The application of FGI Static Var Generator (SVG) in harmonics control in steel works

1.Background

In today's power system, harmonic problem has been paid more and more attention. The existence of harmonics will not only affect the normal operation of power equipment, but also threaten the stability of the entire power grid. The application of a large number of power electronic equipment increases the harmonics in the system, such as frequency converters, inverters, rectifiers, etc., these devices in the process of converting current and voltage, due to the nonlinear working characteristics, will produce a large number of harmonics; In the process of iron and steel smelting, some loads such as electric arc furnace and rolling mill will produce a large number of harmonics, which is one of the important harmonic sources in the power system.

2.Difficulties

Harmonics will increase the heat loss of power supply lines and electrical equipment, and even cause short circuit, fire and other accidents in serious cases;

Harmonic current in the motor and transformer will produce additional copper and iron losses, resulting in equipment heating, reducing efficiency, and even damage to equipment;

When harmonic current flows through the cable, it will increase the dielectric loss of the cable, the skin effect of the conductor and the proximity effect, resulting in an increase in the temperature rise of the cable and shorten the service life of the cable. Fourth, the flow of harmonic current in the power grid will increase the power loss of the power grid and reduce the efficiency of the power grid.

Harmonics have adverse effects on electrical equipment, power grid and power supply system, and other systems and equipment. Therefore, effective measures should be taken to control harmonics in the power system to ensure the safe and stable operation of the power system.

3.Solution

FGI high voltage static var generator (SVG) can detect and control harmonics in power grid. SVG detects the harmonic frequency of the power grid, and sends out the reverse harmonic with the same frequency through the control algorithm to achieve the effect of fast tracking and controlling harmonics.

The site is a steel rolling plant in Fujian Province. There are many rolling mills with different power.

After measurement, the field harmonic content exceeds the standard, affecting the safety of other equipment, and it needs to be treated. FGI installed an SVG on the 10kV side in combination with the field situation to detect harmonics in the power grid in real time and control them.

(1)Before harmonic control

Before harmonic control, the field mainly generates 5, 7 and 11 current harmonics, and the current harmonic data on the system side are shown in the figure.

Compensating the first 5 harmonic currents 32A

Compensates the first 7 harmonic currents 9A

Compensates the first 11 harmonic currents 9A

(2)After harmonic control

After using SVG on site to compensate current harmonics, the 5th, 7th and 11th current harmonics on the system side are significantly reduced, as shown in the figure.

Compensates the 5th harmonic current 3A

Compensates the 7th harmonic current 3A

Compensates the first 11 harmonic currents 2A

After the equipment was put into operation, the field harmonics were significantly improved to meet the requirements of relevant standards

4.Product advantages

The FGI configuration scheme is based on the actual site conditions and has the following advantages:

 (1)Static var generator Provides harmonic control functions

SVG equipment can control harmonics below 25 times to protect the safety of electrical equipment.

(2)Static var generator provides excellent high-low voltage crossing function

The high and low voltage crossing range and duration and other indicators are higher than the national standard, which can maintain the equipment in the case of power grid voltage sudden drop or sudden rise, and does not expand the accident.

(3)Static var generator provides high response speed and accurate compensation

The response time of SVG is less than 5ms, which can react quickly to power grid fluctuations, adjust power in time, and reduce fluctuations.

FGI, as a leader in the power quality management industry with leading shipments and market share in the industry, provides a full range of power quality solutions, provides high-quality products and services for users in various industries, and contributes FGI to the construction of a new power system.