Design Of A Multilevel Quasi-Z-source T-type Fault-tolerant Inverter

Power Energy,as the lifeblood of the country's economy,can promote the development of science and technology and industry and agriculture,however,because of industrial and agricultural energy supply shortage,seriously restricting the development of industry and agriculture,we should vigorously develop new energy.Inverter is an essential component of PV system,because of the low efficiency of the traditional power converters,it will result in large power loss,no step-up function,lower output voltage after inverter,higher DC voltage required for the high amplitude AC voltage,more PV panels,and a serious increase in the cost of building and maintaining PV power generation.At the same time,in order to avoid the switch tube breakdown,the topology must have dead time,so the output waveform of inverter is distorted and the output voltage quality is reduced.In addition,when the voltage source inverter switch tube failure,the voltage source inverter can not be used normally,and can not judge the fault of the switch tube in advance.Therefore,the industrial and agricultural applications caused huge economic losses.Firstly,in view of the problem that the current converter is not high enough,the voltage harmonics are more,the waveform quality is not high,and the inverter can't be used normally after the inverter bridge arm failure,the method of phase shift pulse width modulation is designed.The topological structure is composed of two symmetric modified quasi Z-source networks and three-phase T-type inverters,a multilevel quasi z-source T-type fault-tolerant inverter(T-type SL-q ZSI),and the working principle and control method of the new inverter are analyzed in detail.The new inverter can obtain a higher boost factor with a smaller direct-duty ratio,a larger range of modulation ratio,and can output multilevel voltage,while increasing the power utilization.Secondly,when the switch tube of the bridge arm fails,the new inverter can work only by changing the modulation strategy.The inverter not only can guarantee the load power supply reliably,but also has the advantages of Z-source step-up,output multilevel voltage,fault-tolerant ability of switch pipe and high output power quality.Finally,the existing traditional inverter and the traditional quasi-Z-source inverter and multilevel inverter are analyzed in detail.By comparing the topological structure,control strategy and fault-tolerant scheme,the paper verifies the shortcomings of the existing inverter,and discusses the simple step-up control strategy,maximum boost control strategy,constant step-up control strategy and space vector Control strategy principle of Z-source inverter,and points out the advantages and disadvantages of these control strategies.At the same time,the hardware design,software design,control strategy design and component selection of the inverter are presented.In the garden Test station of northeastern Agricultural University,phase shift sine pulse width modulation(PS-PWM)method was used to simulate and test the PV shed system,the simulation and experiment prove that the new inverter is running normally,the amplitude of the output voltage is increased greatly,the power utilization rate and the power quality are improved,and the correctness and superiority of the novel topology are verified.