低载波比下三电平NPC逆变器同步SVPWM算法

Comparative study on synchronized space vector PWM for three level neutral point clamped VSI under low carrier ratio

如何在低载波比(f_(sw)/f)下保证输出较低的谐波含量,是设计脉宽调制算法时要解决的关键问题。以二极管箝位型(NPC)三电平逆变器为研究对象,基于输出电压波形同时满足同步、三相对称(TPS)、半波对称(HWS)的脉冲发生规律,采用一种新的开关序列设计方法,以1/4周期对称(QWS)作为不必要条件,设计两种参考矢量分布模式下的矢量序列,并以输出线电压加权总谐波畸变(WTHD)作为性能评价指标,对比分析不同矢量序列的谐波性能,分别通过仿真和半实物实验验证各调制算法的可行性。研究表明:新的开关序列设计方法在选择矢量序列时自由度更大,可得到许多新的开关序列,不同的开关序列在不同的调制区段局部较优,且不考虑QWS约束的开关序列在部分调制区段具有更优的谐波性能。

The way to ensure low harmonic content in the output voltage is the key issue to solve when de-signing pulses width modulation algorithms under low carrier ratio. Taking a three level neutral point clamped voltage source inverter as the research object, a new switching sequences dedopted based on the pulse generation law^ of the output voltage waveforms satisfied synchronous, three-phase symmetry （TPS） and half-wave symmetry （ HWS） simultaneously, and the quarter-cycle symmetry （QWS） was used as an unnecessary condition. Some switching sequences ferent reference vector distribution mode respectively , and the inverter line voltage of different switching sequences were comparatively analyzed. Simulation and the validity of the proposed PWM. The research results show that the new switching sequences design method has more freedom when selecting vector sequences, many new switch sequences can be obtained, and different switching sequences are locally optimized in different modulation regions. Moreover, switc-hing sequences wit!iout regard to QWS constraints posess beter harmonic performance in the part of t!ie modulation regions.