载波移相调制死区时间对模块化多电平换流器的影响研究

Research of influence of dead time by carrier phase shifted modulation on modular multilevel converter

分析了死区时间对模块化多电平换流器单个子模块的影响,得出了以下结论:桥臂电流大于零时,子模块从投入状态转向切除状态会产生正极性的死区电压;桥臂电流小于零时,子模块从切除状态转向投入状态会产生负极性的死区电压。分析了死区电压对模块化多电平换流器理想基波电压的影响,推导了输出死区基波电压等效幅值、实际输出电压基波幅值及角度偏移量的公式,得出了以下结论:直流侧电压一定时,死区电压对模块化多电平换流器的影响与载波比、死区时间和输出电压与电流的相位差有关,与投入模块数无关;提高电压调制度和降低死区时间可有效降低死区时间对模块化多电平换流器的影响。仿真结果验证了上述结论的有效性。

The paper analyzed influence of dead time on single sub-module of modular multilevel converter and reached conclusions that the sub-module will produce positive dead voltage from inserted state to cut-off state when arm current is positive and negative dead voltage from cut-off state to inserted state when arm current is negative. It analyzed influence of dead time on ideal fundamental voltage of modular multilevel converter, and deduced formulas of equivalent amplitude of output fundamental wave of dead voltage, actual amplitude of fundamental wave and offset of angle of output voltage, so as to reach conclusions that when voltage of DC side is fixed value, influence of dead time on modular multilevel converter relates to carrier wave ratio, dead time and phase-difference between output voltage and output current and unrelates to numbers of input module, improving modulation depth of voltage and reducing dead time can reduce influence of dead time on modular multilevel converter effectively. Simulation result validates effectiveness of the above conclusions.