An Kerui Hu Wei
Jiangsu Ankerui Electric Manufacturing Co., Ltd. Jiangyin 214405
Abstract: This article describes the static var generator products from the aspects of power quality control effect and market demand, expounds its basic principle and market demand, and analyzes its advantages relative to traditional reactive compensation cabinets.
Keywords: static var generator function market demand
1 Introduction
Due to the rapid development of power electronics technology, a large number of non-linear loads and unbalanced loads (such as LED lights, UPS, frequency converters, etc.) and new power generation methods and energy storage methods have emerged in large-scale industrial sites. Rectifiers and inverters, all of which lead to the generation of a large number of harmonics; and in these large industrial sites, there are generally rapidly changing loads such as crane equipment, elevators, electric welders, and mixers. In places where a large number of harmonic waves are generated and the load changes rapidly, the traditional capacitive reactive power compensation device has been difficult to meet the demand for reactive power compensation. At this time, it is necessary to use a static var generator to perform reactive power compensation.
2 Static var generator product introduction
The 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 electronic technology, computer technology and modern control systems to power systems. Through the control of the phase of the output current of the device, continuous reactive power regulation is performed from the inductive to the capacitive range and the demand for reactive power is quickly compensated for by the system. SVG can dynamically compensate for 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 to the power grid in parallel by a reactor, and the phase and amplitude of the output voltage of the AC side of the bridge circuit is appropriately adjusted or the AC side current is directly controlled, and the circuit can be absorbed or issued to meet the requirements. The reactive current, to achieve the purpose of dynamic reactive compensation. The working principle and compensation mode are shown in the figure below.
Figure 2-1 SVG working principle of static var generator
Figure 2-2 Static var generator SVG output current compensation mode
3 Functions of Static VAR Generator
3.1 SVG Product Features
Line status acquisition: LCD screen display, to detect the voltage, current value and waveform, power factor, harmonic content and other important power quality parameters of the SVG where the compensation circuit is required.
Dynamically compensated reactive power: linear output, reactive power full-capacity - full-inductive output, compensation no dead angle, system power factor after compensation ≥ 0.99 and response time <5ms.
Unbalanced governance: With three-phase unbalanced control and voltage regulation, improve the safety of 0.4kv distribution.
3.2 Technical Specifications of SVG Products
Working temperature: -10°C～+45°C;
Storage temperature: -25°C～+60°C;
Altitude: ≤1000m, more than 1000m in accordance with GB/T 3859.2 derating;
Relative humidity: 5%-95%, no condensation;
Compensation method: rated inductive reactive power to rated capacitive reactive power continuously and continuously adjustable;
Compensation effect: power factor up to 0.99;
Response time: 5ms;
Overload protection: automatic limit to rated current output;
Active loss: <4% rated power module;
Working mode: automatic or manual;
Communication interface: RS 485, Ethernet;
Expansion capability: direct parallel with the same model, the number is not less than 10 units;
Noise: ≤65Db;
Grid voltage: 400V, allowing fluctuation ± 20%;
Grid frequency: 50Hz±2%
Weight: 50kg
Protection class: IP20
3.3 SVG Product Appearance
Figure 3-1 SVG cabinet appearance
Figure 3-2 SVG module appearance
3.4 Product advantages
In addition to the wider application environment, SVG has excellent performance when used in a conventional power distribution environment. Refer to Table 3-1 for details.
Table 3-1 Performance Comparison between Static VAR Generator (SVG) and Conventional SVC
4 Market demand
4.1 The Importance of SVG
All areas where low-voltage transformers are installed and large-scale power equipments should be equipped with reactive power compensation equipment (specified by the State Power Bureau), especially those with low power factor, such as mining, enterprises, and residential areas. Large-scale asynchronous motors, transformers, welding machines, punch presses, lathes, air compressors, presses, cranes, smelting, steel rolling, aluminum rolling, large-scale switches, irrigation equipment, electric locomotives and other special needs. Apart from incandescent lighting in residential areas, air conditioners, freezers, etc. are also non-negligible power consumers. The situation of electricity consumption in rural areas is rather poor. In most areas, the power supply is insufficient, the voltage fluctuation is large, and the power factor is particularly 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 demand, and in the use environment of the following industries, the advantages of SVG's infinite compensation and real-time performance are particularly obvious, and its importance is reflected:
1) Metallurgical industry: It is mainly a rolling mill existing on the production line;
2) Oil industry: mainly winch motors that are frequently started quickly, hoists for pumping units, turntables, etc.;
3) Rail transit: a large number of long-distance cable transmissions and severe three-phase imbalance due to demand characteristics;
4) Automobile manufacturing industry: A large number of electric welding machines or laser welding machines are used, which are followed by no-load operation after a short interval of welding.
