1. Static var generator product introduction
Static Var Generator (SVG) is a device that uses a bridge converter composed of fully-controlled power electronics to perform reactive power compensation. It applies power electronics technology, computer technology and modern control system to the power system. Through the control of the output current phase of the device, continuous reactive power regulation is performed from the whole range of inductive to capacitive, and the system's demand for reactive power is quickly compensated. SVG can dynamically compensate reactive current, thereby reducing line losses and increasing the active transmission capacity of the line.
The basic principle is that the three-phase bridge circuit is connected in parallel to the power grid through the reactor, and the phase and amplitude of the output voltage of the AC side of the bridge circuit are properly adjusted or the current of the AC side is directly controlled, so that the circuit can be absorbed or issued to meet the requirements. The reactive current achieves the purpose of dynamic reactive power compensation. The working principle and compensation mode are shown in the figure below.
Figure 1-2 Static var generator SVG output current compensation mode
2, the function of the static var generator
2.1 SVG product features
l Line status acquisition: LCD LCD display, detecting the voltage, current value and waveform, power factor, harmonic content and other important power quality parameters of the SVG.
l Dynamic compensation reactive power: linear output, reactive power full capacitive - full inductive output, no dead angle compensation, system power factor ≥ 0.99 after compensation and response time <5ms.
l Unbalanced treatment: It has three-phase unbalanced control and voltage regulation function to improve the safety of 0.4kv distribution.
2.2 SVG product technical parameters
l Working temperature: -10 ° C ~ +45 ° C;
l Storage temperature: -25 ° C ~ +60 ° C;
l Altitude: ≤1000m, above 1000m, according to GB/T 3859.2 derating;
l Relative humidity: 5%-95%, no condensation;
l Compensation method: rated inductive reactive to rated capacitive reactive continuous stepless adjustable;
l Compensation effect: power factor up to 0.99;
l Response time: 5ms;
l Overload protection: automatic limit to rated current output;
l Active loss: <4% rated power module;
l Working mode: automatic or manual;
l Communication interface: RS 485, Ethernet;
l Expansion capability: the same model is directly parallel, the number is not less than 10;
l Noise: ≤65Db;
l Grid voltage: 400V, allowed to fluctuate ±20%;
l Grid frequency: 50Hz ± 2%
l Weight: 50kg
l Protection level: IP20
2.3 SVG product appearance
Figure 2-2 Appearance of the SVG module
2.4 SVG product advantages
In addition to the wider application environment, SVG also has excellent performance when used in a conventional power distribution environment. Refer to Table 2-1 for details.
Table 2-1 Performance comparison between static var generator (SVG) and traditional reactive power cabinet (SVC)
3. Market demand for static var generators
3.1 The importance of SVG
All places where low-voltage transformers are installed and large-scale electrical equipment should be equipped with reactive power compensation equipment (specified by the national power department), especially those industrial and mining enterprises, enterprises and residential areas with low power factor must be installed. Large asynchronous motors, transformers, electric welders, punching machines, lathes, air compressors, presses, cranes, smelting, steel rolling, aluminum rolling, large switches, power filling equipment, electric locomotives, etc. are especially needed. In addition to incandescent lighting in residential areas, air conditioners, freezers, etc. are also objects that cannot be ignored for reactive power. The rural electricity consumption is relatively bad. In most areas, the power supply is insufficient, the voltage fluctuation is very large, and the power factor is especially low. The installation of reactive power compensation equipment is an effective measure to improve the power supply status and improve the power utilization rate.
Therefore, reactive power compensation is a rigid requirement, and in the following industry environment, SVG's infinite compensation and real-time advantages are particularly obvious, and its importance is reflected:
1) Metallurgical industry: mainly rolling mills existing in production lines;
2) Petroleum industry: mainly for motors for winches that frequently start up quickly, hoists for pumping units, turntables, etc.;
3) Rail transit: heavy-duty cable transmission over long distances and severe three-phase unbalanced conditions due to demand characteristics;
4) Automotive industry: A large number of electric welders or laser welding machines are used, which are followed by no-load operation after a short interval of welding.
In these environments, the load demand for reactive power is short and high. If a conventional capacitor compensation cabinet is used, the capacitor pack has a fixed capacity and cannot be compensated for dead angles. For other reasons, it is often unable to meet the actual needs of use. At this time, SVG is needed for governance, because its application can overcome the slow response speed of traditional reactive compensators such as LC compensator, the compensation effect cannot be accurately controlled, and it is easy to parallel resonance with the power grid. Disadvantages such as switching shocks.
In addition to the environment where the load is fluctuating frequently, there are some more difficult environments for SVG, such as:
1. The higher THDu causes the SVC to not be put into normal operation or even burn the machine;
2. The load three-phase is unbalanced, and the SVC cannot be effectively compensated and adjusted;
3, photovoltaic end-connected system, there may be a case of active power is 0, SVC controller can not determine the direction, resulting in SVC can not be put into normal use......
The above traditional conditions can not be applied or the effect is very poor, and SVG can completely overcome this kind of working condition. SVG has stronger applicability and can be applied to various complicated and difficult working conditions. It is the best reactive power compensation product at present.
3.2 SVG market prospects
Reactive power compensation plays a role in improving the power factor of the power grid in the power supply system, reducing the loss of the power supply transformer and the transmission line, improving the power supply efficiency, and improving the power supply environment. Therefore, the reactive power compensation device is in an indispensable and important position in the power supply system. Reasonable selection of compensation devices can minimize the loss of the power grid and improve the quality of the power grid. Conversely, if selected or used improperly, it may cause many factors such as power supply system, voltage fluctuation, harmonic increase and so on.
For the domestic low-voltage reactive power compensation market, it is closely related to the low-voltage governance that the power grid company is advancing. Strengthening the optimal configuration of reactive power compensation of low-voltage distribution network and maintaining reactive power balance plays an important role and significance for ensuring power quality and reducing power grid loss, and meets the requirements of the State Grid Corporation's “12th Five-Year” reactive power development plan. With the increase of the grid company's investment in the low-voltage network market, the low-voltage governance market will show a rapid growth trend from 2015 to 2020. It is expected that the scale of the low-voltage governance market will increase from 200 million yuan in 2014 to 82 in 2020. 100 million yuan. According to the market share of reactive power compensation occupying 20% of low voltage control, it is estimated that by 2020, the market scale of low voltage reactive power compensation will reach 1.64 billion yuan. At present, reactive power compensation on the market is still dominated by the application of SVC. With the development of technology, SVG is better than SVC because of its performance, and the cost is also declining in recent years. It has a certain price competitiveness and will become a low-voltage reactive power compensation. The important development direction of the market.
Figure 3-1 Market Forecast of Low Voltage Reactive Power Compensation in China Network from 2010 to 2020
Static VAR generators (SVG) are one of the power quality products. In terms of governance performance, it integrates power monitoring, equipment protection, and communication functions. It has powerful governance capabilities and can perfectly respond to various reactive power compensation needs. One strengthens the transmission and distribution capabilities of the power grid, and the other avoids users. Being fined due to insufficient power factor has brought great economic benefits to users; in the sales market, with the development of the national economy and the continuous expansion of the domestic low-voltage reactive power compensation market, the market demand for ANSVG is extremely fast. The speed of growth; in terms of customer experience, due to its highly integrated module design, post-maintenance and expansion becomes easier and more convenient, and the humanized intelligent human-machine interface and host computer communication function make device monitoring easier. . It can be seen that the selection of static var generator products is of great benefit to both grid facilities and users, achieving a win-win situation for both parties.