Development Of High Frequency And High Efficiency GaN Inverter

With the continuous expansion of inverter applications,the high power density of the device has become a new trend and hotspot of research.To increase the power density of the device,it is necessary to use a high switching frequency to reduce the volume of the passive components therein,but high switching frequency can cause low efficiency of the device.The soft switching technique is needed to reduce the switching loss caused by the high frequency.The traditional soft-switching technology requires additional auxiliary circuits,which undoubtedly hinders the implementation of high power density.At the same time,GaN devices are more easily applied in high-frequency and high-efficiency designs due to their high switching speed and low on-resistance.Therefore,this paper will carry out research on GaN high-frequency high-efficiency inverter from the perspective of control improvement.Firstly,based on the full-bridge inverter topology,the working principle of critical current mode control and the realization process of soft switch are analyzed in detail.Three critical current mode control methods are compared and analyzed from the perspective of switching frequency.The zero-crossing point based on three control methods is analyzed.The spike problem was optimized and a new critical current mode control strategy was proposed.Under this control strategy,the selection of the parameters such as inductance and negative current in the actual circuit is elaborated,and the simulation circuit of the optimized critical current mode control is built in PSIM,and the open loop,closed loop and the network simulation diagram verifies the feasibility of the theory.Secondly,a 500W full-bridge inverter prototype was designed to explain the hardware and software design process in detail.The experimental results show that the new critical current mode is less than zero at the zero-crossing point of the three critical current modes,so the peak is smaller and consistent with the theoretical analysis.At the same time,compared with the full-bridge inverter using sinusoidal pulse width modulation(SPWM),since the critical current mode achieves zero voltage turn-on,the switching loss is smaller than that of the SPWM control,and the critical current mode control is used under the full load condition.Efficiency is nearly 1%higher than SPWM control.Aiming at the problem that the output current ripple is large due to the critical current mode,the three-bridge interleaved circuit is selected from the perspective of topology improvement,and the improved angle selection triangle carrier phase shift control and the new critical current mode are combined to control the strategy.Analyze how it works.Secondly,the theoretical basis and implementation process of the triangular carrier phase shift control strategy are elaborated.The triangular carrier phase shift control simulation circuit is built in PSIM,and the continuous triangular carrier whose amplitude changes with sinusoidal law is generated,which proves the feasibility of the theory;The circuit simulation of the interleaved inverter based on the triangular carrier phase shift control shows that the total harmonic distortion rate(THD)of the output current is 1.9%,which satisfies the requirements of grid-connected current index and verifies the correctness of the theory.