Research On Improving Power Quality Of Microgrid Based On ESS-APF

With the continuous improvement of the power quality requirements of electrical equipment,the ripple problem of the bus voltage in the DC microgrid has attracted more and more attention.In addition,my country proposed in the 14 th Five-Year Plan to continuously improve energy storage technology to support the rapid development of new energy.The energy storage unit in the DC microgrid is often idle,and its redundant capacity is often not fully utilized.From the perspective of cost saving,the energy storage system can be combined with the DC active power filter.On the basis of meeting the power regulation function of the energy storage system,the ripple suppression function of DC-APF is realized,and the combined device is fully utilized in one machine and multiple functions.This article introduces the main structure of the DC microgrid and the causes of bus voltage ripple.Aiming at the ripple problem of the bus voltage,a new type of DC-APF control strategy is proposed based on the research of DC active power filter.This article analyzes the multi-modal work of DC-APF,and optimizes the ripple detection and compensation control method.It proposes a DC bus voltage ripple detection method based on the wavelet transform Mallat algorithm,and compares it with the traditional ripple detection method.In contrast,an improved fuzzy adaptive PI control strategy is proposed in the control method.The designed DC-APF is verified and analyzed by simulation research and experimental prototype.Secondly,in order to improve the reliability of DC-APF work,this paper has carried out the fault-tolerant research of DC-APF.A fault-tolerant DC-APF based on the H-bridge circuit structure is proposed.Its working principle,applicable fault types and working modes are analyzed.Aiming at the problem of uncertain control parameters due to topology changes before and after the fault of the fault-tolerant DC-APF,a variable domain adaptive fuzzy PI control strategy is proposed,which can adjust the PI parameters online.The simulation results verify that the designed fault-tolerant DC-APF has good compensation performance for the bus voltage ripple before and after the device failure,which can ensure the stable operation of the system.On the basis of the research of DC-APF,this paper has carried out the research on the combined device of energy storage system and active power filter.The advantages of the combination of energy storage system and active power filter are introduced,and the combination principle of ESS-APF combined device is analyzed.The topological structure of the three types of ESS-APF combined devices are studied and analyzed,and they are optimized.Its advantages and disadvantages and implementation functions are compared and discussed.Finally,the ESS-APF combined device based on the three-port structure is selected as the research object.The article analyzes the working mode of the ESS-APF combined device and proposes a multi-function control strategy.The simulation results verify that the proposed ESS-APF combined device can not only realize the power adjustment function of the energy storage unit,but also realize the ripple suppression function of the DC-APF.It can provide a novel and low-cost solution to the power quality problem in the DC microgrid.