| As the last power conversion equipment for new energy generation,grid-connected inverter plays a critical role in the regulation of grid-injected power.In order to improve the quality of grid-injected power and satisfy various standards,it is necessary to study efficient and reliable control technologys of grid-connected inverter.In this paper,active disturbance rejection control(ADRC)technology is applied to the aspects of grid phase tracking and output current control of grid-connected inverter.A phase tracking method without AC voltage sensors is proposed for the purpose of reduce hardware cost and enhance system reliability.And active disturbance rejection current controller is designed to improve the dynamic and steady-state control performances of the grid-injected current.This article first introduces the current research status of related technologies of gridconnected inverter at home and abroad,including the mainstream circuit topologys,control methods,etc.Basic principles of ADRC technology and extended state observer(ESO)are explained;The mathematical models of voltage source three-phase grid-connected inverter in different coordinates are derived.And the principles and implementation methods of inverter output voltage reconstruction,output power decoupling control and space vector pulse width modulation(SVPWM)are analyzed in detail.Then the equivalent transfer function of three-phase software phase-locked loop(PLL)is derived,and the tuning method of its control parameters is given.On this basis,an ESO is designed to estimate the grid voltage in real time to reach the purpose of phase tracking without AC voltage sensors.Combined with the PLL,the angle information required for coordinate transformation can be quickly and accurately obtained under different initial phases of the grid.Simulation results show that the proposed method has more advantages than the virtual flux method in terms of error convergence speed and steady-state phase-tracking accuracy.In addition,in order to improve the dynamic and steady control effects of grid-injected current,an active disturbance rejection current controller with the ability of estimating and compensating disturbances is designed.Theoretical analysis and simulation results show that this controller can achieve better dynamic decoupling control effects of dq axis current when inductance parameters are not matched,and the low frequency harmonic current caused by the dead zone effect can be controlled more effectively by increasing the bandwidth of ESO,compared to the traditional PI controller.Finally,experiments are carried out on a three-phase grid-connected inverter platform and the results confirm the correctness and effectiveness of the proposed theorys and methods. |
