The chain SVG with delta connection can effectively control the unbalanced load of 27.5kV railway system based on Steinmetz balance compensation theory, and the harmonic generated by the load can be filtered based on active filter technology.
Compensation effect:
Background:
Electrified railway has the advantages of high speed, heavy load, high energy efficiency and good economic benefits, so it is widely used in railway system. There are mainly two types of railway traction load: AC-DC and AC-DC-AC electric locomotives. AC-DC trains are generally used for freight and ordinary passenger trains, while AC-DC-AC trains are mainly used for high-speed railway system. At present, Russian electrified railway locomotives adopt the traditional AC-DC transmission mode. When the train is running, it will produce a lot of reactive power and odd harmonic current. Reactive power causes low voltage of traction network line, which leads to the decline of train operation efficiency. Harmonic current causes abnormal line voltage, which is not conducive to the safe and stable operation of equipment.
Qingdao Sifang Bombardier Railway Transportation Equipment Co., Ltd. (BST) was established in 1998. It is a Sino-foreign joint venture funded by China Sifang locomotive and Bombardier company. Its main products are high-speed railway and EMUs. (1) The parameters of test power supply in the plant area of Qingdao Sifang Bombardier railway transportation equipment Co., Ltd. are as follows: rated voltage: 27.5kV, rated capacity: 10MW (2) problem description: when eight CRHiEMUs were tested with pantograph rising at the same time, serious subsynchronous oscillation began to appear in the 27.5kV power grid, which led to the blocked pulse of all trains and could not operate normally. The figure below shows the voltage and current waveforms at 27.5kV side of eight test locomotives, and the voltage and current have serious subsynchronous oscillation problem. We know from the data after current FFT analyzing , the main harmonic components are 45 Hz and 55 Hz.