一种单相逆变器并离网切换的统一控制策略

A Unified Control Strategy for Inverter Grid-connected/Islanded Transfer

分布式能源系统中,逆变器通常具有并网运行与孤岛运行两种模式。当逆变器并网运行时,一般表现为电流源特性,向电网输送功率;当逆变器孤岛运行时,一般表现为电压源特性,控制本地电网电压与频率稳定;逆变器并离网切换过程时需进行两种控制模式的模式切换。提出一种基于下垂控制的单相逆变器统一控制策略,构造一种电压源电网支撑型逆变器,在并网与离网模式下均可稳定运行,从而实现并离网工况的无缝切换。建立逆变器阻抗模型,基于阻抗模型设计了下垂控制策略和下垂曲线,给出了逆变器并离网切换的控制逻辑,构建了实验样机,通过实验验证了所提出的理论分析和控制策略的可行性。

Inverters in distributed energy networks usually can operate in both grid-connected mode and islanded mode.The inverters delivery active and reactive powers to the grid when operating in grid-connected mode and control the grid frequency and voltage amplitude close to their rated values when operating in islanded mode.During the process of traditional transfer methods, the control strategy of the inverters changes between current-controlled and voltage-controlled modes.A control strategy of single-phase inverters is carried out based on droop control and a kind of voltage-source-based grid-supporting inverters is represented.This kind of inverters can operate in dual-mode with the same control strategy and transfer seamlessly.Builds the inverter＇s impendence model, the droop control strategy and droop characteristics are designed based on this model and the control logic for inverter grid-connected/islanded transfer is carried out.And the availability of the proposed method is proved by experimental results.