Fast extraction method of grid voltage sequence components in unbalanced conditions

Abstract

The basic requirement for implementing high-performance grid-connected inverter control is to quickly and accurately obtain the sequence components (i.e., positive, negative and zero sequence components) of the three-phase unbalanced grid voltage. This paper proposes a practical extraction method of sequence components, and it can significantly improve the extraction speed of voltage sequence components in unbalanced grid. The method first uses the virtual quadrature signal construction method and the single-phase locked operation to obtain the virtual three-phase voltage phasor. Next, the symmetrical component method and the single-phase-locked inverse operation can be used to quickly obtain the amplitude and real-time phase of the sequence component. The method only needs the grid voltage and its virtual orthogonal signal to calculate the amplitude and phase of the voltage sequence component, and the method does not require parameter design and debugging process. Meanwhile, its calculation accuracy can meet engineering requirements. The correctness of the method is verified by MATLAB/Simulink real-time simulation platform. 快速准确地获取三相不平衡电网电压的序分量（即正、负、零序分量）是实现高性能并网逆变器控制的基本要求。文中提出了一种实用的瞬时序分量提取方法，可提高不平衡电网电压序分量的提取速度。首先，使用虚拟正交信号构建法和单相锁相运算获得虚拟三相电压相量，之后利用对称分量法和单相锁相逆运算，即可快速获得序分量的幅值和实时相位。该方法仅需电网电压及其虚拟正交信号，即可直接获得瞬时电压序分量，无需闭环检测方法中的参数设计和调试过程，且计算精度能够满足工程要求。通过MATLAB/Simulink实时仿真平台验证了该方法的正确性。