A Method for Power Electronic Transformer to Reduce Voltage Unbalance of Distribution Network

Abstract

The invention discloses a method for reducing voltage unbalance of a distribution network by use of a power electronic transformer in the technical field of voltage unbalance of the distribution network. According to the method, an optimization model is established by collecting operation parameters of an AC / DC hybrid distribution network containing the power electronic transformer, and the minimum of the sum of squares of negative sequence voltage and zero sequence voltage of each node of the AC network is taken as a target function for optimizing calculation, so that the port control value of the power electronic transformer is solved. As for the AC / DC hybrid distribution network formed by the power electronic transformer, the DC network can provide energy support for the AC network. Reduction of the voltage unbalance of all nodes of the AC network is taken as a target, and besides, negative sequence voltage and zero sequence voltage are considered, so that the unbalance of the negative sequence voltage and zero sequence voltage can be reduced, and voltage unbalance of multiple nodes can be comprehensively inhibited. Compared with existing methods for reducing the voltage unbalance, the method is more economical, accurate and reliable.

Description

technical field [0001] The invention belongs to the technical field of reducing the voltage unbalance degree of a power distribution network, and in particular relates to a method for reducing the voltage unbalance degree of a power distribution network by a power electronic transformer. Background technique [0002] The low-voltage distribution network usually adopts a four-wire power supply mode. Single-phase and three-phase loads coexist, and the problem of three-phase imbalance will be unavoidable. The connection of unbalanced loads will lead to three-phase voltage imbalance, which will adversely affect the safety and efficiency of the power grid. . An unbalanced power distribution system will generate more losses and thermal effects, and unbalanced three-phase voltage will also negatively affect or even harm equipment such as induction motors, power electronic converters, and variable speed drives. In addition, the negative sequence current generated by the three-phase...

AI Technical Summary

Problems solved by technology

However, due to the randomness of load use, manual commutation adjustment is lagging and inaccurate, and the actual effect is not ideal; and although the commutation switch composed of thyristors can quickly and safely commutate phases, it needs to design complex driving devices, and the commutation cost too high

This method can only achieve temporary three-phase balance, and the commutation process may cause important loads to be powered off, so the reliability is too poor

Generally speaking, there is currently a lack of an economical, accurate and reliable solution to the problem of reducing the voltage imbalance of the distribution network.

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