具备电压稳定和谐波抑制的分频下垂控制器研究

针对以分布式发电为主的微网中可能存在的谐波问题，设计出同时兼备能量转换和谐波抑制的复合型逆变器，可有效解决此类问题。利用分频下垂控制策略和虚拟阻抗技术有效解决多逆变器并联运行时各逆变器在基波及谐波域均按照各自的容量承担负载。通过研究目前分频下垂控制策略谐波抑制效果不佳及没有考虑新逆变器并入系统带来的问题。本文在谐波域下垂控制中引入电压闭环负反馈，避免了新逆变器并入系统带来的冲击对公共节点电压偏移和谐波抑制的影响，提高了下垂控制的鲁棒性。并且讨论不同容量逆变器下垂系数与虚拟阻抗设计时的比例问题，使得各逆变器在基波及谐波域均能按各自容量分配功率。最后设计出符合谐波抑制效果明显，电压偏移小，基波及各次谐波域内均能按容量分配功率的分频下垂控制器。通过PSCAD仿真结果验证了该方不但可以抑制谐波，改善公共节点电压偏移，而且各逆变器在基波及谐波域均可功率精确分配。

A Novel Frequency Dividing Droop Controllers Based on Voltage stabilization and harmonic suppression

The harmonic problem is very serious in micro-grid based on distributed generation. It is one of the main ways to solve these problems if inverter has compound functions of voltage harmonics suppression and electrical energy conversion. While, the strategy of frequency divided droop control and the technology of virtual impedance are the key to achieve this goal. But, the current frequency divided droop control strategy cannot achieve power accurate distribution and with poor harmonic suppression effect, and ignored the solution that a new inverter added to the system. Based on this, the public connection point voltage feedback loop was introduced at fundamental and harmonics, avoiding the influence of harmonic suppression when a new inverter added to the system. Finally a novel frequency divided droop controller is proposed. The simulation results show that the method is effective at the improvement of harmonic suppression.