Research On Harmonic Control Technology In Microgrid

Since the global energy shortage,electric energy,as the most widely used energy,faces enormous challenges in the power industry.As a result,microgrids consisting of renewably generated clean energy are being developed with great vigor.However,as frequency conversion and energy saving technologies are widely used in daily production,a large number of harmonics are introduced into the microgrid,which poses a problem to the stability of microgrid operation.Therefore,this article selects harmonics in the microgrid as the research object,and mainly conducts research on harmonic current detection algorithms and current tracking control algorithms.The main research contents are as follows:Firstly,a microgrid model and simulation are established.Microgrid consists of four parts:wind power generation,photovoltaic power generation,energy storage system,and load,which are analyzed and modeled;Matlab/Simulink is used as the simulation platform to build the simulation model and lay the foundation for harmonic detection and harmonic control.Secondly,the harmonic detection algorithm is studied.On the basis of analyzing the ip-iq harmonic detection algorithm based on instantaneous reactive power theory,it is found that when the grid voltage is in an asymmetric state,the phase locked loop will generate twice the power frequency AC component,which will cause detection errors.Therefore,an adaptive notch filter is introduced to improve the phase locked loop;The selection of the cutoff frequency of the lowpass filter will cause errors,so a sliding average filter is introduced to eliminate the errors.After simulation verification,it shows that the detection accuracy and speed of the improved harmonic detection algorithm are better than the traditional ip-iq detection algorithm.Then,the control technology of a single harmonic source is studied.The harmonics generated by a single harmonic source are controlled using an Active Power Filter,focusing on the current tracking control algorithm of APF.Based on the analysis of hysteresis control and space voltage vector control algorithms,a space voltage vector dual hysteresis control algorithm combining the two algorithms is adopted.The simulation verification shows that the algorithm has the advantages of high compensation accuracy,low switching frequency and good dynamic compensation performance.Finally,the control technology of multi harmonic sources is studied.The harmonic generated by multiple harmonic sources adopts a combined device combining energy storage unit and APF to achieve harmonic control while providing active power to the system.Study the structure and modeling of combined energy storage unit and APF device,focus on the research of command current tracking control algorithm,and select a composite controller composed of PI control and repetitive control.After the relevant simulation verification,it can be seen that the combination of energy storage unit and APF device can manage the harmonics in the microgrid and provide active power to the microgrid at the same time.