Research Of Related Technology On The Three-level T-type Inverter

Because of simple structure and less devices, the traditional two-level inverters have been widely used in the low-voltage and low-power applications. Howerer, in the presence of high-voltage power context, each power switches of two-level structure withstand voltage of the DC-side bus, and electromagnetic interference issues and so on, which is difficult to apply in the high-voltage high-power applications.After more than thirty years of development, the multilevel inverter has been extended to a variety of topologies and modulation methods, so in this paper, the three-level T-type NPC inverter is studied. It has been widely concerned because of its less devices, but there are also some problems that can't be ignored. Because of the structure of the DC side for two sub voltage capacitors, it also has the main problem of traditional NPC Inverter – the voltages of the DC side capacitors are not balanced, secondly, of all the carrier PWM modulation methods, the frequency doubling modulation can effectively improve the equivalent switching frequency of the inverter's output voltage, but this modulation is not suitable for the three-level T-type inverter. So, we study a kind of hybrid clamped NPC inverter which is an improved topology based on the T-type NPC inverter, it can not only guarantee the balance of the capacitor voltages, but also achieve double frequency output. Then, aiming at the loss of the T-type inverter becausing of working in hard switching condition, a soft switching T-type NPC inverter is studied. All the power switchs can be soft switching by adding an auxiliary circuit to the T type inverter.Finally, the experimental platforms of the two kinds of inverter are built. We use the frequency doubling modulation and the voltage and current dual loop control method in the Hybrid clamped inverter. The simulation and experimental results verify the balance of the DC side capacitors voltage and double frequency output can be achieved. All the power switchs in the soft switching T-type inverter can be soft switching because of adding the auxiliary circuit.