微电网中不同容量逆变器经线路并联的环流特性分析和功率分配控制

Circulating-Current Analysis and Power Distribution Control of Parallel Inverters with Different Power Ratings in Microgrid

为解决微电网中多逆变器并联的功率分配问题,建立了逆变器单机控制和两机并联模型,在此基础上分析了环流和功率分配的相互作用机理。针对中低压微电网的线路参数阻性和感性相当时,有功功率和无功功率的耦合现象,通过添加虚拟电抗补偿实现微电网线路达到高压电路阻感比,使有功功率和无功功率能分别解耦控制。其后研究了线路为感性阻抗时实现环流抑制和功率精确分配的控制策略应该满足的条件,针对下垂控制无功功率分配不与感性线路阻抗解耦的缺点,提出了改进的下垂控制策略,实现了功率分配和环流抑制的目标。最后通过PSCAD/EMTDC仿真验证了理论分析和所提出的控制策略的正确性。

To deal with power distribution problems of multiple parallel inverters in microgrid, the interaction mechanism between cir- culating-current and power distribution is elaborated firstly. Under the situation that the low-voltage microgrid line parameters is equiv- alent in resistance and reactance, by adding virtual reactance to compensate microgrid transmission line and achieve the resistance and inductance ratio like high-voltage transmission lines, the coupling problem of active power and reactive power is solved. Then the con- ditions are studied that the control strategy should meet for precise power distribution and circulating-current restraint with inductive im- pedance line. Improved droop control is put forward aiming at the coupling of reactive power distribution and inductive line imped- ance, which can realize reactive power distribution and circulating-current restraint. Finally, the correctness of the theoretical analysis and the proposed control strategy is verified by PSCAD/EMTDC simulation.