High Frequency Driver Design Of SiC MOSFET And Application In Grid-connected Inverter

In order to realize the sustainable development for low carbon emission and environmental protection,development of clean renewable energy has become an inevitable trend,distributed generation closely related to renewable energy has also received much attention from researchers.At present,distributed generation research at home and abroad is mainly based on photovoltaic power generation and wind power generation.Among them,solar photovoltaic power generation has developed rapidly on a global scale.Grid-connected inverter is the core of distributed generation system.Its performance directly affects the stability and service life of the system.IGBT and MOSFET are the devices most used for grid-connected inverters.The development goals of new energy devices are: high efficiency,high reliability,and high power density.In order to meet the goal of high power density,the market has a higher demand for switch frequency of switch tubes.New broadband semiconductor devices such as SiC MOSFET have also received more and more attention.In this paper,parameters of SiC devices and Si devices are analyzed and drive design requirements based on SiC MOSFET are summarized.In the selection of isolated drive scheme,compared with the modulation demodulation scheme and the pulse signal transmission scheme,theory and experiment verify that the pulse signal transmission scheme has less time delay and higher reliability.A short circuit protection scheme with RC delay regulating the blanking time is proposed.The protection circuit structure is simple and the dynamic response is within 300 ns.A double-pulse test platform is established to verify the pulse signal transmission scheme and the proposed short-circuit protection scheme.For the most rapid development of solar power generation,the topology and modulation of H6 topology are introduced by using the industry's common H6 topology to build the connected inverter.The transfer function of the inverter bridge is obtained by modeling H6 topology inverter using state space averaging method.The common mode analysis of H6 topology shows that the common mode voltage is small,the leakage current is small,and the system is safe and stable.The hardware design of the single L filter 20 kHz H6 topology inverter includes selection of power devices with parameters that meet the requirements,design of drive schemes with low impedance loops to prevent crosstalk of bridges,design of fully isolated sampling schemes,design of filter inductors and busbar capacitance;Finally,the layout of PCB is analyzed,and its reliability is verified by subsequent experiments.Two different phase-locked loop schemes are analyzed.The phase locked loop based on SOGI and the current loop parameter of H6 topology grid-connected inverter based on L filter are designed.The stability of the loop is verified by bode diagram.The loss model of H6 grid-connected inverter is established to analyze theoretical distribution of loss.The switching loss of SiC device is small,and it has more advantages than Si device under high frequency operating conditions.The efficiency of SiC 20 kHz,SiC 100 kHz and Si 100 kHz were tested through resistance load experiments;Design safe and reliable process sequence,verify the correctness of hardware design and loop design on the built prototype;The effect of different current control links on harmonic suppression was verified on the LCL-type inverter platform.PI control had lower gain at harmonic frequency and the harmonic suppression ability was the weakest.QPMR control can effectively reduce the harmonic at the center frequency of the parallel branch,but the parallel link is limited by the loop stability;Repetitive control further optimizes the harmonics,and its harmonic suppression ability is the strongest.