The unbalanced and distorted grid phenomena are expected to be a critical factor for future microgrids due to extensive use of unbalanced and nonlinear loads. These microgrid conditions keep changing depending on the load profile. The active power oscillation, which happens due to polluted grid conditions, results in dc-link voltage fluctuation. Therefore, not only lifetime of the batteries and dc-link capacitors are compromised but also the stability of the system is affected. Active power oscillation can only be reduced by compromising with the harmonic distortion of the grid currents. Therefore, to cope with various expected abnormal microgrid conditions, a tradeoff between active power oscillation and total harmonic distortion of grid current is required. This article proposes a novel flexible reference current generation technique by using a tuning parameter to reduce the active power oscillation flexibly. The generated reference current comprises not only the positive and negative sequence currents but also lower order harmonic components. The peak values of all the components present in the reference current are decided in a stationary reference frame. Since model predictive controller tracks multifrequency reference currents without any additional requirement and with good stability margin, it has been used to control the neutral point clamped grid-tied three-level inverter. The concept is validated through simulation and experimental results.

中文翻译：

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微电网不平衡和畸变条件下并网多电平逆变器有功振荡灵活降低的模型预测控制

由于不平衡和非线性负载的广泛使用，不平衡和扭曲的电网现象预计将成为未来微电网的关键因素。这些微电网条件根据负载情况不断变化。由于受污染的电网条件而发生的有功功率振荡会导致直流母线电压波动。因此，不仅电池和直流链路电容器的寿命受到影响，而且系统的稳定性也会受到影响。有功功率振荡只能通过妥协电网电流的谐波失真来减少。因此，为了应对各种预期的异常微电网情况，需要在有功功率振荡和电网电流总谐波失真之间进行权衡。本文提出了一种新颖的灵活参考电流生成技术，通过使用调谐参数来灵活地减少有功功率振荡。产生的参考电流不仅包括正序电流和负序电流，还包括低次谐波分量。参考电流中存在的所有分量的峰值在静止参考系中确定。由于模型预测控制器无需任何额外要求即可跟踪多频参考电流且具有良好的稳定性裕度，因此它已被用于控制中性点钳位并网三电平逆变器。该概念通过模拟和实验结果得到验证。产生的参考电流不仅包括正序电流和负序电流，还包括低次谐波分量。参考电流中存在的所有分量的峰值在静止参考系中确定。由于模型预测控制器无需任何额外要求即可跟踪多频参考电流且具有良好的稳定性裕度，因此它已被用于控制中性点钳位并网三电平逆变器。该概念通过模拟和实验结果得到验证。产生的参考电流不仅包括正序电流和负序电流，还包括低次谐波分量。参考电流中存在的所有分量的峰值在静止参考系中确定。由于模型预测控制器无需任何额外要求即可跟踪多频参考电流且具有良好的稳定性裕度，因此它已被用于控制中性点钳位并网三电平逆变器。该概念通过模拟和实验结果得到验证。已用于控制中性点钳位并网三电平逆变器。该概念通过模拟和实验结果得到验证。已用于控制中性点钳位并网三电平逆变器。该概念通过模拟和实验结果得到验证。