Study Of Distribution Transformer/Capacitor Unit Micro-impact Voltage Reactive Comprehensive Control Device

The voltage becomes an important index that measures the power quality. Fluctuation range exceeds allowable value would bring great harm for the stability and economic operation of the grid. In addition, inductive load more used in the distribution network, making the power factor drop, grid voltage drop loss increase in power, the economy drop. The balance of the power system reactive power is the basic condition of ensuring voltage stability, voltage quality and running economy. Therefore, studying voltage and reactive power control in the distribution network is of great significance.Transformer OLTC and switching capacitor unit are the main measures of common voltage regulation and reactive power compensation in the current distribution network. However, common OLTC transformer tap and capacitor unit switching switch is not operated frequently, because the switching surge current is relatively large, which greatly limits the effect of using OLTC transformer and capacitor unit.In this paper, the composite switch with both advantages of AC contactor and solid state relay is used, which not only has the feature of solid state relay zero-voltage turn on, zero-current turn off and simple no inrush current control, but also has the characteristics of AC contactor conduction with large capacity, low pressure drop and low loss. The adjustment process of the OLTC transformer tap and the switching process of the capacitor unit is divided into transient and steady-state processes:In the transient process, the solid state relay works, in order to suppress inrush current and over-voltage, realize arc-free and fast switching. In the steady state process, the AC contactor works with large conducting capacity, low pressure drop and low loss.In this paper, the distribution transformer-capacitor unit micro-impact voltage reactive comprehensive control device is studied, to the composite switch as the implementation component, to the programmable controller PLC as the control center, to constitute a micro-impact, low-loss distribution transformer-capacitor voltage reactive comprehensive control system. Control system control the distribution transformer-capacitor by nine-zone diagram control strategy, based on the real-time information of voltage and power factor, which ensure the voltage quality, improve power factor and reduce network losses.