不平衡非线性负载下基于下垂控制的组合式三相逆变器并联技术

Control strategy of non-communication paralleled inverters based on droop is one of the most important and active research topics in microgrid. Considering that impact on inverter output voltage quality owing to the variousness of loads and precise power sharing and power circulation between inverters with different power levels in low voltage microgrid, in this article, combination three-phase paralleled inverters with different power levels in micro-grid is studied, system mathematical model and circuit model are built and analyzed. For the unbalanced load, a novel droop control method is proposed with voltage and current loop to realize the symmetry of inverter output voltage. For the nonlinear loads, compound voltage control loop composed with quasi proportion resonance and repetition control is proposed to restrain the voltage harmony content effectively and improve the volatege quality.The system equivalent output impedance is changed to decouple between the active and reactive power. Reactive power circulation adjustment is injected into the system control to restrain the reactive power circulation between the inverters. Lastly, a high performance, high credibility, perfect function and easily expansive paralleled inverters are realized and it can establish the theory and technology basis for the practicability and controllable performance for all kinds loads in micro-grid.

基于下垂控制技术的无信号互连线逆变器并联控制是目前微电网最重要和活跃的研究课题之一。针对低压微电网内负载的多样性对逆变器输出电压质量的影响以及不同容量下逆变器之间的功率精确分配和环流问题，本项目以微电网中不同容量的组合式三相逆变器并联电路为研究对象，建立并分析系统数学模型和电路模型；针对负载的不平衡型，对包含电压电流环的功率下垂结构提出了新的下垂控制策略，实现了逆变器输出电压的对称性；针对非线性负载，提出准比例谐振和重复控制结合的复合电压环控制方法有效地抑制输出电压谐波，提高输出电压质量，并改变系统等效输出阻抗，使其实现功率解耦；增加无功环流调节项来抑制逆变器间无功环流的产生。最终实现一套高性能、高可靠性、功能完善以及易扩展性的并联逆变器，为各种负载环境下微电网实用性和可控性奠定理论技术基础。

针对低压微电网内负载的多样性对逆变器输出电压质量的影响以及不同容量下逆变器之间的功率精确分配和环流问题，本项目以微电网中组合式三相逆变 器并联电路为研究对象，建立并分析系统数学模型和电路模型；针对非线性负载下并联逆变器之间谐波功率不均分问题，提出了各逆变器根据其谐波电流的有效值构造实时变化的虚拟谐波阻抗，动态调整谐波电流分配，且兼顾了公共交流母线的电压质量。针对负载的不平衡引起逆变器三相输出电压不对称问题，通过改进下垂控制策略实时调节三相参考电压的幅值和频率，同时补偿系统阻抗压降来保证三相输出电压的对称性。同时采用了自适应开关频率的重复控制电压环控制方法来有效地抑制输出电压谐波，提高输出电压质量。最终实现一套高性能、高可靠性、功能完善以及易 扩展性的并联逆变器，为各种负载环境下微电网实用性和可控性奠定理论技术基础。