变流器并网系统复电路模态功率分析

Complex Circuit Modal Power Analysis of Grid-connected Converters

复电路可用来刻画变流器并网系统中原分量和对偶分量的耦合关系,且系统振荡等价于复电路发生串并联谐振。该文引入复电路模态功率的概念,将模态功率和特征根灵敏度联系起来,讨论了变流器并网系统的稳定机理和控制器设计原则。首先,提出了广义导纳的模态功率概念,并说明模态功率是RLC电路中功率概念的推广。其次,推导了模态功率与系统稳定性的关系,据此分析了复电路的谐振机理。在此基础上,分析了变流器导纳的实部与系统稳定性的关系,研究表明导纳的实部与系统稳定性没有一一对应关系,但广义导纳模态功率的实部和系统稳定性存在对应的关系。最后,基于模态功率初步给出了变流器导纳的整定方法。数值仿真验证了基于复电路模态功率的变流器并网系统稳定性分析和控制方法的有效性。

The analysis based on primal-dual complex circuit transforms the oscillation analysis of grid-connected converter system into the resonance of the primal-dual circuit.This paper further proposed the concept of modal power to elucidate the mechanism of resonance.Firstly,the concept of modal power was put forward,which is the extension of the concept of power in the RLC circuit.Secondly,the relationship between the system stability and modal power was analyzed.Further,the resonance mechanism of primal-dual complex circuit was analyzed.Thirdly,the relationship between system stability and the converter’s admittance was analyzed.It is shown that the modal power’s negative real part can indicate the system instability and there is no certain relationship between the converter admittance’s real part and system stability.Finally,the method of converter admittances sharping was given based on modal power.The effectiveness of the modal power and all analysis were validated by simulation.