Static var generator STATCOM

Wide application of sudden-change loads with nonlinear characteristics causes the need for special devices to provide normative values of power quality parameters, since the reactive power consumed from the network, voltage fluctuations (flicker), harmonic distortions, unbalance of voltages, etc.have a negative impact on the networks and reliability of power supply to consumers ‘ equipment.
One of the most common devices for solving this problem is a static thyristor compensator (SVC). With the advent of powerful high-voltage fully controlled devices such as IGCT and IGBT, it is possible to implement a new type of devices called SVG (static synchronous compensator).
This equipment has found a wide application in the world power engineering and possesses all advantages of the traditional equipment, and also surpasses it with many characteristics.

Application:

1. Power factor correction.
2. Reduction of losses in transmission and distribution of electricity through fast-acting reactive power compensation.
3. Control of harmonic distortions, elimination of their influence.
4. Improving the sustainability of transients and emergency conditions.
5. Increase in the capacity of electrical equipment by eliminating the reactive energy component consumed from the network.

SVG fundamentally solves the problem of electric power quality in power systems and has many advantages compared to analogues in its class.

Application scope

SVG is widely used in electric power systems, petrochemical and metallurgical industries, power supply of electrified rail transportation, etc. SVG is used in application of such renewable energy sources as wind and sun.

SVG main applications:

• arc steel furnaces
• lifting mechanisms of coal mines and ports
• rolling metallurgical mills
• traction substations of electrified railway transport
• wind, solar power generation
• machine-building production lines

Symbol structure

The structure of symbols consists of model type, design code, rated power, rated voltage, characteristics.

1                                2                               3                                 4                              5

1. Type code
2. Design code
3. Rated power, MVAr
4. Rated voltage, kV
5. Code of characteristic

Code type – SVG
Structure code consists of two-digit number (assigned by the manufacturer)
Characteristic code consists of two symbols:

1. S – single-phase
   Y – scheme of connection – star
   D – scheme of connection – triangle
2. N – natural cooling
   А – air cooling
   W – water cooling

Operation principle

SVG is a device for dynamic compensation of reactive power, the main element of which is a fully controlled inverter, built on the basis of bipolar transistors with a controlled shutter (IGBT).

U_s – network voltage
U_L – output voltage SVG applied to reactor
Reactor current I_L – occurs as a result of difference of network voltage and output voltage of SVG and controlled by it.

To reduce distortions, a corresponding harmonic voltage is generated by SVG when compensating the reactive power at the output.

Advantages

1. Minimal impact on the supply network at a startup.
2. Flexible range of reactive power compensation. Regulation is carried out both in the capacitive and in the inductive range.
3. High-speed response of the control system. SVG high-speed performance is about 10 MS, which allows compensation of the reactive power for a sudden-change load, a more effective reduction of flicker oscillations.
4. Improved filtering of harmonic distortions.
5. Smaller dimensions and floor space compared to analogues.
6. High efficiency.
7. The lack of power generation dependence from network voltage.
8. High reliability with automatic shunting of damaged in-series module.
9. Multi-compensation function allows to monitor the overvoltage in real time, which improves a system voltage stability, to maintain the voltage in the transmission lines in dynamic modes, to damp power oscillations of energy system.

Structure and distinctive features

1. A modular structure of the circuit. The main element SVG is an inverter of chain type, based on IGBT thyristors. Each phase of the inverter consists of several power modules connected in series.
2. Monitoring and interface. The monitoring function is implemented by the main controller and touch panel. Personnel interaction with the system is carried out using a special interface and is as flexible as possible. The information board/display displays various parameters such as voltage of power module, fault current/input current/output current of the power module, load current, faults and errors, and can also display the current waveform of voltage and current.
3. Using communication interfaces RS232/RS485 there is a communication with external network through communication protocols Modbus, Profibus, TCP/IP, etc. according to IEC 61850.
4. There is a real-time monitoring via a remote computer. The device transmits operational data, alarm information, etc. to the server via a network connection into the system. Operation monitoring is carried out in real time mode, the reliability of system operation and maintenance significantly increases.
5. There is a programming of parameters. Multifunctional programming of parameters is also carried out locally directly from the controller.
6. There is an uninterruptible power system. When the supply voltage is switched off, the power comes from a backup source, which does not affect the operation of the device and qualitatively affects the safety and reliability of the equipment.
7. Electromagnetic compatibility. The power supply module and the main control unit are connected via an optical communication channel, which can significantly reduce all kinds of interference. Specially designed cabinet is equipped with a protective screen that prevents external electromagnetic interference.
8. It is possible to manufacture equipment in the insulated container with placement category UHL1 according to GOST 15150-69

SVG technical characteristics