Static reactive power generator is the self-commutating bridge circuit through the reactor or directly connected to the power grid, adjust the phase and amplitude of the AC side of the bridge circuit output voltage, or directly control its AC side current, so that the circuit absorbs or sends out the reactive power to meet the requirements, to achieve the purpose of dynamic reactive power compensation.
sketch
Static Var Generator, English description: Static Var Generator, SVG for short. Also known as high voltage dynamic reactive power compensation generator, or static synchronous compensator. It refers to a free commutating power semiconductor bridge converter to carry out dynamic reactive power compensation device. SVG is the best scheme in the field of reactive power control. Compared with the traditional modulation camera, capacitor reactor and traditional SVC with thyristor control reactor TCR as the main representative, SVG has incomparable advantages.
Application situation
Where there is a low-voltage transformer installed and next to large electrical equipment should be equipped with reactive power compensation devices (this is the provisions of the national power department), especially those with low power factor industrial mines, enterprises, residential areas must be installed. Large asynchronous motors, transformers, welding machines, punches, lathes, air compressors, presses, cranes, smelting, steel rolling, aluminum rolling, large switches, electric irrigation equipment, electric locomotives, etc. In addition to incandescent lighting in residential areas, air conditioning, refrigerators, etc., are also reactive power consumption objects that can not be ignored. The rural electricity situation is relatively bad, most areas lack of power supply, voltage fluctuation is very large, power factor is especially low, installing compensation equipment is an effective measure to improve the power supply situation and improve the utilization rate of electric energy.
Advantage
1, compensation method: the domestic reactive power compensation device is basically the use of capacitors for reactive power compensation, the compensated power factor is generally about 0.8-0.9. SVG uses a power module for reactive power compensation, and the compensated power factor is generally above 0.98, which is the most advanced power technology in the world. 2, compensation time: the domestic reactive power compensation device to complete a compensation at the fastest time of 200 milliseconds, SVG in 5-20 milliseconds can complete a compensation. Reactive power compensation needs to be completed in the instant, if the compensation time is too long, it will cause no reactive power when it should be, but not when it should be reactive power.
3, graded stepless: the domestic reactive power compensation device basically uses 3-10 levels of compensation, each increase or decrease is tens of thousands of watts, can not achieve accurate compensation. SVG can carry out stepless compensation from 0.1 kilobar, which fully realizes accurate compensation.
4, harmonic filtering: domestic reactive power compensation device because the use of capacitive, capacitor itself will amplify harmonics, so it can not filter harmonics, SVG does not produce harmonics will not amplify harmonics, and can filter more than 50% of harmonics;
5, service life: the domestic reactive power compensation device is generally used contactor or thyristor control, resulting in a short service life, generally in about three years, its own loss and frequent maintenance. SVG has a service life of more than ten years, its own loss is minimal and basically do not need to be maintained.
Why use
Reactive power compensation technology is a very traditional power technology, it represents the level of a country’s power, reactive power compensation is the low-voltage transformer transmission to the idle work into useful work. This is how:
(1) Reduce the line loss by more than 50%. As far as the country is concerned, the line loss accounts for about 12%, which is mainly the loss caused by the reactive power component, if the reactive line loss is reduced by 50% to 60%, a year can save about 50 billion degrees of electricity, equivalent to half of the Three Gorges project power generation. This kind of project that can increase the power generation without consuming primary energy is an excellent green project. And the investment is very small, quick effect.
(2) Avoid fines. China’s Ministry of Power and Price Bureau “on the issuance of the” power factor adjustment electricity rate Measures “notice”, power factor 0.94, reduce the electricity rate by 1.1%, power factor 0.6 increase electricity rate by 15%. For example, a 315KVA transformer, the power factor increased from 0.6 to more than 0.94, the annual reward and penalty difference of 30,000 to 40,000 yuan.
(3) Expansion will be achieved without additional investment. After reactive power compensation, the power load ratio can be increased, and the transformer can run at full load. For example, a 315KVA transformer, power factor COS Phi =0.6 load transformer can only provide quality service 189KW active power, can not withstand the capacity of about 300KW, need to buy a 500KVA transformer replacement. The power factor is increased from 0.6 to 0.98, which is equivalent to an expansion of 63%, and the active power is increased from 189KW to 309KW, which can basically meet the required capacity, saving a 500KVA transformer, and the cost is about 300,000 yuan.
(4) Improve power quality, extend the life of electrical appliances, and improve product quality.
Working principle
SVG uses power electronic devices (such as IGBT) that can be turned off to form a self-commutating bridge circuit, which is connected to the power grid in parallel through the reactor to properly adjust the amplitude and phase of the output voltage on the AC side of the bridge circuit, or directly control the current on the AC side. 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.
The voltage source type inverter consists of two parts: DC capacitance and inverter bridge, wherein the inverter bridge is composed of a semiconductor device IGBT that can be turned off
In operation, by adjusting the switch of the IGBT device in the inverter bridge, the amplitude and phase of the voltage from DC inverter to AC can be controlled, so the whole device is equivalent to a phase-modulated power supply. By detecting the required reactive power in the system, equal and opposite reactive power can be emitted quickly, and the reactive power can be locally balanced to keep the system running at a high rate factor.
1, static var generator, English description: static var generator, SVG for short. Also known as dynamic reactive power compensation generator, or static synchronous compensator. The utility model refers to a device for dynamic reactive power compensation by a self-commutating power semiconductor bridge converter.
2. In the power system, in order to reduce the power loss caused by the large amount of reactive current provided by the distribution network to the load, reactive power compensation devices with corresponding voltage levels should be configured at each power receiving point to improve the power grid transmission capacity and save energy. At present, the capacitor switching compensation used by industrial and mining enterprises for a long time, but the capacitor compensation configuration is relatively low, and the operation stability of the switching compensation device is poor, which is manifested in:
1, low voltage fixed capacitor bank compensation capacity is not adjustable. The switching capacitor bank is graded switching, which often causes the transformer to run in the best economic condition, increase the side line loss of the upper power supply, and decrease the economic benefit.
2. The capacitor cannot be continuously switched frequently, because the capacitor requires discharge time.
3, the corresponding speed of the switching capacitor is slow, and the dynamic reactive power cannot be compensated, that is, the fast load cannot be compensated. Using AC contactor to switch capacitor, the corresponding speed is slow and will produce surge impact, operating overvoltage, arc and other phenomena, the switch and capacitor damage is serious.
4, each group of capacitors has a stage difference, can not be continuously compensated, the power factor will not be compensated very high
5, harmonic occasions can not be used, will break down the capacitor, will cause resonance, cause capacitor explosion, should be selected active filter (APF) or reactor.
Application field
Metallurgical industry: mainly exists in the production line of rolling mills.
Petroleum industry: mainly frequent and fast start winch motor, pumping unit hoist, turntable and so on.
Rail transit: Extensive use of cables for long-distance transmission, and serious three-phase imbalance due to demand characteristics.
Automotive manufacturing: A large number of welding machines or laser welding machines, in the short interval of welding followed by no-load operation, and will produce two voltage steps.