Application Of High Voltage Frequency Converter For Coal Mill In Power Plant

In recent years, energy-saving has become more and more widespread concern in society. Auxiliary power of thermal power plant is generally required to account for10%of the annual energy production. The large fan、coal mill and pump power consumption accounted for30%of the auxiliary power. These devices are long-term low-load and variable load operation state, which consumes huge quantities and is not economical. Energy saving for these devices is one of the important issues for power plants. Frequency control technique, which is by changing the frequency of the input power of the high-voltage motor, is studied in this paper.This paper describes the unit of the Second Thermal Power Plant of Baotou, Inner Mongolia. The working principle of the coal mill is analyzed. The output and power calculation methods for coal mill are derived. Energy-saving principle of frequency conversion technology is studied. A cascaded multilevel voltage source type high-voltage inverter topology is used, then the phase-shift pulse width modulation method are analyzed in detail. A modulation method based on the zero sequence component injection is adopted to optimize the original method. The control modes of the frequency conversion system are analyzed. Then the notes of frequency transformation is studied. Finally, the energy saving effect of the coal mill before and after reconstruction is comparative analyzed.