基于虚拟阻抗相角补偿的并联逆变器谐振抑制方法

Resonance Analysis and Suppression Strategy for Multi-Parallel Inverters Based on Phase Angle Compensation of Virtual Impedance

逆变器是新能源发电系统中的重要接口装置。虚拟阻抗控制是并联逆变器谐振抑制主要方法。针对控制延时导致虚拟阻抗策略失效的问题,首先建立了考虑控制延时的并联逆变器等效电路和传递函数模型。在此基础上,定量分析了控制延时对传统虚拟阻抗相角特性的影响,揭示了虚拟阻抗在高频段呈现负阻尼而导致谐振抑制策略失效的机理。提出了基于虚拟阻抗相角补偿的并联逆变器谐振抑制方法,通过恢复虚拟阻抗在谐振频率附近的正阻尼特性,实现了并联逆变器系统的谐振抑制。进一步,采用根轨迹方法得到了保障系统稳定性的虚拟阻抗取值范围。最后,利用Matlab/Simulink软件分别对不同虚拟阻抗、电网电压暂降以及参考电流变化等多种工况进行了仿真,验证了所提控制方法的正确性和有效性。

With development and utilization of renewable energy,inverters,acting as main interfaces of renewable energy sources,are more and more widely employed in power grids. Virtual impedance is a principal method of resonance suppression in parallel inverters.To solve the problem that control delay would lead to failure of virtual impedance strategy,firstly,this paper establishes an equivalent circuit and a transfer function model of multi-parallel inverter system considering the control delay.Then resonance mechanism of the inverters is revealed.It is shown that traditionaI virtual impedances present negative damping at high frequency, resulting in failure of resonance suppression.The phase shift caused by the control delay is investigated quantitatively,and the virtual impedance is reshaped with phase angle compensation to restore positive damping characteristics.Then stability of the proposed method is analyzed and the range of virtual impedance is determined.Finally,simulation results basedon Matlab/Simulink are demonstrated,verifying correctness and effectiveness of the proposed control strategy in various conditions.