The Research Of Large-capacity High-voltage High-frequency Power Supply And Control System For Desulphurization And Denitridation

The high energy electrons (5～20eV), produced by high-voltage pulsed-corona discharge, inelastically collide with neutral gas molecules (O₂ and N₂, etc) and generate some active radicals with strong oxidizability (O, OH, HO₂, O₃, etc). These radicals react with SO₂ and NO_x. Finally, (NH₄)₂SO₄ and NH₄NO₃ are produced by the chemical reaction with NH₃. The method above is pulsed-corona discharge FGD. The current power supply for corona-discharging FGD could only be used in the laboratory rather than be applied in the industry. Consequently, a novel, high-frequency and high-voltage AC+DC power supply is designed.The principle of the AC and DC power source is described in detail. Series resonance in the circuit is analyzed. The AC power supply adopts the mode of series load and series resonance. The DC power supply adopts the mode of parallel load and series resonance. Series resonance and transformer are both adopted to increase the voltage class on reactor. Finally, the voltage rising rate of AC power source is greater than 200V/us. The amplitude of the DC power source is up to 40kV. The parameters used in the experiments are calculated.In order to increase the frequency of the AC power source, the phase-shifted full-bridge control strategy aiming at inductance load is adopted. The loss of soft-switching and hard-switching are compared through analysis, simulation and experiment. Soft-switching helps to improve switching frequency.The power control system is designed. Two digital PID controllers can control amplitudes of DC and AC at the same time. The interface with LCD and keys facilitates users' operations.The AC+DC power supply produces effective and steady streamer at a broad range. AC makes the discharge stronger and increases the energy density and free radical quantity in the reactor. DC spreads cation and free radical to a broad range and increases the chance of DeSO₂ and DeNO_x reaction.The EMI condition of the system is analyzed. Grounding, shield, isolation are adopted to improve the EMC of the FGD system.