure the safe operation of SVC
Friendly Human-Machine Interface
The SVC can be seen as a dynamic reactive power source. It can supply capacitive reactive power to the grid or consume the spare inductive reactive power from the grid. Normally, the system can absorb the reactive power from a capacitor bank, and the spare part can be consumed by an air-core shunt reactor.
Typically, there is one or more banks of fixed or switched shunt capacitors or reactors in one SVC system, of which at least one bank is switched by thyristors. The widely applied elements in SVCs include: thyristor controlled reactor (TCR), thyristor switched reactor (TSR),thyristor switched capacitor (TSC), breaker switched capacitor/ filter capacitor (BSC/FC).