1.The role of SVG
Static Var Generator is a typical power electronic equipment, which is composed of three basic functional modules: detection module, control operation module and compensation output module. Its working principle is to detect the current information of the external CT system, and then analyze the current information, such as PF, S, Q, etc., through the control chip; Then the controller gives the compensated drive signal, and finally the inverter circuit composed of the power electronic inverter circuit sends out the compensated current.
The SVG Static Var Generator consists of a self-commutating bridge circuit composed of a turn-off power electronic device (IGBT), which is connected to the power grid in parallel through the reactor, and the amplitude and phase of the output voltage on the AC side of the bridge circuit can be properly adjusted, or the current on the AC side can be directly controlled. Quickly absorb or emit the required reactive power to achieve the purpose of rapid dynamic adjustment of reactive power. As an active compensation device, it can not only track the impulse current of impulse load, but also track and compensate the harmonic current.
2.Difference between SVG and SVC
SVG is the abbreviation of Static Var Generator, which is also known as static synchronous compensator (STATCOM);
SVC is an acronym for Static Var Compensator.
(1)SVG
It can be divided into voltage type and current type, which can provide both lagging reactive power and leading reactive power. Simply put, the basic principle of SVG is that the self-commutating bridge circuit is connected to the power grid through the reactor or directly in parallel, and the phase and amplitude of the output voltage on the AC side of the bridge circuit are properly adjusted, or the current on the AC side is directly controlled, so that the circuit can absorb or emit reactive current to meet the requirements and achieve the purpose of power reactive compensation.
(2)SVC
It is a typical power electronic device for reactive power compensation, which uses thyristor as a solid-state switch to control the capacity of the reactor and capacitor in the access system, thereby changing the admittance of the transmission system. According to the different control objects and control methods, it is divided into the static reactive power compensation device (FC+TCR) used with thyristor control reactor (TCR) and thyristor switching capacitor (FC) and the device used with TCR and mechanical switching capacitor (MSC).
3.The advantages of SVG and SVC comparison
STATCOM has the following advantages compared with synchronous modulation camera and SVC device:
Using digital control technology, the system has high reliability, basically does not need maintenance, and can save a lot of maintenance costs;
The performance of improving the transient stability of the system and damping the oscillation of the system is much better than that of the traditional synchronous modulation camera;
The control is flexible, the adjustment speed is faster, the adjustment speed is wide, and the response speed can be adjusted continuously and quickly under the inductive and capacitive operating conditions.
static operation, safe and stable, no large rotating equipment like the adjusting camera, no wear, no mechanical noise, will greatly improve the life of the device, improve the environmental impact;
The capacitor capacity requirements are not high, can save the conventional device in the large inductance and large capacitance and huge switching mechanism, so that STATCOM small volume, low loss;
Small connection reactance. The connection reactance of STATCOM to the power grid is to filter out the higher harmonics existing in the current, and to connect the converter to the power grid, so its inductance is far less than the inductance required to compensate SVC devices such as TCR with the same capacity.