Study Of Flicker Detection And Flicker Transfer Characteristics Based On Dynamic Phasors Method

With the rapidly increase of impulse loads in power system, the voltagefluctuations and flicker of some areas have reached a very serious level. It ismeaningful for calculation of flicker limit,location and governance of flickersource to study flicker propagation.An improved detection algorithm of flicker value was proposed firstly asflicker detection was the basis of flicker analysis. The algorithm can solve theproblem that the measurement errors increased with higher flicker frequencies.A calculation method of flicker transfer factors based on dynamic phasorsmethod was proposed to study flicker transfer in power system. The existingmethods adopted calculation methods of steady circuit or steady power flow todescribe flicker propagation rules, lacking special study method of flickerpropagation rule.The dynamic phasor models of the general components of powersystem which are suitable in flicker study were established by dynamic phasorsmethod. With the Kirchhoff’s voltage and current law in dynamic phasor domain，the dynamic phasor models of the electric power grids were established and asimplified flicker transfer regularity were derived finally. The above flickertransfer regularity was compared with the current flicker transfer calculationmethods. The analysis shows that the current flicker transfer calculation methodsare more accurate only when the impedance angle of various impedances of powersystem are close and the method proposed in this paper is more generic.To study the effect of induction motor on flicker transfer,the dynamic phasemodel of three-phase induction motor applicable for flicker study was established.The basis of the model was the voltage equations, electromagnetic torque equationsand basic equations of motion. In the case of fluctuant source voltage, the modelrealized the quantitative calculation of stator current inter-harmonics componentsand variation quantity of rotor mechanical angular velocity of induction motors. Onthe basis of that, the frequency characteristics of flicker transfer under motor loadswere deeply studied. The study shows that when induction motors exist in powersystem, the flicker transfer from the source to the motor shows obvious frequencycharacteristics and the flicker transfer coefficients are concerned with the distribution of various flicker frequency components. The analysis also shows thatfor most flicker frequencies the induction motors help attenuation of flicker.To study the mechanism of voltage flicker caused by arc furnace operation, annew arc furnace model was proposed. The new model was dynamic model of arcfurnace described by multiple value volt-ampere characteristic curves, reflectingthe actual influence of arc length variation on volt-ampere characteristic curves. Onthe basis of that, the influencing factors of arc furnace flicker were furtheranalyzed.