基于DPWM的T型三电平逆变器中点平衡研究

Research on Neutral Point Balancing in Three-Level T-Type Inverters Based on DPWM

T型三电平逆变器广泛应用于光伏发电设备。本文提出一种新型DPWM(discontinuous pulsewidth modulation,DPWM)方法实现中点平衡控制。T型三电平逆变器的性能受到中点平衡的影响。因此,直流侧电容电压需要控制平衡。传统SVPWM和注入零序分量通过改变零矢量实现中点平衡控制,但是上述方法开关损耗较大。为此本文在DPWM基础上通过改变调制波的作用角度实现中点平衡控制,而且上述方法能够降低开关损耗。仿真和实验验证了新型DPWM调制能够实现中点平衡控制和良好的输出电流波形。

Three-level T-type inverter is widely used in the PV generating equipment. In this paper, a new type of DPWM（discontinuous pulse width modulation, DPWM） is proposed to balance the neutralpoint（NP） potential. The performance of the T- type three level inverter is affected by the midpoint balance. Therefore, it is needed to control DC-link capacitor voltage balance. In the traditional SVPWM and injecting zero sequence components method, the balance point control is achieved through changing zero-vector. But the switching loss is large. On the base of DPWM, this paper realizes the balance of NP voltage by changing the angle of the modulation wave. This method can reduce the switching loss. The simulation and experiment verifies that this new DPWM modulation can realize the midpoint balance control and the good output current waveform is obtained.