三电平逆变器SHEPWM方法及其应用研究

特定谐波消除SHEPWM,通过开关时刻的优化选择,消除选定的低频次谐波,具有波形质量高、效率高、直流电压利用率高、直流侧滤波器尺寸小等显著优点,所以受到人们的普遍关注.首先针对1/4周期对称的脉宽调制波形,以频率50Hz为例研究了三电平SHEPWM非线性方程组的求法,提出了以三角载波法生成非线性方程组初值的方法,使得求解非线性方程组的速度明显加快;根据非线性方程组的数值解,用POWERSIM电力电子专用仿真软件对三电平SHEPWM进行了仿真研究;用小功率MOSFET管构成二极管钳位三电平逆变器实验电路模型,以双DSP中压变频控制平台为控制器,对三电平SHEPWM方法进行实验研究.仿真和实验结果证实了SHEPWM的谐波消除效果和SHEPWM方法所具有的一系列显著优点.

Research of Selected Harmonic Elimination PWM Techniques Applicable to Three-level Voltage Inverters

SHEPWM, a method to eliminate the selected low order harmonics by optimizing switching time sequence, has been concerned greatly because of its advantages such as high quality in output waveform, high efficiency, full use of DC side voltage and small size of DC side filter. Taking frequency of 50Hz for instance, it studied in detail the Selected Harmonic Elimination techniques applicable to three-level voltage inverters. In order to get a high convergence speed of the nonlinear equations, an effective method of using multi-carrier SPWM technique for producing initial values of the nonlinear equations is proposed. The SHEPWM switching time sequence obtained by solving the nonlinear equations numerically is simulated with POWERSIM 4.0, and experimentally verified through a diode-clamped three-level voltage type inverter composed of MOSFET controlled by a two-DSP (TMS320LF2407A) control flat-form. Simulation and experiment results proved the advantages of SHEPWM technique.