弱电网下LCL逆变器的有源阻尼控制策略研究

Research on Active Damping Control Strategy for LCL Inverter in Weak Grid

在弱电网中,由于电网阻抗的存在,会导致新能源并网LCL滤波器固有谐振频率发生偏移,传统有源阻尼控制策略则无法保证系统的稳定性。而且随着新能源发电在电力系统中的占比不断提高,如何降低运营成本成为了研究热点。因此本文提出一种基于并网电流和公共耦合电压反馈的新型控制策略,该控制策略不仅提供了有源阻尼以抑制LCL谐振,而且减少了传感器的使用,还能对大范围变化的电网阻抗有较强的适应能力。通过仿真和实验表明,与传统的控制策略相比,在改进的策略下弱电网的实用范围增加,系统的稳定性得到提高,对谐波的抑制能力提升,并网电流质量有了良好的改善。

In a weak grid,due to the existence of grid impedance,the natural resonant frequency of a new energy grid-connected LCL filter will shift,and the traditional active damping control strategy cannot guarantee the system stability.Moreover,as the proportion of new energy power generation in the power system continues to grow,how to reduce the operating costs is a hot topic for research.Therefore,a novel control strategy based on grid-connected current and common coupling voltage feedback is proposed in this paper,which not only provides active damping to suppress LCL resonance,but also reduces the use of sensors.In addition,it has a strong adaptability under wide-ranging changes in grid impedance.Simulation and experimental results show that,compared with that under the traditional control strategy,the practical range of weak grid under the improved strategy increases,the system stability is enhanced,and the capability to suppress harmonics is raised,indicating that the quality of grid-connected current is well improved.