基于模糊控制的分布式光伏并网主动支撑方案研究

Research on Active Support Scheme for Grid-connected Distributed Photovoltaic Based on Fuzzy Control

当前,光伏逆变器通常采用最大功率跟踪技术,功率波动性强,严重时可能引起电压越限、光伏脱网等问题,阻碍了光伏渗透率的提升。针对上述问题,本文结合光伏的有功功率削减和无功电压下垂控制技术,研究了光伏逆变器主动支撑控制方案。同时,在改进扰动-观测法的有功功率削减控制中,针对定步长情况下的功率波动大、响应速度慢问题,提出了基于模糊控制的步长自整定方案,提高响应速度并平抑了波动。针对Boost电路采用恒定参数的PI控制器时存在的光伏功率跟踪速度慢和波动大的问题,基于模糊控制技术,提出一种电压环PI参数自整定方法,提高光伏功率跟踪速度和稳定性。最后,通过在MATLAB/SIMULINK中建立光伏逆变器并网的仿真模型,对主动支撑控制策略进行了仿真验证。通过搭建光伏电源并网实验平台对提出的有功削减步长自整定的方法进行了实验验证。结果表明,所提出的方法能够提高光伏逆变器对并网点电压的主动支撑能力,提高光伏主动支撑控制下的功率跟踪速度和稳定性,进而提高配电网的电压质量。

When the photovoltaic inverter is running in the maximum power tracking mode,it may cause the voltage and frequency of the photovoltaic grid connection point to fluctuate.In severe cases,the bus voltage may deviate from the standard seriously,and the photovoltaic grid will be disconnected in a large area,which hinders the application of photovoltaic power generation technology.In response to this problem,this paper combines the active power control and reactive voltage droop control of photovoltaics,and explores an active support control scheme for photovoltaic inverters.In order to solve the problems of large power fluctuations and slow stabilization speed in the active power reduction control based on the improved perturbation and observation method under the fixed step size,an auto-tuning step-length based on fuzzy control is used to improve the speed and stability of the active power reduction control strategy.Aiming at the slow speed and large fluctuation of photovoltaic power tracking when the Boost circuit adopts the PI controller with constant parameters,a fuzzy control-based PI parameter self-tuning scheme is used in voltage loop to improve the speed and stability of photovoltaic power tracking.Finally,the active support control strategy is simulated and verified by establishing the active support simulation model of the photovoltaic inverter in MATLAB/SIMULINK.And the proposed self-tuning method of step size is tested by building the grid-connected photovoltaic power experimental platform.The results show that the proposed method can improve the active support ability of the photovoltaic inverter to the grid-connected point voltage,improve the speed and stability of power tracking under the control of photovoltaic active support,and then improve the stability of the distribution network.