变流器外特性下垂并联控制方法的分析、设计和性能比较

外特性下垂并联控制方法主要有两种实现形式:负载电流前馈方式和减弱电压控制环方式.本文通过建立数学模型给出了这两种方式的实用设计方法,并对其动、静态性能进行了对比分析,指出减弱电压控制环方式单位输出阻抗的带宽约等于电压环带宽,而负载电流前馈方式下则约为电压环带宽的一半.如果负载电流通过观测器得到,则带宽最差情况下将下降到电压环带宽的三分之一.最后通过实验验证了理论分析的结果.

Analysis, design and performance comparison of droop method of parallel power converters

There are mainly two approaches to provide output voltage droop characteristics in droop method: program voltage reference by load current and limiting the DC gain of the voltage loop compensator. In this paper, detailed design guidelines of these two approaches are provided based on mathematical model analysis, and the transient and steady performance of these two approaches are analyzed and compared. It is observed that, for the approach of limiting DC gain, the bandwidth frequency of the output impedance in per unit is approximately equal to the bandwidth frequency of the voltage control loop, while the approach of programmable voltage reference, the bandwidth frequency is only about half of that of the voltage control loop. If the load current of the approach of programmable voltage reference is obtained through load current observer, in the worst condition the corresponding bandwidth may decrease to one third of the bandwidth of the voltage control loop. Finally, theoretical analyses are verified by experimental results.