一种多DG并联系统分布式控制策略

Distributed Control Strategy for Multi-DG Parallel System

受线路物理属性、下垂特性等因素的影响,传统下垂控制无法精确调节功率分配以及会导致DG输出端电压跌落。提出一种基于分布式控制的自适应电压平移法,各DG通过自身与其相邻DG加权功率间的偏差调节各自的电压偏置值,可减小因线路阻抗差异而导致的无功功率无法均分的影响。在此基础上,进一步提出一种改进型下垂控制策略,通过引入DG输出电压幅值与电压偏置值的差值反馈,构建改进型下垂特性曲线,可有效改善逆变器无功下垂系数、无功负载和输出电压幅值跌落之间的内在矛盾,进一步提高系统性能。建立了基于改进型下垂控制的2台三相逆变器并联系统小信号数学模型,分析了各参数对系统受扰动后的动态以及稳定性影响。仿真以及实验结果验证了所提控制策略的有效性。

Due to the influences of factors such as the physical properties of transmission line and the droop characteristics of distributed generations(DGs),the traditional droop control cannot precisely arrange the power distribution and will cause voltage drop at the DG output terminal.In this paper,an adaptive voltage shifting method based on distributed control is proposed.Each DG adjusts its own voltage offset value by means of the deviation between its weighted power and that of its neighbor,thus reducing the effects of unequal partition of reactive power caused by the line impedance difference.On this basis,an improved droop control strategy is proposed.Through the introduction of difference feedback between the DG output voltage amplitude and voltage offset value,an improved droop characteristic curve is constructed,which can effectively solve the inherent contradiction among the inverter’s reactive power droop coefficient,reactive load,and output voltage amplitude drop.As a result,the system performance is further improved.A small-signal mathematical model of two three-phase inverter parallel systems based on improved droop control is established,and the effects of various parameters on the dynamics and stability of the system under disturbance are analyzed.Simulation and experimental results verified the effectiveness of the proposed control strategy.