具有限流能力的交流微网并网控制策略

Grid-Connected Control Strategy of AC Microgrid with Current-Limiting Capability

英国8·9大停电事故的发生让我们思考高比例分布式发电系统存在一定的技术瓶颈。基于此,本文提出了一种适应于交流微网接地故障的限流控制策略,该方法可以将故障电流限制在两倍额定电流以内,进而使得分布式电源在电网故障情况下不会瞬时脱网运行。同时,该方法不需要在电网正常和故障运行状态时切换参考电流,且在两种状态下可实现较小的电流谐波和较低的电流幅值不对称度。首先,通过含有washout滤波器的改进下垂控制策略获得电压参考值和锁相环,并通过准PR控制器实现对外环参考电压的无静差跟踪;其次,将外环控制器的输出的滤波电感参考电流与实际电感电流的差值通过具有抗参数扰动能力的改进无源控制控制器以实现对参考电流的跟踪;最后,仿真搭建的含有4台分布式电源的交流微网模型验证了本文提出方法的有效性。

The occurrence of the 8·9 blackout in the United Kingdom makes us think that there are certain technical bottlenecks in the high proportion of distributed generation systems(DGs).Based on this,this paper proposes a current-limiting control strategy adapted to AC microgrid ground faults,which can limit the fault current to within twice the rated current,so that DGs will not be instantaneously disconnected in the event of a grid fault.Meanwhile,the method does not need to switch the reference current in the normal and faulty states of the power grid,and can achieve smaller current harmonics and lower current amplitude asymmetry in the two states.Firstly,the reference value of the voltage and phase-locked loop are obtained by the improved droop control strategy with washout filter,and the static error-free tracking of the outer-loop voltage is realized by the quasi-PR controller;Secondly,the difference between the filter inductor reference current output by the outer-loop controller and the actual inductor current is passed through an improved passivity-based control controller with anti-parameter disturbance capability to realize the tracking of the reference current.Fianlly,an AC microgrid model with four distributed generation built by simulation verifies the effectiveness of the method proposed in this paper.