Research On The Single-phase Voltage-fed Cascade Quasi-Z-Source AC/AC Converter

At present,our country's economic and industrial level has developed rapidly,the demand for quality of electricity is getting higher and higher, improve the quality of electricity is imperative. However, the pollution problem of the harmonics of the power grid is becoming more and more serious,which requires better stability of the power equipment. Switching power supply is gradually come into the people's vision due to its advantages of light weight and miniaturization,and more and more used in electrical equipment. Chop-controlled voltage regulation and phase-controlled voltage regulation are the two kinds of AC/AC voltage regulation that commonly used in industrial production, however, due to the phase-controlled voltage regulation has many shortcomings, it is far from using in the actual production than chop-controlled voltage regulation technology. The AC/AC chop-controlled voltage regulation technology is an AC/AC voltage regulation technology that based on PWM and full controlled switching device, it has the advantages of rapid response,and simple filtering and so on, its development prospect is very broad. The quasi-Z-source converter has a unique circuit network,this it can control the AC/AC chopper, so that to achieve the effect of boost and buck. The quasi-Z-source network can couple the circuit load and power of the AC/AC chopper together, the inductor and capacitor inside the network has the function of storing power and filtering out harmonics.In this thesis,a new cascaded quasi-Z-source network is proposed based on the traditional quasi-Z-source network,and it is applied to the single-phase AC/AC'voltage regulator. Studies the working principle of the single-phase cascaded quasi-Z-source AC/AC voltage regulator, analyzes its work process, and deduces the relationship between input and output voltage, gets the boost ratio, compares with the ordinary single-phase quasi-Z-source AC/AC voltage regulator. And studies and analyzes the control mode of the two groups of the switches of the main circuit topology, and determines the choice of complementary control mode in the cascaded quasi-Z-source circuit control.Through analysis and calculation, designs the related parameters of cascaded quasi-Z-source network, buffer circuit of IGBT and output filter circuit. The working principle of single-phase voltage-type cascade quasi-Z-so-urce AC/AC voltage regulator in closed-loop control is studied and analyzed,the conclusion that using the single-cycle control theory is the most appropriate control method is achieved, and determines to use the single-cycle theory control scheme, so as to make the AC/AC voltage regulator has excellent working condition and performance. A simulation model of the system is built,and the experimental circuit on the basis of simulation is built, the simulation results and experimental results verify the excellent voltage regulation capability and reliability and correctness of the proposed singlephase voltage-fed cascaded quasi-Z-source AC/AC voltage regulator.