Locomotive needs DC power supply, which is a typical non-linear load. During the operation of the locomotive, the harmonic voltage and harmonic current can be sent back to the power grid through the overhead line system. Electric equipment such as air conditioning, ventilation, lighting, storage battery and the like of the locomotive are provided by auxiliary inverters on the locomotive, and direct current drawn to the locomotive is non-linear load, which also generates harmonics. Air conditioning, elevators and lighting systems in the electromechanical systems of subway stations are increasingly taking into account the need for energy conservation. The use of a large number of non-linear power electronic devices, such as variable frequency air conditioners, variable frequency speed elevators, energy-saving lamps, UPS, etc., will generate more harmonics, so that the power quality problems of subway stations are more serious; according to the analysis on the subway stations, the main power quality problems are harmonics, reactive power and imbalance. Harmonics is the most serious problem.

Working Principle：

FGAPF active power filter is a new generation of harmonic control solution to filter out harmonics dynamically. Advanced dynamic real-time tracking compensation method is adopted to eliminate power grid harmonics. FGAPF is a high-power power electronic device based on current detection and current injection technology. Through monitoring the current waveforms generated by nonlinear load in real time, harmonic part is separated, and harmonic currents with opposite magnitudes and directions are injected into the power grid by controlling the trigger of IGBT, so as to realize the function of filtering (canceling) harmonics, and then the safety and reliability of the electrical system are improved, and the purposes of energy conservation and efficiency enhancement are achieved.