Research On Control Strategy Of Microgrid Inverter Based On Adaptive Control

Microgrid technology has been widely researched because of its high flexibility and controllability and its ability to effectively improve the consumption rate of new energy sources.However,with the increase of installed capacity of distributed generation devices and the structural characteristics of microgrid itself,it often works in complex operating conditions,which brings the problem of decreasing control performance of microgrid inverters under complex operating conditions.Microgrid inverter is the interface between distributed power supply and busbar,and its control performance has a profound impact on the power quality of microgrid.Based on the idea of adaptive control,this paper designs corresponding adaptive control strategies to solve the control performance problems of two typical inverters in microgrid under complex operating conditions,which are mainly as follows:For PV inverters operating under current control,which are susceptible to three-phase voltage imbalances on the grid side that affect the inverter control performance.A phaselocked loop with adaptive filtering based on a double second-order generalized integrator is designed to solve the problem that it cannot be accurately phase-locked under this operating condition.An adaptive trap-based DC-side voltage control strategy is designed,which can change the center frequency of the trap in real time according to the working conditions to reject the DC-side disturbance components and solve the DC-side control problem under this working condition.It achieves the purpose of reducing the harmonic distortion rate of the grid-connected current,so that the control performance of the inverter can be effectively improved.For voltage source inverters operating under voltage control,which are susceptible to different types of load affecting the inverter control performance.The adaptive control strategy based on Narendra theory is designed to compensate the command voltage in real time under complex operating conditions,and this control strategy can recover the amplitude of the port voltage in all complex operating conditions,and the control performance of the inverter is effectively improved.For the problem that the adaptive control strategy based on the Narendra theory still has a high output voltage harmonic content under harmonic conditions and that the dynamic performance of the system is reduced due to the initial setting of the adjustable parameters of the adaptive controller.Therefore,the adaptive controller based on Narendra theory is improved by using the idea of active disturbance rejection control.The uptake of adjustable parameters inside the system is classified as internal disturbance,and the cast of unknown loads outside the system is classified as external disturbance,and both are classified as total disturbance,which is estimated by an expansion state observer and compensated according to the amount of its disturbance action.The problem of still high harmonic content of output voltage under harmonic conditions is solved,and the dynamic performance and steady-state performance of the system are further improved.Based on the above,the proposed control strategy is verified with the existing control strategy under the same operating conditions.The verification results show that the harmonic distortion rate of the PV grid-connected inverter working under complex operating conditions is reduced from 5.87% to 1.8% under the proposed control strategy.The port voltage amplitude of the voltage inverter operating in islanding mode under complex conditions is effectively recovered,and the harmonic distortion rate under nonlinear load throwing condition is reduced from 30.16% to 11.46% in the control strategy proposed in Chapter 4 and further reduced to 1.84% in the control strategy proposed in Chapter 5,and the dynamic performance is further improved.The results verify the effectiveness of the control strategy proposed in this paper,which has certain reference value for the control and management of power quality problems in microgrid.