A low-voltage microgrid multi-inverter parallel voltage unbalance control method

Abstract

The invention discloses a multi-inverter parallel voltage unbalance control method of a low-voltage microgrid. The multi-inverter parallel voltage unbalance control method is suitable for a multi-inverter parallel control system of a low-voltage microgrid with unbalanced load, and comprises the following steps: calculating a voltage unbalance factor by sampling three-phase unbalanced load voltages, and applying the voltage unbalance factor to a voltage control ring to correct an instruction voltage reference value and realize voltage unbalance compensation; a robust droop control method under a resistive equivalent output impedance condition is adopted to satisfy the electrical parameter characteristics of the low-voltage microgrid, and meanwhile, a good power equalizing effect can be obtained even in the multi-inverter parallel control systems different in capacity; due to the adopted dead-beat current control, the control accuracy is high and the dynamic response is fast. The multi-inverter parallel voltage unbalance control method of the low-voltage microgrid simultaneously meets two implementation conditions of microgrid isolated island operation with serious unbalanced load and relatively greater feeder resistance, has excellent practicability, and achieves a good control effect in the multi-inverter parallel control system of the low-voltage microgrid with unbalanced load.

Description

technical field [0001] The invention belongs to the technical field of new energy distributed power generation, micro-grid operation and control, and in particular relates to a voltage unbalance control method for parallel connection of multiple inverters in a low-voltage micro-grid. Background technique [0002] In order to solve the technical problems of connecting distributed power sources to the power grid, scholars related to power systems have proposed the concept of micro-grids. A microgrid is a local power generation system that is composed of distributed micro sources, energy conversion devices, and local loads interconnected through a network, and can realize self-control, protection, and management. In the microgrid, most distributed micro-sources are connected to the AC bus through the inverter interface, thus forming a multi-inverter parallel operation environment. [0003] The key difficulty of the low-voltage microgrid operating in an island is that the resis...

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Problems solved by technology

The method adopts a circuit topology in which the output ends of three single-phase full-bridge inverter circuits are respectively filtered through a filter circuit and then output according to a three-phase four-wire transformer, and each phase is connected to a low-voltage three-phase four-wire grid after passing through a line impedance. This structure is relatively complicated, and it is necessary to control three single-phase full-bridge inverters at the same time; especially the use of transformers further increases the volume of the device; in addition, the current controller adopting pure proportional control mode, its current control effect needs improvement

[0008] To sum up, the existing technology does not solve the problem that when the low-voltage microgrid has three-phase unbalanced loads, the supporting voltage of the microgrid will appear unbalanced in three phases, which will affect the stability of the microgrid system operation and cause large energy losses. technical problems

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