Main Functions of Static Synchronous Compensator
1. Improve the stability of power transmission
Installing a static synchronous compensator in a long-distance transmission system can not only compensate the reactive power losses of the line, increase line voltage, and improve effective transmission capacity under normal operation, but also provide timely reactive power regulation, reduce system oscillation, and improve system stability in case of fault.
2. Maintain the receiving-end voltage level
As the high capacity load center lacks reactive power support, grid voltage dip, even voltage collapse, may be caused. However, STATCOM is able to adjust the reactive power quickly, so the load side voltage level can be maintained.
3. Compensate reactive power, increase power factor, reduce line loss
Many types of loads, such as arc furnace, rolling mill, asynchronous motor, and large-capacity rectifier, in the electric power system require a lot of reactive power during operation. Meanwhile, the upstream transformer and line impedance also generate a certain amount of reactive power, which results in low power factor.
For the power system, loads with low power factor will increase the line loss and voltage drop and deteriorate voltage quality. Additionally, reactive power will reduce the efficiency of power generation, transmission and distribution. For users, low power factor will increase electricity costs.
4. Restrain voltage fluctuation and flicker
Voltage fluctuation and flicker are mainly caused by the drastic changes in loads. This rapid change causes the load current to fluctuate dramatically which then results in the rapid change in the system voltage loss, thus leading to the voltage flicker in the receiving end of the grid. The typical loads that cause voltage flicker are arc furnaces, rolling mills, electric locomotives, etc.
Static synchronous compensator, STATCOM/SVG, can offer fast reactive power regulation, which easily alleviate voltage fluctuation and flicker caused by load variation. So far, static synchronous condenser is the best solution to restrain voltage fluctuation and flicker compared with MCR, TCR, and other similar devices.
5. Inhibit 3-phase unbalance
A large number of three-phase unbalanced loads exist in the distribution network. Typical ones include arc furnaces and electric locomotives. In the meantime, three-phase impedance unbalance of the line and transformers can also lead to voltage imbalance. STATCOM is capable of quickly compensating negative sequence current caused by load unbalance and always ensuring the balance of the three-phase current flowing into the grid, thereby improving the power supply quality greatly.
6. Eliminate harmonics including even-order, odd-order, sub-harmonic and inter-harmonics
The static synchronous compensator performs very well in suppressing harmonics, including even-order harmonic, odd-order harmonic, sub-harmonic and inter-harmonic. It uses the instantaneous power theory to detect and calculate harmonic current automatically, control PWM converter, and input compensated current, which is of the right magnitude with harmonic current, but with inverse polarity, into the power grid.