Improved the two DC capacitors’ voltage balancing of three-level NPC inverters applied in electric vehicles

Excessive unbalance of the DC capacitor voltages of the inverter can cause overvoltages on power components and capacitors, causing unintended low-order harmonics on the load side such as second harmonics, 3rd, 4th, 5th,..., causing direct harm to the motor load, reducing the controllability of the reverse voltage and filter compensating current for the active filter circuit, affect to the performance of electric vehicles (EVs).