提高并网逆变器在弱电网下稳定性的虚拟阻抗附加相角补偿控制

在LCL型并网逆变器中,为了减少传感器的使用,并网电流反馈的闭环控制得到了广泛的应用。然而一方面LCL型并网逆变器自身存在谐振现象,从而限制了电流控制器的设计；另一方面,由于弱电网中电网阻抗的存在,使该控制性能下降,对系统稳定产生不利影响。针对上述问题进行改进：一是采用特定的并网电流反馈有源阻尼控制器来虚拟电网侧的串联阻抗,即基于有源阻尼的虚拟阻抗法来抑制谐波尖峰；二是采用相位超前补偿的方法,增大逆变器输出阻抗的相角,极大地减少不稳定区域。保证了当电网阻抗变化时,该系统仍具有较强的稳定性。最后在MATLAB/Simulink上进行仿真,验证了所提方法的有效性和可行性。

Virtual Impedance Additional Phase Angle Compensation Control to Improve the Stability of Grid-connected Inverter in Weak Grid

In the LCL grid-connected inverter, the closed-loop control of grid-connected current feedback is widely used in order to reduce the use of sensors. However, on the one hand, LCL grid-connected inverter has resonance phenomenon, which limits the design of current controller. On the other hand, due to the existence of impedance in weak grid, the performance of the control decreases and the system stability is adversely affected. Firstly, a specific grid-connected current feedback active damping controller is used to virtual series impedance of the grid side, that is, the virtual impedance method based on active damping is used to suppress harmonic spikes. Second, the phase lead compensation method is used to increase the phase angle of the inverter output impedance and greatly reduce the unstable region. The stability of the system is guaranteed when the impedance changes. Finally, the simulation on MATLAB/Simulink verifies the effectiveness and feasibility of the proposed method.