【摘要】 为了研究基于三电平中性点箝位(NPC)逆变器的高压变频器采用SPWM时死区设置对变频器输出共模电压的影响,利用双重Fourier法推导得逆变器不带吸收回路空载条件下采用SPWM调制策略时不同方式设置死区后逆变器输出共模电压的表达式,研究了逆变器带感性负载及开关器件带RC吸收回路条件下死区设置对逆变器输出电压及输出共模电压的影响。利用MATLAB对以上问题进行了仿真研究。对表达式分析得:逆变器不带吸收回路空载时,不论是否设置死区及以何种方式设置死区,逆变器输出共模电压均主要含有调制波3的奇数倍次谐波;逆变器带上RC吸收回路及感性负载时,单边设置死区时正方向的负载电流使输出电压减小,负方向的负载电流使输出电压增加,从而影响了逆变器输出的共模电压。仿真研究验证了以上分析结果。研究表明,当逆变器带上RC吸收回路及感性负载时,分析SPWM死区与变频器输出共模电压的数学关系较复杂。更多还原

【Abstract】 This paper tries to investigate the effects of sinusoidal pulse width modulation (SPWM) dead-time on the common-mode voltage (CMV) in high-voltage adjustable speed drive (ASD) system with three-level neutral point clamped (NPC) inverter. Firstly, the relationship of the CMV between the motor and the three-level NPC inverter is analyzed and the correlative expression is derived. Secondly, the CMV expressions of the NPC inverter without snubbers and load under different dead-time inserted modes are deduced and analyzed using the dual-Fourier method. Then, the impacts of the SPWM dead-time on the output voltage and the CMV of the inverter with RC snubbers and inductance load are studied. Finally, Simulations are carried out to research above problems based on MATLAB. Some useful outcomes can be gained by observing the deduced expressions. When the inverter has not snubbers and load, the output CMV of the inverter comprises the odd time of triple-harmonic mainly, inserting dead-time does not generate the magnitude change of first-harmonic and the new low order harmonic, and the dead time change provokes the magnitude change of the same time harmonic, whether inserting dead-time or not and also regardless of the dead-time inserted modes. When the inverter has RC snubbers and inductance load and adopts the asymmetric dead-time inserted mode, the forward load current makes the output voltage reduced and the negative-going load current makes the voltage raised. This may bring the change of the output CMV of the inverter. Simulation study verifies the above outcomes. Results indicate that: The direction and magnitude of load current and the structure and parameter of the switches’ snubbers influence the output voltage and may further influence the output CMV of the inverter. Analyzing the mathematic relation between the SPWM dead-time and the output CMV of the inverter is very difficult.更多还原