Digital control system of high frequency bipolar pulse power supply for acid pickling process

Acid pickling is one of the industrial processes used for removal of scales. To overcome some severe problems when using aggressive acids, such as corrosion of metallic substrates and hydrogen embrittlement phenomenon, a digital control system of high frequency bipolar pulse power supply has been designed. The load characteristic of the acid pickling system is analyzed and the corresponding output current waveform scheme has been put forward. The main circuit topology, which is on the basis of two-stage inverter structure, and its working principle are described. A digital control system based on digital signal processor (DSP) is proposed. Control schemes of inverter circuits and control algorithm are also explained in detail. A prototype with a peak output power up to 15 kW has been constructed and tested. The power source can output anodic direct current (DC), high frequency bipolar pulse and cathodic DC waveforms. The pulses have a repetition rate up to 10 kHz, and the current pulse is influenced by loop electrical parameters. The experimental results demonstrate that the high frequency bipolar pulses are very effective for acid pickling of steel.