基于自适应下垂控制的多机逆变器双模式运行及平滑切换研究

Study on two-modes operation and seamless transfer of multi-inverter based on adaptive droop control strategy

使多机分布式发电单元无互联线并联组网系统工作于独立运行和并网运行两种模式,已成为可再生能源应用的重要技术手段。针对实际应用中存在的技术问题,文中提出了自适应下垂控制策略,其主要包括带低通滤波器的虚拟阻抗控制、主动同步控制和P-D/Q-I下垂控制三部分。首先改进了传统的虚拟阻抗控制,即在该环节加入了低通滤波器,从而在改善基波阻抗特性的同时提高了输出电压质量;然后提出了主动同步控制算法,该算法适用于采用下垂控制的分布式发电单元与电网的同步控制,实现了独立运行到并网运行过程中公共耦合点电压的平滑过渡;最后提出了P-D/Q-I改进下垂控制,改善了传统下垂控制实现电压型并网的性能。仿真分析与实验结果都验证了所提控制策略的有效性,实现了多机组网系统的双模式运行及平滑切换。

Making the wireless paralleled multi-distributed generation system work in both islanded mode and grid-connected mode has become an important technique for renewable energy application.Aiming at the technical problems in practical application,the adaptive droop control strategy is proposed in this paper,which mainly includes virtual impedance with low-pass filter algorithm,active synchronous control and P-D/Q-I droop control.Firstly,the traditional virtual impedance control is improved,that is,a low-pass filter is added in this part,thus the impedance characteristic at fundamental frequency is changed and the output voltage quality is improved.Then active synchronous control is proposed,which is suitable for droop control method,making a smooth transition of the point of common coupling voltage when the system changes into grid-connected mode.Finally,the P-D/Q-I droop control is proposed,which improves the performance of the traditional droop control working in grid-connected mode.Simulation and experiments both prove the effectiveness of the proposed control strategy which can make the multi-inverter work stably in islanded mode and grid-connected mode and achieve the seamless transfer.