一种改进线性扩张状态观测器的自抗扰控制宽频带振荡抑制方法研究

针对自抗扰控制策略在并网系统参数变化时能否维持逆变器接入弱电网的稳定性展开了进一步研究。首先，建立了计及频率耦合的自抗扰控制型并网逆变器等效单输入单输出序阻抗模型，并采用Nyquist稳定判据定量分析逆变器输出功率、电网短路比、锁相环以及自抗扰控制器参数变化对并网系统稳定性的影响。其次，针对上述参数变化所导致的弱电网下自抗扰控制型逆变器稳定性降低、宽频带振荡等问题，提出了一种改进线性扩张状态观测器(enhanced linear expansion state observer, e-LESO)的自抗扰控制宽频带振荡抑制方法。通过在传统一阶自抗扰控制器中LESO内部增添比例支路和滤波环节，重塑自抗扰控制型并网逆变器输出阻抗，拓宽其中频段(100 Hz~1 kHz)内呈正阻尼特性的频率范围，从而增强自抗扰型并网逆变器鲁棒性，实现宽频带振荡抑制。最后，通过仿真验证了所提方法的有效性。

A wideband oscillation suppression method for active disturbance rejection control with an enhanced linear expansion state observer

When the parameters of a grid-connected system change, whether the active disturbance rejection control (ADRC) strategy can maintain the stability of the connection between the inverter and the weak grid is an issue. First, the equivalent single input single output sequence impedance model of an ADRC grid-connected inverter considering frequency coupling is established, and the Nyquist stability criterion is used to quantitatively analyze the influence of inverter output power, grid short circuit ratio, phase-locked loop and ADRC parameter changes on grid-connected system stability. Second, given the problems of the stability degradation and broadband oscillation of the ADRC inverter under the weak grid caused by the above parameter changes, an ADRC broadband oscillation suppression method with enhanced linear expansion state observer (e-LESO) is proposed. By adding proportional branches and filtering links inside the LESO in the traditional first-order ADRC, the output impedance of the ADRC inverter is reshaped, and the frequency range with positive damping characteristic in the middle frequency band (100 Hz~1 kHz) is widened, so as to enhance the robustness of the ADRC grid-connected inverter and achieve broadband oscillation suppression. Finally, the effectiveness of the proposed method is verified by simulation.