A static var compensator is a type of static compensator for reactive power. A static var compensator is composed of thyristor-controlled reactors and capacitors. Due to the rapid response of thyristors to control signals and the unrestricted number of switching times, a static compensator can quickly and smoothly adjust when there are voltage changes to meet the needs of dynamic reactive power compensation. It can also provide phase compensation, SVC static var compensator has strong adaptability to three-phase unbalanced loads and impact loads. However, the control of thyristors during the switching process of reactors will generate high-order harmonics, so a dedicated filter needs to be installed.
Currently, a long-standing issue in the construction and operation of the power grid in China is insufficient reactive power compensation capacity and unreasonable equipment allocation, especially the lack of adjustable reactive power capacity and fewer rapid response reactive power control devices. In recent years, with the continuous increase of high-power nonlinear loads, the reactive power shock and harmonic pollution of the power grid have been on the rise. The lack of reactive power regulation means that bus voltages vary greatly with changes in operating conditions. This leads to increased line losses and a decrease in voltage qualification rate. In addition, with the development of the power grid, the issue of system stability has become more important. A static var compensator is an economic and effective measure to improve voltage stability.
Furthermore, there is also a strong demand for static var compensators in industries such as wind power plants, metallurgy, electrified railways, and coal. In the current situation, static-type dynamic reactive power compensators are effective in dealing with the reactive power shocks caused by various loads. They significantly improve power grid voltage fluctuations and power factors, and are a new type of energy-saving device with high technical content and significant economic benefits. Thyristor-based converters and control systems can achieve this functionality. They collect the reactive current and voltage values of the bus, synthesize the reactive power value, compare it with the set constant reactive power value, and calculate the triggering angle size. By using the thyristor triggering device, the thyristor passes through the required current.
The Static Synchronous Compensator utilizes new generation power electronic devices (such as gate turn-off thyristors, insulating gate bipolar transistors, integrated gate-commutated thyristors) and modern control techniques (such as inverse systems, direct feedback linearization, etc.) It has multiple functions such as compensating for inductive and capacitive reactive power, improving system power factor, improving power quality, and enhancing power system stability.