Research On Design And Application Of Passive Compensation Network

Unbalanced currents in three-phase systems can cause problems such as increased complexity in power system measurement and analysis methods,load neutral offset,and instantaneous power ripple,which make it one of the three major steady-state interferences(harmonics,reactive power,and asymmetry)facing the current power system(especially in the low-and middle-voltage distribution networks).It turns out that connecting the compensation device at the load is an effective way to compensate for the asymmetry of the three-phase power system.And because of its low cost and easy maintenance,the passive compensation device still has strong market competitiveness.In the design of passive compensation network topology and parameter calculation,traditional design methods usually need to consider the load delta connection or Y wiring,and then consider the use of inductance or capacitance(usually capacitance)for compensation.In addition,the traditional design method usually considers that the power supply is three-phase symmetrical,and the loss of inductance or capacitance is also negligible.The above design deficiencies have limited the use of passive compensation networks to some extent,and have also hindered the development of passive compensation devices.In order to obtain a universal passive compensation network topology and parameter design equation,the load is considered as a "black box",ignoring the topology of the load and only focusing on its three-phase load current.When the compensation network is designed,this paper fully considers the asymmetry of the power supply voltage and the loss of inductance or capacitance in the compensation network,and designs a general parameter equation for the passive compensation network.When the power supply voltage,the load current,the quality factor of the inductor and the loss angle of the capacitor are tangent,all the inductance or capacitance value of the compensation can be calculated,and the compensation element of a certain position is the inductance or the capacitance according to the positive and negative numbers.Finally,the quality factor of the electrical inductance and the loss angle of the capacitance are positive.It is cut to calculate the loss resistance of the inductance and capacitance.In actual operating conditions,the supply voltage is not constant and tends to fluctuate over time;the quality factor of an inductor and the loss angle of a capacitor also tend to change over time and load current is also constantly changing in actual operating conditions.In fact,it will be shown that the impact of load current changes on the compensation network is much greater than that of the supply voltage,inductance,and capacitance.In order to analyze the influence of power supply voltage,load current,inductance and capacitance on compensation effect of compensation network,this paper will discuss the influence of these factors on the power factor of the system,the negative order of power current and the zero sequence asymmetry,and then make a quantitative analysis.Finally,some items which affect the complex relation are simulated.Wave form,so as to observe and analyze.Because the influence of load current on compensation effect of compensation network is very significant,how much the load current is within the range of variation will be analyzed.In that condition,the compensation network can still control the supply current within the range specified by the national standard.Finally,the allowable variation range of the load current through an example will also be analyzed.