Micro-grid multi-inverter parallel voltage unbalanced compensation method

Abstract

The invention discloses a micro-grid multi-inverter parallel voltage unbalanced compensation method. The method relates to an unbalanced compensation ring, a power droop control ring and a voltage and current ring. On the basis of traditional power droop control, three-phase negative sequence voltages and currents are detected, the negative sequence reactive conductance Q-G unbalanced droop control ring is introduced, directive current reference values are synthesized and revised, and then unbalanced compensation of micro-grid voltage is achieved. Through P-f, Q-E and Q-G droop control, distributed power inverters can independently adjust and output fundamental wave frequency, voltage amplitude and unbalanced compensation conductance, and therefore active and reactive equilibrium distribution can be achieved among the inverters. Quasi-resonance PR control is adopted by the voltage and current control ring, astatic control of the voltage is achieved, dead-beat control is adopted, and then accurate control of currents in an inner ring is achieved. According to the method, the three-phase inverters in a micro-grid possess the unbalanced compensation capacity, and therefore micro-grid three-phase voltage balance is maintained.

Description

technical field [0001] The invention relates to the technical fields of new energy distributed power generation, microgrid operation and control, in particular to a method for compensating voltage unbalance in parallel with multiple inverters in a microgrid. Background technique [0002] As an effective carrier of distributed generation (DG), the microgrid is mainly composed of power electronic conversion devices, energy storage devices, protection and load control equipment, and can operate in both island and grid-connected states. It is a distributed generation of DG. An effective way to access the large power grid is also an important part of the smart grid. [0003] However, in a low-voltage microgrid composed of three-phase inverters, three-phase load asymmetry often exists, which will lead to a three-phase imbalance in the supporting voltage of the microgrid, resulting in a large energy loss and affecting the microgrid system. stability. When the voltage of the point...

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Problems solved by technology

However, when the load is seriously unbalanced, the magnitude of the compensation current injected by the parallel power quality conditioner will increase sharply, even exceeding the rated value of the power quality conditioner

At the same time, the external power quality regulator increases the complexity of the microgrid system, which not only increases the system hardware cost, but also reduces the system reliability.

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