微源逆变器多模式运行协调控制策略研究

针对微源逆变器运行过程中存在的无缝切换及负荷功率分配问题,提出一种新的协调控制策略。该策略由直接电压内环、虚拟阻抗环和功率外环构成,其中直接电压内环采用自适应三阶滑模控制,将逆变器始终控制为电压源,避免运行模式变化时内环控制策略的切换,同时提高逆变器的动态性能和抗干扰性能;在分析逆变器闭环等效阻抗及其对功率分配影响机理的基础上,针对不同功率等级逆变器设计虚拟阻抗系数,使其输出阻抗呈阻性并满足功率分配的要求;最后利用下垂特性分别设计功率外环,从而实现并网运行时基于下垂控制的间接恒功率控制和离网运行时的无线对等控制。仿真和实验结果验证了控制策略的有效性。

Coordination control strategy of multi-mode operation for micro-source inverters

Seamless formation and load power sharing are two crucial problems in microgrids.In order to solve these problems,a coordination control strategy, which is composed by direct voltage inner loop, virtual output impedance loop and power outer loop, is proposed for micro-source inverters.The direct voltage inner loop is based on adaptive three-order sliding-mode control and makes the inverter be controlled as voltage source, so that the switch of the inner-loop control strategies can be avoided when the operation mode changes.Meanwhile, the dynamic characteristic and the disturbance rejection performance can be improved.On the basis of analyzing the equivalent output impedance and the impact mechanism to power sharing, the virtual impedance loop was designed to make the equivalent output impedance to be resistive and meet the requirement of power sharing.Then the power outer loop was designed based on droop characteristic, so the indirect power control in grid-connected mode and wireless peer-to-peer control in islanding mode can be realized.Finally, simulation and experiment results are presented to validate the effectiveness of the proposed control strategy.