Controlling the output power of soft switching arc welding inverter by two-stage continuous PWM method

The full bridge zero voltage zero current switching(FB-ZVZCS),which could adjust the output power by keeping the duty ratio of lagging leg constant and changing the duty ratio of leading leg,was a common circuit of soft switching arc welding inverter power source.However,when the duty ratio of leading leg was reduced to zero,the output power stayed the constant value instead of becoming zero.The working status and waveforms of some major parameters were studied in this paper while the duty ratio of leading leg was zero.It was concluded that the minimum output power of soft switching inverter was related to the charging voltage of parallel capacitors,and the output power also could be reduced by reducing the duty ratio of lagging leg.A novel two-stage continuous PWM control method that could switch working-mode between full bridge and half bridge was put forward in this paper.This kind of control method could further reduce the output power of soft switching inverter in order to meet the requirement of low heat input of sheet metal welding.

脉冲变极性弧焊逆变电源数字化控制系统

在采用数字信号处理器(DSP)DSP56F805构建基于双DSP的脉冲变极性弧焊逆变电源全数字化控制系统的基础上,针对数字化脉宽调制(PWM)控制脉冲存在的脉冲宽度保持和延迟对电源输出动态响应和稳态精度等控制性能的影响,提出了基于电源输出电感电阻(LR)负载模型的电流预估计算法,进而对简单数字比例积分微分(PID)控制算法进行了修正。同时,系统通过对电流/电压检测信号的预处理、A/D采样与PWM同步、数字滤波等措施有效地提高了系统的抗干扰性能。脉冲变极性输出特性控制试验验证了基于电流预估计的数字PID控制算法的正确性和有效性。