New Method Of Deadbeat Current Predictive Control Of Three-phase Grid-connected Inverter

Grid-connected inverters are the core power conversion equipment in applications such as microgrids,new energy generation and new power electronic power systems.The current control inner loop(also known as the current regulator)is the core control link of the grid-connected inverter,and its bandwidth determines the dynamic performance and steady-state sine of the grid-connected current.At present,the current regulators of grid-connected inverters all use proportional-integral(PI)control in the synchronous coordinate system and proportional-resonance(PR)control in the static coordinate system,and both methods have bandwidth in the realization of digital control.limits.Deadbeat predictive control is a current regulator that reaches the limit of theoretical dynamic performance.Although it is widely used in motor control,it has not yet been applied in grid-connected inverter control.This paper applies deadbeat current predictive control to the current regulator of a grid-connected inverter for the first time;at the same time,new solutions are proposed for its steady-state error and high-frequency noise problems;and the two methods are seamlessly integrated A new type of deadbeat current predictive control method suitable for L-type and LCL-type grid-connected inverters is obtained.By comparing with the traditional PI and PR controllers for grid-connected experiments,the obvious advantages of the bandwidth of the new method and the higher current harmonic suppression capability are verified.In the second chapter,the traditional deadbeat current predictive control algorithm is applied to the grid-connected inverter for the first time.By establishing the closed-loop transfer function of the system,the current steady-state error caused by parameter deviation and the sensitivity of this high-bandwidth system to high-frequency sampling noise are quantitatively analyzed;and the traditional parallel integrator and sliding mode observer are used to analyze the parallel The effect and limitation of the steady-state current error compensation of the grid inverter.In the third chapter,in view of the two major problems of deadbeat current predictive control applied in grid-connected inverters,a new method of direct compensation for steady-state errors and high-frequency sampling noise from the perspective of current and voltage are proposed respectively.Suppress new methods;and then seamlessly integrate these two new methods to obtain a new deadbeat current predictive control method for grid-connected inverters.Through the analysis of the closed-loop transfer function of the new method,even in the case of a parameter deviation of 60%,zero steady-state error can be achieved;at the same time,it also has a strong ability to suppress high-frequency sampling noise.The simulation verifies that the new method can complete the current step within a few switching cycles,and the dynamic performance is an order of magnitude higher than that of the traditional PI and PR methods;and the new method can effectively suppress higher harmonics that exceed the theoretical limit bandwidth of the traditional method.Through comparison experiments with the traditional method,it is verified that the current step time of the new method is shorter than that of the traditional method;at the same time,when the grid voltage has the 5th harmonic component of 2%,the new method will be the fifth time of the grid current.The harmonic component is suppressed to 0.48%.Under the same conditions,the PI and PR control are 2.05% and 2.63% respectively.In order to verify the high bandwidth of the new method,a harmonic of up to the 38 th order(1.9k Hz)was superimposed on the command current,and the experimental current output effectively tracked the high-frequency command.Chapter 4 further extends the new deadbeat current predictive control method of grid-connected inverters to LCL-type grid-connected inverters.It is analyzed that the difference of high frequency band causes the new method to be unable to achieve the dynamic performance and harmonic suppression ability in the LCL grid-connected inverter when it is applied to the LCL grid-connected inverter.For this reason,this article further proposes an improved scheme that combines the new method with a multi-rotation coordinate system.In the LCL type grid-connected inverter experiment,under the condition that the grid voltage THD is 4.32%,the grid-connected current harmonic THD of the new method is only 2.26%,and the traditional PI and PR control are 5.95% and 3.81% under the same conditions.At the same time,the current step time of the improved scheme of the new method is shorter than that of the traditional method.This paper not only successfully applied the deadbeat predictive control to the three-phase grid-connected inverter for the first time,but also further proposed its solutions to the steady-state error and high-frequency noise problems in the grid-connected inverter.It is verified through experiments that the current step response speed of the new method is an order of magnitude faster than that of the traditional control method,and it has a superior harmonic suppression capability.Therefore,this paper proves to a certain extent that the deadbeat predictive control has considerable application prospects in three-phase grid-connected inverters.