| In modern industrial systems,such as AC electric arc furnace,electrified railway and large rolling mill,all belong to dynamic non-linear load.The characteristic of this kind of load is that the active power and reactive power change rapidly with time,Because of its non-linear and unbalanced electrical characteristics,The voltage waveform of the power supply network is distorted,It causes voltage fluctuation,flicker and three-phase unbalance,and even system frequency fluctuation,And inject a lot of harmonics into the system,It poses a serious threat to the power quality of power grid.Static Var Compensation(SVC)developed in recent years is a fast reactive power regulating device,It has been successfully applied to the compensation of impact loads such as metallurgical,mining and electrified railways.The device has fast regulation,multiple functions and reliability.It has obvious advantages over synchronous camera,and has achieved better technical and economic benefits.Therefore,it has been developed and applied rapidly at home and abroad.Firstly,according to the configuration and power supply characteristics of high voltage power supply system of Titanium slag smelting furnace,the unbalanced three-phase power is restrained by comparing the three-phase current and voltage control under the three structural arrangements;secondly,in view of the total harmonic voltage distortion rate,the short-term voltage flicker and the long-term voltage flicker exceeding the national standard,the data of SVC device is calculated and designed;lastly,by installing DSP.Full digital control system to ensure that the system indicators meet the requirements.In the design of filter,the maximum reactive power impact and reactive power variation of large titanium slag electric furnace are determined by calculating the impedance of electric furnace power supply system,and the capacities of filter and phase-controlled reactor are determined by calculating the reactive power compensation needed to improve the power factor.According to the harmonic standard of the State Grid,the harmonic quantity of each electric furnace is calculated,and then the harmonic current of multiple harmonic sources is superposed according to the principle of harmonic superposition calculation.Finally,according to the criterion of harmonic voltage and harmonic current limit,according to the principle of filter design,it is better to simulate and calculate several schemes on the computer,considering that the filter has four groups of filtering channels of 2,3,4 and 5 times.In order to balance the excess reactive power in shunt filter and ensure that the voltage of compensation point is close to constant,the protection measures of thyristor components and valve groups are analyzed.By adjusting the trigger angle of thyristor,the reactive power of compensation device can be continuously regulated.Using DSP full digital control system,the controller can adopt open loop feedback control mode to satisfy the system.The fast response capability of the SVC device is required to ensure that the voltage fluctuation and flicker of the system meet the requirements of the national standard,and the closed-loop feedback control mode can be used to ensure the stability of the power factor of the system.Finally,before and after the static dynamic var compensator(SVC)is put into operation,the test results of power quality show that the design of TCR type SVC device has been successfully realized,the power quality indexes have reached the international limit,and the expected effect of harmonic control has been achieved. |
PDF Full Text Request