中点箝位型三电平逆变器空间矢量与虚拟空间矢量的混合调制方法

中点电压偏移是中点箝位型(neutral point clamped，NPC)多电平逆变器的主要缺点。空间矢量脉宽调制(space vector pulse-width modulation，SVPWM)由于算法本身的缺陷，在调制度较高且功率因数较低时，电容电压出现低频波动。虚拟空间矢量调制(virtual SVPWM, VSVPWM)方法能够在全范围内处理中点电压偏移问题，但存在开关次数较多，谐波特性较差的缺点。该文建立含电容电压的NPC三电平逆变器的PWM模型，讨论SVPWM和VSVPWM的约束条件。在特定的区域采用SVPWM，其他区域采用VSVPWM，给出了这2种调制策略的切换条件。实验结果表明，混合调制方法(hybrid PWM，HPWM)较之以前的解决方案能够更好的平衡电容电压，并且也能够有效的降低开关次数和提高逆变器输出的谐波特性。

Hybrid PWM Strategy of SVPWM and VSVPWM for Neutral Point-clamped Three-level Voltage Source Inverter

The neutral-point voltage drift is the main technical drawback of neutral-point clamped (NPC) three-level inverter. The modulation approaches based on the space vector pulse width modulation (SVPWM) is incapable of controlling the capacitor voltage for high modulation indexes and low power factors in NPC three-level inverter. Virtual SVPWM is capable of controlling capacitor voltage under full modulation index and full power factor, but the modulation strategy will increase switching frequency and deteriorate the output waveform of inverter. A novel PWM theory including capacitor voltage was modeled. A new hybrid modulation scheme for the complete control of the capacitor voltage in diode clamped three-level inverter was presented. The performance of this modulation approach and its benefits of balancing ability and switch frequency over other previously proposed solutions were verified experimentally.