恒功率区无零矢量SVM对功率器件结温的改善

Improvement of Junction Temperature of Power Devices by Applying None Zero Vector SVM to Constant Power Area

电动汽车变流器功率器件的损耗不仅浪费了有限且宝贵的车载能量,而且会造成功率器件过高的结温,严重影响其可靠性。空间矢量调制SVM(space vector modulation)工作在线性调制范围虽然可以保持较低的电压谐波畸变,但高的开关频率会带来高的开关损耗。过调制虽然在一定程度上导致相对较高的谐波,但在提高逆变基波电压的同时还降低了器件的开关次数。为了能兼顾逆变电压谐波与功率器件损耗,基于已有的过调制研究,采用了一种不需要零矢量的过调制点,将该特定调制度点(无零矢量)运用于驱动电机基速以上的弱磁调速区,并推导了其损耗表达式。研究表明,与线性范围内调制对比,该方法能显著降低变流器功率器件的损耗,且谐波也在可接受范围内。

The power losses of power devices in the inverter for electric vehicle(EV)not only waste the limited and valuable energy in EV,but also lead to an over-high junction temperature of power devices,which severely affects their reliability.Space vector modulation(SVM)can keep a relatively lower harmonic distortion of voltage in the range of line-ar modulation;however,a higher switching frequency will bring in larger switching losses.Over-modulation may lead to higher harmonic distortion to a certain degree,but it increases the inverter output voltage while reducing the switching times of power devices.To take both the harmonic distortion of inverter voltage and the power losses of power devices into account,on the basis of the existing researches on over-modulation,a specific over-modulation point that does not need zero vectors is applied to the weak magnetic modulation area,where the drive motor runs at a speed higher than the base speed.Moreover,the mathematical expressions of power losses are derived.The research result of this paper shows that,compared with the modulation method in the linear range,the proposed method can remarkably reduce the power losses of power devices in the inverter;meanwhile,the harmonic distortion is also acceptable.