Research On The Control Strategy Of Dynamic Voltage Restorer Based On Neural Network

With the industrialization degree higher and higher,a large number of highly intelligent power equipments and power electronic equipments are put into use,these devices are more sensitive to interference,and require high quality of power.At the same time these non-linear devices exacerbated the deterioration of power quality.In many power quality problems,the probability of voltage sag is the biggest,and the damage is the most serious.Dynamic voltage restorer(DVR)is currently recognized as the most effective and most cost-effective compensation device to solve the voltage sag.For the low-voltage grid in China,the three phase four-wire system is adopted,and the unbalanced situation is more.Three single-phase inverter bridge structure DVR can provide zero sequence voltage to solve the problem.In this paper,the main research object is the three single-phase inverter bridge structure DVR.Fast and accurate detection of the voltage of grid is the premise of the DVR to solve the voltage sag.In this paper several common methods of voltage sag detection are discussed,and analyzed their advantages and disadvantages.The method of single phase dq transform detection is studied,and an improved method is put forward.The simulation results show that the developped method improved the speed of voltage sag detection.In this paper,the three phase inverter bridge structure DVR mathematical model is established,then the advantages and disadvantages of the traditional linear control strategies such as feed forward control and feedback control are analyzed.The inverter unit in the DVR is a nonlinear device,which is not good in the complex and changeable environment.Based on the analysis of the principle of the inverter,the neural network model of the inverter is built,and applies the model in DVR control,developped a DVR control strategy based on radial basis(RBF)neural network.The RBF neural network controller is designed and the gradient descent algorithm is used to adjust the parameters of the RBF network,ensuring DVR can well compensate the load voltage.Finally,the simulation model of DVR system is built in Matlab/Simulink simulation environment,and the RBF network operation is realized by S-Function module.Simulate and analysis of the DVR model,the simulation results verify the feasibility and effectiveness of the proposed scheme.