Modulation And Control Of High Frequency Link Three-phase Four-leg Matrix Inverter

High frequency link matrix converter (MC) is a new kind of circuit topology, and itscontrol performance is good. Not only can it solve the inherent problems of traditionalpower frequency inverter, but also can achieve high frequency and miniaturization.Because of its good control performance and low cost, high frequency link MC isbecoming a new trend of inventer. With the development of Power Electronics Technology,the potential advantages of high frequency link MC are more and more obvious. Itsapplication field is expanded with the development of distributed power generationtechnology. The high frequency three-phase four-leg MC topology is mainly studied in thepaper, and it can provide three-phase balanced output voltage for three-phase unbalancedload.Firstly, the research status of MC and three-phase four-leg inverter is introduced.Then the high frequency inverter technology is discussed. Combining MC withthree-phase four-leg inverte, the high frequency three-phase four-leg MC topology isstudied. It has the advantages of both two converters. The high frequency of transformer isimproved and the enegy of MC is bi-directional flow. The unbalanced three-phase outputvoltage can also be restrained.In order to achieve the commutation function of MC, the structure of circuit topologycan be decoupled. Two modulations of the MC are introduced in the paper. They arede-re-couple SPWM modulation and integration SPWM modulation. The implementationmethods of the two modulations are studied, respectively. The work mode of topologywith integration de-re-couple SPWM modulation is analyzed and the correspondingsimulation is achieved.Then, based on the implement of safe commutation with the modulation strategy,closed-loop control strategies of high frequency three-phase four-leg MC are studied inthe paper. The performance of the system can be improved. Three kinds of control modesare studied in the paper, and they are traditional PI regulater closed-loop control mode,symmetrical components closed-loop control mode in double synchronous rotating reference frame and notch filter double-loop control mode, which can filter second ACharmonics in synchronous rotating reference frame. The implement of control methods isverified by simulation. And the control system performance with the three methods isanalyzed.At last, the software and hardware circuit platform is built. The main circuit uses theMC boards, and the control circuit is composed of DSP and CPLD circuit. The abovemodulation strategies and control methods are verified by experiments in the end.