In these environments, the reactive power demand of the load is short time and high frequency. If the traditional capacitor compensation cabinet is used, the dead capacitor can't be compensated because of the fixed capacity of the capacitor bank, and the capacitor bank input and removal speed is slow. For other reasons, it is often impossible to meet practical use requirements. In this case, SVG is required to govern because its application can overcome the slow response speed of traditional reactive power compensators such as LC compensators, the compensation effect cannot be accurately controlled, and parallel resonance can easily occur with the power grid. Switching shocks and other shortcomings.
In addition to the environment where load reactive power fluctuates frequently, there are some harsher use environments where SVG is more advantageous, such as:
1. Higher THDu causes the SVC to fail to invest and even burn the machine.
2. Unbalanced three-phase load, SVC cannot compensate and adjust effectively;
3. In the photovoltaic terminal grid-connected system, there may be a situation where the active power is 0. The SVC controller cannot distinguish the direction, resulting in failure of the SVC to be used normally.
The traditional compensation for the above conditions cannot be applied or the effect is very poor. SVG can completely overcome this condition. SVG is more applicable and can be applied to a variety of complex and harsh working conditions. It is currently the best reactive power compensation product.
4.2 Market Prospects of SVG
Reactive power compensation plays a role in increasing the power factor of the power grid in the power supply system, reducing the loss of the power 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 very 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, improper selection or use may cause power supply systems, voltage fluctuations, harmonics, and other factors.
For the domestic low-voltage reactive power compensation market, it is mainly related to the low-voltage control that grid companies are advancing. Enhancing the optimal configuration of reactive power compensation for low-voltage distribution networks and maintaining reactive power balance has important roles and significance for ensuring power quality and reducing power grid losses, and meets the requirements of the State Grid Corporation's "12th Five-Year Plan" for reactive power development. As the grid companies invest more in the low-voltage network market, the low-voltage control market will show rapid growth from 2015 to 2020. It is expected that the scale of the low-voltage control market will increase from 200 million yuan in 2014 to 82 by 2020. 100 million yuan. According to the market share of reactive power compensation accounting for 20% of low-voltage control, it is expected that by 2020, the scale of low-voltage reactive power compensation in the network will reach 1.64 billion yuan. At present, reactive power compensation in the market is still dominated by the application of SVC. With the development of technology, SVG is better than SVC because of its performance. The cost has been declining in recent years, and it has certain price competitiveness and will become a low-voltage reactive power compensation. The important development direction of the market.
Figure 3-1 Forecast of Low-Voltage Reactive Power Compensation Market in China's Network from 2010 to 2020
5. Conclusion
Static var generator (SVG) is 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 a variety of reactive power compensation needs. It enhances the power transmission and distribution capabilities of the power grid and avoids users. Because of the lack of power factor, it was fined and brought great economic benefits to the user. In the sales market, with the development of the national economic level and the continuous expansion of the domestic market of low-voltage reactive power compensation, the market demand for ANSVG is extremely fast. The speed of growth; in terms of customer experience, due to its highly integrated module design, it has become easier and more convenient for future maintenance and expansion, and humanized intelligent human-machine interface and host computer communication functions have also made device monitoring easier. . It can be seen that the selection of static var generator products is of great benefit to the power grid facilities and users, achieving a win-win situation for both parties.
Reference materials
[1] Acrel Power Quality Monitoring and Management Selection Manual. 2015.08 version
[2] Ancorui Electric Co., Ltd. Product Manual, 2013.01.
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