The Digital Control Research Of The Single-Phase Inverter Based GaN Device

With the development of the society,people raise more and more requirements to inverter.The traditional analog control has many disadvantages which include single control mode,the tedious debugging and the high hardware cost.The emergence of microprocessor ARM and its price reduction make the digital control become the mainstream of inverter control.The emergence of new devices is significant for the development of power electronics.Compared to the traditional MOSFET,IGBT and other devices,the gallium nitride devices with high-frequency,high-efficiency and low-loss gets a lot of attention.In this paper,according to the principle of double loop control,the current loop in the static coordinate system is designed for the proportional controller and the coupling of current loop is decoupled.Aiming at the voltage loop,this paper adopts PI control in two different coordinate systems and makes a comparative analysis.It can be proved that there are obvious phase error and amplitude error of the PI double loop control in the stationary coordinate system at the fundamental frequency,therefore,the amplitude loop is compensated for the amplitude error,and the capacitor current feedforward compensates for the phase error.The PI control of the voltage loop in the dq coordinate system can be equivalent to the proportional resonance(PR)control under the static coordinate system through a series of derivations and the controller has a large amplitude gain at the fundamental frequency which ensures a zero steady-state error at this frequency and the sine wave can be well tracked.Inverter provide AC power for the industry and life and many other occasions,but the harmonic distortion must be very low to put into use,harmonic on the electrical equipment and power grid will cause great harm and loss.Power electronic equipment with nonlinear load characteristics is the main cause of single-phase inverter waveform distortion.Harmonic caused by nonlinear load produce pressure drop on the output impedance,so output impedance is evaluation effect standard of output voltage distortion.Reducing the voltage distortion can directly apply control strategy to reduce the inverter output impedance.Repetitive control is introduced to control a cyclical high order harmonic.The stability relationship between the repetitive control and the voltage loop PI control in two coordinate systems is analyzed.Load current feedforward control method is always used to get fast dynamic response when load changes,at the same time,the output impedance of the inverter can be reduced.Through this composite control strategy to reduce the high-order harmonics on the output impedance of the voltage drop,reduce the harmonic content of the output voltage.Finally,the control strategy mentioned above is simulated,and the controllers in continuous domain are discretized.The digital control system based on STM32F405 is designed.On this basis,a experimental prototype based GaN devices is built.The validity of the proposed control strategy is proved by the consistency of the final simulation and the experimental waveform,and the superior performance of the novel GaN device in the inverter application is also highlighted.