| In recent years,the people’s development of electricity demand is increasing and distributed energy is continuously connected.At the same time,there are a large number of asynchronous electric motors,transformers,transmission lines and other power equ ipment in the power system,which consumes a large amount of inductive reactive power in order to establish an alternating magnetic field.The non-linear load will bring a series of problems of harmonic pollution and insufficient reactive power,which will affect the safe and stable operation of the system in severe cases.The importance of using reactive power compensation devices to improve power quality is becoming increasingly prominent.The traditional reactive power compensation device has a slow response speed and a large loss,and dynamic reactive power compensation cannot be achieved well.The Static Var Generator(SVG)has the advantages of high compensation accuracy,fast response,and effective harmonic reduction,enabling efficient real-time dynamic reactive compensation.Therefore,this thesis takes the Static Var Generator device as the research object,realizes the rapid reduction of the phase difference between voltage and current,and effectively solves the problem of reactive power shortage and harmonic pollution.The main researches are reactive current detection,tracking compensation of reactive current and DC side voltage control,and design the hardware and software parts of three-phase three-wire SVG.The main research contents are as follows:Firstly,the current development status of SVG devices and control strategies is analyzed.Based on the single-phase equivalent circuit,the basic working principle of SVG is deeply analyzed.The three-phase three-wire LCL NPC is designed as the SVG main topology and the selected topology is established.Based on the mathematical model of the abc coordinate system,the mathematical model of the static var generator in the dq coordinate system is derived by dq transformation.On this basis,based on the voltage distortion of the system,the ip-iq detection method based on instantaneous reactive power theory is designed as the current detection method of SVG system.Secondly,the SVG control strategy was designed.As a whole,current and voltage doubl e closed loop control is adopted.In the design of the current loop,the fuzzy PI control strategy is designed and the fuzzy control rules are designed in detail.It is then combined with three-level voltage space vector control(SVPWM).The voltage loop c ontrol adopts PI control to make the DC side voltage quickly stabilize.Then build a simulation model of the overall Static Var Generator in MATLAB/Simulink.Through the analysis of the simulation results,the voltage and current phase difference can be significantly reduced after inputting SVG,and the harmonics can be effectively suppressed.The fuzzy PI control is compared with the simulation result of PI control.The fuzzy PI control is one cycle faster than the PI control,which proves that the fuzzy P I has fast response speed and good compensation effect.The dynamic compensation effect of the sudden increase and load reduction analysis is also set.The main module simulation model of three-level SVPWM is built,and the simulation results of DC voltage side PI control are analyzed.The effectiveness of SVG control method in this design is verified by simulation waveform and spectrum analysis results.Finally,the hardware and software design of the SVG device is performed.The hardware part mainly designs the sampling circuit,the driving circuit,the auxiliary power supply circuit and the protection circuit.The software part is designed for the main circuit,AD interrupt sampling,and SVPWM software program.Using the laboratory resources,the experime ntal platform with DSP28335 as the main controller is built.The experimental and simulation results show that the control method designed in this paper can play a good dynamic reactive power compensation effect and play a leading role in improving the performance of SVG. |
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