基于有功功率注入控制的风电及光伏并网系统改进LVRT控制策略

Improved LVRT Control Strategy for Wind Power and Photovoltaic Grid-connected Systems Based on Active Power Injection Control

  • 摘要: 为解决风电和光伏联合并网系统随机波动导致传统低电压穿越(Low voltage ride through,LVRT)控制存在并网点电压支撑能力较弱的问题,提出一种基于有功功率注入控制的改进LVRT控制策略,该策略能够提升系统对故障后的电压支撑能力,增强系统的低电压穿越能力。首先,根据风光联合并网系统拓扑结构,分别建立光伏发电系统和风力发电系统数学模型,以此建立风光联合发电系统状态空间模型;其次,在Matlab中编写风光系统数值模型,在PSCAD/EMTDC平台上搭建相应的系统电磁暂态仿真模型,对比两者的仿真结果,验证了数值仿真模型的正确性,进一步地,分析参数变化对系统稳定性的影响;再次,探究负荷侧发生三相短路故障时,光伏并网点及风机并网点的电压跌落情况以及变流器输出功率的动态响应特性,基于LVRT技术指标,提出一种改进LVRT控制策略,其中,功率等级较小的光伏逆变器优先进入LVRT控制,功率等级较大的双馈风机(Doubly-fed induction generator,DFIG)变流器保持有功输出;最后,分析故障发生后,采用三种不同的LVRT控制策略组合对并网点电压的支撑效果,仿真结果表明,风光并网系统发生故障时,所提控制策略可将并网点电压抬升至0.21 p.u.,满足标准对并网点电压的支撑要求,同时兼顾了有功功率的输出效率。所提方法可有效提升风光联合并网系统在低电压穿越时的电压支撑能力及有功功率的输出,增强了可再生能源并网系统的供电持续性。

     

    Abstract: To address the problem of weak voltage support capability at grid-connected points caused by random fluctuations in wind power and photovoltaic(PV) hybrid grid-connected systems, an improved low voltage ride through(LVRT) control strategy based on active power injection control is proposed. This strategy aims to enhance the system's voltage support capability following faults and improve its LVRT performance. Firstly, based on the topology of the wind-PV hybrid grid-connected system, mathematical models of the PV generation system and wind power generation system are established respectively, forming the state space model of the hybrid generation system. Secondly, a numerical model of the wind-PV system is developed in Matlab, and the corresponding electromagnetic transient simulation model is constructed on the PSCAD/EMTDC platform. By comparing the simulation results of both models, the accuracy of the numerical simulation model is verified. Furthermore, the impact of parameter variations on system stability is analyzed. Thirdly, the voltage dip drop at the point of common coupling(PCC), as well as the dynamic response characteristics of the converter's output power, are investigated when a three-phase short circuit occurs on the load side. Based on LVRT technical specifications, an improved LVRT control strategy is proposed, wherein smaller-capacity PV inverters prioritize LVRT control, while larger-capacity DFIG converters maintain active power output. Finally, the effectiveness of three different LVRT control strategies in supporting the voltage at the grid connection point is analyzed post-fault. Simulation results show that the proposed control strategy can raise the voltage at the grid connection point to 0.21 p.u. when a fault occurs in the wind-PV grid-connected system, meeting the standard requirements for voltage support at the grid connection point, while also ensuring the efficiency of active power output. The proposed method effectively enhances the voltage support capability and active power output of wind-PV grid-connected systems during low voltage ride-through, thereby improving the power supply continuity of renewable energy grid-connected systems.

     

/

返回文章
返回