Application Of Adaptive Dynamic Programming In Grid-connected Inverters

With the application of new energy,how to make the stable and efficient operation of grid-connected inverters is an indispensable part,and it is the focus of current research.This paper mainly studies the application of adaptive dynamic programming(ADP)in grid-connected inverters,including the application in three-phase grid-connected inverters,the application in virtual synchronous generators(VSG)and the dynamic voltage regulators(DVR).For the algorithm of grid-connected inverters,the traditional method is to use a PI controller,but PI control only plays a role in error-free control of the DC component.In the inverter control,dq coordinate transformation is often required to obtain the DC component,Especially when there is an imbalance in the system,the positive and negative sequence must be separated,increasing the complexity of the system.In this paper,the ADP algorithm is applied to the grid-connected inverter.The optimal controller is designed in the abc coordinate system.When the grid voltage is unbalanced,the power balance controller is designed in the abc coordinate system.According to the simulation results,the follow-up algorithm can quickly respond to the grid-connected current reference command and ensure power balance even when the grid voltage is unbalanced.For the VSG algorithm,the traditional VSG first calculates the output power,and then obtains the VSG output power angle and the active voltage according to the active-frequency to obtain the VSG output voltage amplitude,and then synthesizes the inverter-side reference voltage.It can be seen that the output voltage amplitude of the inverter is only related to the reactive power,but in practice,it is also related to the physical quantities such as frequency and power angle.In this paper,the ADP algorithm is applied to the VSG.First,the nonlinear model of the VSG is converted to a linear model by an accurate linearization method,then the optimal controller is designed,and the active-frequency and reactive-voltage are combined to control.Finally,the simulation proves that The control algorithm can reduce the system oscillation and improve the system’s dynamic steady-state performance.For the DVR control algorithm,the traditional algorithm is to detect the compensation amount of the grid voltage distortion,and then control it through the PI controller.It also needs to perform dq coordinate transformation.When there is harmonics in the system,the dq component is not a DC quantity,which will cause the system error.In this paper,the ADP algorithm is used in the DVR control algorithm,and the optimal controller is designed directly in the abc coordinate system.The simulation results show that the load side voltage can be compensated into the standard three in the case of grid voltage harmonics and imbalances.Phase sinusoidal voltage.In the power system,the optimal parameters of ADP can be solved first,and then the obtained parameters are brought into the system simulation.The simulation shows that the power system controlled by ADP can improve the dynamic and steady-state performance of the system,and the control process is also better than The traditional control method is simple.