Power distribution network triphase load automatic adjusting device and control method thereof

Abstract

The invention discloses a power distribution network triphase load automatic adjusting device and a control method thereof. The device comprises a triphase unbalance adjusting controller, a switch loop, a interline compensation unit and an inter-phase compensation unit, the interline compensation unit and the inter-phase compensation unit are controlled by the triphase unbalance adjusting controller, the interline compensation unit can set number and capacity of branches therein according to capacity of a power distribution transformer, and the inter-phase compensation unit can set number and capacity of branches therein according to inactive capacity of the power distributor transformer. The triphase unbalance adjusting controller can automatically calculate active power and inactive power of a triphase line of the power distribution network online and select proper interline compensation capacity and inter-phase compensation capacity to control automatic switching of a combination switch to compensate each phase of the power distribution network so as to guarantee load balance among phase lines of the power distribution network. The device has the advantages of simple structure, convenience in mounting and high in universality, is low in temperature rise, loss and noise during working.

Description

technical field [0001] The invention relates to a three-phase load automatic adjustment device for a distribution network and a control method thereof, which are suitable for controlling three-phase unbalanced loads in a low-voltage power supply system, and belong to the fields of electric power technology and electronic technology. Background technique [0002] In the power system, the consumption of electric energy is mainly realized by the distribution network, especially by the low voltage of the distribution network. my country's low-voltage power load usually refers to the load carried by the AC 220V / 380V system. AC 220V / 380V system usually consists of three-phase four-wire, namely A phase, B phase, C phase and N phase. The low-voltage electric energy of the distribution network is transmitted and distributed by a certain distance of cable lines or wire lines, and the inductance in the low-voltage lines is inevitable. Thus, the reactive power in the load does exist. ...

AI Technical Summary

Problems solved by technology

[0003] The unbalanced three-phase load, the first major harm to the power system is the increase of line loss

For the power sector, it increases the number of emergency repairs and operation and maintenance costs, and reduces the reliability of power supply

[0004] The unbalanced three-phase load, the second biggest harm to the power system is the increase of transformer core loss

Distribution transformers with Y / Y0 or △ / Y0 wiring mostly adopt a three-core column structure. When the three-phase current imbalance occurs, there is no zero-sequence current on the primary side, but there is zero-sequence current on the secondary side. The current is Pure excitation current produces zero-sequence magnetic flux, because the magnetic flux does not have a closed magnetic circuit, it needs to pass through the tank wall to close, thus generating heat and loss in the iron core, fuel tank and magnetic accessories

[0005] Unbalanced three-phase loads, the third major harm to the power system is voltage offset, which will lead to unbalanced three-phase voltages in severe cases, affecting the output of three-phase motors and even burning the motors

It can be seen from the above formula that after the common compensation capacitor is connected, because the U / X values ​​of each phase are equal, the current of each phase has the same amount of change in value, so it cannot play the role of balancing the load, and can only change a certain amount on the vector. Angle

The traditional sub-compensation method is to connect different capacitors between phases of the three-phase system. The capacitor current on a certain phase is perpendicular to the active current on this phase, and the projection of the capacitor current on the active current is zero, so the active current and active current cannot be changed. power

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