基于自适应虚拟阻抗的逆变器并联控制策略

低压微网中，各并联逆变器之间的连接线路因长度、损耗等不同导致各逆变器并联线路阻抗存在明显差异，在常规下垂控制下，各并联逆变器间有功功率存在无法均分的问题。针对上述问题，提出了一种基于虚拟阻抗的自适应控制策略。首先，以逆变器功率传输特性与阻性下垂控制方程为基础，分析并联逆变器在线路呈阻性时有功功率分配不均的原因；其次，在传统定值虚拟阻抗基础上，通过引入并联逆变器的输出功率差构造虚拟阻抗，自适应地补偿线路阻抗差异，在不获取本地线路阻抗参数的情况下实现功率均分；最后，在MATLAB/Simulink仿真平台上建立逆变器并联系统的仿真模型，进行验证和分析。结果表明，所提方法能有效实现逆变器间有功和无功功率的均匀分配，且适用于本地负载不同的情形。基于自适应虚拟阻抗的控制策略改善了并联逆变器间功率的均分水平，可为低压微网中并联逆变器功率控制的优化设计提供参考。

Parallel inverters control strategy based on adaptive virtual impedance

In the low-voltage microgrid, the connection lines between parallel inverters are different due to the different length and loss, and the active power of the parallel inverters cannot be evenly distributed under the conventional droop control. Aiming at this problem, an adaptive control strategy based on virtual impedance was proposed. Firstly, based on the inverter power transmission characteristics and the resistive droop control equation, the reason of the uneven power distribution of parallel inverters when the line was resistive was analyzed. Then, based on the traditional fixed virtual impedance, the virtual impedance was constructed by introducing the output power difference of the parallel inverters, and the line impedance difference was compensated adaptively, so that the power sharing can be realized without obtaining the local line impedance parameters. Finally, the simulation model of parallel inverters system was established on the MATLAB/Simulink simulation platform for verification and analysis. The results show that the proposed method can effectively realize the sharing of active and reactive power among inverters, and is also suitable for different local loads. The control strategy based on adaptive virtual impedance improves the level of power sharing among parallel inverters, which provides some reference for the optimal design of power control of parallel inverters in low-voltage microgrid.