It is well known that there is a design tradeoff between voltage regulation and load current sharing in conventional linear droop control for several parallel-connected distributed sources in a DC microgrid. To improve both performance areas, this article proposes a design method to identify the nonlinear droop curve coefficient with the desired bus voltage regulation and current sharing accuracy in a specified heavy load range, while a linear droop function with a negative droop resistance is used to tighten the bus voltage regulation in the light load range. The design procedure of load boundary and the effect of negative droop resistances on the system stability are analyzed in detail. Also, a boost-up and curve-fitting method can further improve the voltage regulation and achieve smooth transition between light load and heavy load. In this way, no additional voltage compensation loop is needed. Two parallel-connected DC converters are finally built to verify the theoretical analysis.

中文翻译：

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期望的电压调节和均流精度的直流微电网非线性下垂控制设计

众所周知，对于直流微电网中的多个并联连接的分布式电源，在常规线性下降控制中，在电压调节和负载电流共享之间存在设计折衷。为了改善这两个性能领域，本文提出了一种设计方法，以在指定的重载范围内识别具有期望的母线电压调节和均流精度的非线性下垂曲线系数，同时使用具有负下垂电阻的线性下垂功能来紧固轻载范围内的总线电压调节。详细分析了负载边界的设计过程以及负压降电阻对系统稳定性的影响。另外，升压和曲线拟合方法可以进一步改善电压调节，并实现轻负载和重负载之间的平滑过渡。这样，无需额外的电压补偿环路。最后构建了两个并联的直流转换器，以验证理论分析。