Experiment Research On Active Power Filter With Improved LCL Topology

With the development of science and technology,the extensive use of power electronic equipment has brought serious power quality problems.The power quality determines the overall level of the national economy.However,harmonic and reactive power pollution has been regarded as two main factors to affect the power quality,so it has been a key research field in the study of compensating the harmonic and reactive power current pollution caused by power electronic devices.As a dynamic suppression of harmonics and compensation of reactive power of the new power electronic device,active power filter has broad development prospects.At present,more active power filters are connected to the grid through the LCL topology.Although the current waveform of the injected grid is relatively smooth,the resonant point of the LCL topology can cause resonance and severe oscillation,which can amplify sub-harmonic.As a result,it pollutes the public grid,and even causes serious accidents.Therefore,it is necessary to improve the LCL-type output filter topology of the active power filter with grid-connected structure,so that it can suppress the resonance.At the same time,it can filter out the harmonics,compensate for the reactive power and improve the power quality.The article completed the following research work:(1)The generation and harm of the harmonics and reactive power were introduced,and pointed out the importance of harmonic control.The classification and working principle of active power filter were introduced in detail,and the development status of active power filter was expounded.(2)The main circuit topology of the active power filter was introduced,and the mathematical model of the three-phase three-wire active power filter was deduced.The output filter topology of the active power filter was studied deeply,and the topology of the improved LCL filter was proposed,deducing its mathematical model.And the main circuit parameters of the active power filter were designed.(3)The harmonic detection method and control method of the active power filter were discussed in detail.The advantages and disadvantages and the working characteristics of the various detection and control methods were analyzed.Finally,I selected the ip-iq harmonics detection method based on the instantaneous reactive power theory and triangular wave comparison control method.And I used the PSIM software to build the digital simulation model of the active power filter system.The validity of the detection method and the control method,and the feasibility and applicability of active power filter with the improved grid-connected topology were verified.(4)Combining with the experimental device,the hardware and software design of the active power filter control system were completed.(5)Based on ADSP-21489 control system,a prototype experiment platform was built.Harmonic compensation comparison experiments about LCL topology and improved LCL topology were completed.Besides,the harmonic and reactive power comprehensive compensation experiment of improved LCL topology was carried out.The experimental results showed that the improved LCL filter can suppress the resonance,and verify the validity of the detection and control algorithm and the correctness of parameter design of the active power filter.