A DSP Based Three-level Speed Regulation System

Traditional two-level inverter is restricted by the power level and collector-emitter voltage of the power electronic device, and therefore it is not suitable for high voltage and high power output. With the rapid development in power electronic technology, a new inverter emerges--multi-level inverter. It not only reduce the requirement on collector-emitter voltage of the power electronic device, but also decrease output voltage's harmonic components and du/dt, lower the switching frequency and reduce the switching loss. And it has been widely concerned in the high voltage and high power AC speed regulation field. However, the increase in output voltage level does make it more difficult to control, and increase the size and cost of the hardware. Thus, self-researched multi-level inverter product is rare in our country at present. According to the design requirement of this topic, the design of this system mainly focused on the optimization of control algorithm in three-level SVPWM, tackling the unbalanced problem of neutral point potential, and researching the three-level AC speed regulation system based on DSP.In this thesis, we firstly present a literature review for multi-level inverter's emerging background, research status, and topological structure. And then we explore an optimized control algorithm of SVPWM and two modulation schemes in particularly after analyzing the three-level neutral point clamped PWM inverter's working principal and SVPWM modulation principal. After primarily researching on fundamental reason of unbalance problem of neutral point potential, we design a control algorithm of neutral point potential according to different sector, and propose a closed-loop controller which based on neutral point potential and three-phase current measurement, in order to adjust the neutral point potential precisely and rapidly.In this thesis, we set up a three-level AC speed regulation system's hardware experiment platform, and develop the main program and other module's sub program on DSP. The experiment result proved that control algorithm we discussed in this thesis successfully control three-level inverter by SVPWM and effectively reduce the fluctuation of neutral point potential. In the meantime, we realized the synchronous motor driving with close current loop and open speed loop.