基于附加单位延时反馈的LCL型并网变换器鲁棒电流控制策略

LCL型并网电力电子变换器在运行过程中存在谐振现象，有源阻尼法因其无需额外增加硬件成本、低有功损耗而被广泛采用，但往往需要额外的传感器进行控制信号采集，故提出一种仅对并网电流进行采样的附加单位延时反馈鲁棒电流控制。建立传统单环有源阻尼策略的阻抗模型，分析传统策略中有效阻尼区的局限性；考虑数字延迟和弱电网，提出一种基于附加单位延时反馈的控制策略，采用该策略后，可缓解由延时效应导致的相位滞后并扩大有效阻尼区，且无需额外的传感器即可实现有源阻尼。相比于传统方法，所提方法无需重新设计硬件、调制改进等措施，仅从控制模型角度重塑了并网变换器的虚拟阻抗。进一步地，详细设计了单位延时反馈环节的参数，当LCL参数和电网阻抗变化时，变流系统在奈奎斯特频率区间仍能保持稳定，提升了对复杂电网的适应性。

Robust current control strategy for LCL-type grid-connected converter based on additional unit time-delay feedback

The resonance phenomenon generally exists during the operation of LCL-type grid-connected power electronic converters. The AD(Active Damping) approach is widely used because it does not require additional hardware cost and has relatively low active power loss. However, additional sensors are often required for control signal acquisition. An additional unit time-delay feedback robust current control strategy that only samples the grid-connected current is proposed. The impedance model of traditional single-loop AD strategy is established, and the limitations of the effective AD zone for traditional strategy are also analyzed. Then, considering the digital delay and weak grid, a control strategy based on additional unit time-delay feedback is proposed, which can alleviate the phase lag caused by the time-delay effect and expand the effective damping area. In addition, the proposed strategy can achieve AD without additional sensors. Compared with traditional strategy, the proposed strategy does not require hardware redesign and modulation improvement, and only reshapes the virtual impedance of the grid-connected converter from the perspective of control model. Furthermore, the parameters of the unit time-delay feedback link are designed in detail. When the LCL parameters and grid impedance change, the converter system can still maintain stability within the Nyquist frequency range, which improves the adaptability to complex power grid.